INTRODUCTION
ANU Photonics comprises an élite vanguard of scientists working in four of the Departments in the Research School of Physical Sciences and Engineering: the Department of Electronic Materials Engineering (EME, Prof. J. Williams); the Laser Physics Centre (LPC, Prof. B. Luther-Davies); the Optical Sciences Centre (OSC, Prof. A. Snyder, FRS) ; and the Plasma Processing Group in the Plasma Research Laboratory (PRL, Dr R. Boswell) and all concerned with futuristic devices for photonics. Themes include: the theory of linear and nonlinear waveguiding; guiding light by light; multi-layer III-V compound semiconductors; organic nonlinear optical materials; and silica thin film composites produced by plasma deposition.
Harold Persing of the Plasma Research Laboratory works on a new Helicon reactor
In all more than 30 academic staff and 15 PhD students are involved with ANU Photonics making the ANU program one of the largest in the field in Australia. Some areas of ANU Photonics are supported by the Australian Photonics Cooperative Research Centre: the local node director being Professor Allan Snyder. The experimental programs at the ANU in general complement those undertaken in the Cooperative Research Centre and are primarily directed towards the development of planar devices in various materials systems including semiconductors; organics (polymers); and silica; towards nonlinear devices for all-optical switching; or active devices for amplification or switching.
DEPARTMENT OF ELECTRONIC MATERIALS ENGINEERING
Photonics research in EME covers a broad range of experimental activities from developing and understanding new optical materials and their properties to the fabrication of planar photonic devices. Currently there are 9 academic staff and 8 PhD students contributing to EME's photonics programs which also involve extensive collaboration with major national and international research laboratories.
Hoe Tan and Andrew Clark are PhD students in Electronic Materials Engineering
In the area of III-V Compound Semiconductors, the programs (led by Dr.C.Jagadish) are mainly focussed towards state-of-the-art active and passive photonic devices. These include Semiconductor Quantum Well Lasers, Ultrafast Photodetectors, Visible Light Modulators and Photonic Integrated Circuits. Most of these programs rely heavily on the epitaxial growth of atomically abrupt multilayered III-V compound semiconductors using an in-house Metal Organic Chemical Vapour Deposition (MOCVD) reactor. It is the growth of novel structures and understanding of intriguing material properties that form the basis for the exciting fundamental physics programs in this area. Examples are:-
i) In a project to develop ultrafast photodetectors, semiconductor materials with very short carrier lifetimes and high carrier mobilities are being produced and studied. To date, carrier lifetimes of ~600 femtoseconds with carrier mobilities around 1000 cm2/V.s have been achieved using a combination of MeV ion implantation and MOCVD growth to produce novel materials.
Renate Egan and C. Jagadish in the optical testing facility in the Department of Electronic Materials Engineering.
ii) In another project, the ability to tune the Quantum Well energy levels by ion beam mixing will enable us to fabricate photonic devices of different functionality on the same semiconductor wafer. Proton implantation and rapid thermal annealing of quantum wells has shown that both red shift and blue shift could be achieved in these structures.
iii) In III-V devices areas, Double Heterostructure (DH) and Graded Refractive Index Separate Confinement Heterostructure (GRINSCH) lasers based on GaAs/AlGaAs system have been successfully grown. Current device programs include the development of novel semiconductor quantum well lasers as pump sources for fibre lasers, which are essential for future optical communications and high density data storage.
iv) As part of a major Australian collaborative project to develop visible fibre devices, the ANU group is developing visible light modulators based on AlGaAs/AlAs multiple quantum wells. At present there is no means of reliably modulating light at the required visible wavelengths of 490 nm and 520 nm. We are designing and growing novel multiple quantum wells which selectively absorb light at these wavelengths (depending on an applied electric field). Fabry-Perot cavities and Bragg mirrors are being developed as part of an integrated modulator. The underlying physics of this visible modulator project is challenging.
Germanium-Silicon epitaxial alloys are new materials which exhibit optical properties more usually associated with direct band-gap compound semiconductors. The production and study of such alloys and their properties is a major EME research program led by Dr. R.G. Elliman. The stability of strain and also crystallization processes in these materials are currently under study. These are important issues for device fabrication. EME has recently demonstrated the improved performance of devices fabricated in germanium-silicon alloys compared to silicon devices.
EME also supports research into the rare-earth doping of semiconductors, lithium niobate and glasses with the aim of developing active planar devices in such materials. The current research involves selective ion implantation of rare-earth species and the optical activation of such species by appropriate annealing and materials processing. Work is also being performed on passive waveguides produced by ion-implantation in a project being undertaken jointly with Telecom Research Laboratories. Some funding is received from Telecom for this study. Finally, a new project is currently being developed in which metallic impurities will be implanted into glasses to form dispersed metal precipitates which are known to exhibit stable non-linear optical behaviour. These projects present challenging solid-state materials problems which must be addressed before the full potential of planar devices can be realised.
LASER PHYSICS CENTRE
The research is concentrated on the development of nonlinear photonic devices for all-optical networks and includes both theory (carried out in collaboration with the Optical Sciences Centre) and experimental work. The experimental programs include research into novel organic materials with large, ultra-fast third order nonlinearity for all-optical switching; the fabrication of waveguide devices using these materials; the development of novel waveguide lasers; and photorefractive waveguide devices. Theory and modelling of various concepts for all-optical switching including the excitation and interaction of spatial solitons underpins the experimental program.
Nonlinear Optical Materials
Our materials research program is focussed on the development of organic materials with large third order optical nonlinearity which are suitable for all-optical switching and can be fabricated into low loss planar waveguides. The program involves materials modelling; chemical synthesis - carried out in cooperation with the Research School of Chemistry (RSC): materials processing to form waveguides; and materials testing where both the nonlinear and linear optical properties are evaluated.
Barry Luther-Davies, Jason Christou, David Fotheringham, Marek Samoc and Anna Samoc are part of the team in the Laser Physics Centre working on the development of organic nonlinear optical materials.
Currently most of our interest is focussed on the polymer poly(p-phenylenevinylene). This material has been studied widely as an interesting organic semiconductor which can be used to make organic transistors and light emitting display screens. As a nonlinear optical material it has exceptional properties and our best material has one of the highest nonresonant ultra-fast nonlinearities ever measured at least in the first telecom window around 800nm.
PPV is a sufficiently promising material to warrant further study and we are now starting a collaborative program with RSC with the aim of obtaining purified material with even better nonlinear optical properties.
In evaluating material for eventual use in Photonics a wide spectrum of measurements must be made. One of the most comprehensive test and measurement facilities existing in any laboratory are being assembled at the ANU for this research. This includes a fs Ti:sapphire laser and in 1995 a fs OPO/OPA system for nonlinear optical measurements across the three telecom windows; a photodeflection spectrometer and other instruments for waveguide loss measurements; etc. Waveguide fabrication involves straightforward spin coating techniques and new equipment for direct UV writing of waveguide structures and pulsed laser deposition of films are planned in the near future.
Photorefractive Waveguide Devices
Photorefractive effects in waveguide have attracted a lot of interest ever since "permanent" changes in silica optical fibres were demonstrated as a route to the creation of in-fibre gratings. In crystalline materials, such as Lithium Niobate, photorefractive gratings can be written and erased dynamically opening up possibilies for a range of new devices. We have recently extended our research into photorefractive effects in bulk materials to the waveguide geometry using Ti in-diffused waveguides formed in Lithium Niobate (provided by RMIT). We have observed a number of novel effects such as the creation of linear or chirped coupling gratings; amplification of guided beams by free space beams; and waveguide optical phase conjugation.
Waveguide Lasers.
We are developing miniature mode-locked and q-switched lasers as sources for optical communications of metrology. One concept involves fabrictaion of nonlinear waveguide structures to act as passive mode-locking elements. Our main interest has been in the use of nonlinear directional couplers and we are now attempting to fabricate prototype devices in the fibre geometry (fibre fabrication is carried out at the Universities of New South Wales and Sydney).
In other programs we are investigating the use of waveguide lasers as low cost sources for consumer applications; or as the basis for compact ranging lasers. This research is partly sponsored by Electro-Optic Systems Pty Ltd of Queanbeyan.
Theory
Projects on guiding light by light; the properties of spatial solitons, are undertaken in collaboration with Optical Sciences Centre.
OPTICAL SCIENCES CENTRE
Light Guiding Light
The concept of guiding and manipulating light by light itself without any intervening fabricated structures has been a passion at the Optical Sciences Centre since 1990 and was featured in the New Scientist, (Vol. 12 January 1991, p. 14.). This concept revolves around the physics of dynamic spatial solitons and is relevant to futuristic all-optical devices. Various theoretical predictions have now been realised in collaboration with the experimental program in the Laser Physics Centre.
Professor Allan Snyder leads work on nonlinear photonics in the Optical Sciences Centre
Unification of Linear and Nonlinear Wave Optics
We have developed a new conceptual approach whereby nonlinear optics is viewed from the perspective of linear physics. This philosophy not only unifies nonlinear waves, but it has also been the crucial inspiration for several discoveries of major significance, including dynamic solitons and the universal stability criterion of nonlinear guided waves.
Nonlinear Dynamics of Multi Component Solitons
Research in this area covers several modern problems in optics: short pulse propagation in birefringent optical fibres, solitary waves in nonlinear couplers, and spatial and temporal vector solitons in nonlinear media, etc. The theory of Hamiltonian dynamical systems with an infinite number of degrees of freedom is applied to describe these type of phenomena and to predict novel effects.
Yijiang Chen and Javid Atai from the Optical Sciences Centre
Nonlinear Waves and Solitons in Higher Dimensions
The aim here is to observe and identify spatial and temporal solitons in experiments, with the higher dimensions effects being analysed in detail. This includes two and three- dimensional spatial (dark, grey and bright) solitons as well as soliton-like objects ("light bullets") in waveguide structures. One of the purposes is to establish a link between realistic physical models and exact integrable equations.
Optically Written Photonic Circuitry
A collaborative program is underway to develop techniques and materials for direct writing of waveguides and passive, active and nonlinear devices for the processing of light in photonic circuitry. A computer-controlled focussed laser beam will be used to irradiate trilayers of optically transparent material containing a doped central region with a high photorefractive response.
Planar Waveguides & Devices
Novel planar optical devices, such as mode combiners, separators and transformers, multiport couplers, multilayered guides, grating assisted devices and integrated-optics interfaces, are being devised for a broad range of applications, including optoelectronic circuitry, telecommunications networks, optical sensing and confocal microscopy. Part of this work is supportrd by Telecom Research Laboratories and by Ericsson Australia Pty Ltd.
John Love is involved in theoretical work relevant to the development of planar waveguides for advanced optical circuitry
Optical Fibres & Devices
Collaborative development of practical application-specific fibres, such as multicore fibres for devices and capillary and evanescent field fibres for optical sensing, as well as optimised fibre devices, including multicore connectors, grating-assisted wavelength demultiplexers and hybrid couplers for confocal microscopy applications.
THE SPACE PLASMA AND PLASMA PROCESSING GROUP OF THE PLASMA RESEARCH LABORATORY
The group conducts research into planar waveguide devices fabricated in materials systems based on silica. Passive devices such as 1:2 and 1:8 splitters are fabricated in house using sophisticated plasma etch and deposition systems. A unique feature of the systems is that all processing can be carried out at low temperature, ie at 30Callowing the integration of sensitive microelectronic circuits (either in silicon or III-V) with these optical waveguide devices. Miniature optical devices such as GRINN lenses can also be constructed. Micro-machining of components is also possible for sensors, switches, detectors, etc.
Antoine Durandet working on a Helicon reactor in the Plasma Research Laboratory
Diagnostic equipment for the films includes single and multiple wavelength ellipsometry and Fourier Transform Infra-red Spectroscopy. Plasma diagnostics include electrical and magnetic probes and fast scanning optical spectrometers.
A new deposition system allows for doped layers of material to be deposited onto 4 inch wafers. At present SiO2 layers are being characterised preliminary to fabricating Ge doped SiO2, allowing direct write of gratings using UV lasers. Rare earth doping can also be carried out to investigate active waveguide devices, e.g. amplifiers and lossless splitters.
The basic physics of the plasma, plasma deposition and thin films is studied to support the fabrication process.
Facilities
ANU Photonics has a very wide range of major facilities to support its research. These include a high energy ion implanter; and MOCVD faciliites for semiconductor fabrication and materials modification. A wide range of processing and characterization equipment equipment such as rapid thermal annealing; photoluminescence; secondary ion mass spectrometry; and Rutherford backscattering spectrometry; supports the research into semiconductors.
A wide range of laser faciltiies for spectroscopy and testing nonlinear optical materials are available in the Laser Physics Centre as well as instruments for characterization of the linear properties of thin film organic waveguides.
The Plasma Research Laboratory has developed its own plasma etching and deposition technology based around the use of a helicon plasma source. These reactors are available commercially. Recently electron beam evaporation has been incorporated into the helicon system vastly improving the range of materials that can be deposited and minimising the need for noxious gases.
These departmental facilities are underpinned by a wide range of ancilliary equipment housed in the Institute of Advanced Studies. Examples are: electron microscopy; ion microprobe analysis; NMR; x-ray diffraction; etc.
Extensive computing facilites are also available with the numerically
intensive work on nonlinear waves benefitting in particular from the ANU VP2200
and CM-5 supercomputers.
STAFF (academic)
Professor Barry Luther-Davies (Director)
Professor John Mitchell
Professor Allan Snyder FRS
Professor Jim Williams
Dr Vsevolod Afanasiev
Dr Nail Akmediev
Dr Adrian Ankiewicz
Dr Rod Boswell
Dr Christine Charles
Dr Yijiang Chen
Dr Antoine Durandet
Dr Renata Egan
Dr Robert Elliman
Dr Nick Hauser
Dr Simon Hewlett
Dr C Jagadish
Dr Yuri Kivshar
Dr François Ladouceur
Dr Rosa Leon
Dr John Love
Dr Jeff McCallum
Dr Andrew Perry
Dr Harold Persing
Dr Mark Ridgway
Dr Tim Thompson
Dr Maneerat Woodruff
Dr Yanjie Wang
Students
Mr Tony Ash
Mr Javid Atai
Mr Daniel Beltrami
Mr Douglas Body
Mr Alexander Buryak
Mr Jason Christou
Mr A Clark
Mr David Fotheringham
Mr Hugo Giordano
Mr Gang Li
Mr Matthew Ma
Mr Robert Michallef
Mr Adrian Sheppard
Ms Victoria Steblina
Mr H Tan
Mr Wenquian Yu
Support Staff
Mr Michael Aggett
Mr Peter Alexander
Mr Joel Anderson
Mr Steven Hyde
Mrs Maryla Krolikowska
Mr Ian McRae
Ms Rebessa Pallavicini
Mrs Andrea Robins
Mr Tom Halstead