Examples of Projects Available in FSM-Optics for 2010.

Below you will find a list of projects that are available for Honours students commencing in 2009. Some of these projects are industry related and thus might attract a small bursary for an Honours student or a top-up for a Ph.D. student. Many of these Honours projects can be expanded to provide a deep and interesting Ph.D. project. After this list you will find another list of projects which for one reason or another fail to make it into the top list. This may be because the project is too limited as a basis for an Honours project, or because I haven't had time to think it through sufficiently (if one of these projects really grabs you then come and see me and we will work it out for you), or because it is already being undertaken by someone else and we would need to do some careful demarcation so you don't end up standing on each others' toes. Anyway, the best advice is always to come and have a chat. You will find a list of the key people involved in each project after the title.

Measuring Boltzmann's constant: Andre, Gar-Wing Truong (PhD) and Eric May (Processing Engineering, UWA)

The SI definition of temperature is based on the triple-point of water. Many researchers would like to redefine temperature so that it is based upon some fundamental microscopic property of nature that is readily available and easy to realise with a high degree of precision. A few years ago we developed just such a process based on precision laser spectroscopy. In recent times a first demonstration of a similar technique was made by another group which shows that it is a very promising approach (Daussy et al, Phys. Rev. Lett. 98, 250801 (2007)). We would like you to implement our technique over the next year. Hopefully, your initial measurements will result in a better measurement of Boltzmann's constant than that presently used for the definition. Into the future, if this technique proves to be as good as we think it can be, then it might result in a new definition of temperature.

Exploring the Photochromic and Photoluminescent behaviour of Coloured Argyle Diamonds: Andre, Clayton and John Chapman of Rio Tinto Diamonds

Pink diamonds owe their colour primarily to a broad absorption centred at 550 nm. It is known that UV exposure will remove this absorption and render a pink diamond brownish or colourless. In addition, this colour change can persist for periods of several months at least. Exposure to white light will restore the initial colour; however, it is also known that some visible wavelengths do not contribute to the restoration or enhancement of the pink colour component. There has been no published document which characterises the photochromic behaviour of pink diamonds. It is believed that the colour arises from an interaction with a defect in the crystal rather than an impurity and that these defects arose during the creation of the diamond. The particular defect that causes the colouration and the strange colour-changing behaviour is not yet identified. Your project will be aimed at identifying the origin of these effects as well as explaining them. You may use techniques (in addition to standard optical spectroscopy of the diamond) such as Raman laser spectroscopy and electron spin resonance. We may need to employ a smart theoretical condensed matter physicist (I can think of at least one local one from the top of my head) to assist us in understanding the behaviour from a microscopic point of view.

Accurate Spectroscopy of Metallic Elements: Andre, Clayton Locke, John McFerran.

Victor Flambaum (Uni of NSW) has been analyzing spectra of quasars in order to test for temporal changes in the values of one of the fundamental constants (the fine structure constant). He has generated some tantalizing evidence that it might have indeed have changed its value over the last 10 billion years. One of the present error sources for his measurements is the lack of high quality measurements of the spectra of many important atoms and ions (see here). In this project you will make highly accurate frequency measurements of some of the elements of interest to this group. In addition, this type of data is useful for atomic physicists to check their theoretical models of the atom.

Spectroscopy (both linear and nonlinear) of vapours stored in the hollow core of photonic crystal optical fibre - with Fetah Benabid of Uni of Bath, Clayton Locke of UWA and Anna Lurie (Ph.D student) and Chris Parrella (PhD).

We have just completed experiments on Rubidium vapor that has been loaded into the hollow core of optical fibre. The fibre allows very strong interaction of the light with the vapour which allows (1) observation of very weak optical transitions, also allows for (2) high levels of nonlinearity in the interaction and (3) potentially allows us to subject the vapour to mechanical forces from the light. The first possibility provides a means by which we can build very compact atomic or molecular clocks - the weak line can also be very spectrally narrow. People are interested in these compact clocks for lots of different applications. The high level of nonlinearity allows one to do a whole lot of interesting things - i.e. very efficient frequency conversion through tripling the wavelength or by using other processes to produce tunable light that is still spectrally narrow. This is interesting because in principle one can create new wavelengths of light. The holy-grail in this work would be to build a fibre that could take continuous radiation from a laser and allow one to shift it to any desired place in the spectrum - including to very short wavelengths (like in the UV or vacuum-UV).

Microsphere and toriodal optical resonators: Andre, Clayton with Warwick Bowen at University of Queensland and Mike Tobar and Eugene Ivanov of FSM.

Some remarkable recent work has been performed on so-called microsphere and micro-toroidal resonators in which radiation is stored in tiny (few tens of microns in diameter) dielectric spheres or toriods. The losses of these resonators are extremely low and therefore can be used a precision tools to stabilize laser frequencies. I have a colleague in Queensland who is willing to make some of these devices for us. There are many things one can do with these devices: (1) stabilize the freqeuncy of lasers - compact optical oscillators and clocks, (2) build accelerometers or vibration sensors or perhaps pressure gauges - sense anything that will change the resonator shape, (3) build sensors for vapours - by filling the space around the resonator with some vapour it is possible to sense changes in frequency of the resonance and hence detect the presence of the gas, (4) exploration of the high optical non-linearity of the interaction of the material with the light. This is a new project and you will be the first to couple light to such devices in our laboratory and undertake the first measurements on their performance.

Laser Cooling of Calcium atoms: Andre and John McFerran.

We are in the process of building an optical clock based on an extremely narrow transition in laser-cooled Calcium atoms. At the moment we make use of an atomic beam on which we are performing high precision non-linear spectroscopy - this is the only Australian optical clock. We need to laser cool these Calcium atoms and then perform spectroscopy on the ultra-cold sample in order to construct a world-class optical clock. The steps to get to his point are as follows: - (1) build a strong source of 423nm radiation - say 30-50mW of light. This is now partially working and should be fully operational in a month's time. (2) Set-up a magneto-optical trap to capture perhaps 1-10 million atoms and cool using this blue source to a temperature of below a few milliKelvin. This would be the first of your jobs. (2) set-up a control and data acquisition system to cool and interrogate the atoms and determine the performance of the laser cooling. This would also be your job. This field is a massive area of investigation internationally as most researchers believe it will provide the conditions for a new generation of clocks with substantially higher levels of performance. This project will give you familiarity with laser-atom interaction, optics, frequency locking and control systems.

Understanding Mode-Locked Lasers - particularly as applied to Optical Frequency Measurement: McFerran, Locke, Luiten.

Over the last few years we have been building devices that allow us to synthesize optical frequencies i.e. we can take a microwave signal and then coherently multiply its frequency by 100,000 times into the optical domain while preserving the phase stability of the original signal. We use femtosecond pulsed lasers combined with highly nonlinear fibre to do this trick. John McFerran was responsible for building these devices and during his absences (typically he has been working at NIST in the USA) we have been trying to use them and find that they are not that user-friendly or reliable. There are a number of things to be done which could make them much much better. I would like to implement these changes e.g. 1) we would like a way of controllably varying the dispersion in the laser cavity in order to change the properties of the emitted pulse train - we have an original idea of how to implement this with Brewster plates driven by remote mounts 2) we want to understand in detail the process by which mode-locking is initiated in the ultra-fast laser. At the moment this is done by hand which results in misalignment and contamination of the mirror surfaces. After recent brilliant work in an Honours project this year we now have a much better experimental understanding of what is going on in these lasers and the system is very close to being self-starting. While doing this however we have uncovered a theoretical mystery and it would be great to further investigate this outcome: the detailed theoretical explanation of how a laser enters a mode-locked state are presently not well understood and this would be part of your project.

Other Projects

Calibration of Anglo-Australian Telescope Spectrographs - for Michael Murphy of Swinburne University of Technology.

Astronomers are very interested in making very high resolution spectroscopic measurements upon light collected by their telescopes. This is both for the purposes of looking for changes in the values of the constants since the early Universe (see above) but also to study in detail the motion of gases at the levels of below a metre per second via Doppler spectroscopy. This pushes the performance of their spectrographs beyond the present ability to calibrate. One proposal is to make use of the frequency comb delivered by the mode-locked lasers to accurately calibrate the spectrographs (Murphy, Mon. Not. R. Astron. Soc. 380, 839–847 (2007)). Unfortunately, to do this with a high degree of accuracy it requires very high repetition rate lasers which are not readily available. You would undertake an optical modification to the laser in order to multiply the repetition rate of the laser by 10 to 100 times so that is can be usefully employed in this application.

High Performance Diode Lasers: Using a high performance narrow band interference filter to stabilize a laser diode rather than a grating

Traditionally laser diodes used in spectroscopy are operated with a diffraction grating external to the diode laser to enable tuning. This diffraction grating is adjusted so that one of the diffracted beams is retro-reflected in to the diode laser and this has the effect of narrowing the spectrum and delivering tuning (by changing the diffraction angle). Recently I have become aware of another method of doing this using narrow band optical filters as the frequency selecting element. We have not tried this out but we have the equipment ready to go. The objective of the project would be to demonstrate that this approach is substantially better for delivering high power and narrow-linewidth light for atomic physics or quantum optics experiments.

Interaction of femtosecond light pulses with cold atoms.

This is a continuation of Milan Maric's project - who finished his Ph.D. in 2008. He has completed a system in which it is possible to launch short pulses of light at laser-cooled Rb atoms. We see modifications in the various state populations of the atom in response to the characteristics of the light. Milan has only just completed a very preliminary understanding of what is going on and there is a great deal of interesting things to do now - figure out what is going on at a deep level. Use different light sources. Use the light to create well defined quantum coherent states. Try out new types of spectroscopy etc etc. There is a only one other group doing this seriously at the moment

An instantaneous method for estimating mirror dispersion

We have been building a device that enables us to make accurate measurements of the dispersion of a flat mirror surface. This is based on white-light interferometry and a CCD camera looking at the reflected beam which has been spectrally dispersed in one direction, and time delayed in the other direction. The resulting interferogram can be used to accurately and instantaneously estimate the dispersion of the mirror surface. One student has worked on this project for six weeks over our holidays and it looks promising but is not working properly as yet. We are using a very cheap CCD camera and home written software. I would like to complete this, improve the camera and software, and give it the ability to measure other things (i.e. spherical mirrors, transmissive materials).

Locking a fibre mode-locked laser to a high finesse cavity (Clayton, Eugene and Andre) and Generating Low-Noise Microwave Signals for Stabilized Mode-Locked Lasers

Clayton Locke has commenced the work to launch ultra-short pulses of light into storage cavities. In order to succeed it will require constructing appropriate locking systems that can calm the natural fluctuations of the pulsed lasers so that they can be efficiently delivered into a storage cavity. There are two ideas revolving around this work for an Honours project : (1) build up extremely intense optical pulses by coherently summing thousands of output pulses from the laser inside the cavity - by this means you can create an extremely intense pulse that can be used to explore non-linear optics at the extreme limit, (2): one can think to control the parameters of the pulsed laser and thereby build a very stable optical and microwave source based around this stable pulsed laser.

Laser Cooling in Photonic Crystals

We are interesting in thinking of ways we can combine laser cooling and photonic crystals so that we can cool atoms within special locations in a photonic crystal. We have developed a theoretical suggestions of how this can happen and are ready to undertake the experiment with your assistance.

Searching for flaws with the current conception of the Universe (Andre, Fred Baynes and Mike Tobar)

We (principally Fred Baynes) are undertaking experiments to search for a variation of the speed of light (inside materials) that might occur with motion of the material or orientation of the material. This is essentially a modern Michelson-Morley experiment inside crystalline materials.

Measurement of Beam Wavefronts.

There are several traditional techniques for generating complete information about the wavefront curvature and beam size of a laser beam using a single measurement. I would like to compare the various techniques and then implement the best in a completely automated and high speed system. You would need to do some data acqusition and imaging processing in real time to complete this objective.