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Photonics

Photonics is the science that studies light and its creation, propagation, manipulation and interaction with matter. The result is a multidisciplinary technology with applications in communications, industry, nanotechnology, biology, medicine, etc. For decades, photonics has given way to endless applications that have a positive effect on our futures and on our day-to-day lives. To name a few examples, modern fibre-optics-based communications systems, optical diagnostic and therapeutic tools in medicine, laser-based means of production, optical sensors and metrology, and photovoltaic energy are photonic solutions to current problems.

.The doctoral programme in Photonics at the Universitat Politècnica de Catalunya (UPC) is taught by The Institute of Photonic Sciences (ICFO) within the framework of the UPC’s Doctoral School. The ICFO is a research centre dedicated to the study of light-related sciences and technologies, and it has been accredited as a Severo Ochoa Centre of Excellence. Created in 2002 by the Government of Catalonia and the UPC, the ICFO also accepts ambitious sponsorship programmes financed by the Fundació Privada Cellex and Mir-Puig foundations, both in Barcelona. The Institute has a threefold mission: to conduct cutting-edge research, to transfer knowledge and technology and to train postgraduates, mainly doctoral degree holders. Currently, it is one of the leading centres in the world in its field.

. Theses revolve around four lines of research that make up the doctoral programme in Photonics: biomedical photonics, quantum optics, nonlinear optics and nano-photonics. These four lines of research prioritise photonic applications in healthcare, renewable energies and information technologies and they are carried out in long-term programmes and medium-term projects in a range of fields, including quantum information technologies, advanced screens, nano-photonic devices, graphene photonics, remote sensors, solar cells, optoelectronics, integrated optics, ultra-fast optics, super-resolution imaging techniques and therapeutic and diagnostic biomedical technologies, among others.

COORDINATOR

Artigas Garcia, David

CONTACT

The Institute of Photonic Sciences (ICFO)
Av. Carl Friedrich Gauss, 3
08860 Castelldefels

Tel.: +34 935 534 055
E-mail: training@icfo.es

http://phd.icfo.eu/

General information

Access profile

The doctoral programme in Photonics is designed for students with excellent records at the international level who wish to complete a doctoral project in one of the various fields related to photonics.

Regarding the ideal background for applicants, it should be noted that photonics is a far-reaching discipline and that the ICFO is made up of various research groups that work in a variety of branches of the photonic sciences. Thus, applicants to the doctoral programme in Photonics can have a range of backgrounds, from physics to electronics, electrical, material and telecommunications engineering, to mathematics, chemistry, biology, bioengineering and biophysics.

With regards to knowledge of languages, the ICFO is a research institute with a markedly international character, and as such, English is the common language. So, students admitted to the doctoral programme in Photonics must have a high level of both written and spoken English.

Regarding objectives, the doctoral programme in Photonics will admit both students pursuing futures in academia as well as those aiming to be leaders in knowledge and technology transfer in R&D in the business world.

Thus, desirable personal characteristics among applicants include having high potential and being motivated and demanding when it comes to completing quality projects at the highest international level.

Output profile

Doctoral candidates who complete a doctoral degree will have acquired the following competencies, which are needed to carry out quality research (Royal Decree 99/2011, of 28 January, which regulates official doctoral studies):

a) A systematic understanding of the field of study and a mastery of the research skills and methods related to the field.
b) An ability to conceive, design or create, put into practice and adopt a substantial process of research or creation.
c) An ability to contribute to pushing back the frontiers of knowledge through original research.
d) A capacity for critical analysis and an ability to assess and summarise new and complex ideas.
e) An ability to communicate with the academic and scientific community and with society in general as regards their fields of knowledge in the manner and languages that are typical of the international scientific community to which they belong.
f) An ability to foster scientific, technological, social, artistic and cultural progress in academic and professional contexts within a knowledge-based society.

The award of a doctoral degree must equip the graduate for work in a variety of settings, especially those requiring creativity and innovation. Doctoral graduates must have at least acquired the personal skills needed to:

a) Develop in contexts in which there is little specific information.
b) Find the key questions that must be answered to solve a complex problem.
c) Design, create, develop and undertake original, innovative projects in their field.
d) Work as part of a team and independently in an international or multidisciplinary context.
e) Integrate knowledge, deal with complexity and make judgements with limited information.
f) Offer criticism on and intellectually defend solutions.

Finally, with respect to competencies, doctoral students must:
a) have acquired advanced knowledge at the frontier of their discipline and demonstrated, in the context of internationally recognised scientific research, a deep, detailed and well-grounded understanding of theoretical and practical issues and scientific methodology in one or more research fields;
b) have made an original and significant contribution to scientific research in their field of expertise that has been recognised as such by the international scientific community;
c) have demonstrated that they are capable of designing a research project that serves as a framework for carrying out a critical analysis and assessment of imprecise situations, in which they are able to apply their contributions, expertise and working method to synthesise new and complex ideas that yield a deeper knowledge of the research context in which they work;
d) have developed sufficient autonomy to set up, manage and lead innovative research teams and projects and scientific collaborations (both national and international) within their subject area, in multidisciplinary contexts and, where appropriate, with a substantial element of knowledge transfer;
e) have demonstrated that they are able to carry out their research activity in a socially responsible manner and with scientific integrity;
f) have demonstrated, within their specific scientific context, that they are able to make cultural, social or technological advances and promote innovation in all areas within a knowledge-based society;
g) have demonstrated that they are able to participate in scientific discussions at the international level in their field of expertise and disseminate the results of their research activity to audiences of all kinds.

Number of places

30

Duration of studies and dedication regime

Duration
The maximum period of study for full-time doctoral studies is three years, counted from the date of admission to the programme to the date of submission of the doctoral thesis. The academic committee of the doctoral programme may authorise a doctoral candidate to pursue doctoral studies on a part-time basis. In this case, the maximum period of study is five years, counting from the date of admission to the programme to the date of submission of the doctoral thesis. For calculating these periods, the date of admission is considered to be the date of the first enrolment for tutorials, and the date of submission the moment in which the Doctoral School officially deposits the doctoral thesis.

For full-time doctoral candidates, the minimum period of study is two years, counted from the date of an applicant's admission to the programme until the date on which the doctoral thesis is deposited; for part-time doctoral candidates it is four years. When there are justified grounds for doing so, and the thesis supervisor and academic tutor have given their authorisation, doctoral candidates may request that the academic committee of their doctoral programme exempt them from the minimum period of study requirement.

The calculation of periods of study will not include periods of absence due to illness, pregnancy or any other reason provided for in the regulations in force. Students who find themselves in any of these circumstances must notify the academic committee of the doctoral programme, which, where appropriate, must inform the Doctoral School. Doctoral candidates may also temporarily withdraw from the programme for up to one year, and this period may be extended for an additional year. Doctoral candidates who wish to interrupt their studies must submit a justified request to the academic committee of the doctoral programme, which will decide whether or not to approve the request. Each programme will establish conditions for readmission to doctoral studies.

Extension
If full-time doctoral candidates have not applied to deposit their thesis by the end of the three-year period of study, the academic committee of the programme may authorise an extension of up to one year. In exceptional circumstances, a further one-year extension may be granted, subject to the conditions established by the corresponding doctoral programme. In the case of part-time doctoral candidates, an extension of two years may be authorised. In both cases, in exceptional circumstances a further one-year extension may be granted by the Doctoral School's Standing Committee, upon the submission of a reasoned application by the academic committee of the doctoral programme.

Dismissal from the doctoral programme
A doctoral candidate may be dismissed from a doctoral programme for the following reasons:

  • The doctoral candidate submitting a justified application to withdraw from the programme.
  • The maximum period of study and of extensions thereof ending.
  • The doctoral candidate not having enrolled every academic year (unless he or she has been authorised to temporarily withdraw).
  • The doctoral candidate failing two consecutive assessments.
  • The doctoral candidate having disciplinary proceedings filed against him or her that rule that he or she must be dismissed from the UPC.

Dismissal from the programme implies that doctoral candidates cannot continue studying at the UPC and the closing of their academic record. This notwithstanding, they may apply to the academic committee of the programme for readmission and the committee must reevaluate them in accordance with the criteria established in the regulations.

Enrollment aid

The ICFO and the professors of the doctoral programme in Photonics commit to providing all doctoral candidates with a grant/salary that allows them to concentrate full-time on their doctoral theses. This aid covers all enrolment costs.

Organization

COORDINATOR:
ACADEMIC COMMISSION OF THE PROGRAM:
STRUCTURAL UNITS:
  • Institute of Photonic Sciences (PROMOTORA)
Specific URL of the doctoral program:
http://phd.icfo.eu/

CONTACT:

The Institute of Photonic Sciences (ICFO)
Av. Carl Friedrich Gauss, 3
08860 Castelldefels

Tel.: +34 935 534 055
E-mail: training@icfo.es


Agreements with other institutions

The ICFO has collaboration agreements with a number of important businesses, including Leica Microsystems, Corning, Nikon-Izasa, the Sorigué group, Accelerate Diagnostics, SL, Fyla All-Fiber Ultrafast Lasers and GRAPHENEA, to name a few. The Institute also participates in networks of excellence (Eurobioimaging, Laserlab Europe, Corbel, etc.) and coordinates various projects for Graphene Flagship and Quantum Flagship under the EU’s Horizon 2020 programme.

Access, admission and registration

Access profile

The doctoral programme in Photonics is designed for students with excellent records at the international level who wish to complete a doctoral project in one of the various fields related to photonics.

Regarding the ideal background for applicants, it should be noted that photonics is a far-reaching discipline and that the ICFO is made up of various research groups that work in a variety of branches of the photonic sciences. Thus, applicants to the doctoral programme in Photonics can have a range of backgrounds, from physics to electronics, electrical, material and telecommunications engineering, to mathematics, chemistry, biology, bioengineering and biophysics.

With regards to knowledge of languages, the ICFO is a research institute with a markedly international character, and as such, English is the common language. So, students admitted to the doctoral programme in Photonics must have a high level of both written and spoken English.

Regarding objectives, the doctoral programme in Photonics will admit both students pursuing futures in academia as well as those aiming to be leaders in knowledge and technology transfer in R&D in the business world.

Thus, desirable personal characteristics among applicants include having high potential and being motivated and demanding when it comes to completing quality projects at the highest international level.

Access requirements

Applicants must hold a Spanish bachelor’s degree or equivalent and a Spanish master’s degree or equivalent, provided they have completed a minimum of 300 ECTS credits on the two degrees (Royal Decree 43/2015, of 2 February)

In addition, the following may apply:

  • Holders of an official degree awarded by a university in Spain or any other country in the European Higher Education Area, pursuant to the provisions of Article 16 of Royal Decree 1393/2007, of 29 October, which establishes official university course regulations, who have completed a minimum of 300 ECTS credits on official university degrees, of which at least 60 must be at the master's degree level.
  • Holders of an official Spanish bachelor’s degree comprising at least 300 credits, as provided for by EU regulations. Holder of degrees of this kind must complete bridging courses unless the curriculum of the bachelor’s degree in question included research training credits equivalent in value to those which would be earned on a master's degree.
  • Holders of an official university qualification who, having passed the entrance examination for specialised medical training, have completed at least two years of a training course leading to an official degree in a health-sciences specialisation.
  • Holders of a degree issued under a foreign education system. In these cases, homologation is not required, but the UPC must verify that the degree certifies a level of training equivalent to an official Spanish master's degree and qualifies the holder for admission to doctoral studies in the country where it was issued. Admission on this basis does not imply homologation of the foreign degree or its recognition for any purpose other than admission to doctoral studies.
  • Holders of a Spanish doctoral qualification issued under previous university regulations.
  • Note 1: Doctoral studies entrance regulations for holders of an undergraduate degree awarded before the introduction of the EHEA (CG 47/02 2014)

    Note 2: Governing Council Decision 64/2014, which approves the procedure and criteria for assessing the fulfilment of academic admission requirements for doctoral studies by holders of non-homologated foreign degrees (CG 25/03 2014)

Admission criteria and merits assessment

The application to the doctoral programme in Photonics can be found at http://jobs.icfo.eu/, where all interested students are sent. On this page, detailed information is published regarding the specific number of openings available for doctoral candidates at each moment and in each of the ICFO’s research groups.

As for selection criteria in particular, the body responsible for admission to the doctoral programme in Photonics will assess applications according to the following merit-based considerations and weights:

1. A high level of previous academic achievement: including the applicant’s academic transcript and other proof of grants and awards (55 %).
2. An advanced level of English: English level certificates will be considered, along with proof, in the applicant’s CV, of stays abroad and the level of conversation demonstrated in a personal interview (15 %).
3. High potential: via the applicant’s CV, proof of prior participation in research projects, scientific publications, student mobility programmes during previous studies and other related merits specified by the applicant. The appropriateness of the applicant’s previous studies for the proposed project will also be considered, as well as proof of extracurricular activities (entrepreneurial, community service and other related merits) and information provided in letters of recommendations (15 %).
4. A high level of motivation, which will be assessed based on a personal interview and the motives expressed in the student’s letter of introduction (15 %).

Finally, it is worth mentioning that during the admission process to the doctoral programme in Photonics, compliance with the principles of transparency, efficiency and international openness will be pursued as per the European Charter for Researchers and the European Code of Conduct for the Recruitment of Researchers. Thus, during this process, there will be no discrimination based on gender or nationality.

Training complements

No bridging courses will be required of those students coming from the following affiliated master’s programmes: Master’s programme in Photonics and the Erasmus Mundus Master’s programme in Photonics Engineering, Nanophotonics and Biophotonics.

For students who have completed master’s programmes in Photonics at other universities, their transcripts and the projects on which they will work will be assessed in order to determine, on a case-by-case basis, if specific bridging courses must be taken.

For students holding master’s degrees from other areas, their specific transcripts and the projects on which they will work will be assessed to determine, on a case-by-case basis, if specific bridging courses must be taken. If required, these students will have to take the following bridging courses in the master’s programme in Photonics offered by the UPC:
• Introduction to Photonics. Optics and Lasers (5 ECTS).
• Photonics Laboratory (5 ECTS).

Enrolment period for new doctoral students

Enrolment is open all year within the calendar established by the Doctoral School.

More information at the registration section for new doctoral students

Enrolment period

During the month of September.

More information at the general registration section

Monitoring and evaluation of the doctoral student

Procedure for the preparation and defense of the research plan

Doctoral candidates must submit a research plan, which will be included in their doctoral student activity report, before the end of the first year. The plan may be improved over the course of the doctoral degree. It must be endorsed by the tutor and the supervisor, and it must include the method that is to be followed and the aims of the research.

At least one of these annual assessments will include a public presentation and defence of the research plan and work done before a committee composed of three doctoral degree holders, which will be conducted in the manner determined by each academic committee. The examination committee awards a Pass or Fail mark. A Pass mark is a prerequisite for continuing on the doctoral programme. Doctoral candidates awarded a Fail mark must submit a new research plan for assessment by the academic committee of the doctoral programme within six months.

The committee assesses the research plan every year, in addition to all of the other activities in the doctoral student activity report. Doctoral candidates who are awarded two consecutive Fail marks for the research plan will be obliged to definitely withdraw from the programme.

If they change the subject of their thesis, they must submit a new research plan.

Formation activities

The doctoral programme in Photonics does not specify a minimum number for published articles, conferences attended or other activities. However, the programme’s Academic Committee does aim to ensure that each individual thesis meets the highest international standards before it will be allowed to be presented publicly.

Hereafter, details are provided about the educational activities included in the programme, their length and whether they are compulsory or optional:

• Tutorial (meetings with thesis supervisor), 288 hr/year, compulsory.
• Assessment of/follow-up with the doctoral student activity report and research plan, 4 hours, compulsory.
• Scientific seminars, 25 hr/year, optional.
• ICONS seminars (organised by doctoral candidates for doctoral candidates), 40 hr/year, optional.
• Coffee with prominent researchers, 2 hr/year, optional.
• Programme workshops, 1 day/year, mandatory participation at least once per year.
• Stays in international centres, 3 months, optional.
• Doctoral classes: Theory Lectures and Bio Lectures, 65 hr/year, optional.
• Outreach activities: 18 hours, compulsory.
• Training in technical skills: 5 hours per technique, optional.
• Training in information skills: 1.5 hours, optional.
• Effective oral presentations: 10 hours, optional.
• ICFO-ESADE, ‘From science to business’: 24 hours, optional.
• Introduction to drafting and administering patents: 7.5 hours, optional.
• Language courses (English, Catalan, Spanish): 40 hours, optional.
• Visits to installations and laboratories: 4 hr/visit, optional.

Procedure for assignment of tutor and thesis director

The academic committee of the doctoral programme assigns a thesis supervisor to each doctoral candidate when they are admitted or enrol for the first time, taking account of the thesis supervision commitment referred to in the admission decision.

The thesis supervisor will ensure that training activities carried out by the doctoral candidate are coherent and suitable, and that the topic of the candidate’s doctoral thesis will have an impact and make a novel contribution to knowledge in the relevant field. The thesis supervisor will also guide the doctoral candidate in planning the thesis and, if necessary, tailoring it to any other projects or activities undertaken. The thesis supervisor will generally be a UPC professor or researcher who holds a doctoral degree and has documented research experience. This includes PhD-holding staff at associated schools (as determined by the Governing Council) and UPC-affiliated research institutes (in accordance with corresponding collaboration and affiliation agreements). When thesis supervisors are UPC staff members, they also act as the doctoral candidate’s tutor.

PhD holders who do not meet these criteria (as a result of their contractual relationship or the nature of the institution to which they are attached) must be approved by the UPC Doctoral School's Standing Committee in order to participate in a doctoral programme as researchers with documented research experience.

The academic committee of the doctoral programme may approve the appointment of a PhD-holding expert who is not a UPC staff member as a candidate’s thesis supervisor. In such cases, the prior authorisation of the UPC Doctoral School's Standing Committee is required. A UPC staff member who holds a doctoral degree and has documented research experience must also be proposed to act as a co-supervisor, or as the doctoral candidate’s tutor if one has not been assigned.

A thesis supervisor may step down from this role if there are justified reasons (recognised as valid by the committee) for doing so. If this occurs, the academic committee of the doctoral programme will assign the doctoral candidate a new thesis supervisor.

Provided there are justified reasons for doing so, and after hearing any relevant input from the doctoral candidate, the academic committee of the doctoral programme may assign a new thesis supervisor at any time during the period of doctoral study.

If there are academic reasons for doing so (an interdisciplinary topic, joint or international programmes, etc.) and the academic committee of the programme gives its approval, an additional thesis supervisor may be assigned. Supervisors and co-supervisors have the same responsibilities and academic recognition.

The maximum number of supervisors of a doctoral thesis is two: a supervisor and a co-supervisor.

For theses carried out under a cotutelle agreement or as part of an Industrial Doctorate, if necessary and if the agreement foresees it this maximum number of supervisors may not apply. This notwithstanding, the maximum number of supervisors belonging to the UPC is two.

More information at the PhD theses section

Permanence

The academic committee of the programme may authorise an extension of up to one year for full-time doctoral candidates who have not applied to deposit their thesis by the end of the three-year period of study, in the terms outlined in the Academic Regulations for Doctoral Studies of the Universitat Politècnica de Catalunya. In the case of part-time candidates, an extension of two years may be authorised. In both cases, in exceptional circumstances a further one-year extension may be granted by the Doctoral School's Standing Committee, upon the submission of a reasoned application by the academic committee of the doctoral programme.

A doctoral candidate may be dismissed from a doctoral programme for the following reasons:

  • The doctoral candidate submitting a justified application to withdraw from the programme.
  • The maximum period of study and of extensions thereof ending.
  • The doctoral candidate not having enrolled every academic year (unless he or she has been authorised to temporarily withdraw).
  • The doctoral candidate failing two consecutive assessments.
  • The doctoral candidate having disciplinary proceedings filed against him or her that rule that he or she must be dismissed from the UPC.

Dismissal from the programme implies that doctoral candidates cannot continue studying at the UPC and the closing of their academic record. This notwithstanding, they may apply to the academic committee of the programme for readmission and the committee must reevaluate them in accordance with the criteria established in the regulations.

International Mention

The doctoral degree certificate may include International Doctorate mention. In this case, the doctoral candidate must meet the following requirements:

a) During the period of study leading to the award of the doctoral degree, the doctoral candidate must have spent at least three months at a respected higher education institution or research centre outside Spain to complete courses or do research work. The stays and activities carried out must be endorsed by the thesis supervisor and authorised by the academic committee of the programme. The candidate must provide a certifying document issued by the person responsible for the research group of the body or bodies where the stay or activity was completed. This information will be added to the doctoral student’s activity report.
b) Part of the thesis (at least the summary and conclusions) must be written and presented in one of the languages commonly used for science communication in the relevant field of knowledge, which must not be an official language of Spain. This rule does not apply to stays and reports in Spanish or to experts from Spanish-speaking countries.
c) At least two PhD-holding experts belonging to a higher education institution or research centre outside Spain must have issued officially certified reports on the thesis.
d) The thesis examination committee must have included at least one PhD-holding expert from a higher education or research institution outside Spain who was not responsible for the candidate’s stay abroad (point a) above).
e) The thesis defence must have taken place on UPC premises or, in the case of joint programmes, at the location specified in the collaboration agreement.

Learning resources

Beyond the support teams and services available at the University, the ICFO’s management team is made up of highly specialised personnel in various fields; thus, they are able to provide specific hands-on assistance to candidates in the doctoral programme in Photonics. Specifically, the ICFO has the following:

• Human Resources and Education Unit: procedures related to academics, contracts, permissions with the foreigner’s office, accommodations, predoctoral aid for carrying out doctoral studies and mobility aid for doctoral students.
• Technology and Knowledge Transfer Unit: https://www.icfo.eu/lang/industry
• ICFO Projects Unit: in charge of finding potential financing, counselling researchers when preparing proposals and filing applications.

Additionally, candidates in the doctoral programme in Photonics have access to the NanoFabrication Laboratory, the Super-resolution Light Microscopy and Nanoscopy Service, the Advanced Engineering Laboratory, the Biology Laboratory and the Chemistry and Post-Processing laboratories: https://www.icfo.eu/lang/research/facilities

Doctoral Theses

List of authorized thesis for defense

  • BORDACCHINI, IVAN: Discerning between thermal and electronic effects in plasmonenhanced organic reactions
    Author: BORDACCHINI, IVAN
    Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Deposit date: 30/09/2020
    Reading date: 30/10/2020
    Reading time: 11:00
    Reading place: Auditori de l¿ICFO_ Mediterranean Technology Park, Avinguda Carl Friedrich Gauss, 3, 08860 Casteldefels, Barcelona - Videconferència: http://s.ic.fo/1dpcR
    Thesis director: QUIDANT, ROMAIN
    Committee:
         PRESIDENT: PERICAS BRONDO, MIQUEL ANGEL
         SECRETARI: KONSTANTATOS, GERASIMOS
         VOCAL: BALDI, ANDREA
    Thesis abstract: Since the pioneering work of Fujishima and Honda on titanium dioxide, TiO2, for the electrochemical photolysis of water under ultraviolet (UV) irradiation, semiconductor-based photocatalysis and photovoltaics have become a rapidly growing field of investigation. However, UV light accounts for only 4% of the solar spectrum, whereas the visible light represents 42% of the total solar radiation. Therefore, the scientific community focused their efforts on the optimization and extension of the absorption spectrum of semiconductor-based materials to the visible region of the solar spectrum. Well-established techniques include doping of the semiconductor or the deposition of a different element or substance on the surface of the material. Since 2004, the deposition of plasmonic nanoparticles (NPs) on semiconductors emerged as a possible solution to generate energetic electrons capable of driving reactions under visible irradiation. Since then, numerous contributions have been published in the field of plasmonenhanced photocatalysis with relevant applications in water splitting, organic synthesis, and photovoltaics. In the field of heterogeneous photocatalysis, plasmon-generated energetic electrons were widely accepted as responsible for the observed catalytic effect of plasmonic NPs. Recently, several scientific contributions have questioned the actual mechanism triggering plasmonenhanced reactions, hypothesising that thermal effects are instead the predominant factor that influences the activity of a plasmonic catalyst. In this work, we aimed at differentiating between the thermal and electronic effects of plasmonic NPs in a test reaction¿the reductive ii coupling of nitrobenzene to azobenzene¿under irradiation with 532 nm and/or 875 nm lasers. Moreover, we also aimed at developing a methodology that could be easily replicated in other laboratories and used as a benchmark test for plasmon-enhanced reactions run in solution. We optimized the size and shape of AuNPs plasmonic catalysts to obtain materials with different absorption in the visible and near-infrared (NIR) region to tune the electronic and thermal effects of the catalyst. The activity of the synthesised catalysts for the test reaction was compared with the activity of the Gold World Council reference catalyst type A. Characterization of the synthesised Au/TiO2 catalyst with diffuse reflectance measurements evidenced that the presence of small amounts of AuNPs did not modify the band gap position of the support, hence suggesting that, under visible light irradiation, the catalysis occurred on the surface of the AuNPs. The determination of the enthalpy of activation for each step of the reaction showed that the second step of the reaction was strongly influenced by the 532 nm laser irradiation. Indeed, our calculations demonstrated an energy difference between the illuminated and the dark reactions in the first step of reaction of 1.1 ¿¿¿¿¿¿¿¿ ¿¿¿¿¿¿!" whereas the one for the second step was 5.9 ¿¿¿¿¿¿¿¿ ¿¿¿¿¿¿!". We further analysed the results of designed experiments running the test reaction in the presence of two catalysts differing by the shapes of the AuNPs and under different laser sources and irradiances. The results were processed to obtain predictive phenomenological models for the intermediate and the product of the reaction, azoxybenzene and azobenzene, respectively. iii The obtained models allowed to confirm that the investigated reaction was triggered by electronic effects and that the contribution of thermal effects, generated by the electron-phonon decay of elongated AuNPs, was not significantly influencing the reaction outcome.
  • MUÑOZ GIL, GORKA: Anomalous diffusion: from life to machines
    Author: MUÑOZ GIL, GORKA
    Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: (164)
    Mode: Normal
    Deposit date: 02/10/2020
    Reading date: pending
    Reading time: pending
    Reading place: pending
    Thesis director: LEWENSTEIN, MACIEJ | GARCÍA MARCH, MIGUEL ANGEL
    Committee:
         PRESIDENT: KRAPF, DIEGO
         SECRETARI: WIESER, STEFAN
         VOCAL: MASSON, JEAN-BAPTISTE
    Thesis abstract: Diffusion refers to numerous phenomena, by which particles and bodies of all kinds move throughout any kind of material, has emerged as one of the most prominent subjects in the study of complex systems. Motivated by the recent developments in experimental techniques, the field had an important burst in theoretical research, particularly in the study of the motion of particles in biological environments. Just with the information retrieved from the trajectories of particles we are now able to characterize many properties of the system with astonishing accuracy. For instance, when Einstein introduced the diffusion theory back in 1905, he used the motion of microscopic particles to calculate the size of the atoms of the liquid these were suspended. Initially, most of the experimental evidence showed that such systems follow Brownian-like dynamics, i.e. the homogeneous interaction between the particles and the environment led to its stochastic, but uncorrelated motion. However, we know now that such a simple explanation lacks crucial phenomena that have been shown to arise in a plethora of physical systems. The divergence from Brownian dynamics led to the theory of anomalous diffusion, in which the particles are affected in a way or another by their interactions with the environment such that their diffusion changes drastically. For instance features such as ergodicity, Gaussianity, or ageing are now crucial for in the understanding of diffusion processes, well beyond Brownian motion.In theoretical terms, anomalous diffusion has a well-developed framework, able to explain most of the current experimental observations. However, it has been usually focused in describing the systems in terms of its macroscopic behaviour. This means that the processes are described by means of general models, able to predict the average or collective features. Even though such an approach leads to a correct description of the system and hints on the actual underlying phenomena, it lacks the understanding of the particular microscopic interactions leading to anomalous diffusion. The work presented in this Thesis has two main goals. First, we will explore how one may use microscopical (or phenomenological) models to understand anomalous diffusion. By microscopical model we refer to a model in which we will set exactly how the interactions between the various components of a system are. Then, we will explore how these interactions may be tuned in order to recover and control anomalous diffusion and how its features depend on the properties of the system. We will explore crucial topics arising in recent experimental observations, such as weak-ergodicity breaking or liquid-liquid phase separation. Second, we will survey the topic of trajectory characterization. Even if our theories are extremely well developed, without an accurate tool for studying the trajectories observed in experiments, we will be unable to correctly make any faithful prediction. In particular, we will introduce one of the first machine learning techniques that can be used for such purpose, even in systems where previous techniques failed largely.

Last update: 24/10/2020 05:09:06.

List of lodged theses

  • WINKLER, PAMINA: Novel planar photonic antennas to address the dynamic nanoarchitecture of biological membranes
    Author: WINKLER, PAMINA
    Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Deposit date: 19/10/2020
    Reading date: pending
    Reading time: pending
    Reading place: pending
    Thesis director: GARCÍA PARAJO, MARÍA
    Committee:
         PRESIDENT: WIENTJES, INA EMILIA
         SECRETARI: VAN HULST, NIEK
         VOCAL: SEZGIN, ERDINC
    Thesis abstract: The cell membrane is the encompassing protective shield of every cell and it is composed of a multitude of proteins, lipids and other molecules. The organization of the cell membrane is inextricably intertwined with its function, and sensitive to perturbations from the underlying actin cytoskeleton and the extracellular environment at the nano- and the mesoscale. Elucidating the dynamic interplay between lipids and proteins diffusing on the cell membrane, forming transient domains and (re)organizing them according to signals from the juxtaposed inner and outer meshwork, is of paramount interest in fundamental cell biology. The overarching goal of this thesis is to gain deeper insight into how lipids and proteins dynamically organize in biological membranes at the nanoscale. Photonic nano-antennas are metallic nanostructures that localize and enhance the incident optical radiation into highly confined nanometric regions (< 20 nm), leading to greatly enhanced light-matter interactions. In this thesis, we exploit an innovative design of planar gold nano-antenna arrays of different gap sizes (10-45 nm) and embedded in nanometric-size boxes. To elucidate nanoscale diffusion dynamics in biological membranes with high spatiotemporal resolution and single-molecule detection sensitivity, we further combine our nanogap antenna arrays with fluorescence correlation spectroscopy (FCS) in a serial and multiplexed manner. In this dissertation, we first describe the fabrication process of these planar gold nanogap antennas and characterize their performance by means of electron microscopy and FCS of individual molecules in solution. We demonstrate giant fluorescence enhancement factors of up to 104-105 times provided by our planar nanogap antennas in ultra-confined detection volumes and with single molecule detection sensitivity in the micromolar range. Second, we apply these planar plasmonic nano-antennas in combination with FCS for assessing the dynamic organization of mimetic lipid membranes at the nanoscale. For a ternary composition of the model membranes that include unsaturated and saturated lipids together with cholesterol, we resolve transient nanoscopic heterogeneities as small as 10 nm in size, coexisting in both macroscopically phase-separated lipid phases.Third, we add a Hyaluronic Acid (HA) layer on top of the model lipid membranes to emulate the effect of the extracellular environment surrounding native biological membranes. We extend our nano-antenna-FCS approach with atomic force microscopy and spectroscopy. We reveal a distinct influence of HA on the nanoscale lipid organization of mimetic membranes composed of lipids constituting the more ordered lipid phase. Our results indicate a synergistic effect of cholesterol and HA re-organizing biological membranes at the nanoscale. Fourth, we apply our planar nano-antenna platform combined with FCS to elucidate the nanoscale dynamics of different lipids in living cells. With our nanogap antennas we were able to breach into the sub-30 nm spatial scale on living cell membranes for the first time. We provide compelling evidence of short-lived cholesterol-induced ~10 nm nanodomain partitioning in living plasma membranes. Fifth, we demonstrate the multiplexing capabilities of our planar gold nanogap antenna platform combined with FCS in a widefield illumination scheme combined with sCMOS camera detection. Our approach allows recording of fluorescence signal from more than 200 antennas simultaneously. Moreover, we demonstrate multiplexed FCS recording on 50 nano-antennas simultaneously, both in solution as well as in living cells, with a temporal resolution in the millisecond range. The dissertation finishes with a brief discussion of the main results achieved in this research and proposes new avenues for future research in the field.

Last update: 24/10/2020 05:08:01.

List of defended theses by year

  • ALCARAZ IRANZO, DAVID: Study of Graphene Hybrid Heterostructures for Linear and Nonlinear Optics
    Author: ALCARAZ IRANZO, DAVID
    Thesis link: http://hdl.handle.net/10803/669309
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 23/06/2020
    Thesis director: KOPPENS, FRANK

    Committee:
         PRESIDENT: POLINI, MARCO
         SECRETARI: PRUNERI, VALERIO
         VOCAL: MORTENSEN, NIELS ASGER
    Thesis abstract: Graphene is the first of the 2D-material family. It is formed by carbon atoms arranged in a honeycomb lattice, which confers it intriguing physical properties that are still being discovered nowadays. A fundamental advantage found in graphene is the ability to gate tune ¿in-situ¿ its optical response from reflective (metallic) to absorptive (lossy dielectric). It is in the reflective conditions when it becomes more interesting since it supports surface plasmon polaritons in the mid-infrared, similar to metals in the near-infrared and visible spectral regions. Surface plasmons in metals are known to be more confined than free space propagating light. But graphene naturally excels in this aspect by offering a confinement factor around 100, which causes light to couple in inefficiently.Several studies on metal plasmonics have shown the possibilities of confining light into tiny spatial dimensions with applications in molecular sensing as an example. Often, metal plasmons are used in the visible and IR regions with moderate confinement. However, Landau damping limits the optical field confinement due to penetration in the material and the consequent losses. In this thesis, it is shown that graphene-insulator-metal hybrid heterostructures can overcome that limitation by efficiently exciting plasmons in unpatterned graphene with vertical confinement down to the ultimate one-atom insulator thickness. It is accomplished by encapsulating graphene with a single layer of h-BN (or thicker oxide layers for the systematic study) and fabricating metallic nano/micro-ribbons on top. The transmission extinction of the samples was measured and compared with theoretical models accounting for material nonlocal permittivity. The ultimate confinement and the validity of the excitation method are confirmed enabling a path towards ultrastrong light-matter interaction.An example application of the aforementioned method to graphene nonlinear optics is also presented. The large intrinsic graphene third-order nonlinear optical response has been of great interest and it has been studied both theoretically and experimentally. However, there were not experiments covering all the expected features from the theory in the mid-infrared.This thesis expands the measurement range to cover the mentioned gap in planar graphene. Additionally, field enhancement and confinement provided by the hybrid heterostructure was exploited to increase the nonlinear third-harmonic generation signal in more than three orders of magnitude. Intriguingly, it was found that some structures presented further modulation of the nonlinear signal which is attributed to the oscillatory nature of graphene plasmons. This opened an extra channel for extreme nonlinear gate tunability for the optimized parameters.To summarize, this thesis presented means to achieve the regime of ultrastrong light-matter interaction, it fully characterizes it down to the one-atom spacer limit, and provides an example while demonstrating its applicability in graphene nonlinear optics.

  • ALDA FERRERO, IRENE: Levitodynamics on-a-chip: from planar Paul traps to near-field optical nanocavities
    Author: ALDA FERRERO, IRENE
    Thesis link: http://hdl.handle.net/10803/669278
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 09/07/2020
    Thesis director: QUIDANT, ROMAIN

    Committee:
         PRESIDENT: NOVOTNY, LUKAS
         SECRETARI: SEWELL, ROBERT
         VOCAL: SEIDELIN, SIGNE LOUISE
    Thesis abstract: The field of levitation optomechanics---or levitodynamics---studies the manipulation and control of small trapped objects in an isolated environment, providing a gateway to answer fundamental questions in physics and expanding the range of applications at the nanoscale.Levitation of particles can be achieved through different tools and techniques such as Paul traps and optical tweezers. Paul traps are created by alternating electric fields to levitate charged particles, while optical traps are based on optical forces that confine and manipulate nano-objects with high polarizability and low absorption.Both have the potential to be reduced to on-a-chip systems, enabling the miniaturization of the experiment, its interface with other photonic devices, and the expansion of trapping tools to on-a-chip technologies. In particular, a nanocavity coupled with a levitated particle is a promising platform to attain higher per-photon sensitivities than far-field detection schemes. The further study of on-a-chip levitated optomechanics systems will allow for new applications that enable sub-wavelength control and near-field detection in vacuum conditions.In this thesis, we describe our work with two on-a-chip levitodynamics experiments. Firstly, we have designed and built a planar Paul trap to levitate nanoparticles. This integrated device allows to manipulate and interrogate the trapped specimen, even over long periods of time. We optimized the geometry of the trap to a confinement of 4 microns in each direction. This on-a-chip levitation tool has potential to become a clean loading mechanism to trap particles in vacuum, avoiding current techniques that are unsuitable for contamination-sensitive experiments.Secondly, we have also designed, fabricated and tested a 1D photonic crystal nanocavity suspended on a silicon nitride membrane to study near-field levitodynamics. We have approached a levitated nanoparticle by an optical tweezer to the near-field of the nanocavity and measured the dynamics of the nanoparticle through the nanocavity. From the output signal of the nanocavity, we have estimated the single-photon optomechanical strength g0 along each axis. We have also characterized the thermal dynamics of the nanocavity. The power circulating inside the cavity increases the temperature of the device, inducing rich and tunable behavior in the transmission, such as bistability and self-induced oscillations.Control over these thermal effects is fundamental to create all-optical integrated circuits. This technology, exploited alongside the miniaturization of Paul traps and near-field schemes, could enable on-a-chip levitodynamical devices that are able to trap, manipulate, and detect nano-objects with unprecedented precision.

  • ALOY LÓPEZ, ALBERT: Exploring quantum many-body systems from an entanglement and nonlocality perspective
    Author: ALOY LÓPEZ, ALBERT
    Thesis link: http://hdl.handle.net/10803/669581
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 16/07/2020
    Thesis director: LEWENSTEIN, MACIEJ

    Committee:
         PRESIDENT: CIRAC, IGNACIO
         SECRETARI: CHANG, DARRICK
         VOCAL: SANGOUARD, NICOLAS
    Thesis abstract: Entanglement and non-local correlations give rise to unprecedented phenomena with no classical analogue. As a result, they have settled themselves as fundamental properties in the study of quantum many-body systems, as well as key resources for emerging quantum technologies. However, the lack for general and efficient criteria to characterize them in many-body systems poses many challenges, often intractable. Consequently, despite the growing interest in their properties, the role of entanglement and non-local correlations in many-body systems remains largely unexplored.The subject of the present Thesis is to explore quantum many-body systems from an entanglement and non-local correlations perspective, aiming at expanding the interplay between quantum information processing and quantum many-body physics. We examine adequate properties, like symmetries, that allow us to delve into entanglement and non-local correlations in many-body systems of physical relevance. The original results that we present are achieved at the fundamental level, even though many practical methods that can be experimentally implemented stem from them.First, we explore the complexity to characterize entanglement in simplified cases. In particular, we consider the separability problem for diagonal symmetric states. We establish a connection with the field of quadratic conic optimization that allows us to provide significant sufficient criteria. Furthermore, it allows us to prove that obtaining necessary and sufficient criteria remains an NP-hard problem, even for a case with such a simplified structure.Second, the elusiveness of the characterization of entanglement motivates certification criteria for its detection, specially in the multipartite scenario. By means of non-local correlations, we provide device-independent certification criteria that characterizes the amount of entanglement present on a quantum many-body system. This type of certification does not rely on assumptions about the internal workings of the measuring device nor about the system itself. Moreover, by relying solely on non-local correlations, the criteria dismisses all the correlations that have a classical analogue, thus being a natural candidate as a certifier for emerging quantum technologies.Third, we explore non-local correlations in the vicinity of quantum critical points, which are known to stabilize large-scale entanglement. We show the presence of non-local correlations across the phase diagram via a certain Bell inequality. Furthermore, we show that the Bell inequality is maximally violated at the quantum critical point, hinting at a possible connection between many-body Bell correlators and quantum phase transitions.Fourth, we present a solution to the quantum marginal problem restricted to symmetric states. This allows to partially circumvent the inefficient representability inherent to the multipartite Hilbert space in cases of interest. In addition, we illustrate some of the applications that our solution brings on central quantum information problems. Namely, (i) as an undemanding and efficient variational method to optimize local Hamiltonians over symmetric states, (ii) to optimize few-body symmetric Bell inequalities over symmetric states and (iii) to explore which symmetric states cannot be self-tested solely from their marginals.Finally, we conclude by presenting a methodology to derive two-body symmetric Bell inequalities for three-outcomes. These novel Bell inequalities are natural candidates to explore the role of non-local correlations on quantum phenomena tailored to qutrit or spin-1 many-body systems. We select a particular Bell inequality to characterize and show that it reveals non-local correlations in the ground state of many-body Hamiltonians physically relevant to, e.g., nuclear physics.

  • CHARALAMBOUS, CHRISTOS: Quantum Brownian Motion in Bose-Einstein Condensates
    Author: CHARALAMBOUS, CHRISTOS
    Thesis link: http://hdl.handle.net/10803/668822
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 31/01/2020
    Thesis director: LEWENSTEIN, MACIEJ | GARCÍA MARCH, MIGUEL ANGEL

    Committee:
         PRESIDENT: SANPERA TRIGUEROS, ANNA
         SECRETARI: CAVALCANTI, DANIEL
         VOCAL: WIDERA, ARTUR
    Thesis abstract: Quantum Brownian motion is one of the most prominent examples of an open quantum system, a system which cannot be treated in isolation from its environment. The simplest method to study the dynamics of a system undergoing such a type of motion, that satisfies Heisenberg Uncertainty principle is the approach of Quantum Generalized Langevin Equations (QGLE), which was used throughout this thesis. A Quantum Brownian motion approach is used in this work to study the Bose polaron problem. In this case, one transforms the original problem into one where the impurities are treated as quantum Brownian particles interacting with a bath composed of the Bogoliubov modes of the condensate. Then by deriving the relevant QGLE, it was shown that the dynamics of the Bose polaron exhibit memory effects. This was studied for both a free Bose-Einstein condensate (BEC) and a harmonically trapped one, in both cases for experimentally relevant parameters. Taking advantage of this recent theoretical development, we study a number of phenomena that can be examined under this prism and show how various microdevices can be constructed and controlled. In the first project, we study the creation of entanglement and squeezing of two uncoupled impurities that are immersed in a single common (BEC) bath. We treat these impurities as two quantum Brownian particles. We study two scenarios:(i) In the absence of an external potential, we observe sudden death of entanglement;(ii) In the presence of an external harmonic potential, where entanglement survives even at the asymptotic time limit. In our second work, we studied the diffusive behavior of a Bose Polaron immersed in a coherently coupled two-component BEC. The particle superdiffuses if it couples in the same manner to both components, i.e. if it couples either attractively or repulsively to both of them. This is the same behavior of an impurity immersed in a single BEC. Conversely, we find that it exhibits a transient nontrivial subdiffusive behavior if it couples attractively to one of the components and repulsively with the other. We show how the magnitude of the anomalous exponent reached and the duration of the subdiffusive interval can be controlled with the Rabi frequency of the coherent coupling between the two components and the coupling strength of the impurity to the BEC. Then we proceeded with the construction of two microdevices, a quantum sub-nk thermometer and a heat diode. In the first project, we introduced a novel minimally disturbing method for sub-nK thermometry in a BEC. In this case, the impurity acted as a thermometer, where one detects temperature fluctuations from measurements of the position and momentum of the impurity. Crucially, these cause minimal backaction on the BEC and hence, realize a nondemolition temperature measurement. Following the paradigm of the emerging field of quantum thermometry, we combine tools from quantum parameter estimation and the theory of open quantum systems to solve the problem in full generality. We thus avoid any simplification, such as demanding thermalization of the impurity atoms. In our final work, we investigated the heat transport and the control of heat current among two spatially separated trapped BECs, each of them at a different temperature. To allow for heat transport among the two independent BECs we consider a link made of two dipole-dipole interacting harmonically trapped impurities, each of them interacting with one of the BECs. We address the dependence of heat current and current-current correlations on the physical parameters of the system. Interestingly, we show that heat rectification, can occur in our system, when a periodic driving on the trapping frequencies of the impurities is considered. Therefore, our system is a possible setup for the implementation of a phononic circuit, and hence contributes in the general framework of using BECs as platforms for quantum information processing.

  • DE BONIS, SERGIO LUCIO: Polaron physics in carbon nanotube electro-mechanical resonators
    Author: DE BONIS, SERGIO LUCIO
    Thesis link: http://hdl.handle.net/10803/668846
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 06/02/2020
    Thesis director: BACHTOLD, ADRIAN

    Committee:
         PRESIDENT: LAIRD, EDWARD
         SECRETARI: QUIDANT, ROMAIN
         VOCAL: COLLIN, EDDY
    Thesis abstract: Carbon nanotube (CNT) mechanical resonators are unique systems because they combine remarkable mechanical properties with rich charge transport characteristics. Thanks to their intrinsically low-dimensional nature, their mass is extremely low. The mechanical resonance frequency reaches the GHz regime, can be widely tunable and they showquality factor as high as several million. Nanotubes hold great promise for sensing applications. Nanotubes are an excellent system to study quantum electron transport, which range from abry-Pérot interference to Coulomb blockade. These completely opposite regimes can be very efficiently coupled to the mechanics, since the two degrees offreedom, electrons and phonons, are embedded in the same system.In the first section of this thesis we develop a detection scheme utilizing a RLC resonator together with a low-temperature HEMT amplifier.This allows us to lower the current noise floor of the setup and carry out sensitive electrical noise measurements, demonstrating a displacement sensitivity of 0.5 pm/Hz^(1/2) and a force sensitivity of 4.3 zN/Hz^(1/2). This surpasses what has been achieved with mechanical resonators to date and paves the way for the detection of ndividual nuclear spins. We also improve the device fabrication enhancing the capacitive coupling between mechanical vibrations and electronsflowing though the nanotube.In the second part of this work, we study the electron-phonon coupling in CNT resonators in the Coulomb blockade regime and report on the long-sought-after demonstration of the ultra-strong coupling regime. Mechanical vibrations and electrons are so strongly coupled that it no longer makes sense to think of them as distinct entities, but rather as a quasi-particle: a polaron. First, we demonstrate that the polaronic nature of charge carriers modifies the quantum electron transportthrough the device. In previous electromechanical devices, the coupling was too weak to have any effect on the DC electrical conductance.Second, we show high tunability of polaron states by electrostatic means. This is something not possible to do with polarons in other systems, such as bulk crystals. Notably, this interaction createsa highly nonlinear potential for the phonon mode which establishes nanotube resonator as a possible platform for the demonstration of mechanical qubits.

  • DE VEGA ESTEBAN, SANDRA MARIA: Plasmon-electron interactions in low dimensional materials
    Author: DE VEGA ESTEBAN, SANDRA MARIA
    Thesis link: http://hdl.handle.net/10803/668847
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 17/02/2020
    Thesis director: GARCÍA DE ABAJO, JAVIER

    Committee:
         PRESIDENT: ORTEGA CONEJERO, JOSÉ ENRIQUE
         SECRETARI: BIEGERT, JENS
         VOCAL: MARINI, ANDREA
    Thesis abstract: Ever since the advent of modern technology, major developments have come hand in hand with miniaturization and speed of operation. A proof of this is provided by the impressive success of Moore's law, which predicted that the number of transistors per affordable microprocessor would double every two years. That would not have been possible if transistors kept their initial physical dimensions. By the end of 2018, MIT and University of Colorado researchers broke a new record for the smallest 3D transistor yet with a lateral size of only 2.5 nm. As of 2019, there are commercially available 5 nm transistors. Considering these sizes it is then remarkably important to understand and to be able to manipulate materials at the nanoscale, where they behave differently compared with macroscopic structures.Hence, researchers have put substantial efforts towards finding the explanation of diverse phenomena at the nanoscale, engineering new nanodevices, and proposing or predicting new mechanisms to achieve the next generation of chips and integrated circuits. Indeed, the rise of the so-called low dimensional materials (graphene, transition metal dichalcogenides, cuprates, hBN, black P, carbon nanotubes, and others), i.e., those whose atomic planes are bonded by weak van der Waals forces (2D) or whose atoms are arranged in chains or tubes (1D), has been influenced by the quest for new more efficient and compact designs. In this thesis we study the optical properties of some of these materials and how they are modified by the interaction with electrons that, depending on the specific case, we consider to be either dopants, or impinging in highly-focused beams, or via tunneling.Specifically, we start with a comprehensive analysis of plasmons, the collective oscillations of free electrons coupled to light, in finite highly-doped carbon nanotubes. Next, we explore how to select the proper plasmon mode excited by electron beams depending on the orientation and position of the latter and also how to improve the interaction between two quantum emitters when mediated by the main plasmonic mode in our structures. We predict record-high Purcell factors of the order of 10^8, which supports the use of carbon nanotubes as active plasmonic elements with high potential in optoelectronics and quantum optics.We then continue with one dimensional systems, but now focusing on atomic chains to emulate simple solid-like structures where to inspect strong-field driven electron dynamics in solids. Specially, we tackle several still pending questions about the role of electron-electron interactions and the proper choice of material to achieve better high-harmonic generation yields. After that, we test these findings in more realistic 1D systems: carbon nanotubes. Eventually, we find that the addition of a small number of doping charges to semiconductors can enable intraband plasmon excitations that concentrate the impinging light and boosts the high-harmonic generation efficiency.Next, we investigate how to use two dimensional heterostructures (stacked layers) for new compact ways of generating plasmons that do not need external light sources. More precisely, we propose tunneling electrons as plasmon triggers. We thus design a device consisting of a 1 nm-thick sandwich of graphene-hBN-graphene whose activation mechanism would be by an electron that tunnels from one graphene layer to another losing energy in the process that is invested into exciting plasmons. We predict a generation efficiency that can reach one plasmon per tunneled electron and that is robust upon distortions and variations in doping. We then complete this study by analyzing graphene-insulator-metal structures, which unfortunately present less efficient generation rate.In summary, the outcomes of this thesis open new paths towards a more efficient generation of nonlinear processes in solid nanoarchitectures and optics-free manipulation at the nanoscale for future optoelectronic devices.

  • DI PALO, NICOLA: Ultrafast carrier and structural dynamics in graphite detected via attosecond soft X-ray absorption spectroscopy
    Author: DI PALO, NICOLA
    Thesis link: http://hdl.handle.net/10803/669097
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 26/03/2020
    Thesis director: BIEGERT, JENS

    Committee:
         PRESIDENT: ERNSTORFER, RALPH
         SECRETARI: GARCÍA DE ABAJO, JAVIER
         VOCAL: GARCIA, MARTIN
    Thesis abstract: Understanding most of the physical and chemical phenomena determining the world around us requires the possibility to interrogate their main characters on their natural scale in space and time. The insulating or conductive behavior of matter, its magnetic properties or the nature of chemical bonds are strongly dependent on the nuclear and electronic structure of the atoms, molecules or solids considered. Hence, tools are needed to probe electrons and nuclei directly at the atomic scale with a temporal resolution allowing the observation of electron dynamics (on the attosecond-to-femtosecond timescale)and structural dynamics (on the femtosecond-to-picosecond timescale) in real time.Attosecond science offers unique opportunities to investigate electronic and structural dynamics at the heart of important processes in atomic, molecular and solid-state physics. The generation of attosecond bursts of light, in the form of train of pulses or of isolated pulses, has been achieved on table-top sources by exploiting the high-order harmonic generation (HHG) process. The photons constituting the attosecond emission have energies that range from the extreme ultra-violet (XUV) up to the soft X-ray (SXR) region of the spectrum, allowing to interrogate the electronic structure of the probed material directly at the level of the inner electronic shells. Because of this property of accessing the characteristic electronic structure of the elements constituting the target, XUV and, especially, SXR spectroscopy are considered element-specific techniques. Attosecond pulses have already proven to be able to observe ultrafast phenomena in atoms, molecules or solids previously inaccessible.In this thesis, the application of time-resolved X-ray absorption fine-structure (XAFS) spectroscopy using attosecond SXR pulses to the study of carrier and structural dynamics in graphite is reported. In chapter 1, an introduction to the field of attoscience and the presentation of the state of the art of ultrafast dynamics in graphite are given. The established technique to generate attosecond pulses is described and a review of the most significant application of attosecond pulses to the study of electron dynamics is presented. The electronic and structural properties of graphite are then discussed, highlighting some of the most representative experiments detecting electron and lattice dynamics.The experimental setup developed at ICFO in the group of Prof. Dr. Jens Biegert and used for this Ph.D. thesis project is described in details in chapter 2. The system needed for the generation, propagation and detection of the attosecond SXR radiation is presented. The performances of the SXR source in terms of spectral tunability, photon flux and stability are discussed. The implementation of a IR pump - SXR probe scheme is reported, allowing beams' recombination in both collinear and non-collinear fashion. To conclude, the results of an attosecond streaking experiment are presented, through which a temporal characterization of the HHG emission has been achieved.A discussion on the spectroscopic capabilities of XAFS technique to interrogate the electronic and lattice structure of the observed material is presented in chapter 3. The potential of this technique has been demonstrated with an experimental investigation of a graphite thin film, with the results showing the possibility to probe the first unoccupied electronic bands andthe characteristic distances defining the lattice structure.Finally, the XAFS capabilities have been exploited in a time-resolved experimental study of graphite to observe light-induced carrier and lattice dynamics, presented in chapter 4. The interpretation of the experimental data reveals insights on the ultrafast interaction of the pump laser field with charge carriers and on the effects of carrier-carrier and carrier-phonon scatteringfollowing photoexcitation.

  • GELLINGS, ESTHER: Spectral response of individual molecules and nanoantennas with two-beam excitation
    Author: GELLINGS, ESTHER
    Thesis link: http://hdl.handle.net/10803/668853
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 21/02/2020
    Thesis director: VAN HULST, NIEK

    Committee:
         PRESIDENT: ZHANG, DAI
         SECRETARI: GARCÍA PARAJO, MARÍA
         VOCAL: CICHOS, FRANK JOACHIM
    Thesis abstract: At room temperature, individual molecules can be found in different conformations due to intrinsic and extrinsic factors which are reflected in spectral variability. When detecting single molecules, the ensemble average is lifted and the spectral variability no longer obscured by the inhomogeneously broadened ensemble spectrum. Yet, only about one in every 10^7 photons interacts with the molecule, so that detection necessarily relies on background-free fluorescence. Fluorescence emission spectra only contain information about the ground state of molecules. In this thesis two new detection techniques are introduced to overcome this limitation: fluorescence excitation spectroscopy and stimulated emission detection. Moreover, the latter method is adapted to probe individual plasmonic nanoantennas. First, Fourier transform excitation spectroscopy is introduced as a sensitive and robust method to probe the excited state manifold of single molecules. Fluorescence excitation and emission spectra complement each other, the former probing the excited state, and the latter the ground state manifold. Both spectra are routinely measured at cryogenic temperatures, though excitation spectroscopy has only recently reached single molecule sensitivity at room temperature. Here, Fourier transform spectroscopy is adapted to measure excitation spectra of single molecules. The working of the technique is demonstrated on synthetic dye molecules, where a spectral variability of more than 100nm has been uncovered. It is then applied to photosynthetic light-harvesting complexes LH2 that exhibit near-unity energy transfer efficiencies despite large environmental differences. Excitation spectra were routinely measured alongside emission spectra and it was found that variations in the two absorption bands B800 and B850 are uncorrelated, while the Stokes shift between the B850 and emission band becomes larger for more red-shifted complexes. The single complex Stokes shift was found to be about 20% larger than the ensemble result. Second, a stimulated emission pump-probe setup with single molecule sensitivity is developed, which does not rely on fluorescence detection and can directly probe excited state dynamics. The necessary steps to achieve shot noise limited sensitivity will be explained. Stimulated emission depletion measurements are performed to verify the alignment of the setup and to find the best experimental parameters. The stimulated emission measurements achieved sensitivities of up to 10^-8, which in principle is sufficient for single molecule detection.Third, single molecule techniques are applied to study the scattering and absorption of single plasmonic nanoantennas in focused Gaussian beams using the stimulated emission setup. In photothermal microscopy, the contribution of the scattering component and focal position to the signal has been largely ignored. Here, a comprehensive model including all relevant parameters is developed and systematically probed on nanoantennas of various lengths, positions in the focus, and surrounding media. It will be shown that the interaction of an antenna with a single probe beam results in a dispersive interference signal that mainly depends on the antenna dimensions, and that flips sign when passing through the antenna resonance. Adding a modulated pump beam that heats the antenna's environment leads to a combination of the probe beam scattering off the refractive index gradient around the nanoantenna, and the antenna resonance shifting, which affects the interference between the incident and scattered light. It will be demonstrated that both effects are relevant for antennas with a significant scattering cross-section and that photothermal measurements strongly depend on the photothermal properties of the surrounding medium and the antenna dimensions, which lead to strong signal variations around antenna resonance.

  • GÓMEZ GARCÍA, PABLO: Development and application of localization-based microscopy methods to study the structure and dynamics of chromatin through the process of cellular differentiation
    Author: GÓMEZ GARCÍA, PABLO
    Thesis link: http://hdl.handle.net/10803/669121
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 24/04/2020
    Thesis director: COSMA, PIA | WIESER, STEFAN

    Committee:
         PRESIDENT: NOLLMANN, MARCELO
         SECRETARI: GARCÍA PARAJO, MARÍA
         VOCAL: SOLON, JEROME
    Thesis abstract: Recent advancements in single-molecule localization-based microscopy have made it possible to visualize biological structures and dynamic processes within the cell with unprecedented spatial resolution. Determining the spatial organization of these complex structures, like chromatin, under physiological and pathological conditions is an important biological goal. Currently, one of the main limitations of this family of techniques is the difficulty to extend them to multiple colors, so that multiple target molecules can be imaged simultaneously. We developed an approach for simultaneous multi-color super resolution imaging which relies solely on fluorophore excitation, rather than fluorescence emission properties. By modulating the intensity of the excitation lasers at different frequencies, we show that the color channel can be determined based on the fluorophore¿s response to the modulated excitation. We use this frequency multiplexing to reduce the image acquisition time of multi-color super resolution DNA points accumulation in nanoscale topography (DNA-PAINT) while maintaining all its advantages: minimal color cross-talk, minimal photobleaching, maximal signal throughput, ability to maintain the fluorophore density per imaged color, and ability to use the full camera field of view. One outstanding biological question that will benefit from the development and application of advanced imaging technologies is the relationship between chromatin structure and gene activity. Chromatin is a complex of DNA and histone proteins, which helps compact and spatially organize the genetic code within the small space of the nucleus. Applying super resolution microscopy, previous work in the lab showed that nucleosomes within folded chromatin fibers are organized in heterogeneous groups named nucleosome clutches, unlike the textbook model that suggested a much more ordered and hierarchical folding of nucleosomes. Nucleosome clutches are smaller and less densely compacted in embryonic stem cells (ESCs) compared to neuronal progenitor cells (NPCs), in correlation with the more open chromatin state of ESCs. We applied modelling of chromatin and Single Molecule Tracking (SMT) to compare the structure of synthetic fibers and local nucleosome dynamics with the super resolution images of chromatin fiber in ESCs and NPCs. First, using coarse-grained modeling, we simulated the spatial arrangement of chromatin fibers corresponding to the pluripotency gene Oct4 in mouse ESCs (mESCs) and mouse NPCs (mNPCs), taking into account nucleosome positions from MNASE-Seq data, the ratio of linker histone H1 per nucleosome, and the amount of histone tail acetylation. The resulting folded fiber configurations showed higher compaction of the overall fiber and of the nucleosome clutches in mNPCs compared to mESCs, recapitulating the super resolution imaging data. We further use SMT both at short (15ms) and long (500ms) exposure times to show that nucleosome turn over and local dynamics within the chromatin fiber correlate with the structural features observed in super-resolution data and the polymer models.

  • PADHYE, ANUJA ARUN: Novel continuous-wave infrared parametric sources and noise analysis of infrared upconversion detectors
    Author: PADHYE, ANUJA ARUN
    Thesis link: http://hdl.handle.net/10803/669321
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 04/06/2020
    Thesis director: EBRAHIM-ZADEH, MAJID

    Committee:
         PRESIDENT: LEO, GIUSEPPE
         SECRETARI: LOZA ALVAREZ, PABLO
         VOCAL: ROSO FRANCO, LUIS
    Thesis abstract: The ability to manipulate frequency of light, through parametric frequency conversion sources based on ¿(2) nonlinear materials, offers an effective route to spectral regions unapproachable by conventional lasers. Most importantly, three-wave mixing processes provide tunable coherent radiation over a broad spectral range. Among the most important tunable devices, narrow linewidth continuous-wave (cw) infrared (IR) optical parametric oscillators (OPOs) are indispensable excitation sources for many applications in molecular spectroscopy and precision metrology. In order to exploit such applications, the development of cw OPOs deploying different wavelength tuning schemes and novel nonlinear materials is highly dezirable, as presented in this thesis. We demonstrated a rapidly tunable cw OPO based on fan-out grating design periodically-poled KTiOPO4 (PPKTP) crystal at room temperature. This approach allows continuous wavelength tuning by avoiding increased thermal fluctuations at higher operating crystal temperatures. The 532 nm-pumped, output-coupled singly-resonant oscillator (OC-SRO) provides widely tunable near-IR radiation across 741-922 nm and 1258-1884 nm, with total output power of 1.65 W. The use of output coupling for the resonating wave reduces thermal loading and enables 30% enhancement in the OPO extraction efficiency over the pure SRO configuration. Towards the goal of developing a next-generation cw source >4 µm using a new found quasi-phase-matched semiconductor material, orientation-patterned gallium phosphide (OP-GaP), we demonstrated the first realization of a tunable cw mid-IR source based on OP-GaP by exploiting single-pass difference-frequency-generation (DFG) between a Tm-fiber laser at 2010 nm and a home-built OPO based on MgO-doped periodically-poled LiNbO3 (MgO:PPLN) crystal. The DFG source generates up to 43 mW of output power, with >30 mW across 96% of the tuning range 4608-4694 nm, in high beam quality. As the tunable mid-IR sources are making great strides, the availabilityof fast and sensitive mid-IR detectors become equally important. However, the conventional mid-IR detectors demand cryogenic systems for low-noise operation which sets a major drawback as these devices are often bulky and expensive. In this context, the nonlinear frequency upconversion technique has emerged as a promising alternative to the direct detection of mid-IR radiation at room temperature. An upconversion detector (UCD) can be further optimized by identifying and suppressing its noise sources. In order to do so, we experimentally and theoretically investigated noise properties of 1064 nm-pumped single-pass UCD designed for signal detection in telecom and mid-IR range using MgO:PPLN crystals. We studied the dependence of newly discovered SHG (532 nm)-induced spontaneous parametric downconversion (SHG-SPDC) noise intensity on the pump power and crystal temperature, and compared it with the well-known UCD noise source upconverted spontaneous parametric downconversion (USPDC). The measurements deduce that SHG-SPDC must be given a careful consideration since it can act as a dominant noise source under certain operating conditions. However, SHG-SPDC can be avoided by choosing a proper combination of MgO:PPLN grating period,operating temperature, and bandpass filter.

  • PÉREZ ROSAS, JUAN MIGUEL: IMAGING CYTOMETRY TECHNOLOGY FOR ENVIRONMENTAL AND BIOMEDICAL APPLICATIONS
    Author: PÉREZ ROSAS, JUAN MIGUEL
    Thesis link: http://hdl.handle.net/10803/669608
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 28/07/2020
    Thesis director: PRUNERI, VALERIO

    Committee:
         PRESIDENT: LLOBERA ADÁN, ANDREU
         SECRETARI: LOZA ALVAREZ, PABLO
         VOCAL NO PRESENCIAL: CORZO GARCIA, BEATRIZ
    Thesis abstract: Early detection of microorganisms in environmental and biomedical applications is critical for the effective response to potential pathogenic treats. Most traditional methods and instrumentation for the analysis of these samples are becoming obsolete due to the fact that they are time-consuming and have long response times. Modern solutions are limited to high-end centralized facilities and specialized trained personnel, given their high-cost and complexity. There is thus a clear need to develop and introduce low-cost, easy to use, high-performance devices capable of rapidly identifying and quantifying pathogenic microorganisms in environmental and biomedical samples. The work behind this thesis was devoted to the design, development and validation in relevant industrial environments of two image cytometry devices capable of characterizing biological and industrial samples in terms of their microorganism content. Bringing a potentially high-impact solution to the current industry need. The first technology, defined within the context of this thesis as Fourier image cytometry, is an optical device capable of increasing the sample volume tested when compared to traditional state-of-the-art counterparts. By evaluating the sample in the Fourier domain, the device is capable of measuring characteristics of particulate within a sample volume larger than other imaging systems. The result is an enhancement of both field of view (FOV) and depth of field (DOF) of the target sample. Furthermore, the implementation of the Fourier image cytometer in this thesis is a portable and compact device comprising of low-cost optics and electronics. The design of the entire device was performed with the objective to minimize the cost and maximize the capabilities. This was possible mainly due to the recent advances in image sensor technologies that simplify the device¿s optics. In our Fourier imaging cytometry, LED light sources and conventional achromatic optical lenses are at the basis of device¿s optics as opposed to high-end lasers or optical microscopes. For the detection scheme, a CMOS image sensor was used.After optimizing the prototype and going through rigorous validation in a laboratory, the Fourier image cytometry introduced in this thesis was validated in two relevant industrial environments. The device was tested using real environmental samples. In the first industrial validation, it was used for the microorganism¿s identification and quantification in water coming from cooling towers. The second industrial validation used a further optimized implementation of the cytometer to analyze fresh and marine waters for their microorganism population, specifically phytoplankton within the context of ballast water and ballast water treatment systems. The second image cytometry designed, developed and implemented within the scope of this thesis, focused on detection of microorganisms spread over surfaces. Following the motivation for low-cost compact devices, a Surface cytometer was designed. The Surface cytometer is an optical device capable of quantifying bacterial population over a surface of over 300 mm2. The device was completely autonomous thanks to the integration of a single-board computer within its design. The light source and detection scheme continued to be LED source and CMOS sensor detection. Similarly to the validation process of the Fourier cytometer, the Surface cytometer was tested in controlled samples in a laboratory environment, before it was put to test on a biomedical application for bacterial growth monitoring and compared to standard devices of measurement of optical density, used today in the industry. In summary, in this thesis we present two novel image cytometers and three clear industrial applications in which the devices were validated. This clearly indicates the potential of image cytometry as an effective low cost and portable tool for the analysis of microorganisms in the environmental and biomedical

  • PIGA, ANGELO: Entanglement and Bell Correlations in Strongly Correlated Many-Body Quantum Systems
    Author: PIGA, ANGELO
    Thesis link: http://hdl.handle.net/10803/669100
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 30/03/2020
    Thesis director: LEWENSTEIN, MACIEJ | RAN, SHI JU

    Committee:
         PRESIDENT: JULIA DIAZ, BRUNO
         SECRETARI: ACÍN DAL MASCHIO, ANTONIO
         VOCAL: CELI, ALESSIO
    Thesis abstract: During the past two decades,thanks to the mutual fertilization of the research in quantum information and condensed matter, new approaches based on purely quantum features without any classical analog turned out to be very useful in thecharacterizationofmany-bodyquantumsystems(MBQS).Apeculiarroleis obviously played by the study of purely quantum correlations, manifesting in the ¿spooky¿ properties of entanglement and nonlocality (or Bell correlations), which ultimately discriminate classical from quantum regimes. It is, in fact, such kind of correlations that give rise to the plethora of intriguing emergent behaviorsofMBQS,whichcannotbereducedtoameresumofthebehaviorsof individual components, the most important example being the quantum phase transitions. However, despite being indeed closely related concepts, entanglement and nonlocality are actually two different resources. With regard to the entanglement, we will use it to characterize several instances of MBQS, to exactly locate and characterize quantum phase transitions in spin-lattices and interacting fermionic systems, to classify different gapped quantum phases according to their topological features and to provide a purely quantum signature of chaos in dynamical systems. Ourapproachwillbemainlynumericalandforsimulatingthegroundstates of several one-dimensional lattice systems we draw heavily on the celebrated ¿densitymatrixrenormalizationgroup¿(DMRG)algorithminthe¿matrixproduct state¿ (MPS) ansatz. A MPS is a one-dimensional tensor network (TN) representation for quantum states and occupies a pivotal position in what we have gained in thinking MBQS from an entanglement perspective. In fact, the success of TNs states mainly relies on their ful¿llment, by construction, of the socalled ¿entanglement area law¿. This is a feature shared by the ground states of gapped Hamiltonians with short-range interactions among the components and consists of a sub-extensive entanglement entropy, which grows only with the surface of the bipartition. This property translates in a reduced complexity ofsuchsystems,allowingaffordablesimulations,withanexponentialreduction ofcomputationalcosts. BesidestheuseofalreadyexistingTN-basedalgorithms, an effort will be done to develop a new one suitable for high-dimensional lattices. Whilemanyusefulresultsareavailablefortheentanglementinmanydifferent contexts, less is known about the role of nonlocality. Formally, a state of a multi-party system is de¿ned nonlocal if its correlations violate some ¿Bell inequality¿ (BI). The derivation of the BIs for systems consisting of many parties is a formidable task and only recently a class of them, relevant for nontrivial states, has been proposed. In an important chapter of the thesis, we apply these BIstofullycharacterizethephasetransitionofalong-rangeferromagneticIsing model, doing a comparison with entanglement-based results and then making one of the ¿rst efforts in the study of MBQS from a nonlocality perspective

  • PLANES CONANGLA, GERARD: Levitation and control of particles with internal degrees of freedom
    Author: PLANES CONANGLA, GERARD
    Thesis link: http://hdl.handle.net/10803/669610
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 30/06/2020
    Thesis director: QUIDANT, ROMAIN | SCHELL, ANDREAS

    Committee:
         PRESIDENT: ULBRICHT, HENDRIK
         SECRETARI: BACHTOLD, ADRIAN
         VOCAL: MILLEN, JAMES NEIL
    Thesis abstract: Levitodynamics is a fast growing field that studies the levitation and manipulation of micro- and nanoobjects, fuelled by both fundamental physics questions and technological applications. Due to the isolated nature of trapped particles, levitated systems are highly decoupled from the environment, and offer experimental possibilities that are absent in clamped nanomechanical oscillators. In particular, a central question in quantum physics is how the transition between the classical and quantum world materializes, and levitated objects represent a promising avenue to study this intermediate regime.In the last years, most levitation experiments have been restricted to optically trapped silica nanoparticles in vacuum, controlling the particle's position with intensity modulated laser beams. However, the use of optical traps severely constrains the experiments that can be performed, because few particle materials can withstand the optical absorption and resulting heating in vacuum. This completely prevents the use of objects with internal degrees of freedom, which---coupled to mechanical variables---offer a clear path towards the study of quantum phenomena at the macroscale. In this thesis, we address these issues by considering other types of trap and feedback schemes, achieving excellent control on the dynamics of optically active nanoparticles. With stochastic calculus, simulations and experiments, we study the dynamics of trapped particles in different regimes, considering also a hybrid quadrupole-optical trapping scheme. Then, using a Paul trap of our own design, we demonstrate the trapping, interrogation and feedback cooling of a nanodiamond hosting a single NV center in vacuum, a clear candidate to perform quantum physics experiments at the single spin level. Finally, we discuss and implement an optimal controller to cool the center of mass motion of an optically levitated nanoparticle. The feedback is realized by exerting a Coulomb force on a charged particle with a pair of electrodes, and thus requires no optics.

  • SANCHEZ PEACHAM, DANIEL ALEXANDER: Development of a High Intensity Mid-Ir OPCPA Pumped by a HO:YLF amplifier
    Author: SANCHEZ PEACHAM, DANIEL ALEXANDER
    Thesis link: http://hdl.handle.net/10803/668836
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 27/01/2020
    Thesis director: BIEGERT, JENS

    Committee:
         PRESIDENT: PETROV, VALENTIN
         SECRETARI: ARTIGAS GARCIA, DAVID
         VOCAL: CHALUS, OLIVIER
    Thesis abstract: The continuous development of laser sources delivering ultra-short light pulses underpins much of the current progress in experimental science, particularly in the domain of physics concerned with strong-field phenomena. Laser systems that allow scaling of strong-field experiments to unexplored regions of the electromagnetic spectrum, specially the mid-IR range (2 µm < ¿ < 20 µm), have proved to be a powerful tool enabling the study of new physical processes. It is becoming clear however, that conventional laser sources are unsuited for this purpose, and in order to fully investigate these novel regimes a new generation of laser systems is required. This thesis describes a new laser source of high-intensity, mid-IR light. A long-wavelength pumped optical parametric chirped pulse amplifier (OPCPA) design is chosen as the architecture for this laser, overcoming many of the drawbacks hindering other approaches. This thesis presents two novel sub-systems required for the successful development of a mid-IR OPCPA. The first is a compact, fibre-driven source of broadband mid-IR pulses relying on difference frequency generation (DFG) in the nonlinear crystal CdSiP2. This laser is the seed source in the OPCPA and supports transform-limited pulses corresponding to less than 3 optical cycles at the operating wavelength of 7 µm. The second sub-system is a pump source based on a Ho:YLF chirped pulse amplifier (CPA) pumped by commercial Tm-fibre laser. The pump system delivers over 0.25 J of pulse energy at a wavelength of 2052 nm.The laser system described in this thesis is a developmental milestone towards the realisation of a multi-mJ source of few-cycle duration, carrier-to-envelope phase (CEP) stable mid-IR pulses. The system is designed to operate at a centre wavelength of 7 µm, delivering pulses with an energy of 0.2 mJ and a temporal duration of 180 fs at 100 Hz repetition rate. The output parameters of the laser presented in this work lead to a peak power of 1.1 GW and potentially a peak intensity of 7·1014 W/cm2. These values are already compatible with strong-field experiments and enable a ponderomotive force 77 times larger than a standard Ti:Sapphire laser.

  • SANZ SÁNCHEZ, JULIO: Two-component Bose-Einstein condensates with competing interactions
    Author: SANZ SÁNCHEZ, JULIO
    Thesis link: http://hdl.handle.net/10803/668865
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 10/02/2020
    Thesis director: TARRUELL, LETICIA

    Committee:
         PRESIDENT: SANTOS SANCHEZ, LUIS
         SECRETARI: BORONAT MEDICO, JORDI
         VOCAL: BOURDEL, THOMAS, ALBERT, MARCEL
    Thesis abstract: This thesis reports the experimental study of two-component Bose-Einstein condensates with tunable interactions, which are exploited as a platform to perform quantum simulation of many-body quantum systems. To perform this experiments, we have implemented an atomic source consisting on a glass cell 2D MOT vacuum chamber and a high resolution optical system to image and manipulate the atoms. Furthermore, we develop and characterize a polarization phase contrast technique which is able to probe optically dense atomic mixtures at intermediate and high magnetic fields in open transitions. This technique has been used to either probe the total column density of a two-component atomic cloud or the difference in column density between both components. We report on the first observation of composite quantum liquid droplets in an incoherent mixture with residual mean field attraction. Strikingly, this novel phase is stabilized due to the repulsive beyond mean field corrections in a weakly interacting system. Moreover, we have characterized the liquid to gas phase transition which occurs for small atom numbers. Additionally, we have compared two different self-bound states in a quasi-1D geometry with incoherent mixtures: quantum droplets and bright solitons. Depending on the atom number and interaction strengths both states can be smoothly connected through a crossover or be distinct entities separated by a transition. We have measured its composition, its phase diagram and mapped out the soliton to droplet transition. Finally, we report on a technique to modify the elastic and inelastic interactions in a two-component Bose-Einstein condensate with very unequal and competing interactions under the presence of strong coherent coupling. This technique provides a wide flexibility and has allowed us to observe bright solitons in quasi-1D in a coherently coupled dressed state. We exploit the fast temporal control of the effective interactions to quench them into the attractive regime and study the resulting modulational instability which develops into a bright soliton train.

  • TIRRITO, EMANUELE: Investigations of topological phases for quasi-1D systems
    Author: TIRRITO, EMANUELE
    Thesis link: http://hdl.handle.net/10803/669331
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 13/07/2020
    Thesis director: LEWENSTEIN, MACIEJ | BERMÚDEZ CARBALLO, ALEJANDRO

    Committee:
         PRESIDENT: AHUFINGER BRETO, VERÓNICA
         SECRETARI: ACÍN DAL MASCHIO, ANTONIO
         VOCAL: MAZZA, LEONARDO
    Thesis abstract: For a long time, quantum states of matter have been successfully characterized by the Ginzburg-Landau formalism that was able to classify all di¿erent types of phase transitions. This view changed with the discovery of the quantum Hall e¿ect and topological insulators. The latter are materials that host metallic edge states in an insulating bulk, some of which are protected by the existing symmetries. Complementary to the search of topological phases in condensed matter, great effortshavebeenmadeinquantumsimulationsbasedoncoldatomicgases. Sophisticated laser schemes provide optical lattices with di¿erent geometries and allow to tune interactions and the realization of arti¿cial gauge ¿elds. Atthesametime,newconceptscomingfromquantuminformation,basedonentanglement, are pushing the frontier of our understanding of quantum phases as a whole. Theconceptofentanglementhasrevolutionizedthedescriptionofquantummany-body states by describing wave functions with tensor networks (TN) that are exploited for numerical simulations based on the variational principle. Thisthesisfallswithintheframeworkofthestudiesincondensedmatterphysics: it focuses indeed on the so-called synthetic realization of quantum states of matter, more speci¿cally,oftopologicalones,whichmayhaveonthelong-runoutfallstowardsrobust quantum computers. We propose a theoretical investigation of cold atoms in optical lattice pierced by e¿ective (magnetic) gauge ¿elds and subjected to experimentally relevant interactions, by adding a modern numerical approach based on TN algorithms. More speci¿cally, this work will focus on (i) interacting topological phases in quasi-1D systems and, in particular, the Creutz-Hubbard model, (ii) the connection between condensed matter and high energy physics studying the Gross-Neveu model and the discretization of Wilson-Hubbard model, (iii) implementing tensor network-based algorithms.

Last update: 24/10/2020 05:07:30.

Theses related publications

Research projects

START DATEEND DATEACTIVITYFINANCING ENTITY
01/01/201831/12/2020Células solares con contactos posteriores basadas en substratos delgados de silicio cristalinoAGENCIA ESTATAL DE INVESTIGACION
01/12/201727/12/2017Prestación de servicios COSENTINOCOSENTINO RESEARCH AND DEVELOPMENT
01/01/201731/12/2021ICREA ACADEMIA 2016-04INSTITUCIO CAT DE RECERCA I
01/01/201731/12/20192017 SGR 1400 Nonlinear and Quantum Photonics GroupAGAUR. Agència de Gestió d'Ajuts Universitaris i de Recerca
17/06/201617/06/2016Procedimiento para la fabricación de resonadores esferoidales sobre un substrato monocristalino.
01/06/201631/05/2019Reducció energètica i flexibilitat en edificis en rehabilitacióACC10
01/01/201631/12/2018Explotación de las propiedades de las ondas de DyakonovMinisterio de Ciencia e Innovación
01/10/201530/09/2016BEQUES DOCTORAT FUND.LA CAIXA 2015-2FUNDACIO LA CAIXA
01/03/201528/02/2018Células y módulos de alta eficiencia basadas en el silicio negro y técnicas de eliminación de defectosMIN DE ECONOMIA Y COMPETITIVIDAD
01/01/201531/12/2017Células solares de silicio cristalino con contactos posteriores basadas en el procesado láser de capas dieléctricasMIN DE ECONOMIA Y COMPETITIVIDAD

Teaching staff and research groups

Research projects

START DATEEND DATEACTIVITYFINANCING ENTITY
01/01/201831/12/2020Células solares con contactos posteriores basadas en substratos delgados de silicio cristalinoAGENCIA ESTATAL DE INVESTIGACION
01/12/201727/12/2017Prestación de servicios COSENTINOCOSENTINO RESEARCH AND DEVELOPMENT
01/01/201731/12/2021ICREA ACADEMIA 2016-04INSTITUCIO CAT DE RECERCA I
01/01/201731/12/20192017 SGR 1400 Nonlinear and Quantum Photonics GroupAGAUR. Agència de Gestió d'Ajuts Universitaris i de Recerca
17/06/201617/06/2016Procedimiento para la fabricación de resonadores esferoidales sobre un substrato monocristalino.
01/06/201631/05/2019Reducció energètica i flexibilitat en edificis en rehabilitacióACC10
01/01/201631/12/2018Explotación de las propiedades de las ondas de DyakonovMinisterio de Ciencia e Innovación
01/10/201530/09/2016BEQUES DOCTORAT FUND.LA CAIXA 2015-2FUNDACIO LA CAIXA
01/03/201528/02/2018Células y módulos de alta eficiencia basadas en el silicio negro y técnicas de eliminación de defectosMIN DE ECONOMIA Y COMPETITIVIDAD
01/01/201531/12/2017Células solares de silicio cristalino con contactos posteriores basadas en el procesado láser de capas dieléctricasMIN DE ECONOMIA Y COMPETITIVIDAD

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