Institute of Photonics
Dedicated to high quality research
in Photonics, the Institute of Photonics is always keen to recruit highly
motivated and academically suitable candidates of research projects leading
to a PhD qualification. Funding for such students is available from a
number of sources.
Established in 1995, the Institute of Photonics is a partnership between
the University of Strathclyde, industry and government. Its objective
is to bridge the gap between university research and industry in the area
of photonics research and development. This is achieved through a portfolio
of collaborative research and development projects which includes strategic
long-term research, industrial contracts, academic:industrial collaborative
research programmes, and consultancy. The Institute’s vision is
built around the following three key priorities:
Research excellence
Research leadership
International collaborations
Mixing the purely academic with the real world requirements of industry,
the Institute’s research activities focus on all-solid-state and
semiconductor light sources, spanning materials, device, and system development,
as well as applications work. Research is organised around four research
teams, detailed below, although significant cross team working is a key
feature of how we work.
Solid-state laser engineering, led by Dr
David Burns
Gallium nitride materials growth, led by
Dr Ian Watson
Semiconductor optoelectronics –
materials and devices, led by Prof Martin Dawson
Applications, led by Prof John Girkin
The Institute provides an excellent research environment with a suite
of dedicated optical laboratories and support infrastructure. In addition
the Institute has it own MOCVD growth reactor and plasma etch tool for
gallium nitride research, located off-campus at the West of Scotland Science
Park about 5 miles to the north-west, and is a collaborator in the Centre
for Biophotonics, located on-campus, which is equipped with four state
of the art multi-photon and confocal microscopes.
The Institute is a self-funded unit within the Faculty of Science, with
close ties to the Department of Physics, where Professor Allister Ferguson,
the Institute’s Technical Director, holds the Chair of Photonics.
Postgraduate students in the Institute of Photonics participate fully
in the postgraduate training programme of the Department of Physics.
In the past year, Institute students have given presentations at international
conferences in San Jose, Long Beach, Moscow and Switzerland, as well as
within the UK. The local IEEE/LEOS chapter holds regular meetings in Scotland
during the academic term with speakers of international renown giving
presentation on a wide range of topics.
Previous students have since found employment in both large and small
companies both in the UK (Agilent) and overseas (Samsung). The atmosphere
within the Institute engenders close collaboration between experienced
post-doctoral staff and PhD students to mutual benefit.
Opportunities exist for research studentships across all areas of the
Institute’s research activities. If you have an interest in postgraduate
study with a strong industrial flavour in a commercially-oriented research
environment, please contact us to discuss further.
For further information on the Institute of Photonics, see our web-site
at www.photonics.ac.uk or telephone
us on 0141-553-4120.
Solid-State Laser Engineering
The Solid-State Laser Engineering Group underpins the
ethos of the Institute of Photonics in that its activities range from
basic laser research through to the design, characterisation and build
of high performance systems to meet commercial and industrial demand.
Close interaction with the other groups within the IoP is crucial in this
process as modern laser systems utilise advanced semiconductor devices
to enhance their functionality, and also these systems are in principle
applications focussed. Collaboration with other university research groups
and industrial partners is also key to the success of this activity.
Since the formation of the Institute of Photonics in 1996, the Solid-State
Laser Group has been involved in ultrafast optical pulse generation using
semiconductor saturable absorbers, design and characterisation of semiconductor
saturable absorbers, power-scaling of picosecond pulse lasers, slab, thin-disc
and quasi-cw lasers (see figure 1), and the build of high performance
systems for industrial use.
Some examples of our commercial laser contract work include:
1. Medusa – a high repetition rate, high-power, Q-switched Nd:YVO4
laser system – this custom system is still in use, and working to
specification, some 4 years after delivery.
2. Aurora – a femtosecond pulse, diode laser pumped Cr3+:LiSAF laser
- initially build for a demonstration at the Royal Society, but now currently
deployed in our applications group as a source of high intensity optical
pulses for non-linear fluorescence microscopy.
3. SG-1 (‘the spudgun’) – currently being built this
high-power, picosecond pulse Nd:YVO4 laser featuring an optical fibre
pulse compressor will be used in a project led by the Agricultural College
to sterilise potatoes!
4. GOPO - a high-energy, nanosecond pulse, 3micrometer OPO system for
chemical analysis
5. GAZDAC – a multi-channel, amplified, digital to analogue converter
controlled by an embedded micro-processor.
More recently we have expanded our research portfolio to include mid-infrared
lasers and devices, and the exploitation of adaptive optics in lasers.
The mid-IR (2-14 micrometer) lasers are an important class as many advanced
applications exist in this spectral region. Gas and pollution sensing,
free-space optical communications (FSO), crime prevention, medical and
military applications all rely on mid-IR optical sources. To date, only
gas lasers (e.g. CO2, CO), cumbersome OPO devices, and a few dubious performance
semiconductor lasers (lead-salt, antimonide, and quantum cascade) have
been available as mid-IR sources. Our work in this area will focus on
two laser types, vibronic Cr2+:chalcogenide lasers, and InGaAsSb VECSELs.
The Cr2+:chalcogenide is underpinning basic research activity whereas
the mid-IR VECSEL work is focussed towards applications in enhanced FSO,
and sensing.
Figure 1. Stabilising the output pulse train from a high-peak power quasi-cw
Nd:YLF laser. Top left – unstabilised output, top right –
corresponding stabilised output, bottom left – detail of pulse train,
bottom right – intensity autocorrelation.
Adaptive optics (AO) have for a long time been synonymous
with advanced astronomical telescopes, and not surprisingly the cost of
such systems have also been astronomical. However, recent advances in
adaptive optic device architecture has led to the possibility of AO techniques
being used in a wide range of low(er) cost applications. The basic property
of any AO is to compensate or correct for any wavefront distortions present
in an optical beam, such as in astronomy where distortion due to atmospheric
turbulence is corrected to yield higher resolution images. Many other
areas in optics and lasers would benefit by the application of AO, e.g.
high quality output beams from lasers having large thermally distorted
gain media, medical imaging through turbid media (i.e. tissue), ground-based
optical communications where turbulence is present, to name just a few.
Our work focuses mainly on the intracavity use of adaptive optics to enhance
the performance and usability of modern laser sources. As mentioned above,
this branch of AO has been driven by new cost-effective AO devices, e.g.
the deformable membrane mirror (see figure 2), however, all the other
components in the control loop require to be addressed before a truly
affordable system can be developed. To this end, our research covers all
areas of laser AO deployment, from software design, to computer interfacing
through to system implementation. This, therefore, is a truly multi-disciplinary
activity requiring and instilling a breadth of experience, which is, more
and more, becoming a strong underlying theme in applied photonics.
Figure 2. Left - Micro-machined deformable membrane mirror. Right –
electrostatic transducer array.
Potential Ph.D Projects
The Solid-State Laser Group welcomes applications on
an ongoing basis from suitably-qualified individuals for projects across
its areas of interest, and we encourage interested parties to get in touch
for an informal visit and discussion. Currently we have two Ph.D students,
one visiting researcher and three post-doctoral research fellows, working
on a range of projects including thin-disc lasers, high-power Nd-lasers,
intra-cavity laser AO and related electronics, and mid-IR laser development.
Gallium Nitride Materials Growth
Introduction
The Institute has its own capability for growing semiconductor structures based on the wide-bandgap semiconductor gallium nitride (GaN) and related alloys. This work is led by Dr Ian Watson, and currently involves two researchers and a PhD student. Each team member combines hands-on growth work with post-growth measurements or processing. Often we must characterise samples by various different techniques to evaluate them fully, and to obtain input for further optimisation of growth conditions. The equipment used for growth is a commercial metal organic chemical vapour deposition (MOCVD) reactor, shown in Fig. 1, located at an off-campus facility.
Fig 1.
This reactor is a sophisticated, computer-controlled system, and one of only five growing similar structures in the UK. A complex growth system is essential to produce GaN-based devices consisting of multiple layers of single crystal, or ‘epitaxial’ material, which must be deposited with exacting compositional and thickness control. An illustration is provided by a simple light-emitting diode (LED) structure shown in Fig. 2.
Fig 2.
Interest in semiconductors from the GaN family is largely motivated by their proven potential for commercial exploitation in light-emitting devices. However, this success has been achieved in spite of an immature scientific understanding of the materials, and unique technological challenges in the production of epitaxial device structures. This situation leaves many opportunities for research oriented towards next-generation devices. The most familiar GaN-based devices in everyday experience are blue and green LEDs, used in applications such as full-colour outdoor displays. The active regions in these are ultra-thin quantum well (QW) layers of the three-component alloy indium gallium nitride (InGaN). Similar LEDs can be made emitting from the yellow visible to near-UV region, and can also excite white light emission from suitable phosphor materials. This latter capability provides a route to long-life, high-efficiency lamps for room and vehicle lighting. Other photonic device applications of GaN-based structures include ultraviolet detectors, which generally use the alloy aluminium gallium nitride (AlGaN).
The research topics addressed in GaN MOCVD at the Institute support work on advanced light-emitting device concepts, much of which is pursued in collaboration with the Department of Physics. General themes include structures emitting in a surface-normal geometry, and fabrication of resonant cavities using oxide-based multilayer mirrors, known as distributed Bragg reflectors (DBRs). Characterisation of material grown in the reactor also benefits greatly from collaborations with colleagues from Physics, who have a particular expertise in spectroscopy of InGaN, in addition to various external collaborations.
Specific themes in MOCVD growth to date can be summarised as follows:
GaN Growth Optimisation on Sapphire
A major challenge in GaN technology is the high cost and limited availability of bulk GaN substrates. For photonic device applications, most GaN structures are grown on sapphire (single-crystal aluminium oxide) substrates, which have a substantial mismatch in interatomic spacing with the GaN itself. To grow defect-free, epitaxial films of GaN on sapphire, specialised multi-step growth initiation techniques have been developed. Our work has paid great attention to optimisation of these early growth stages, as a prerequisite for producing more advanced device structures. Techniques applied include in situ reflectometry, which provides real-time information on the microstructure of the growing film, and post-growth characterisation using atomic force microscopy (AFM) and X-ray diffraction. A counter-intuitive feature of optimised GaN growth conditions is that the films are microscopically rough in the early growth stages, as illustrated in the AFM image Fig. 3.
Fig 3.
Growth and characterisation of InGaN Structures
GaN-based LEDs depend on InGaN QW layers, typically 2-3 nm in thickness, as their active regions. The emission wavelength can be tuned either by adjusting the indium content, up to a practical maximum In:Ga ratio of ~1:2, or the well thickness. It is often convenient to study the light emission properties of InGaN QWs under UV laser excitation, a technique termed photoluminescence (PL) spectroscopy. We have demonstrated PL emission from our samples over the full visible spectrum, and even into the near-IR. In recent collaborative work, we have addressed the challenge of simultaneously measuring layer thicknesses and indium contents in actual QW structures. However, we have also made extensive use of a traditional approach to studying InGaN, involving growth of thick (50-300 nm) InGaN epitaxial layers. These are amenable to several characterisation techniques, including electron probe microanalysis (EPMA) and optical absorption measurements, which cannot be applied to thinner QWs.
Epitaxial Lateral Overgrowth (ELOG)
This technique is a two-stage growth process used to obtain GaN template layers with regions of very high structural quality, as required for laser devices. A schematic of a simple process is shown in Fig. 4. ELOG begins as selective growth, during which GaN nucleates only on exposed GaN seed surfaces between mask stripes. The high-quality GaN then grows laterally over these mask stripes, where it is unaffected by threading dislocations in the GaN seed layer. Our work on ELOG has applied in situ reflectometry and various imaging techniques to elucidate mechanisms of conventional ELOG, involving thin silicon oxide mask layers. However, we are also developing advanced ELOG processes to grow device structures over functional masks, including oxide DBRs. Work on these advanced embodiments of ELOG requires complex processing of the GaN seed layer and depends on skills developed by the Institute’s GaN device and processing team.
Fig 4.
Development of Doped Material and Device Structures
Electrical-injection light-emitting devices require growth of GaN layers with controlled n- and p-type conductivity. The conventional dopants are silicon for n-GaN, and magnesium for p-GaN. Recent work has emphasised growth of doping calibration structures, to assist in the optimisation of conventional LEDs and more advanced emitter structures. Novel aspects of our research include the use of a non-hazardous, liquid silicon source for n-doping in a collaborative project with Epichem Ltd., and application of the EPMA instrument in the Physics Department to characterise magnesium dopant concentrations. The molecular structure of the novel silicon dopant ditertiarybutylsilane is illustrated in Fig. 5. Final evaluation of the quality of doped material depends upon Hall measurements, which indicate the carrier level and mobility, and transmission line measurements, which provide information on contact resistances directly relevant to devices.
Fig 5.
Projects
Advanced ELOG and Area-Selective Growth
Our work on ELOG has established a unique combination of processing and characterisation experience, which can now be applied to more sophisticated variants of the process. Two topics in ELOG using conventional mask materials are now ripe for development, in addition to further optimisation of overgrowth of functional masks. Firstly, growth under ELOG conditions can be stopped at an early stage, leaving non-coalesced GaN ridge or pyramid structures, depending on the detailed geometry of apertures in the mask. These structures have applications in their own right, for example as field-emitter tips, but also can act as templates for growth of InGaN quantum wires and quantum dots. Secondly, there are many opportunities for improving ELOG processes intended to produce planar GaN templates for growth of conventional device structures. These all depend on adjusting conditions one or more times during the overgrowth process. Benefits include faster production of a coalesced, planar structure, and a reduction in the number of residual dislocations reaching the surface of the GaN template. A student working on this project will gain experience of seed layer processing, ELOG runs in the MOCVD reactor, and post-growth characterisation of samples, with an emphasis on imaging techniques.
Electrical-injection Light-emitting Structures
This project will emphasise growth of LED and
associated calibration structures, but will have strong overlaps with
work on ELOG template layers and resonant-cavity structures. The current
status of our conventional LEDs suggests that improvements can be made
both to the InGaN active regions, and the magnesium-doped p-type GaN.
Research on the active regions will comprise systematic evaluation of
more complex InGaN QW systems, for example, containing AlGaN carrier-confinement
layers. Work on doped GaN will initially address further optimisation
of conventional LED structures, but will have a longer term aim of demonstrating
devices with a tunnel-junction contact scheme. Semiconductor tunnel junctions
(TJs) consist of adjacent thin layers of very highly doped n- and p-type
material, which can convert an electron current into a hole current. They
offer the important prospect of fabricating GaN-based devices in which
all external contacts can be to made low-resistance n-type GaN. However,
as few reports so far exist on GaN TJs, their optimisation is likely to
require extensive growth calibration and modelling work. A student adopting
this project will participate in device fabrication and testing, in addition
to growth work, measurements on calibration structures, and modelling.
Research in Semiconductor Optoelectronics: Materials and Devices
Group III-V compound semiconductors form the basis of the modern optoelectronics industry, enabling semiconductor lasers, light-emitting diodes, photodetectors and other specialised devices for applications in areas as diverse as optical data storage, telecommunications, and displays. So ubiquitous is this technology that the current global market for compound semiconductors is some $10 billion per annum, and development of new materials and devices is a major focus of research in universities and industry around the world.
The Semiconductor Optoelectronics research team in the Institute of Photonics, led by Professor Martin Dawson, is working on the development of advanced materials and devices for a broad range of applications, covering the spectral range from the ultraviolet (~300nm) to the near infrared (>1.5micron). Significant strengths of the team are in applying expertise from solid state laser science (diode pumping, ultrashort pulse generation, single frequency operation) to the traditionally separate field of semiconductor lasers, and in combining novel materials and device concepts with extensive capability to custom design structures for specific applications. Themes of the programme include; nitrogen-containing III-V semiconductors (short and long wavelength), surface-emitting devices in a wide range of formats, and high-power, ultrafast and single-frequency operation of semiconductor lasers.
Our programme is supported by EPSRC, Scottish Enterprise (through the “Proof of Concept” fund), DTI, EC, and a range of industrial contracts. Major tools include extensive capability for spectroscopic measurement, diode-pumping, and telecommunications test and measurement, and semiconductor processing tools including oxidation furnace, dry etching, and epitaxial growth. The latter tools are housed off-campus in the Compound Semiconductor Technologies Facility, a £7.5 million industrial standard foundry, located in North-West Glasgow, where we undertake semiconductor growth, processing and optoelectronic device fabrication. The team collaborates with a wide range of academic and industrial partners both in the UK and abroad. Key collaborations include; University of Glasgow, University of Bristol, Tampere University of Technology (Finland), CEA-LETI (Grenoble), Kamelian, Ltd., and Samsung Advanced Institute of Technology (Korea).
Current research falls into four general categories:
Gallium Nitride Micro-devices and Structures
Gallium nitride semiconductors one of the most important category of III-V materials to emerge in the past few years, and are responsible for the blue and green light-emitting diodes (LEDs) which are widely used in street-level lighting, traffic lights and large-screen outdoor displays. These semiconductors have also allowed the development of blue/violet semiconductor lasers that have important implications for next-generation data storage.
The Institute of Photonics has been involved in gallium nitride research since 1998, and operates one of the main materials’ growth, device processing and fabrication programmes in this area in the UK. This programme is strongly linked to colleagues in the Semiconductor Spectroscopy and Devices Group of the Department of Physics. Further details on materials growth activities are given in the entry by Dr. Ian Watson. The Semiconductor Optoelectronics Team concentrates on device development and processing of these materials. In particular, we utilise approaches based on a special form of dry etching, inductively-coupled plasma etching (ICP), together with laser-based micromachining, to fabricate a range of devices and structures. Of particular interest are microcavities, which consist of controlled-thickness ultra-thin layers of material sandwiched between highly reflecting mirrors, and also two-dimensional micro-LED arrays. The former are of interest for surface-emitting laser devices (VCSELs) and for basic investigations of light-matter interaction. The latter are an important new form of emitter array, where ~1000 micro-emitter elements are present per square millimetre (Fig.1). These devices offer an exciting new technology for microdisplays, optical biochips, sensors, and communications.
Fig.1 Illuminated element in 64 x 64 micro-LED array. Element diameter is 20microns.
GaInNAs/GaAs Structures for 1.3micron Operation
The Institute has been a leading advocate of these so-called “dilute nitride” semiconductors since their introduction in the mid-1990’s. There is a range of dilute, mixed III-N-V semiconductors covering a wide span of wavelengths in the visible and near infrared. Of major importance to date has been GaInNAs alloy (known as “gainass” or “guinness”) which allows a new gallium arsenide based technology for the 1.3 – 1.55micron telecommunications band. GaInNAs is being intensively investigated as the basis of 1.3micron surface-emitting lasers for ultra-high-rate data-communications based on single mode optical fibres.
Our research focuses on novel aspects of GaInNAs work. These consist of study of basic materials parameters and processing effects via spectroscopic techniques, and the development of novel devices. The latter include; semiconductor optical amplifiers, vertical cavity amplifiers (VCSOA’s), semiconductor saturable absorber mirrors (SESAMs) and high-power diode-pumped VCSELs and vertical external cavity surface-emitting semiconductor lasers (VECSELs). We have recently achieved world firsts in GaInNAs VCSOA and SESAM demonstrators, and have achieved the highest power single mode output from a GaInNAs VCSEL (4mW coupled into a single mode fibre).
Vertical External Cavity Surface-emitting Semiconductor Lasers (VECSELs)
Traditional semiconductor diode lasers emit highly astigmatic and highly divergent output beams, and are only available in high power at a very limited set of wavelengths. Furthermore, it is difficult to control precisely their output either spectrally or temporally. VECSELs are a new category of semiconductor laser aimed at addressing these needs. They are diode-pumped, but can be formed from a wide range of semiconductor materials that in principle can cover the blue/violet to the mid-infrared.
The Institute, together with colleagues in the Photonics Group of the Department of Physics, have had one of the main activities internationally in VECSELs since 1997. We have concentrated to date on devices operating in the near-infrared wavelength range from 850nm – 1.3micron, and have demonstrated the first mode-locking and the first single-frequency operation of these devices, together with novel techniques for handling heating effects for power scaling to Watt-level output. Programmes to increase the power and functionality of these devices and to extend their spectral coverage further into the infrared and to the red and blue/green are currently underway.
Laser Mode-locking using Semiconductor Mirror Structures
The main technique for generating pulses of picosecond (10-12s) and femtosecond (10-15s) duration from lasers is known as “mode-locking”. Various methods of mode-locking have been applied to a wide range of lasers since the early 1960’s for applications including; communications, materials processing, nonlinear optics, and spectroscopy. In recent years, the most important categories of mode-locked laser have been the diode-pumped solid-state laser and semiconductor lasers. Dr. David Burns’s team within the Institute focusses on mode-locking of solid state lasers using semiconductor saturable absorber mirror structures (SESAMs) and in this activity they are supported by the structure design and characterisation expertise of the semiconductor optoelectronics group.
Recent areas of interest have included multi-Watt mode-locked operation of 1micron wavelength lasers using InGaAs/AlGaAs SESAMs, and extension of SESAM technology to the important wavelength ~1.3micron using GaInNAs-based SESAMs.
Potential Ph.D Projects
The team welcomes applications on an ongoing basis
from suitably-qualified individuals for projects across its areas of interest,
and we encourage interested parties to get in touch for an informal visit
and discussion. Currently we have six Ph.D students, working on projects
including VECSELs, micro-LEDs, device and materials processing, novel
amplifier development and characterisation. Typically, these projects
are industrially sponsored, or involve close interaction with an industrial
organisation, allowing the students to gain perspective both on academic
research and on industrial research needs.
Applications Research in the Institute of Photonics
The main focus of the research team lead by Dr Girkin
is in the application of novel light sources and optical techniques to
solve a wide range of challenges. This frequently involves developing
a deep understanding of the physics behind a problem before selecting
the most suitable optical technique so that an optimal and practical solution
can be found. The light source is often a key element in such work and
technology advances in the development of solid-state light sources are
providing enhanced system performance coupled with improved reliability
and compact, low maintenance packages. One important aspect to the approach
is to liase very closely with the final user and also with groups both
inside and outside the University who are developing novel sources. Frequently
the work thus develops in a highly multidisciplinary manner.
Much of the current work is linked to biological applications both in
a clinical and research laboratory setting. The team has a close relationship
with the Centre for Biophotonics which was created by Dr Girkin, Professor
Allister Ferguson and Professor Alison Gurney (Department of Physiology
and Pharmacology). In this £2,000k project the new centre has been
established to exploit modern optical techniques for biomedical research,
with the initial focus being on multiphoton imaging. Working closely with
the biologists ensures that the correct optical techniques are developed
for their specific applications.
The manner in which the team undertakes it research can be seen in the
range of projects currently underway.
Bio-Medical Imaging Using Ultra-Fast Lasers
The use of femtosecond pulsed lasers for imaging is a rapidly growing field of research and practical application. Using mode-locked lasers with pulse lengths around 100fs and average powers as low as 20mW, two photon absorption effects can be observed in fluorescent materials. The effect is localised in space and hence by scanning the laser across the sample an "optical slice" can be imaged. With the near infrared wavelength of the excitation source the technique has the ability to penetrate more deeply into samples (reduced scattering) and with less harmful effects that the blue or ultra-violet light normally used in imaging techniques. In addition we are also developing the technique for the inspection of optical semiconductors where either the two photon induced fluorescence is examined or the two photon induced electrical current is measured rather than a fluorescence signal.
Fig 1. Two photon image sections through an intact, living, blood vessel stained with DAPI (green), which selectively labels nuclei (Sample prepared by Karen McCloskey Centre for Biophotonics)
Although the multiphoton technique does enable biological researchers to image more deeply and with less damage to the sample optical limits are frequently imposed by the sample. The team is therefore investigating techniques to try and overcome these limitations including the use of adaptive optical elements, originally developed for ground based astronomers, to reduce the optical distortions introduced by the sample. In addition novel techniques are being explored for delivering the light more deeply into the sample using miniature optical elements. The aim is to improve on work already undertaken developing a system to monitor drug uptake. Here the drug has been tagged with a fluorescent marker and the diffusion through the cheek has been monitored in real time.
Fig 2. Multi-photon image of a guinea-pig bladder interstitial cell labelled with actin (green) and DAPI (blue). The image is a reconstruction of a series of optical sections
The multiphoton technique is also being applied to macroscopic samples. In a joint project with the Glasgow Dental School funded by the EPSRC what we believe are the world's first two photon macroscopic images of teeth have been obtained. These images distinguish between healthy tissue and early carious lesions in an attempt to develop an early diagnostic technique for dental disease. If detected early enough the dentist may not need to resort to drilling and filling but can use high doses of fluoride to replace the lost mineral. In an allied project a novel fibre optic system is being developed to assist in the detection of dental problems and in the longer term it is hoped to extend the technique to other areas of disease detection.
Fig 3. 3D reconstruction of a multiphoton image of a tooth showing early stage dental disease
Work is also underway investigating alternative ultra-short
pulse laser systems. This work builds very closely on the expertise of
other groups within the Institute and Department of Physics in both optical
semiconductor design and ultra-short pulse laser systems. This expertise
is being linked with the desire to build practical, potentially low cost
and easy to operate sources. In addition a number of non-linear techniques
are being explored to broaden the range of wavelengths that can be obtained
from a single ultra-short pulse laser.
Other Solid Sate Light Sources and Micro-LED Arrays
Building on expertise in InGaN LEDs and micro LED arrays
the Institute is pioneering their application in a range of areas. The
UV, blue, green light emitted by these devices is of particular interest
in certain chemical processes and medical applications. Instruments have
been developed that can replace expensive, bulky and hot halogen light
sources with devices that can easily be powered from a battery. One potential
area being explored is the use in ophthalmic imaging devices and additional
as novel sources for conventional fluorescence microscopy.
The application of micro-LED arrays (developed by other groups within
the Institute) is also a new area of interest. Using these devices work
is underway to develop novel DNA screening devices. With the completion
of the human genome project in the last year the target is now to use
this vast mass of data for medical purposes. With the micro-LED arrays
we have a potential route to developing screening assays for a range of
diseases based upon DNA recognition and protein chemistry. The work brings
together items from a number of disciplines including flurophores chemistry,
micro-fluidics, cell growth and DNA synthesis and links chemistry, physiology
and pharmacology and the Institute of Photonics.
Potential PhD Projects
In projects linked with both Glasgow and Dundee Dental schools further work is underway to develop novel techniques for dental diagnosis. A range of novel optical probes are under consideration to included both the ability to take optical sections of teeth and also spectroscopic measurements to determine the health, or otherwise of the sample. In addition erosion of enamel due to acid based drinks is a growing problem and instrumentation is being developed to help quantify the effect in vivo.
In a separate but related project there is the
opportunity to develop a probe suitable for obtaining multiphoton images
from deep within a tissue sample. The probe will be aimed in the long
term for internal diagnostics using the multiphoton technique for a range
of diseases from cancer to heart disease and will integrate adaptive optics,
micro-optical techniques and novel methods of ultra-short pulse compression/dispersion
compensation.
