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Photonics

Photonics is the science that studies light and its generation, propagation, manipulation and interaction with matter. The discipline produces multidisciplinary technology with applications in communications, industry, nanotechnology, biology, medicine and other fields. In recent decades, photonics has given rise to a myriad of applications that have a positive impact on our lives, even at the most everyday level. Examples of photonic solutions to present-day challenges include modern fibre optics–based communications systems, optical diagnostic and therapeutic tools used in medicine, laser-based production methods, metrology and optical sensors, and photovoltaic energy.

.The doctoral programme in Photonics of the Universitat Politècnica de Catalunya (UPC) is delivered by the Institute of Photonic Sciences (ICFO) within the framework of the UPC Doctoral School. The ICFO is a research centre dedicated to the study of light sciences and technologies and has been recognised as a Severo Ochoa Centre of Excellence. Founded in 2002 by the Government of Catalonia and the UPC, the ICFO also hosts ambitious patronage programmes funded by the Cellex and Mir-Puig foundations of Barcelona. The Institute has a threefold mission: frontier research, knowledge and technology transfer, and postgraduate training, mainly at the doctoral level. The ICFO is currently one of the leading centres in the world in its field.

Theses are completed in the four research areas at the core of the doctoral programme in Photonics: biomedical photonics, quantum optics, nonlinear optics and nanophotonics. These four research areas focus primarily on photonic applications in healthcare, renewable energies and information technologies. Research is carried out within the framework of long-term programmes and medium-term projects in a range of fields, including quantum information technologies, advanced screens, nanophotonic devices, graphene photonics, remote sensors, solar cells, optoelectronics, integrated optics, ultrafast optics, super-resolution imaging techniques, and biomedical technologies for diagnosis and therapy.

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: hr@icfo.es

Programme website

General information

Access profile

The doctoral programme in Photonics is designed for students with outstanding academic records at the international level who wish to complete a doctoral project in a field related to photonics.

With respect to entrance qualifications, it should be noted that photonics is a very broad discipline and that the ICFO is made up of a number of research groups that work in the various branches of the photonic sciences. Accordingly, the doctoral programme in Photonics is open to applicants with a wide range of qualifications, including degrees in physics; electronic, electrical, materials and telecommunications engineering; mathematics, chemistry, biology, bioengineering and biophysics.

As for language skills, the ICFO is a research institute with a strongly international character and English is the language used for everyday communication. Students admitted to the doctoral programme in Photonics must therefore have a high level of written and spoken English.

As for career goals, the doctoral programme in Photonics admits both students who wish to pursue academic careers and those aiming to become future leaders in knowledge and technology transfer or R&D in the business environment.

When it comes to personal characteristics, we are looking for students with high potential, motivation and the drive to carry out a project of excellence 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 involved in the doctoral programme are committed to ensuring that all doctoral students receive a grant and/or salary that allows them to work on their doctoral thesis full-time. The grants provided cover enrolment fees.

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: hr@icfo.es


Agreements with other institutions

The ICFO has collaboration agreements in effect with a significant number of companies, including Leica Microsystems, Corning, Nikon-Izasa Grupo Sorigué, Accelerate Diagnostics, S.L., Fyla All-Fiber Ultrafast Lasers and GRAPHENEA. The Institute also participates in networks of excellence (Euro-BioImaging, Laserlab Europe, Corbel, etc.) and coordinates various Graphene Flagship and Quantum Flagship projects under the EU's Horizon 2020 Programme.

Access, admission and registration

Access profile

The doctoral programme in Photonics is designed for students with outstanding academic records at the international level who wish to complete a doctoral project in a field related to photonics.

With respect to entrance qualifications, it should be noted that photonics is a very broad discipline and that the ICFO is made up of a number of research groups that work in the various branches of the photonic sciences. Accordingly, the doctoral programme in Photonics is open to applicants with a wide range of qualifications, including degrees in physics; electronic, electrical, materials and telecommunications engineering; mathematics, chemistry, biology, bioengineering and biophysics.

As for language skills, the ICFO is a research institute with a strongly international character and English is the language used for everyday communication. Students admitted to the doctoral programme in Photonics must therefore have a high level of written and spoken English.

As for career goals, the doctoral programme in Photonics admits both students who wish to pursue academic careers and those aiming to become future leaders in knowledge and technology transfer or R&D in the business environment.

When it comes to personal characteristics, we are looking for students with high potential, motivation and the drive to carry out a project of excellence 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

Applications for admission to the doctoral programme in Photonics must be submitted through the website http://jobs.icfo.eu/, to which interested students are directed. Detailed information on specific vacancies available for doctoral students at any given time in each of the ICFO's research groups is published on this web page.

The following admission requirements are assessed on a yes/no basis and must be met to undertake the selection process:

• High level of English.
• High level of academic performance (GPA).
• Motivation to pursue doctoral studies in one of the fields of the doctoral programme.

In the first stage of the selection process, carried out by the admission body for the Photonics programme, requirements are assessed based on documents submitted in the application process, which are standardised to ensure that the assessment process is fair and unbiased. Accepted applications are assessed based on the following criteria, which carry equal weight:

• Previous research and cross-cutting experience (25%).

• Academic excellence and other achievements (25%).
• Statement of research interests (25%).
• Quality of references (25%).

In the second stage of the selection process, carried out by a selection committee appointed specifically for the call, assessment is based on the written proposals submitted by applicants (if applicable), their performance in an interview, and their answers to questions from the selection committee. The following criteria are considered and carry equal weight:

• Presentation of the research project (33%).
• Motivation to pursue doctoral studies in the chosen field and scientific interests (33%).
• Competencies and skills with respect to communication, independence, initiative and teamwork (33%).

Each of these points is assessed by assigning a score from 0 to 5 based on standardised scales. These scores are then combined (with equal weighting) to obtain the final result, which will determine the ranking of applicants.

Finally, measures are taken to ensure that the principles of transparency, efficiency and international compatibility set out in the European Charter for Researchers and the European Code of Conduct for the Recruitment of Researchers are followed throughout the admission process for the doctoral programme in Photonics. The process will also be free of any discrimination based on gender or nationality.

Training complements

Students who hold one of the following UPC master’s degrees, which are linked to the doctoral programme, will not be required to complete bridging courses: Erasmus Mundus master's degree in Photonics; master's degree in Photonics Engineering, Nanophotonics and Biophotonics; master's degree in Engineering Physics; and master's degree in Quantum Science and Technology.

Neither will students who have completed a master's degree in photonics or physics from another university be required to complete bridging courses.

In the case of students who have completed a master's degree in another field – such as a master's degree in biomedical sciences or a multidisciplinary master's degree in experimental sciences – the applicant’s academic record and the project they propose to work on will be assessed, and the academic committee will determine on a case-by-case basis whether specific bridging courses must be completed. If the academic committee so determines, these students will be required to take one of the following subjects as a bridging course:

• Introduction to Photonics. Optics and Lasers (5 ECTS credits), from the master’s degree in Photonics
• Applied Photonics (5 ECTS credits), from the master's degree in Enabling Technologies for the Food and Bioprocessing Industry.

Enrolment period for new doctoral students

Enrolment is open year round, subject to the calendar established by the Doctoral School.

More information at the registration section for new doctoral students

Enrolment period

In 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 any minimum requirements with respect to number of papers published, conferences attended, or other activities. However, the academic committee for the programme will seek to ensure that each thesis meets the highest international standards before it is accepted for oral defence.

The training activities that make up the programme (including details of their duration and whether they are compulsory or optional) are listed below.

Mobility, 3 months (optional)
Preparation and initial defence of research plan, 50 hours (compulsory)
Training in information skills, 1.5 hours (optional)
Research Methodology, 12 hours (optional)
Innovation and Creativity, 8 hours (optional)
Language and Communication Skills, 18 hours (optional)
Scientific seminars, 25 hours/year (optional)
ICONS seminars, 40 hours/year (optional)
Coffee sessions with prominent researchers, 2 hours/year (optional)
Programme-specific workshops, 1 day/year (optional)
Publications, 50 hours (compulsory)
PhD lectures, 65 hours/year (optional)
Outreach activities, 18 hours (optional)
Training in technical skills, 5 hours for each technique (optional)
Effective Oral Presentations, 10 hours (optional)
ICFO-ESADE: From Science to Business, 24 hours (optional)
Introduction to Patent Engineering and Management, 7.5 hours (optional)
Language courses, 40 hours (Spanish, Catalan and English; optional)
Research Integrity, 3 hours (compulsory)
Career Development, 10 hours (optional)
Resilience and Well-Being, 6 hours (optional)
Essential Transferable Skills for Early Career Researchers, 12 hours (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

In addition to the support units and services available at the UPC, the ICFO administration team is made up of staff with a high level of specialisation in various fields who provide specific and accessible assistance to students of the doctoral programme in Photonics. Specifically, the ICFO offers the following services and facilities:

• Human Resources and Education Unit: academic and hiring procedures, permits for foreign nationals, accommodation-related matters, predoctoral grants for doctoral studies, and mobility grants for doctoral students.
• Knowledge and Technology Transfer Unit: https://www.icfo.eu/lang/industry
• ICFO Projects Unit: responsible for seeking funding opportunities, advising researchers on preparation of proposals, and processing applications.

Doctoral students in the Photonics programme also have access to the NanoFabrication Lab, the Super-Resolution Light Microscopy and Nanoscopy Research Facility, the Advanced Engineering Lab, the Biology Lab, the Chemistry Lab and the Post-Processing Lab: https://www.icfo.eu/lang/research/facilities

Doctoral Theses

List of authorized thesis for defense

  • FISCHER, JONAS: Transcranial diffuse optical measurements of pulsatility derived parameters for neuromonitoring applications
    Author: FISCHER, JONAS
    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: Temporary seizure
    Deposit date: 10/09/2021
    Reading date: 26/10/2021
    Reading time: 16:00
    Reading place: ICFO ¿ The Institute of Photonic Sciences - Campus Baix Llobregat - Av. Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona) - SPAIN
    Thesis director: DURDURAN, TURGUT | WEIGEL, UDO
    Committee:
         PRESIDENT: MESQUIDA FEBRER, JAUME
         SECRETARI: KRIEG, MICHAEL
         VOCAL: KAINERSTORFER, JANA MARIA
    Thesis abstract: Diffuse optics are non-invasive and continuous techniques using near-infrared light which allow for comfortable bed-site monitoring of microvascular cerebral hemodynamics, oxygenation and metabolism. Here, diffuse correlation spectroscopy (DCS) to measure microvascular cerebral blood flow (CBF) and time-resolved near-infrared spectroscopy (TR-NIRS) to measure microvascular blood oxygenation are at the center stage. In particular, this work has contributed to the development of fast CBF measurements (=10 Hz) resolving the pulsatile fluctuations due to the cardiac cycle. These signals were exploited to calculate various parameters related to intracranial pressure (ICP), vascular properties and cerebral autoregulation (CA) which are posed as novel new biomarkers for different pathologies.New devices that I have developed set new standards in the group and were replicated several times paving the way for future multi-center studies using same devices. I have utilized said devices employed for neuro-monitoring traumatic brain injury (TBI) and acute ischemic stroke patients at collaborating hospitals.In case of TBI patients and patients with other complex neuropathologies, invasive (probe implanted in the brain tissue through a burr hole in the skull) ICP monitoring is an important tool for patient management. Its invasiveness limits its utility and, here, I present a new approach using new machine learning based on pulsatile CBF to measure ICP non-invasively. My pilot studies show that that method can be both accurate (bias ~0 mmHg) and precise (limits of agreement: <±5 mmHg) in a proof-of-concept and have paved the way towards larger cohorts. In the future, this may open new scenarios and provide clinicians crucial information even in non-critical care patients.Furthermore, pulsatile CBF allowed me to derive ICP surrogate variables that reflect the health of the cerebral vasculature such as the pulsatility index (PI), the critical closing pressure (CrCP) and the resistance area product (RAP). New algorithms were developed and applied to different populations. An exploratory study on acute ischemic stroke patients revealed that these parameters may serve as potential biomarkers for disease and may help to better understand and explain the physiology.Another aspect, targeted in this thesis is related to CA, a mechanism to protect the brain by keeping CBF constant despite changes in the pressure. However, this mechanism may be impaired in TBI and stroke and put the brain at risk of ischemia. Ideally, a non-invasive method monitoring its status is desired. For this purpose, the DCS autoregulation index (CBFx) was introduced and validated in the TBI patients. This index was also applied to the stroke population and compared to healthy subjects confirming impaired CA in TBI and stroke on a group level. If this is taken to the level of an individual this may have implications for personalized treatment of the patients.As a side note, COVID-19 and widespread face mask wearing posed questions and challenges for us which I have addressed by a study of cerebral and systemic physiological response to mask wearing showing that while there are significant changes, they are well within the changes during daily activities demonstrating its safety while highlighting the need for care in special scenarios (patient groups, neuroimaging studies).Taken all together, my contributions in this thesis have provided the hardware and algorithmic basis for new neuromonitoring tools and methods while my studies have shown that these parameters may be useful in personalized treatment of the patients and improve their outcome.
  • HESP, NIELS CASPAR HERMAN: Exploring twisted bilayer graphene with nano-optics
    Author: HESP, NIELS CASPAR HERMAN
    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: 16/09/2021
    Reading date: 20/10/2021
    Reading time: 15:30
    Reading place: ICFO ¿ The Institute of Photonic Sciences - Campus Baix Llobregat - Av. Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona) - SPAIN
    Thesis director: KOPPENS, FRANK
    Committee:
         PRESIDENT: POLINI, MARCO
         SECRETARI: PAPADAKI, GEORGIA
         VOCAL: BASOV, DMITRI
    Thesis abstract: Nano-optics studies the behaviour of light on the nanoscale. In particular, it probes the interaction of light with objects, often of nanometre-size, and reveals fine details of the material's optical properties. Optoelectronics is an integral part of optics and describes the interaction between light and electronics, such as the detection of light and subsequent conversion to an electrical signal. Understanding such mechanisms at the nanoscale is of importance for improving imaging and light-harvesting applications. In this Thesis, we apply near-field microscopy to study optics on the nanoscale. It probes optical properties using light interacting with the near-field electromagnetic field near the material's surface.Twisted bilayer graphene (TBG) is formed by stacking two layers of graphene - a one-atom-thick sheet of carbon atoms - with a small twist angle. This causes an interference pattern in the atomic lattice called a moiré pattern, which affects the electronic properties dramatically.The discovery of unconventional superconductivity in TBG in 2018 made it a thriving field of research. Adding to this, TBG revealed strongly correlating states and topological features, making it a host of tunable exotic phases that may shed light on the origins of unconventional superconductivity. These phenomena motivate us to study the optical properties of TBG on a nanoscale, which have received little attention thus far.In the first part of this Thesis, I describe spatially oscillating patterns within selected regions of TBG that we detected using near-field microscopy. We interpret them as a manifestation of plasmons --- electrons moving collectively in a wave-like pattern --- driven by interband transitions. We model these areas with a reduced interlayer coupling, which enhances the strength of interband transitions and explains the observed plasmon dispersion. After this, I discuss large-scale periodic features observed in minimally twisted bilayer graphene (¿ < 0.1 deg) by photocurent nanoscopy. For these small twist angles, the atoms rearrange in triangular domains separated by a network of domain walls. We find that the domain walls convert heat injected in the domains into a measurable current via the photothermoelectric effect. Our results uncover the sharp changes in electronic properties at the domain walls, which govern the optoelectronic response.I focus in the second part of the Thesis on the development of new experimental techniques, which enable nano-optical studies on exotic states of TBG and its relatives. I show that the semiconducting material WSe2 can be used as an ambipolar transparent top gate for infrared near-field experiments. This enables full control of the carrier density and transverse displacement field without blocking near-field access.Hereafter, I describe a commercial cryogenic near-field microscope with a base temperature of 10 K, which required modifications for reliable operation. I present an active damping system to oppose the vibrations in the system and enhance the mechanical stability. We further improve the AFM stability by changing the AFM excitation position.In the final two Chapters I examine the photoresponse of TBG at low temperature. We observe semi-periodic modulations across our sample, which we believe manifests a second-order superlattice arising from TBG aligned to the hBN substrate in combination with strain. In a different sample, we reveal a spatially inhomogeneous response from which we deduce a map of the local twist angle.
  • SIBILO, RAFAËL: Interactions and optical properties of microorganisms on surfaces
    Author: SIBILO, RAFAËL
    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: Temporary seizure
    Deposit date: 26/07/2021
    Reading date: pending
    Reading time: pending
    Reading place: pending
    Thesis director: PRUNERI, VALERIO
    Committee:
         PRESIDENT: SAGUÉS, FRANCESC
         SECRETARI: WIESER, STEFAN
         VOCAL: SENARATNE, WAGEESHA
    Thesis abstract: Controlling microbial growth is essential to industries such as healthcare, food, pharmacy but also for ship hulls and water systems. Interactions of bacteria with surfaces are highly dynamic and complex. Once a single cell transitions to a persistent multicellular microbial community (biofilm), elimination becomes complicated. Bacterial adherence, growth, and detachment are regulated by biological, chemical, physical, mechanical, and electrical properties of the bacterial cell, the surface, and the surrounding medium. Comprehensive studies in this field therefore require a multidisciplinary approach involving experts from different branches of science and appropriate choices of equipment depending on the question to address. This thesis focuses on the interaction and optical properties of bacteria on surfaces. More specifically, it investigates novel methods for enhanced bacteria detection, growth monitoring and presents an in-depth study of interaction mechanisms of bacteria and surface nano-structures.In the first part of the thesis, we validate a newly in-house built bio-sensing device to detect cells and their growth on surfaces. The proposed surface cytometer is compared with two standard laboratory methods, spectrophotometry and fluorescence microscopy. The results obtained with the three different techniques show similar trends, confirming the suitability of the surface cytometer as a compact, fast and low-cost device for measuring bacterial growth. Distinctively, the surface cytometer possesses both a large field-of view (~200 mm2) and depth of focus (~2 mm), these being particularly interesting for in-situ measurements and point-of-care testing.In order to enhance cell imaging, we propose a new type of surface, ultrathin (<10nm) gold films on a transparent substrate, such as glass. Such a surface has the capability to quench background fluorescence, improving microscopy and imaging. This is demonstrated through both numerical simulations and experiments. The physical mechanism at the basis of our design is that metals can reduce the lifetime of a fluorophore in its proximity. On the contrary, fluorophores further from the surface, because of their separation from the metal due to cell body, will maintain a much higher level of signal, i.e. they are less quenched. The higher signal-to-noise ratio (SNR) compared with a glass bare substrate is observed in both air and water. An improved SNR promotes the collection of a higher number of photons leading to more accurate localization precision, while reducing background, thanks to lower laser powers and shorter acquisition times. The enhanced imaging mediated through an ultrathin metal has potential in single-molecule localization super-resolution microscopy and live-cell imaging applications, especially under controlled conditions to minimize photodamage. In another study of the thesis, we demonstrate that bacterial growth can be regulated by tuning surface wettability. In contrast to commonly used indirect methods such as bacterial colony counting and scanning electron microscopy, we investigated a direct approach for assessment. First, we used molecular dynamics simulations to predict bacterial behavior on flat and nanostructured glass substrates, with wetting characteristics further modulated by chemical coatings. Then, we experimentally assessed these findings using E. coli bacteria and time-lapse fluorescence microscopy. Obtained data confirmed that nanostructured glass simultaneously hydrophobic, repelling water, and oleophilic, attracting fat, is most destructive, avoids cell adherence and promotes total cell disruption. These direct observations reflect a more accurate spatial- and time evolution of the interactions and bactericidal effects due to surface morphology and wettability. The results provide guidelines to design antimicrobial surfaces using simple nano-structuring and chemistry.

Last update: 16/10/2021 04:47:07.

List of lodged theses

  • MORENO MENCÍA, DAVID: The application of broadband ultrafast spectroscopy to reveal structural, magnetic and electronic dynamics in quantum materials.
    Author: MORENO MENCÍA, DAVID
    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: 15/10/2021
    Reading date: pending
    Reading time: pending
    Reading place: pending
    Thesis director: WALL, SIMON ELLIOT
    Committee:
         PRESIDENT: VAN LOOSDRECHT, PAUL
         SECRETARI: EFETOV, DMITRI K.
         VOCAL: GENSCH, MICHAEL
    Thesis abstract: In the last decades, quantum materials have received much attention in the field of condensed matter physics due, in part, to their exotic properties. These are difficult to understand as they result from multiple physical interactions with similar strength, such as charge, spin, orbitals and phonon degrees of freedom.To study and control these interactions, the use of light has emerged as a powerful tool. For example, thanks to recent advantages on X-ray sources it has been possible to improve our understanding of how the atomic structure of quantum materials changes upon photo-excitation. However, these experiments are difficult and there are only a few facilities in the world to perform them. In contrast to X-ray sources, table-top ultrafast laser systems allow us to measure in a systematic manner by performing optical pump-probe spectroscopy. The versatility of this approach enables the simultaneous monitoring of the different degrees of freedom that dictate the properties of quantum materials. In this thesis, we use pump-probe broadband spectroscopy in the visible region to study the structural, electronic and magnetic dynamics with unprecedented detail in two key quantum materials such as Sr3Ir2O7 and V2O3.In Sr3Ir2O7, a compound that undergoes a magnetic phase transition, firstly we study how photo-excitation affects to the reflectivity at a wide range of energies. This provides us information about the electronic and structural properties of this compound. Secondly, we show how to control magnetic order by photoexcitation and demonstrate that light can non-thermally suppress the magnetic long-range order in this material.In V2O3 we characterize its insulator to metal and structural phase transitions. In the metallic state, we show that a key phonon mode is very sensitive to sample inhomogeneity. When taking this into account, we find no evidence for non-thermal lattice dynamics in contrast to existing literature. Furthermore, we show that the light induced transition from the insulator to metallic phase proceeds along a highly damped and incoherent pathway, where vibrational coherence is not observed.

Last update: 16/10/2021 04:30:36.

List of defended theses by year

  • AKGÜL, MEHMET ZAFER: Environmentally friendly nanocrystals synthesized and processed in ambient conditions for solution-processed solar cells
    Author: AKGÜL, MEHMET ZAFER
    Thesis link: http://hdl.handle.net/10803/671521
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 11/02/2021
    Thesis director: KONSTANTATOS, GERASIMOS

    Committee:
         PRESIDENT: GAPONIK, NIKOLAI
         SECRETARI: PRUNERI, VALERIO
         VOCAL: TRIMMEL, GREGOR
    Thesis abstract: Due to the continuously increasing energy demand and the environmental concerns about climate changes raised by international community, alternative energy resources have been put under intense investigation for the past decade. As a consequence, different technologies have been proposed, photovoltaics being a promising one among them. Till now, different structures and methods have been employed to fabricate photovoltaics for energy production. Traditionally, vacuum-based deposition methods have been used to form the stacks required for proper photovoltaic operation. Triggered by the advancements in colloidal synthesis methods, thin films of colloidal semiconductor nanocrystals (CNCs) have gained tremendous attention as cheap substitutes for vacuum-deposited layers. Up to date, various colloidal synthesis methods have been developed to produce semiconductor nanocrystals for applications in photovoltaics. Thanks to the high degree of controllability and high material quality, hot injection methods have been the way-to-go for the past decades. However, the application of CNC films in large-scale photovoltaics has been delayed due to the synthesis constraints originating from hot injection methods itself.In this work, we demonstrate that it is possible to eliminate the need for air-free techniques by careful selection of the precursors and oxygen-aware design of reaction conditions. We use the semiconducting compound silver bismuth sulfide (AgBiS2) as the prototype material to demonstrate the easiness and efficiency of the method. This semiconducting compound is selected as the prototype material thanks to its attractive optical properties for photovoltaics and the environmentally friendly nature of the constituent elements. Solar cells fabricated using CNCs synthesized at room temperature have yielded a power conversion efficiency of 5.5 %, demonstrating the promising potential of the method. The application of the method in the synthesis of AgBiS2 CNCs results in a cost reduction of at least 60 % compared to the previous studies reporting similar photovoltaics-grade AgBiS2 CNCs. Another important challenge in employing hot injection methods is the scalability. Due to the difficulties in maintaining the thermal fluctuations within the reaction volume low and in the maintenance of inert atmosphere inside the reaction vessel, hot injection methods impose an inherent scale constraint on the synthesis. On the other hand, with the elimination of scale constraint by the use of an ambient condition synthesis method, the requirement for high temperature reaction and chemically inert reaction environment is eliminated, enabling us to achieve large-scale volume production of CNCs. This, in turn, can lower the production cost of CNCs further, hence the cost of photovoltaics that are based on CNCs. In addition, we show that the ambient condition method can be adapted for the synthesis of another metal chalcogenide, namely silver bismuth selenide CNCs (AgBiSe2) with an extended absorption spectrum further into the near infrared down to ~ 0.9 eV. The resulting AgBiSe2 CNC solar cells achieved a preliminary efficiency up to 2.6 %. Also, thanks to the structural similarity of these two compounds, the two methods that are developed for the synthesis of AgBiS2 and AgBiSe2 CNCs are combined and optimized to obtain alloyed quaternary AgBiSSe CNCs as a facile means of bandgap tuning in silver bismuth chalcogenide semiconductor family. The formation of AgBiSSe CNCs are verified through optical and structural characterization methods to show the formation of quaternary phase and also the phase purity of the obtained product. Overall, it is shown that the proposed ambient condition synthesis method is capable of providing photovoltaics-grade RoHS-compliant materials at a lower cost and higher throughput compared to the hot-injection based methods, opening a novel way for low-cost environmentally friendly photovoltaics.

  • GUENTHER, NILS ERIC: Dynamics of Quantum Mixtures
    Author: GUENTHER, NILS ERIC
    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
    Reading date: 08/09/2021
    Thesis director: LEWENSTEIN, MACIEJ | MASSIGNAN, PIETRO ALBERTO

    Committee:
         PRESIDENT: CHEVY, FRÉDÉRIC
         SECRETARI: ASTRAKHARCHIK, GRIGORI
         VOCAL: ARLT, JAN
    Thesis abstract: At sufficiently low temperatures, fluids of bosonic particles may undergo a phase transition, below which a Bose-Einstein condensate (BEC) forms. The BEC is one of the most fundamental concepts in many-body quantum physics and provides a paradigmatic example of a collective matter wave. The distinctive mixture of fluid-like and particle-like behavior this state exhibits leads to the emergence of unique features such as vortex quantization, but also to an often exotic interaction with other matter as well as its environment. The goal of my thesis is a further theoretical investigation of the latter, along two specific lines of research. Correspondingly, this manuscript is divided into two main parts. In the first part, I studied the fundamental polaron problem in the case of a bosonic bath: A BEC interacting with a single distinguishable impurity, a quantum particle on the same scale as the constituent particles of the condensate, which can often be described as a 'dressed' quasiparticle, called the polaron. The focus of this thesis is \textit{dilute} BECs of ultra-cold atomic vapors, where historically the BEC state was first observed experimentally and the underlying atomic interactions can be controlled to hitherto unprecedented degree via Feshbach resonances. Of particular interest is the case of strong interactions between the impurity and the bosons, the unitary-limited regime. Such impurity systems have been first probed experimentally in recent years, however due to the theoretical complexity and physical richness of the condensate state as well as experimental limitations, the nature of the compound system is not completely understood at strong interactions. I present two theoretical models in this part of the thesis which predict qualitatively new phenomena. In the first, I extended a scheme used in previous work unrelated to me, including the effect of finite temperature below the transition point to take into account the two-fluid nature of the bosons. This scheme predicts a \textit{splitting} of a single quasi-particle branch at zero temperature into two branches upon heating, and a general strong temperature dependence of the quasi-particle properties. In the second work, I developed a new variational ansatz tailored for describing large dressing of the impurity. This ansatz predicts that for sufficiently weak intra-bosonic repulsion the impurity can bind a \textit{macroscopic} but coherent and dilute cloud of bosons of sizes comparable to the healing length of the condensate.In the second part of my thesis, I present work focusing on the interplay of a condensate and the geometry of its containment. Well known features of condensates are superfluidity and the quantization of vorticity. Considering a superfluid embedded on a two-dimensional surface, I studied the dynamics of point vortices on curved surfaces in the framework of potential flow theory, with a focus on non-simply connected geometry. In a work presented in this thesis revolving around cylinder- and related geometries I derived the generating potential of a single point vortex, which predicts that the dynamics are modified by the quantization of flow around the circumference of the cylinder. In particular, a single vortex is always forced to move along the longitudinal axis of the cylinder, providing a powerful marker for superfluidity. In a following work regarding a torus-shaped embedding as well as related more general surfaces, I derived the generating potential for a single and multiple vortex-anti vortex pairs and predicted a significant change of local dynamics due to the macroscopic quantization of flow and to the non-trivial curvature of the embedding surface.

  • HÜMBELI, PATRICK: Machine Learning for Quantum Physics and Quantum Physics for Machine Learning
    Author: HÜMBELI, PATRICK
    Thesis link: http://hdl.handle.net/10803/672085
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 25/03/2021
    Thesis director: ACÍN DAL MASCHIO, ANTONIO

    Committee:
         PRESIDENT: VAN NIEUWENBURG, EVERT
         SECRETARI: GRASS, TOBIAS DANIEL
         VOCAL: DUNJKO, VEDRAN
    Thesis abstract: Research at the intersection of machine learning (ML) and quan- tum physics is a recent growing field due to the enormous expec- tations and the success of both fields. ML is arguably one of the most promising technologies that has and will continue to dis- rupt many aspects of our lives. The way we do research is almost certainly no exception and ML, with its unprecedented ability to find hidden patterns in data, will be assisting future scientific discoveries. Quantum physics on the other side, even though it is sometimes not entirely intuitive, is one of the most successful physical theories and we are on the verge of adopting some quan- tum technologies in our daily life. Quantum many-body physics is a subfield of quantum physics where we study the collective behavior of particles or atoms and the emergence of phenomena that are due to this collective behavior, such as phases of matter. The study of phase transitions of these systems often requires some intuition of how we can quantify the order parameter of a phase. ML algorithms can imitate something similar to intu- ition by inferring knowledge from example data. They can, there- fore, discover patterns that are invisible to the human eye which makes them excellent candidates to study phase transitions. At the same time, quantum devices are known to be able to perform some computational task exponentially faster than classical com- puters and they are able to produce data patterns that are hard to simulate on classical computers. Therefore, there is the hope that ML algorithms run on quantum devices show an advantage over their classical analog. This thesis is devoted to study two different paths along the front lines of ML and quantum physics. On one side we study the use of neural networks (NN) to classify phases of mater in many-body quantum systems. On the other side, we study ML algorithms that run on quantum computers. The connection be- tween ML for quantum physics and quantum physics for ML in this thesis is an emerging subfield in ML, the interpretability of learning algorithms. A crucial ingredient in the study of phase transitions with NNs is a better understanding of the predictions of the NN, to eventually infer a model of the quantum system and interpretability can assist us in this endeavor. The interpretabil- ity method that we study analyzes the influence of the training points on a test prediction and it depends on the curvature of the NN loss landscape. This further inspired an in-depth study of the loss of quantum machine learning (QML) applications which we as well will discuss. In this thesis we give answers to the questions of how we can leverage NNs to classify phases of matter and we use a method that allows to do domain adaptation to transfer the learned "in- tuition" from systems without noise onto systems with noise. To map the phase diagram of quantum many-body systems in a fully unsupervised manner, we study a method known from anomaly detection that allows us to reduce the human input to a mini- mum. We will as well use interpretability methods to study NNs that are trained to distinguish phases of matter to understand if the NNs are learning something similar to an order parame- ter and if their way of learning can be made more accessible to humans. And finally, inspired by the interpretability of classical NNs, we develop tools to study the loss landscapes of variational quantum circuits to identify possible differences between classi- cal and quantum ML algorithms that might be leveraged for a quantum advantage.

  • PADRÓN BRITO, MARÍA AUXILIADORA: Quantum nonlinear optics at the single-photon level with cold Rydberg atoms
    Author: PADRÓN BRITO, MARÍA AUXILIADORA
    Thesis link: http://hdl.handle.net/10803/672126
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 08/04/2021
    Thesis director: DE RIEDMATTEN, HUGUES

    Committee:
         PRESIDENT: BROWAEYS, ANTOINE
         SECRETARI: TARRUELL, LETICIA
         VOCAL: HENNRICH, MARKUS THOMAS
    Thesis abstract: Photons are good candidates for carrying quantum information because they are very stable particles: they interact weaklywith the medium and barely with each other. However, this has drawbacks when you want to process the informationbecause, in this case, it is preferable to have photon-photon interactions. For example, for applications in quantum repeaters,such interactions would allow deterministic Bell state measurements, increasing the entanglement distribution rate betweentwo remote nodes. Getting two photons to interact with each other efficiently requires mapping them into a nonlinear mediumat the single-photon level, that is, a medium that reacts differently when it interacts with a single photon than when it doeswith two. Such strong nonlinearity has been demonstrated with Rydberg atoms, which are atoms excited to a state with a highprincipal quantum number.In this thesis we have performed nonlinear quantum optics experiments using an ensemble of cold Rydberg atoms, wherewe have studied the properties of the quantum light emitted by these atoms. First, we demonstrated nonlinearities at thesingle-photon level. To reach this stage, we made several improvements to the previous experimental setup available in thegroup, of which the implementation of a dipole trap was especially relevant. We evidence quantum nonlinearity by measuringphoton antibunching for the transmitted light after interacting with the Rydberg state under electromagnetically inducedtransparency (EIT). We also showed the generation of single photons on-demand after storing weak coherent states of lightpulses as collective Rydberg excitations.Then, we studied the variation of the light statistic throughout the output pulse after propagating through the medium asRydberg polaritons, which are superposition states of light and Rydberg excitations. We showed that the properties at thebeginning and the end of the pulse were different from those of the steady state. In particular, the light detected after the inputpulse was abruptly turned off gave much stronger suppression of two-photon events. Then, we investigated how to exploitthis effect to generate single photons on demand. To do this, we analyzed the quality of the single photons detected at theend of the pulse as a function of the detection probability and compared the results with those obtained by storing the inputpulse as collective Rydberg excitations. We showed that the photons were generated more efficiently when increasing thedetection window at the cost of deteriorating the single photons statistics.Finally, we investigated the indistinguishability of the photons emitted by our Rydberg atomic ensemble, a crucial property forusing Rydberg atoms as nodes in quantum networks. We also compared the single photons generated after storage underEIT conditions with those obtained using a two-photon Raman excitation to the Rydberg state. We measured theindistinguishability by making them interfere with weak coherent states of light in a Hong-Ou-Mandel experiment. And weshowed that, although we obtained better photon statistics under EIT conditions, the indistinguishability from those obtainedwith Raman excitation was significantly higher.

  • PALOMBO BLASCETTA, NICOLA: Deterministic control of nanoantenna and single-photon emitter interaction at the nanoscale
    Author: PALOMBO BLASCETTA, NICOLA
    Thesis link: http://hdl.handle.net/10803/672092
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 24/03/2021
    Thesis director: VAN HULST, NIEK

    Committee:
         PRESIDENT: TONINELLI, COSTANZA
         SECRETARI: EFETOV, DMITRI K.
         VOCAL: FRIMMER, MARTIN
    Thesis abstract: Deterministic control of nanoantenna and single-photon emitter interaction at the nanoscale220600 220919 221100 220900The study of light-matter interaction at the nanoscale is a very promising field of research, providing the possibility to manipulate theinteraction with single quantum systems like single atoms, molecules, atomic defects or quantum dots, systems that can emit onephoton at a time, so-called single-photon emitters (SPEs). From the fundamental point of view, light-matter interaction at thenanoscale allows the exploration of the ultrasmall, providing superresolution and decomposition of the ensemble. From the appliedpoint of view, it offers the possibility to manipulate SPEs and control their optical properties for important applications in the field ofultrasensitive detectors development and quantum communications.Yet, the ultrasmall SPEs have a relatively small absorption cross-section, making their interaction with light quite weak. In fact, evenin a tight excitation focus at room temperature they only absorb one photon over ten million. Additionally, in many cases suchemitters have a low quantum efficiency, making them hard to detect. Furthermore, in many cases, they are optically quite fragile andtend to blink and bleach, thus no high illumination powers can be used in order to increase their emission of light.Fortunately, nanoantennas allow to confine light well below the diffraction limit, and through efficient coupling can increase theeffective absorption cross-section of SPEs, allowing effective excitation and high-resolution imaging. Moreover, nanoantennascoupled to SPEs modify the local mode density, shortening the emitters excited state lifetime, increasing the internal quantumefficiency, resulting in bright SPEs.In this thesis, we study the interaction of light and matter at the nanoscale through deterministic coupling between a SPE and ananoantenna, using nanometer scale control. We use scanning probe technology to scan a single nanoantenna in close proximityto a single emitter. First, we show a novel near-field probe based on a dipolar nanoantenna design that provides a higher opticaland topographical resolution compared to the state-of-the-art. Next, we apply such novel antenna probes to the study of recentlydiscovered single atomic defects in hBN, ultrastable SPEs in an atomically thin layer, ideal for nanoscale control. Despite the hBNhigh refractive index, and the low absorption cross-section of the defect, we provide high-resolution imaging of single hBN emissioncenters, enhanced by the hot-spot of our antenna probe. The controlled interaction is demonstrated by lifetime mapping, showing ashorter lifetime for the coupled emitter-antenna case. Finally, we develop a novel light confinement mechanism based on localsubwavelength field suppression by near field interference: generating ¿cold¿ spots. We obtain such dark spots by antenna phaseengineering through length control. We image optically for the first time and with high resolution the cold spots, and measurefluorescence lifetime reduction, inhibition of emission for the coupled system, despite the losses of the metallic nanoantenna.Such low-intensity sub-wavelength dark spots provide novel tools for high-resolution imaging of SPEs with ultralow intensity anda nanoscaling of advanced super-resolution techniques like MINFLUX.

  • SAEMISCH, LISA CHRISTIN: Large-scale imaging of optical antennas and single molecules
    Author: SAEMISCH, LISA CHRISTIN
    Thesis link: http://hdl.handle.net/10803/672130
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 15/04/2021
    Thesis director: VAN HULST, NIEK

    Committee:
         PRESIDENT: NOVOTNY, LUKAS
         SECRETARI: GARCÍA PARAJO, MARÍA
         VOCAL: WERTZ, ESHTER ALEXANDRA
    Thesis abstract: The interaction of light and matter is of crucial importance in fundamental science as well as in high-end technology.Ultimately, this concerns the interaction between a photon and a single quantum system, e.g. the absorption or emission of aphoton by a single molecule. At room temperature this interaction is very inefficient as the absorption cross-section of a molecule is small compared to the wavelength of light, which inhibits many photons from interacting and hence limits theabsorption, emission and scattering of a photon. An equivalent problem, and its solution, is found in our daily lives: small electric circuits (as found e.g. in our smartphones), which radiate very poorly by themselves, are linked to (radio) antennas toradiate and transfer information efficiently. Analogously, antennas working in the visible, so-called nanoantennas, are an effective tool to link matter and light. The strength of the coupling of a single molecule with a nanoantenna depends on many factors: the overlap of the antenna resonance and the molecular absorption/emission spectrum, the molecule¿s dipole orientation, the distance between molecule and nanoantenna, etc. Hence, strong interaction needs rather special conditions, which are hard to engineer. Moreover, to get a full interaction picture, a lot of single molecule encounters with different nanoantennas are needed - on one hand to make a statistically relevant statement including the many different factors and, on the other hand, to be able to observe the rare stronger interactions, that would have stayed hidden in experiments of only afew encounters. The central idea of this thesis is to statistically map and control the interactions of a very large number of single moleculeswith different tailored nanoantennas, to cover the landscape of interaction factors and thus extend the current knowledge of the mutual interaction. For this purpose, a home-built wide-field microscope is combined with a large array of lithographically fabricated nanoantennas, which are all probed by freely diffusing molecules. Thus in time millions of encounters are recorded in parallel.Chapter 2 introduces the necessary knowledge and methodology to understand the research work presented in chapters 3 to 5. Chapter 3 shows super-resolved nanoscale interaction maps of molecules and nanoantennas, linking the strength ofinteraction to the emission polarization and intensity of every encounter. Chapter 4 extends this approach by simultaneously recording the emission fluorescence and spectrum of every single molecule event, revealing strong spectral manipulation.Here, a suppression as well as an extreme enhancement of the vibrational sideband of the used molecule is observed.Additionally, the statistical mapping allows the freely diffusing molecules to encounter rare hotspots of extreme field intensities, enabling the observation of surface-enhanced Raman scattering.Finally, chapter 5 takes the first step in the direction of characterizing the interaction of molecule and nanoantenna with high sensitivity via phase measurements. Here, an interferometric wide-field microscope enables the measurement of the absolute phase of nanoparticles and demonstrates the distinction of different plasmonic and dielectric particles via their phase behavior. Furthermore, we implement a novel two-color excitation method, capable of rapidly identifying two types of nanoparticles in a single-shot image.

  • URGELL FLORES, CARLOS: New phenomena in high-quality suspended nanotube devices
    Author: URGELL FLORES, CARLOS
    Thesis link: http://hdl.handle.net/10803/672093
    Programme: DOCTORAL DEGREE IN PHOTONICS
    Department: Institute of Photonic Sciences (ICFO)
    Mode: Normal
    Reading date: 30/03/2021
    Thesis director: BACHTOLD, ADRIAN

    Committee:
         PRESIDENT: KONTOS, TAKIS
         SECRETARI: CHANG, DARRICK
         VOCAL: STEELE, GARY
    Thesis abstract: Carbon nanotubes (CNTs) have attracted the attention of the scientific community since their discovery in the 90s. They arean excellent material for the development of research fields as diverse as nanomechanics or quantum transport. Nanotubemechanical resonators are endowed with exceptional properties, including extremely small mass, ultra narrow crosssection,and operation over a large frequency range from 10 kHz to 10 GHz. They are also fantastic sensors of both massadsorption and forces.Its electric transport properties are remarkably the long ballistic transport of charge carriers, strong electron-electroninteraction, and the important role of the spin and valley degrees of freedom. It is possible to observe a wide range ofquantum transport phenomena ranging from single-electron tunneling to Kondo physics and Fabry-Pérot interference. Itshould be noted that the electrical transport and mechanical motion of suspended nanotubes can be coupled by a largeamount.In the first part of this thesis, we present an advanced ultra-sensitive fabrication method that allows us to build andfunctionalize a nanotube cantilever for optical measurements. We grow a platinum particle at the end of the nanotube in orderto increase laser reflection. For this, we track the material deposition on the cantilever through the electromechanicalcoupling with the electron beam during the process.Next, we show electron transport measurements in high-quality devices with high transmission. While high-temperaturemeasurements indicate electron-electron correlations, low-temperature transport characteristics point towards singleparticleFabry-Perot interference. We observe this effect both by modifying the temperature and by tuning the source-drainvoltage. This effect is attributed to the interplay between fluctuations and quantum interactions in a correlated Fabry-Pérotregime.In the last part, we show that it is possible to couple the mechanical movement of the CNT to the electron transport. Byapplying an electron current through the system, we can either cool or amplify the mechanical motion of the eigenmode. Wecooled the nanoresonator down to 4.6+-2.0 quanta of vibration. The instabilities present in electron transport measurementsare attributed to self-oscillation induced by the backaction amplification. These effects have an electrothermal origin. Thismethod can be used in the future to cool NEMS into the quantum regime.

Last update: 16/10/2021 05:11:51.

Theses related publications

AUTHOR:GONZÁLEZ CUADRA, DANIEL
Title:A cold-atom approach to topological quantum matter across the energy scale
Reading date:11/12/2020
Director:LEWENSTEIN, MACIEJ
Co-director:BERMÚDEZ CARBALLO, ALEJANDRO
Mention:No
RELATED PUBLICATIONS
González, D. (2017). Classical and Quantum Simulation of Strongly Correlated Phases of Matter.

AUTHOR:MUÑOZ GIL, GORKA
Title:Anomalous diffusion: from life to machines
Reading date:09/11/2020
Director:LEWENSTEIN, MACIEJ
Co-director:GARCÍA MARCH, MIGUEL ANGEL
Mention:No
RELATED PUBLICATIONS
Requena, B.; Dauphin, A.; Muñoz, G.; Lewenstein, M.; Mazzanti, F. (2020). Restricted Boltzmann machines as variational wave functions.

Requena, B.; Muñoz, G.; Lewenstein, M.; Dunjko, V.; Tura, J. (2020). Certificates of many-body quantum properties assisted by machine learning.

AUTHOR:PÉREZ ROSAS, JUAN MIGUEL
Title:IMAGING CYTOMETRY TECHNOLOGY FOR ENVIRONMENTAL AND BIOMEDICAL APPLICATIONS
Reading date:28/07/2020
Director:PRUNERI, VALERIO
Mention:No
RELATED PUBLICATIONS
Perez, J. (2016). Optical cytometer based on angular spatial frequency processing and its application in environmental control and point-of-care diagnostics.

AUTHOR:PLANES CONANGLA, GERARD
Title:Levitation and control of particles with internal degrees of freedom
Reading date:30/06/2020
Director:QUIDANT, ROMAIN
Co-director:SCHELL, ANDREAS
Mention:No
RELATED PUBLICATIONS
Planes, G. (2017). Hybrid quadrupole-optical trapping of nanoparticles containing single emitters.

AUTHOR:POZAS KERSTJENS, ALEJANDRO
Title:Quantum information outside quantum information
Reading date:15/10/2019
Director:ACÍN DAL MASCHIO, ANTONIO
Mention:Mention de Doctor Internacional
RELATED PUBLICATIONS
Pozas, A. (2017). Causal Inference in Quantum Networks.

Ortega González, Álvaro (2019). Work distributions on quantum fields.

AUTHOR:RICCI, FRANCESCO
Title:Levitodynamics toward force nano-sensors in vacuum
Reading date:22/02/2019
Director:QUIDANT, ROMAIN
Co-director:RICA ALARCÓN, RAÚL
Mention:No
RELATED PUBLICATIONS
Ceccaroni, L.; Ricci, F.; Codina, V. (2016). Distributional semantic pre-filtering in context-aware recommender systems. - User modeling and user-adapted interaction, ISSN: 0924-1868 (JCR Impact Factor-2016: 3.625; Quartil: Q1)

Braunhofer, M.; Codina, V.; Ricci, F. (2014). Switching hybrid for cold-starting context-aware recommender systems.

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 groups

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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

Quality

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