School of Physics & Astronomy

Find a PhD Project Here

Opportunities for fully funded PhD or EngDoc research projects are available in all fields of research within the School. You may search for current projects on this page. APPLY HERE for a PhD Place.

 PhD in Photonics
 PhD in Condensed Matter
 PhD in Astrophysics

Search current PhD opportunities in the School of Physics & Astronomy:-




Photonics

organic semiconductor polariton light emitters
Samuel, Prof Ifor - idws@st-andrews.ac.uk
Turnbull, Prof Graham - gat@st-andrews.ac.uk

When light is confined on the nanoscale it is possible to observe light-matter interactions that are not normally observed in bulk materials. One example is the strong coupling of photons and excitons in wavelength-scale microcavities which leads to a number of unusual phenomena [1,2]. The modes of the cavity couple with the exciton to make a hybrid-light-matter state called a polariton. One can make polaritons lasers that emit coherent light [3] and it has been shown that polaritons can form a Bose-Einstein condenstate [4].

This project will explore the properties of polaritons in microcavities based on organic semiconductors [2,4-6]. It will involve the fabrication of microcavities that include J-aggregate dyes or semiconducting polymers to explore how the energy states of organic materials can be modified when coupled to the cavity modes, and be applied in photonic devices including lasers and LEDs.

[1] C. Weisbuch et al., Phys. Rev. Lett. 69, 3314 (1992)
[2] D.G. Lidzey et al., Nature 395, 53 (1998)
[3] S. Christopoulos et al., Phys. Rev. Lett. 98, 126405 (2007)
[4] J D Plumhof, T Stöferle, L Mai, U Scherf & R F Mahrt, Nature Materials 13, 247–252 (2014)
[5] T. Schwartz, J. A. Hutchison, C. Genet, and T. W. Ebbesen, Phys. Rev. Lett. 106, 196405 –(2011)
[6] S Kéna-Cohen*, S A. Maier and D D. C. Bradley, Advanced Optical Materials 1, 827–833, (2013)
Plastic Lasers
Samuel, Prof Ifor - idws@st-andrews.ac.uk
Turnbull, Prof Graham - gat@st-andrews.ac.uk

Conjugated polymers are a very special class of plastics that are both semiconducting and efficient light-emitters. They have been widely applied as flat and flexible light emitting displays, as well as visible lasers, optical amplifiers, solar cells and electronic circuits. As novel laser media, polymers are particularly attractive because they can be easily and inexpensively formed into flexible shapes and structures that are inaccessible to crystalline materials.

This project builds on our internationally recognised research programme in polymer lasers. We have demonstrated plastic lasers driven by a light-emitting diode and are currently developing lasers and optical amplifiers integrated with nitride LEDs and CMOS control electronics. Novel photonic nanostructures are used to control
laser emission, develop new modes of operation and applications in sensing and datacomms.
Advanced Imaging for the Biomedical Sciences (with Dr F Gunn-Moore, School of Biology)
Cizmar, Dr Tomas - tc51@st-andrews.ac.uk
Dholakia, Prof Kishan - kd1@st-andrews.ac.uk

the aim of this project is to explore new routes for imaging both in vitro and in vivo using concepts of light transmission through disorder. In turn this will allow us to shape light at will for example at the end of an optical fibre and use this perhaps in an endoscopic scenarios. Other forms of microscopy to consider will involve using a light sheet for imaging larger biological systems (eg embryos). The study will involve advanced photonics, numerical studies and practical work. The research will also investigate strategies to image beyond the diffraction limit. Samples under investigation will include tissue and, at later stages of the work, potentially neuronal cells/tissue to target advanced understanding of neurological disease using these methods.
Advanced microscopy of nanolaser particles
Schubert, Dr Marcel - ms293@st-andrews.ac.uk

*Opportunity for UK, EU and international students*

**This project must commence before 28th February 2019 - applications are welcome immediately**

Nano- and microlasers have recently gained attention as novel light sources for biomedical applications, including single cell barcoding, refractive index sensing and tissue-integrated pressure sensors [1-3]. Their unique properties renders these devices ideally suited for experiments inside living specimens where many physical process related to development and disease are poorly understood.

Over the past decade, light sheet microscopy has revolutionized our understanding of the development of complex biological organisms [4]. While representing one of the most powerful and innovative microscopy techniques, light sheet microscopes are also typically build from scratch which allows to integrate a vast range of imaging modalities.

In this project, advanced 3D imaging will be combined with the broad capabilities of bio-integrated nanolaser. The goal is to correlate the spectroscopic information of the nanolasers with structural properties of the biological sample, by building a custom-made light sheet microscope. The new instrument will be used to investigate important biological processes like e.g. single cell tracking of invasive circulating tumour cells, cardiac regeneration or pressure sensing during gastrulation. Other aspects of the project are related to applying techniques to reduce effects of scattering by using advanced beam shaping techniques. Good knowledge of optics and microscopy, as well as basic programming skills are preferred but the student will be given the opportunity to learn relevant techniques during the project.

For further information please contact Marcel Schubert [ms293@st-andrews.ac.uk] prior to application.

[1] M. Schubert, A. Steude, P. Liehm, N. M. Kronenberg, M. Karl, E. C. Campbell, S. J. Powis, M. C. Gather, Lasing within Live Cells Containing Intracellular Optical Microresonators for Barcode-Type Cell Tagging and Tracking, Nano Lett. 2015, 15, 5647.

[2] M. Schubert, K. Volckaert, M. Karl, A. Morton, P. Liehm, G. B. Miles, S. J. Powis, M. C. Gather, Lasing in Live Mitotic and Non-Phagocytic Cells by Efficient Delivery of Microresonators, Sci. Rep. 2017, 7, 40877.

[3] A. H. Fikouras, M. Schubert, M. Karl, J. D. Kumar, S. J. Powis, A. di Falco, M. C. Gather, Non-obstructive intracellular nanolasers, arXiv:1806.03366, 2018.

[4] T.-L. Liu et al., Observing the cell in its native state: Imaging subcellular dynamics in multicellular organisms, Science 2018, 360, eaaq1392.
Aligning molecules to improve efficiency in next generation organic LEDs
Gather, Prof Malte - mcg6@st-andrews.ac.uk

Organic light-emitting diodes (OLEDs) are novel type of LEDs in which electroluminescence is generated by plastic-like organic molecules. OLEDs are at the heart of modern smart phone displays and are likely to become the dominant technology for computer screens and large area TVs in the future. In addition, OLEDs are considered for general illumination, an area where efficiency is of key importance. While OLEDs can operate with close to 100% internal electron-to-photon conversion efficiency, typically less than 20-25% of the generated light is extracted into the surrounding air; the rest is trapped in waveguided modes and eventually lost to absorption.

Various strategies have been proposed to improve light extraction from OLEDs. Very recently controlling the average orientation of the electroluminescent molecules inside an OLED has been identified as a promising avenue. However, accurate measurement of molecular orientation is difficult and it remains unclear how molecular orientation can be controlled efficiently. Within this project, these challenges will be approached by making use of different spectroscopic and computational methods. Provided certain formal criteria are met, the student can benefit from placement with a major commercial developer of OLED materials and technology.

Further reading:
Biophysical Aspects of Photodynamic Therapy
Brown, Prof Tom - ctab@st-andrews.ac.uk
Wood, Dr Kenny - kw25@st-andrews.ac.uk

Photodynamic Therapy (PDT) is a treatment for cancer that involves light-activation of a photosensitiser and causes cell death by release of singlet oxygen and free radicals. The Scottish PDT Centre was established in Ninewells Hospital, Dundee in 2000 thanks to a generous donation from the Barbara Stewart Charitable Trust. Since its introduction in Dundee, over 2,000 treatments have been carried out. The photosensiters used for PDT also have the property that they fluoresce and so they can be used for photodiagnosis (PD), which is performed at the Scottish PDT Centre to direct the surgeon towards tissue that is likely to be cancerous.
The purpose of the proposed PhD program is to gain a fuller understanding of the interaction between the incident light and the tumour. Optimal treatment regimes have not been established. We would like to be able to model both PDT and PD. To assist in this, we propose to develop theoretical radiation transfer models using Monte Carlo techniques in order to simulate the incident light and the fluorescent emission. This will be done for the range of tissue types where PDT is performed in Dundee. This includes skin (the most accessible), the oral cavity, the brain and bladder.
The work will also find application in a wide range of other areas in the drive towards minimally invasive and highly targeted therapies. In addition to the PDT described above, the techniques can be applied to so-called ‘caged compounds’ that are a range of biologically active compounds that are activated with light. In order to apply such compounds within a therapeutic environment, understanding the light tissue interactions is of key importance.
Light distribution measurements will be made around a range of light delivery devices, including cylindrical diffusers and miniature balloons filled with light-scattering media. Further measurements will be carried out using optical fibres embedded in tissue samples and using ultrashort pulses to probe two-photon activation at depth within the body. Fluorescent emission spectra will also be measured using a specially constructed optical biopsy system.

This project provides many opportunities for the student to study PDT and other light activated therapies from theoretical, experimental, and clinical perspectives.
There will be joint supervision from Dr Harry Moseley, who is Technical & Scientific Director of the Scottish PDT Centre and Honorary Reader at the University of Dundee, and Drs Tom Brown and Kenny Wood, who are Lecturers in the Department of Physics and Astronomy at the University of St Andrews. Dr Wood will supervise the theoretical aspects of the PhD (Monte Carlo radiation transfer), Dr Brown the experimental light tissue studies and Dr Moseley will supervise the clinical applications at Ninewells Hospital.

Drone detection using millimetre wave radar
Robertson, Dr Duncan - dar@st-andrews.ac.uk

The detection of small unmanned aerial vehicles (UAVs), or drones, is a growing requirement both for the management of intentional drone activity and for the detection of unwanted drones which might cause a risk to security, safety or privacy. Radar is one of the most promising sensors with which drones can be detected at usefully long ranges (km) but they present significant challenges to the radar designer who wishes to detect, track and classify such targets. Drones typically have a low radar cross section (RCS) and fly quite slowly which means conventional air traffic control or air defence radars are ill-suited to their detection. They do, however, possess characteristic micro-Doppler signatures associated with their propellers which can be exploited to discriminate them from other small, slow moving targets. The development of radar systems and signal processing methods specifically designed to detect, track and classify drones is a rapidly developing area of research [1], driven by the explosive growth in drone use and, sadly, the increase in associated risks.

Research in the Millimetre Wave Group has shown that millimetre wave radar may offer some advantages in tackling this problem in terms high Doppler sensitivity and compact system size [2]. We have carried out extensive millimetre wave radar measurements of drones and birds, which are the dominant confusers, both in terms of RCS [3] and micro-Doppler signatures [4]. We have also explored different signal processing techniques for classification of aerial targets, such as the short time Fourier transform (STFT) and wavelet transforms [5].

This PhD will extend these investigations much deeper to cover a range of topics which are currently not well understood. Whilst RCS data has been published by ourselves and others (including numerical simulations), what are the statistical fluctuations associated with manoeuvring drones? The micro-Doppler signals from the rotating propellers are much smaller than the bulk RCS due to their small size and often plastic materials used – how do these signatures along with the bulk vary with aspect angle and polarisation? Can one determine the type of drone, whether it is loaded with a payload, or its intent from its radar signature? Additionally, a key aspect in achieving practical drone detection radar systems which is a focus in our research is being able to process signals and data in real time and there is scope for developing efficient, fast classification algorithms.

The candidate should have a degree in Physics or Electronic Engineering, ideally with some knowledge of radar, signal processing or microwave technology. Familiarity with MATLAB and C programming would be an advantage.

The Millimetre Wave Group is extremely well equipped with test equipment, measurement facilities including an outdoor test range with dedicated lab, and a large array of components and subsystems enabling rapid development. We have built 13 radar systems at frequencies of 24, 77, 38, 94, 220 and 340 GHz, many of which would be available for data collection in this project.

If you are interested in this PhD project please contact the supervisor Dr Duncan A. Robertson (dar@st-and.ac.uk) to discuss it further.

[1] J.S. Patel, F. Fioranelli, D. Anderson, “Review of radar classification and RCS characterisation techniques for small UAVs or drones,” IET Radar Sonar Navig., 2018, Vol. 12 Iss. 9, pp. 911-919, https://doi.org/10.1049/iet-rsn.2018.0020

[2] S. Rahman & D.A. Robertson, “Millimeter-wave micro-Doppler measurements of small UAVs”, Proc. SPIE 10188, Radar Sensor Technology XXI; 101880T (2017); https://doi.org/10.1117/12.2261942

[3] S. Rahman & D.A. Robertson, “In-flight RCS measurements of drones and birds at K-band and W-band”, IET Radar, Sonar & Navig., E-first, pp. 1-10, 2018. https://doi.org/10.1049/iet-rsn.2018.5122

[4] S. Rahman & D.A. Robertson, “Radar micro-Doppler signatures of drones and birds at K-band and W-band”, Nature Scientific Reports, 8, 17396, pp. 1-11, 2018. https://doi.org/10.1038/s41598-018-35880-9

[5] S. Rahman & D.A. Robertson, “Time-Frequency Analysis of Millimeter-Wave Radar Micro-Doppler Data from Small UAVs”, Sensor Signal Processing for Defence conference, pp. 1-5, 2017. https://doi.org/10.1109/sspd.2017.8233269

Hawking radiation in the laboratory
Koenig, Dr Frieder - fewk@st-andrews.ac.uk

Black holes can be understood in a simple picture: Imagine a river flowing towards a waterfall with ever increasing flow speed. Also imagine fishes in the river swimming upstream. At some position in the river the maximum speed of the fish will equal the flow speed and all fish beyond that "point of no return" will be flushed into the waterfall. Here the flow speed corresponds to the gravity of a black hole and the point of no return to the event horizon.
Arguably the most facinating aspects of astronomical black holes is the emission of Hawking radiation from the event horizon, an intriguing quantum effect combining gravity, thermodynamics and quantum mechanics.

Unfortunately, the astrophysical Hawking radiation is far too weak to ever being detected directly. Recently, however, we have invented a method to create moving artificial event horizons with short pulses in optical fibers. Moreover, the expected Hawking radiation is strong enough to be detectable with single photon coincindence counting.

The idea of the PhD programme is the calculation, detection, and characterization of this elusive Hawking radiation for the first time. The work has already gained momentum in our group and a setup is built using optical pulses of just a few cycles pulse length. In addition we will explore further quantum field theory effects in curved spacetime.
Integrated Magnetic Resonance Doctoral Training Centre
Smith, Prof Graham - gms@st-andrews.ac.uk

The new EPSRC Doctoral Training Centre in Integrated Magnetic Resonance is a collaboration between 6 of the UK's leading Universities in Advanced Magnetic Resonance Instrumentation and Techniques and includes St. Andrews, Dundee, Aberdeen, Warwick, Nottingham and Southampton.

The aim is to provide a coherent training program for doctoral students whilst working on new research topics in instrumentation and methodology, associated with Magnetic Resonance Imaging, Electron Magnetic Resonance, Nuclear Magnetic Resonance and Dynamic Nuclear Polarisation (which collectively represent Łmulti-Billion annual markets). Training is delivered from all centres, through residential workshops and over the Access Grid, primarily in the first two years of study.

Funded 4 year PhDs include fees and maintenance of Ł14000 (tax free) per annum as well as an enhanced travel budget. All PhDs will have internal and external mentors from other centres.

At St Andrews, PhD projects are available on themes associated with major advances in Electron Magnetic Resonance and Dynamic Nuclear Polarisation and are likely to involve collaborations with other centres and other interdisciplinary groups.

PhD topics are likely to involve a combination of instrumental, methodological and computational techniques that would normally be associated with Basic Technology programs.

Representative PhDs from all 6 centres are listed on www.imr-cdt.ac.uk, but other PhD topics may be available on request.

For PhDs at St Andrews, applications can be made directly to St Andrews or via Warwick where the DTC program is administered.

Integrating nanolasers into 3D cardiac cultures
Schubert, Dr Marcel - ms293@st-andrews.ac.uk

Growth of functional cardiac tissue and stem cell therapies hold great promise to overcome the limited ability of the human heart to repair itself. However, current progress is strongly limited by the ability to investigate mechanical coupling between transplanted cells and the host environment.

We have recently developed a new method to detect contractions of single heart cells. By integrating micro- or nanoscopic lasers into individual cells the contractile properties of heart cells can be recorded optically [1-3]. The aim of this project is to develop a tissue integrated platform to detect contraction profiles of individual cells in natural and artificial heart muscles. To reach this goal, new microscopic lasers will be developed with optimized spectral and mechanical properties to facilitate long-term integration up to the point where these devices can be applied in-vivo. A passion for optics and biology are recommended to drive this exciting and truly multi-disciplinary project which is most suitable for graduates with a background in physical science, material science or bioengineering.

For further information please contact Marcel Schubert [ms293@st-andrews.ac.uk] prior to application.

[1] M. Schubert, A. Steude, P. Liehm, N. M. Kronenberg, M. Karl, E. C. Campbell, S. J. Powis, M. C. Gather, Lasing within Live Cells Containing Intracellular Optical Microresonators for Barcode-Type Cell Tagging and Tracking, Nano Lett. 2015, 15, 5647.

[2] A. H. Fikouras, M. Schubert, M. Karl, J. D. Kumar, S. J. Powis, A. di Falco, M. C. Gather, Non-obstructive intracellular nanolasers, arXiv:1806.03366, 2018.

[3] M. Karl, J. M. E. Glackin, M. Schubert, N. M. Kronenberg, G. A. Turnbull, I. D. W. Samuel, M. C. Gather, Flexible and ultra-lightweight polymer membrane lasers, Nat. Commun. 2018, 9, 1525.
Linear and nonlinear properties of 3D optical Metamaterials.
Di Falco, Prof Andrea - adf10@st-andrews.ac.uk

Metamaterials (MMs) are man made materials with engineered optical properties. They are made assembling their artificial atoms at a scales much smaller than that of light, so as to appear homogenous. They are at the basis of very thought provoking proposals, including super imaging and cloaking applications.
In the group of Synthetic Optics we have developed a large portfolio of fabrication techniques for one- and two-dimensional MMs.

The aim of this project is to develop the fabrication protocol and applications of three-dimensional MMs obtained with a bottom up approach. The student will combine the extraordinary physical and optical properties of silica based aerogels with the flexibility of the design of nanoplasmonics to realise effective materials with bespoke optical behaviour. The aerogel is an ultra light material with refractive index close to unity and thermally more insulating than air. Combining these features with the field enhancement offered by infiltrated metallic nano particles is specially suited to address nonlinear effects at ultra-low powers.

This challenging but rewarding project requires a thorough understanding of the physics involved and the experimental rigour to fabricate and test the MMs, but offers the student the chance to learn a broad range of design, fabrication and experimental techniques.

Living Lasers: Lasing from biological cells
Gather, Prof Malte - mcg6@st-andrews.ac.uk

Optical phenomena in biological structures have fascinated mankind for centuries and biological materials with optical functionality are currently a major topic of research. In the future, photonic devices may indeed be based on natural or genetically engineered optical function.

Recently, we developed a biological laser – a device based on a single living cell genetically programmed to produce the fluorescent protein GFP. The laser is biocompatible and biodegradable, and thus offers unique physical and biological properties not shared by any existing device.

However, so far our biolasers require an artificial resonator and an external pump source. This project is aimed at gaining a better understanding of lasing and stimulated emission in biological materials and at developing new avenues to biolasers. For example, this can include the study of bio-assembled resonators based on naturally occurring structures, photophysical investigations aimed explaining why fluorescent proteins are such efficient laser materials, or the development of biocompatible nanolasers.

The project is inter-disciplinary, involving photonics, laser physics, genetic engineering, proteomics, and material science and adequate training in these fields will be provided within the school and through external collaborators.

Further reading
MM-wave Radar, Components and Techniques
Smith, Prof Graham - gms@st-andrews.ac.uk

MM-waves represent the area of the electromagnetic spectrum that sits between microwaves and Terahertz frequencies. It is the part of the spectrum where electronics meets optics and a wide variety of physical techniques are used to design components and systems. MM-waves are used in high resolution radar, fusion diagnostics, earth resource studies, magnetic resonance and security systems.

The mm-wave group at St Andrews is one of the largest and most well established groups in this field in the UK, and has a strong track record in designing components, sub-systems and full system. Much recent work ahas concentrated on developing radar imaging systems for earth resource studies (imaging volcanos, monitoring rainfall) and for various security related systems.
There is also a very strong program in mm-wave magnetic resonance.

A variety of PhD topics are always available and any interested student should get in touch with Dr Graham Smith in the first instance.
New photonics tools unravel the mysteries and mechanics of biological cells
Gather, Prof Malte - mcg6@st-andrews.ac.uk

Biologists have compelling evidence that in addition to biochemical signals, mechanical forces have a major impact on a wide range of processes in cell biology, with examples ranging from cell migration and cell growth to the spreading of cancer and the differentiation of stem cells. However, there is at present a shortage of suitable tools to measure the force exerted by a cell which often is well below 1nN (i.e., < 10-6 N (!)).

By developing a novel optical micro-cavity-based sensor technology, the Gather Lab seeks to overcome current limitations in measuring cellular forces and – for instance – investigate the mechanics involved in the formation and the growth and repair of nerve cells.

The basic working principle of our sensors is to detect shifts in the resonance frequency of a micro-cavity due to mechanical forces applied by cells cultured on the sensor. These shifts can be detected with high spatial and temporal resolution and the forces at play are then computed from this by a finite element method.

A PhD in the field of cellular mechanics provides you with a broad, interdisciplinary skill set: You will learn and apply a range of micro- and nano-fabrication methods and work in a state-of-the-art cleanroom. You will use different types of optical spectroscopy and work with atomic force microcopy. You will receive hands-on training in cell culturing techniques and perform studies of e.g. stem cell differentiation.

The project is part of an international collaboration with leading scientists at Harvard Medical School and University of Cambridge which is funded by the Human Frontier Science Program, the leading funding institution for interdisciplinary and international collaborative research into complex biological systems.

 
Non-reciprocal optics
Schulz, Dr Sebastian - sas35@st-andrews.ac.uk

In contrast to traditional, reciprocal optical systems, non-reciprocal systems allow the realization of interesting physical effects, for example optical isolation or the breaking of seemingly fundamental physical limits, such as the link between a system’s delay and its bandwidth [1]. Typically, non-reciprocal optical elements are realized using magneto-optic materials, for example in a Faraday Rotator. However, these materials are not suitable for integration in nanophotonic devices and thus new methods of achieving non-reciprocity need to be explored, for example nonlinear optical effects or time-variant modulations [2-4].

This project addresses the realization of on-chip non-reciprocal optical elements, new applications enabled by these elements and the exciting new physics achieved by combining non-reciprocal elements with components such as absorbers, emitters or resonators [1].

You are expected to have an interest in studying fundamental concepts in physics as well as mastering hands on nanofabrication and laboratory techniques. The project includes collaborations with groups across Europe and North America, offering you opportunities to visit the laboratories of collaborators and to build your own professional network.

The project will be supervised by Dr. Sebastian Schulz, who will join the department in March 2018. For more details on this topic and for any question regarding the project, please contact Dr. Sebastian Schulz (Sebastian.Schulz@cit.ie).

[1] H. Tsakmakidis, L. Shen, S. A. Schulz, X. Zheng, J. Upham, X. Deng, H. Altug, A. F. Vakakis and R. W. Boyd “Breaking Lorentz reciprocity to overcome the time-bandwidth limit in physics and engineering” Science 356, pp1260-1264 (2017). http://science.sciencemag.org/content/356/6344/1260

[2] E. A. Kittlaus, N. T. Otterstrom and P. Rakich “On-chip inter-modal Brillouin Scattering” Nature Communications 8, p.15819 (2017). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5504300/

[3] L. Feng, M. Ayache, J. Huang, Y.-L. Xu, M.-H. Lu, Y.-F. Chen, Y. Fainman and A. Scherer “Nonreciprocal Light Propagation in Silicon Photonic Circuit” Science 333, p. 729 (2011). http://science.sciencemag.org/content/333/6043/729

[4] D. L. Sounas and A. Alu “Non-reciprocal photonics based on time modulation” Nature Photonics 11, p 774 (2017). https://www.nature.com/articles/s41566-017-0051-x
Nonlinear Optical Micromanipulation
Dholakia, Prof Kishan - kd1@st-andrews.ac.uk

New uses of trapped colloid as nonlinear media and uses for observations of soliton-like waves and new forms of in-situ imaging as well as nonlinear processes (eg 4 wave mixing). This is a very exciting project based on novel ordering of colloidal particles in the presence of light fields as well as the use of these colloids as new media for nonlinear effects.
OLED micro-displays as biophotonic platform
Gather, Prof Malte - mcg6@st-andrews.ac.uk

Organic Light Emitting Diodes (OLEDs) are novel optoelectronic devices with potential applications ranging from displays (e. g. in smart phones or for flexible screens) to general illumination. In contrast to conventional LEDs, OLEDs are based on plastic-like organic materials. Thus, they can be mechanically flexible and are believed to offer improved biocompatibility.

In this project, micro-displays based on >200,000 individual OLEDs, each smaller than a single biological cell, are used as a platform for advanced studies in cell biology. Potential applications include lens-free, low-cost, continuous microscopy of cells and structured illumination for optogenetic studies. Optogenetics is a technique which allows controlling the biological activity of genetically modified cells by exposure to light. Over the past decade, the technique has greatly improved the understanding of various fundamental processes in biology, in particular in neuroscience. OLED micro-displays may enable optogenetic experiments, like stimulating growth or movement of neurons, with improved temporal and spatial control, higher degree of parallelization and over longer times than currently possible.

This project is highly interdisciplinary involving photonics and materials science but also cell biology and genetics. Training will be provided in all these aspects from within my group and through collaboration with the School of Biology and external collaborators at University of Cambridge and Harvard Medical School.

Further reading:
optical antennas for visible light communications (Li-Fi)
Samuel, Prof Ifor - idws@st-andrews.ac.uk
Turnbull, Prof Graham - gat@st-andrews.ac.uk

Visible light communications is an emerging field that aims to deliver high-bandwidth wireless data through solid-state (LED) lighting. This project will be part of a multi-disciplinary research collaboration between the Universities of St Andrews, Strathclyde, Edinburgh, Oxford and Cambridge which will develop the next generation VLC technology.

The aim of this project will be to develop nanophotonic hybrid light sources and detectors based on luminescent polymer films. The student will design novel optical antennas, and fabricate these using thin film depostion and nanoimprint lithography. Working with the partner universities, these components will be combined with gallium nitride LEDs and CMOS detectors to develop next generation tranceiver technologies for visible light communications.
Optical Imaging of Biological Specimens
Brown, Prof Tom - ctab@st-andrews.ac.uk

ptical imaging can provide detailed information about a range of biological specimens from whole animals to small tissue samples. A drawback however is that such imaging often only provides data from structures at or near the surface. By contrast Optical Coherence Tomography (OCT), a low coherence interference imaging technique, can provide detailed information on tissue structure at depths of a few mm with resolution of around 10 um in living animals.

In this project we will apply OCT to a range of biological specimens to provide information which has proved to be unobtainable using other techniques. In particular the project will use OCT to provide information on tissue regeneration in amphioxus (fish-like marine chordates with close affinity to vertebrates) which are used as a model for testing concepts in nerve cord growth and repair. We will also apply OCT to Antarctic Krill (Euphasia superba), perhaps the key species in the Antarctic food web. The information these studies provide will be used to develop advanced models for acoustic imaging Krill and may also support studies on the effects of global climate change on this key species. We may also apply the system to recently launched studies of surface vasculature in Southern Elephant Seals to support ongoing studies into the diving physiology of this species.

The projects described are interdisciplinary and will require an open mind and a willingness to work with partners within Biology and Marine Science in the UK and at the Australian Antarctic Division. Australia. In order to fully develop our systems and to enable in vivo testing some travel and extended stays may be required to partner institutions.

The main supervisor for the project will be Professor Tom Brown in the School of Physics, with co-supervision by Dr Ildiko Somorjai within the School of Biology.

Prospective students should have a good background in Physics with an interest in applying their work in other fields. We are also interested in applications from students in Biology who have a strong background in imaging techniques.

Examples of the application of OCT to Krill can be found at:

M.J. Cox, S. Kawaguchi, R. King, K.Dholakia and C.T.A. Brown, “Internal physiology of live krill revealed using new aquaria techniques and mixed optical microscopy and optical coherence tomography (OCT) imaging techniques”, Marine and Freshwater Behaviour and Physiology, 48, p. 455 (2015)

N. Bellini, M.J. Cox, D.J. Harper, S.R. Stott, P.C. Ashok, K. Dholakia, S. Kawaguchi, R. King, T. Horton and C.T.A. Brown, “The Application of Optical Coherence Tomography to Image Subsurface Tissue Structure of Antarctic Krill Euphausia superba”, PLOS ONE, 9, Art. No. e110367 (2014
Optical manipulation: air/vacuum trapping for cavity optomechanics
Dholakia, Prof Kishan - kd1@st-andrews.ac.uk

Optical trapping leads to the confinement of microscopic and nanoscopic objects using light. In the domain of optomechanics we would like to cool small "trapped" mechanical oscillators down to the quantum regime. This project aims to experimentally explore new ways to levitate and trap microparticles in air and vacuum. The ultimate aim is to slow down or 'cool' spheres to the ground state of motion. The topic is currently one of the most exciting and rapidly growing areas of physics and will involve both theory and experiment.
Optomechanical Metasurfaces for Biophotonics Applications
Di Falco, Prof Andrea - adf10@st-andrews.ac.uk

The Synthetic Optics group (www.st-andrews.ac.uk/physics/synthopt) in the School of Physics and Astronomy at the University of St Andrews has a large portfolio of research projects aimed at designing and exploiting light matter interactions at the nanoscale. The range of applications targeted is equally wide and includes the development of advanced materials, nonlinear and complex photonic and biophotonics applications. All these strands converge in the newly funded project “AMPHIBIANS”, which aims at developing a novel biophotonic platform based on the all optical manipulation of photonic metasurfaces in microfluidic environments. This experimental PhD project will focus on the design and fabrication of the photonic metasurfaces.

The current trend in biophotonics is to try and replicate the same ease and precision that our hands, eyes and ears offer at the macroscopic level, e.g. to hold, observe, squeeze and pull, rotate, cut and probe biological specimens in microfluidic environments. The bidding to get closer and closer to the object of interest has prompted the development of extremely advanced manipulation techniques at scales comparable to that of the wavelength of light. However, the fact that the optical beam can only access the microfluidic chip from the narrow aperture of a microscopic objective limits the versatility of the photonic functions that can be realized.

AMPHIBIANS aims to introduce a new biophotonic platform based on the all optical manipulation of flexible photonic metasurfaces. These artificial two-dimensional materials have virtually arbitrary photonic responses and have an intrinsic exceptional mechanical stability. This cross-disciplinary project, bridging photonics, material sciences and biology, will enable the adoption of the most modern and advanced photonic designs in microfluidic environments, with transformative benefits for microscopy and biophotonic applications at the interface of molecular and cell biology.

This experimental project is a unique opportunity for a motivated individual to work at the forefront of a cross-disciplinary and timely topic. The project is challenging but highly rewarding as it gives to the student the opportunity to learn different and highly valued skills, from the advanced design of nanophotonic devices, to the fabrication and characterisation of metasurfaces in the visible range and their applications to biological problems.
Organic light-emitting diodes
Samuel, Prof Ifor - idws@st-andrews.ac.uk

Visible light emission can be stimulated by applying a voltage to a thin layer of an organic semiconductor. The light emitted provides a window on the physics of the material, enabling us to learn about the nature of the excited states in the material. It is also useful for information display, lighting, and even for the treatment of skin cancer. We have developed a new class of light-emitting organic semiconductor, which could be used for high efficiency lighting, thereby reducing energy consumption.
Organic Solar Cells
Samuel, Prof Ifor - idws@st-andrews.ac.uk

The energy crisis is probably the most important problem facing the world today. Sunlight is the most abundant renewable energy source, but at present the cost of photovoltaics is too high for solar cells to be a serious alternative to fossil fuels. Organic semiconductors offer the prospect of low cost solar cells, but their efficiency needs improvement. We are working on new measurements to understand organic solar cell operation, and new materials to improve it.
Single photon optical eigenmodes
Mazilu, Dr Michael - mm17@st-andrews.ac.uk

Structured light is used in imaging, communication and optical micromanipulation to increase resolution, data capacity and optimise optical traps. At the single photon level, structured light offers the perfect system to study fundamental light-matter interaction such as the transfer of linear and angular momentum to microscopic objects. This theoretical study looks at the links between quantum technology and optical micromanipulation. More precisely, coherent electromagnetic radiation can take many forms in general. Indeed, any scattering and interaction of a light field with its environment will change the beam profile and the properties of the light field involved. These effects can be calculated numerically and sometimes analytically by solving the classical Maxwell’s equations. One class of solutions of Maxwell’s equations are the optical eigenmodes that constitute a natural representation of electromagnetic scattering events. These eigenmodes are orthogonal to each other and are useful to optimise beam properties such as linear and angular momentum transfer to microparticles. This is particularly interesting when designing structured illumination for optical micromanipulation, coherent control, single pixel imaging super resolution microscopy and spectroscopy. This project aims at expanding our initial research looking at the use of optical eigenmodes in the context of single photons and quantum optics. The project has a numerical and a theoretical component that together should enable the results to be applicable to experimentally relevant cases.
Single-molecule spectroscopy of organic semiconducting polymers
Penedo-Esteiro, Dr Carlos - jcp10@st-andrews.ac.uk
Samuel, Prof Ifor - idws@st-andrews.ac.uk

Organic semiconductors based on light-emitting conjugated polymers are attracting considerable interest in semiconductor physics and are emerging as exceptional ‘plastic-like’ materials for optoelectronic applications including displays, lasers and solar cells. We have recently reported the first single-molecule studies regarding the conformation of individual polymer chains in organic solvents commonly used for device fabrication [1 ,2]. Now, in this project, we aim to combine this observation method based on single molecule fluorescence spectroscopy with magnetic tweezers to apply force to the polymer chain. By merging both techniques we will be able to stretch the polymer chain at will and understand in more detail how the conformation of the polymer chain impacts its light-emission properties. The results will help to develop new solution-processing methods that improve device performance. The project is a collaboration between the groups of Prof Ifor Samuel and Dr Carlos Penedo

[1] Dalgarno, Paul A., Christopher A. Traina, J. Carlos Penedo, Guillermo C. Bazan, and Ifor D. W. Samuel. 2013. “Solution-Based Single Molecule Imaging of Surface-Immobilized Conjugated Polymers.” Journal of the American Chemical Society 135 (19): 7187–93.
[2] Tenopala-Carmona, F., S. Fronk, Gui Bazan, Ifor DW Samuel, J. Carlos Penedo. (2018) Real-time observation of conformational switching in single conjugated polymer chains. Sci. Adv. In press

Slow and structured light in nanophotonics
Schulz, Dr Sebastian - sas35@st-andrews.ac.uk

Slow light waveguides have the potential to strongly enhance light matter interactions, leading to efficient non-linear optical processes, optical switches and optical modulators amongst other applications [1]. On a photonic chip slow light is typically realized through Photonic Crystal waveguides or coupled optical resonator waveguides [2], with the speed of light typically between 1/ 10 and 1/100 of the free space value. However, all these realizations suffer from optical scattering from fabrication defects [2-4], leading to optical losses and light localization, limiting the current device performance and rendering physical concepts such as the group velocity meaningless. Yet at the same time optical information can travel through completely opaque materials, implying that the current limit – not using photonic devices in the strong scattering regime - is self-imposed.

In this project you will investigate new slow light waveguide designs, leading to further reductions in the group velocity, while simultaneously reducing the optical losses and scattering. You will address fundamental questions about the behaviour of light and information in scattering media, for example: “At what velocity does information travel through a disordered system and how is this dependent on the disorder level in the system?”. You will investigate the effect of slow light on topics at the forefront of integrated photonics research, for example the use of complex polarization states in integrated optics and how this is affected by the disorder present in real world systems.

You will learn nanofabrication, optical simulation and characterisation techniques and gain a deep understanding of complex physical systems. You will interact with collaborators both in the UK and abroad, giving you the opportunity to visit their laboratories and build your own professional network.

The project will be supervised by Dr. Sebastian Schulz, who will join the department in March 2018. For more details on this topic and for any question regarding the project, please contact Dr. Sebastian Schulz (Sebastian.Schulz@cit.ie).

[1] T. F. Krauss “Why do we need slow light” Nature Photonics 2, p 448-450 (2008). https://www.nature.com/articles/nphoton.2008.139
[2] S. A. Schulz, L. O’Faolain, D. M. Beggs, T. P. White, A. Melloni and T. F. Krauss “Dispersion engineered slow light in photonic crystals: a comparison” Journal of Optics 12, 104004 (2010). http://iopscience.iop.org/article/10.1088/2040-8978/12/10/104004/meta
[3] S. Mazoyer, J. P. Hugonin and P. Lalanne “Disorder-induced Multiple scattering in Photonic-Crystal Waveguides” Physical Review Letters 103, 063903 (2009). https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.103.063903
[4] L. O’Faolain, S. A. Schulz, D. M. Beggs, T. P. White, M. Spasenovic, L. Kuipers, F. Morichetti, A. Melloni, S. Mazoyer, J. P. Hugonin, P. Lalanne and T. F. Krauss “Loss engineered slow light waveguides” Optics Express 18, pp.27627-27638 (2010). https://doi.org/10.1364/OE.18.027627
Sub-millimetre wave synthetic aperture radar (SAR) for high resolution imaging
Robertson, Dr Duncan - dar@st-andrews.ac.uk

This PhD is funded as an EPSRC CASE studentship in conjunction with QinetiQ Ltd.

**You must have UK Residency status to be eligible for this project**

**If you are interested in this PhD please contact Dr Robertson.**


Background
Until recently the use of the region of the RF spectrum termed ‘sub-millimetre wave’ (300 to 1000GHz) has received little attention. It sits between the millimetre wave (30 to 300GHz) and Terahertz (>1000GHz) bands where radar and spectroscopy techniques are well-established. QinetiQ is recognised as a World leader in radar techniques applied to predominantly military and security applications at frequencies up to 94GHz. An internally funded QinetiQ study into low Terahertz applications has identified the region between 100 and 400GHz as suitable for extending QinetiQ’s radar capabilities and opens up new opportunities not feasible at lower frequencies. Currently, QinetiQ has no RF capability above 100GHz, in particular, component technology and facilities to carry out work at these frequencies. QinetiQ has strong capability in signal processing techniques and providing innovative, bespoke radar solutions for challenging radar requirements.

The University of St Andrews is one of 2 universities in the UK with strong radar capabilities at sub-millimetre wave frequencies and has demonstrated radars at 220GHz and 340GHz. The PhD is designed to build on the University’s practical capabilities and experience at frequencies up to 400GHz and on QinetiQ’s knowledge of the military and security domains and experience of synthetic aperture radar (SAR).

Scope of the PhD
Radar at sub-millimetre wave frequencies offers new opportunities by exploiting the high angular and range resolutions to provide detailed coherent imaging in a compact physical envelope. Until recently devices for power generation, receiver elements and antennas have been either experimental or prohibitively expensive and achievable radar performance has been limited by noise figure, power generation, propagation characteristics and manufacturability. Currently the main applications are for short range automotive radar and for concealed weapon and IED detection. QinetiQ has an interest in military and security applications especially for imaging difficult targets.

The PhD is intended to investigate novel techniques to use sub-millimetre wave radar to provide very high resolution, coherent imaging against ‘difficult’ targets. ‘Difficult’ includes targets with low radar cross section, fluctuating targets and targets that are difficult to discriminate against other targets. Specifically, this is likely to include change detection techniques, motion compensation, complex SAR imaging and auto-focusing. The scope is focused on SAR but could include real-beam imaging.

It is envisaged, budget permitting, that a linear, rail-mounted sub-millimetre wave radar system will be constructed to record measurements and to evaluate algorithms developed during the PhD. The PhD shall also explore the limits of range resolution, with bandwidths >10GHz, and how this relates to the capability to discriminate and characterise targets. If necessary for a particular application, polarisation and propagation effects shall be considered.

QinetiQ hopes to increase its understanding of the capabilities of sub-millimetre wave radar and, subject to IP considerations, develop the ideas generated into military and security applications. Here are some examples of the types of application that QinetiQ would be interested in;
• Characterisation of surface texture and features, for example, detecting wear and tear on road and airport runway surfaces
• Detection of targets in a high clutter environment, perhaps through gaps or transparent materials
• Geolocation using SAR and/or multiple sensors
• Imaging to detect variations in surfaces, moisture content, cracks in buildings, vegetation, man-made vs natural features, wave profiling
• Vibrometry for engine vibration, fault detection
• Detecting very slight movements of objects exploiting Doppler
• Mounting a sub-millimetre wave radar on an unmanned air vehicle (UAV)

The majority of the PhD work shall be carried out at The School of Physics and Astronomy at St Andrew’s but a minimum of 3 months in total shall be carried out working with the SAR group at Malvern. Working at Malvern will require security clearance although no information disclosed under the PhD will be classified. The requirement for security clearance means that UK residency is required.

The Development of Ultrafast Laser Systems
Brown, Prof Tom - ctab@st-andrews.ac.uk

Ultrafast laser systems generate short pulses of light which may last on a few femtoseconds (fs.) These lasers are used in a wide range of applications from highly sensitive metrology to the 3D imaging of biological specimens.

In this project, we will continue our develops of ultrafast laser systems based on novel-glass gain media supplied by our partners within the UK. The student will be responsible for the design and operation of new laser systems. We will also use these systems to test advanced new components including saturable absorbers based on e.g. graphene and MoS2 and testing new approaches for dispersion compensation. As the project progresses we will also investigate the development of integrated ultrafast sources combining with other staff in the School of Physics and Astronomy and further afield. The lasers developed will be used in a range of new applications including the development of new techniques in dentistry where we will replace worn out enamel using laser sintered materials.

Students undertaking this project should have an interest in lasers and photonics systems. Experience of work within an advanced photonics laboratory would be advantageous (though not necessary) and students should be prepared to work closely with collaborators around the work to develop the laser systems.

Examples of previous work within the group can be seen at:

A. Choudhary, A.A. Lagatsky, Z.Y. Yang, K.J. Zhou, Q. Wang, R.A. Hogg, K. Pradeesh, E.U. Rafailov, W. Sibbett and C.T.A. Brown, “A diode-pumped 1.5 mu m waveguide laser mode-locked at 6.8 GHz by a quantum dot SESAM”, Laser Physics Letters, 10, Art. No. 105803 (2013)

N.K. Metzger, C.R. Su, T.J. Edwards and C.T.A. Brown, “Algorithm based comparison between the integral method and harmonic analysis of the timing jitter of diode-based and solid-state pulsed laser sources”, Optics Communications, 341, p.7 (2015)

A.D. Anastasiou, S. Strafford, O. Posada-Estefan, C.L. Thomson, S.A. Hussain, T.J. Edwards, M. Malinowski, N. Hondow, N.K. Metzger, C.T.A. Brown, M.N. Routledge, A.P. Brown, M.S. Duggal and A. Jha, “β-pyrophosphate; a potential biomaterial for dental applications”, In Press, Materials Science & Engineering C (2017)


A.A. Lagatsky, Z. Sun, T.S. Kulmala, R.S. Sundaram, S. Milana, F. Torrisi, O.L. Antipov, Y. Lee, J.H. Ahn, C.T.A. Brown, W. Sibbett and A.C. Ferrari, “2 µm solid-state laser mode-locked by single-layer graphene”, Applied Physics Letters, 102, Art. No. 013113 (2013)
Ultrafast spectroscopy of Whispering Gallery Mode Nanolasers
Gather, Prof Malte - mcg6@st-andrews.ac.uk
Schubert, Dr Marcel - ms293@st-andrews.ac.uk

Laser miniaturization has advanced to the point where lasers can be integrated into individual biological cells [1,2]. Enclosed by the cells, these lasers have been proposed as multifunctional light sources that allow to identify and track single cells or to optically sense physiological changes. However, future applications of intracellular lasers in large biological systems require data acquisition and throughput orders of magnitudes above state of the art methods.

To overcome the current limitations in detecting lasing spectra with high temporal and spectral resolution, a novel approach will be developed, tested and implemented into a confocal microscope. The newly designed instrument will then be used to acquire 3D maps of tissue-integrated nanolasers alongside with high resolution microscopy images.
The project offers a unique opportunity to gain knowledge of advanced photonic techniques as well as working with biological model systems. Good knowledge of optics and basic experience with software programming are recommended to drive this project.

For further information please contact Marcel Schubert [ms293@st-andrews.ac.uk] or Malte Gather [mcg6@st-andrews.ac.uk] prior to application.

[1] M. Schubert, A. Steude, P. Liehm, N. M. Kronenberg, M. Karl, E. C. Campbell, S. J. Powis, M. C. Gather, Lasing within Live Cells Containing Intracellular Optical Microresonators for Barcode-Type Cell Tagging and Tracking, Nano Lett. 2015, 15, 5647.

[2] A. H. Fikouras, M. Schubert, M. Karl, J. D. Kumar, S. J. Powis, A. di Falco, M. C. Gather, Non-obstructive intracellular nanolasers, arXiv:1806.03366, 2018.