Advanced Solid State Sources and Applications

PhD Projects for 2009-10

Following recent advances in diode laser pump sources and the development of novel focusing techniques it is now possible to longitudinally-pump fibre lasers and solid-state lasers with both very high power and very high intensity. This relatively new regime of operation has opened up a wealth of new possibilities including the opportunity to study some new and interesting aspects of laser physics, and to develop some novel, high-power solid-state and fibre sources with important applications potential. The Advanced Solid-State Sources group currently has vacancies for new students in the following research areas:

Power-scaling concepts for fibre lasers and amplifiers

This project will investigate novel approaches for scaling the output power from cladding-pumped fibre lasers and amplifiers. The project will involve a detailed study into the physics of fibre devices operated at very high power levels with particular emphasis on identifying methods for controlling beam quality, polarisation and operating wavelength. The project will also involve a detailed investigation of the effects of heat generation in the fibre core and nonlinear processes. Single-core and multi-core fibres with novel inner-cladding geometries and resonator designs in continuous-wave and pulsed modes of operation will be studied. One of the main aims of this work will be to develop a strategy for power-scaling of fibre lasers and amplifiers. The final stage of this project is likely to involve an investigation into the use of various nonlinear frequency conversion techniques to extend high power operation to other useful wavelengths regimes.

Cryogenic hybrid fibre-bulk lasers

This project will investigate power scaling of lasers by combining the advantages of cladding-pumped fibre and bulk solid-state lasers in the form of a hybrid laser operating at low temperatures.  A particular attraction of this approach is that it offers a route to much higher pulse energies than can be achieved using conventional solid-state laser or fibre laser geometries.  Operation of solid-state lasers at very low temperature is a very attractive way to reduce to thermal effects and has attracted growing interest within the laser community over the last few years.  The use of this approach in combination with a hybrid laser configuration should offer unprecedented levels of performance, but has so far not been explored. The main ambition of our project is to conduct this study with a view to demonstrating high power lasers with unrivalled performance in the eyesafe wavelength regimes around 1.6 and 2 microns. 

High power superfluorescent fibre sources and their applications 

This project will focus primarily on broadband superfluorescent fibre sources operating in cw and pulsed modes at very high average power levels (i.e. ~ 100W and above).  This is an area which so far seems to have been largely overlooked by those working in the area of high power lasers in spite of the fact that there are a huge range of potential applications and some very interesting physics behind these sources.  The project will investigate various superfluorescent source configurations (based on novel double-clad fibre designs) with a view to understanding the relevant physics and establishing a strategy for power scaling and controlling the spectral characteristics.  In addition, we will also investigate some of the applications of these sources including low coherence interferometry and nonlinear frequency conversion schemes for broadband sources. 

Laser induced refrigeration

This project will investigate laser cooling of various rare-earth ion doped materials using novel pumping schemes and very high power fibre pump sources.  Radiation cooling by anti-Stokes fluorescence was first demonstrated in 1995 and has attracted a great deal of interest.  The basic idea is to absorb light (i.e. from a ‘pump’ laser) on the long wavelength (i.e. low energy) side of a material’s absorption spectrum followed by very rapid thermalisation (i.e. re-establishment of thermal equilibrium) and then re-emission of fluorescence at shorter wavelengths (i.e. higher energies) on average.  This allows vibration-free cooling of very small samples of material with a range of potential applications.  However, there are a number of challenges and as a result progress in cooling to low temperatures has been rather slow.  Nevertheless, the potential of this approach is enormous and, in principle, very low temperatures are achievable.  One of the issues is the pump laser.  This should provide high output power, good beam quality and have flexibility in the operating wavelength.  Our plan is to exploit the advantages of a special design of cladding-pumped fibre source with a number of additional novel features (e.g. pumping scheme configuration) to achieve much lower temperatures than have been achieved before via this technique and, hopefully, to explore the physical limits of the approach.  The project will be quite challenging, but will also be very rewarding in the sense that it will open up many new possibilities. 

For a full list of PhD projects available at the ORC click here.