Diode pumped, solid-state lasers

 Microchip lasers are miniature diode-pumped, solid-state lasers. The laser crystal and frequency doubling crystal are sandwiched together with the diode pump laser in a quasi-monolithic construction only a few millimetres long. Research in our laboratories has led to the licensing and launch of a novel commercial product which has received a number of international design awards.   Information from the microchip laser group.
Principal Contact: Bruce Sinclair

 Solid-state vibronic lasers can be made efficient and compact by using diode-pumped solid state lasers as the pump source. Work in our laboratory has resulted in sources with high mean power, high spectral purity and wide tunability.
Principal Contacts: Malcolm Dunn, Majid Ebrahimzadeh

 Optical parametric oscillators use nonlinear optical crystals to convert the output from a conventional laser into two new frequency bands. This is effective in providing widely tunable, multicolour coherent sources. Our research uniquely covers continuous-wave and nanosecond, picosecond/femtosecond pulse devices.  Information from the groups on cw-opos or ultrashort pulse opos.
Principal Contacts: Malcolm Dunn, Majid Ebrahimzadeh

Semiconductor Nonlinear Optics aims to extend the concepts of nonlinear frequency conversion to GaAs semiconductor heterostructures, by the use of  novel phase-matching techniques. This will provide coherent light throughout the infrared. These devices have inherently high efficiency and practical output powers, and offer the potential for incorporation into future generations of integrated phtonic networks for applications in wavelength division multiplexing (WDM), spectroscopy, gas sensing, frequency synthesis, and quantum optics.  Information from the semiconductor nonlinear optics group.
Principal contact: Majid Ebrahimzadeh

 Ultrashort-pulse lasers are now used for a wide variety of scientific and technological applications. The rapid growth of activity in these fields of ultrafast science and technology can be traced to the research breakthrough at the Univeristy of St Andrews where Wilson Sibbett's group first reported the discovery of the "Kerr-Lens Modelocking" technique. This extensively used methodology forms the basis of most commercial femtosecond laser systems. On-going work includes the further development of diode-laser-pumped femtosecond lasers as well as the use of optical parametric oscillators to produce femtosecond pulses that are tunable into the mid-infrared region (7um); the development and frequency conversion of ultrafast semiconductor lasers; ultrashort pulse characterisation and the development of ultracompact and ultra-high-repetition rate lasers for datacomms and biomedical applications.  Information from Wilson Sibbett's Group
Principal Contacts: Wilson Sibbett, Tom Brown

 Picosecond and Femtosecond OPOs  Nonlinear frequency conversion of ultrashort pulses into the near- and mid-infrared is achieved using optical parametric oscillators based on novel birefringent and quasi-phase-matched materials. Applications include semiconductor spectroscopy, imaging, multiphoton microscopy, photochemistry, and optical communications. More information from Majid Ebrahimzadeh's Group.
Principal Contact: Majid Ebrahimzadeh

Ultrafast Photonics Collaboration - This multi-university collaborative project is led from St Andrews.  It is exploring the optical physics that may be used in future data networks.  Information from the Collaboration directly.

 Underwater vision systems for pipeline inspection will benefit from new laser sources developed in our laboratories. In conjunction with an industrial consortium, through the ELVIS project, we developed microchip laser technology to form part of an optical range-finding/imaging system.
Principal Contact: Bruce Sinclair

"Eye-safe" lasers with a wavelength of two micrometres are being developed for use in remote sensing of air speed, as part of an industrial collaboration supported by the DTI.
Principal Contact: Bruce Sinclair

 Optical Profilometry is used for the inspection of distant, inaccessible or delicate surfaces. At St Andrews a new concept is being developed that involves a measurement of the Stokes polarisation parameters enabling the unambiguous determination of the depth of every pixel element in the field of view of the instrument.
Principal Contacts: Miles Padgett (now at Glasgow University), Wilson Sibbett

 Medical imaging is an area where researchers within St Andrews are working in close collaboration with the department of surgery at Ninewells Hospital, Dundee. The existing project concerns the use of novel light sources and dedicated image processing techniques for early identification of cancer of the oesophagus.
Principal Contacts: Wilson Sibbett, Miles Padgett (now at Glasgow University)

 Commercialisation of its technology is an activity that St Andrews University regards as extremely important. Within optical sources and instrumentation, a number of laser based products have been licensed to Edinburgh Instruments, IE Optomech, Uniphase and a spectrometer product to Siemens UK.

Photonics Innovation Centre - a new Centre has been set up within the School to strengthen further the links between our research and end-users.  This centre has its own web pages.

 Atomic coherence effects in photonics arise from quantum interference between different atomic states within the same atom. When subject to intense coherent optical excitation of a particular atomic transition the induced coherence between the states can lead to remarkable effects. For example, by driving one transition it is possible to eliminate the absorption associated with another. This so-called electromagnetically induced transparency opens the possibility for forming inversionless laser systems. Research at St Andrews has shed new light on these phenomena and identified new effects, such as electromagnetically-induced focusing.
Principal Contacts: Malcolm Dunn

 Laguerre-Gaussian laser modes possess a well defined angular momentum of lh/2p per photon (where l is the azimuthal mode index). The angular momentum arises from the azimuthal phase dependence of the mode, and therefore is termed orbital angular momentum. By focusing a Laguerre-Gaussian laser beam onto a microscopic particle, the angular momentum content of the light can be measured by transferring it to an absorbing particle. Other work includes the study of influence of orbital angular momentum in nonlinear optical processes.
Principal Contact:  Kishan Dholakia

Optical tweezers offer a non-invasive method for trapping and manipulating microscopic objects including biological samples. At St Andrews we use novel laser modes for enhanced manipulation of trapped objects. This includes Laguerre-Gaussian laser modes to induce particle rotation in tweezers for applications in optical micromachines. Other work includes a collaboration with Dr Peter Bryant in Biology to study mechanisms of chromosome aberrations using optical tweezers.
Principal Contact: Kishan Dholakia, Wilson Sibbett

 Atom traps offer the physicist the ability to study cold ensembles of atoms isolated from external influences. When combined with laser cooling, atoms can be trapped and held at temperatures close to absolute zero for long periods. At St Andrews we are studying the use of Laguerre-Gaussian and Bessel light beams for atom guiding. We have also applied these light beams for new studies of Bose-Einstein condensates and 1D quantum gases.
Principal Contact: Kishan Dholakia

 Single-cycle optical pulses represent the limiting case for ultrashort optical pulses. Recent advances in ultrashort-pulse generation techniques, that were pioneered at St Andrews, have opened up exciting new possibilities for the study of light-matter interactions on an unprecedentedly short timescale. The approach being adopted in our research is to exploit parametric frequency-down conversion of ~10 fs pulses from a self-modelocked Ti:sapphire laser such that single-cycle mid-infrared pulses can be generated and used in novel time-domain studies.
Principal Contact: Wilson Sibbett