The University of Sydney carries research in areas not relating to communications or sensing. One particular area is high power fibre lasers with an emphasis on mid-infrared light generation. The fibre lasers are pumped using the diode lasers and the well-known cladding pumping technique. Diode lasers are efficient sources of high power radiation and with suitable beam shaping technology; the output can be easily launched into the cladding of a suitably designed fibre. Diode-cladding-pumped fibre lasers provide very high output power at very high electrical-to-optical efficiencies. These lasers are also compact and have a long operational lifetime. Our main area of interest with respect to cladding-pumped fibre lasers is the development of fibre lasers that operate in the range 1.9-2.1 um with high power and high efficiency.
Another important area of research is to direct the output from high power fibre lasers into long lengths of standard and non-standard low loss optical fibre. The Raman fibre laser uses the non-linearity associated with transparent dielectrics known as Raman scattering to shift to lower frequencies an intense pump beam that is launched into the core of the fibre. A double-clad Yb3+-doped silica fibre laser is generally used as the pump source for these systems; however, we also use the diode-cladding-pumped Nd3+-doped silica fibre laser for pumping Raman fibre lasers. Both of these lasers operate at a wavelength of approximately 1 um. The Raman fibre laser cavity is relatively long (~500 m) and fibre Bragg gratings, which are placed at each end of the fibre, allow the intracavity Stokes fields to resonate. Raman fibre lasers can offer high power laser radiation practically anywhere between 1 and 2 um. We are studying the physics of these lasers and also use these lasers as pump sources for other fibre lasers.