Raman Distributed Feedback Fibre Lasers

This proposal is focused on fibre lasers and will develop a new class of compact (centimetre length), narrow-linewidth (kHz and sub-kHz) fibre laser based on fibre Bragg gratings and Raman gain in silica-based fibres, the so-called Raman Distributed Feedback (R-DFB) fibre laser. This type of laser exhibits superior performance to those of standard rare-earth doped DFB fibre lasers in terms of efficiency, coherence length, low noise-level, and wavelength agility, and will allow for unconstrained single-frequency wavelength operation across the full transmission-window of silica. Continuous wave (CW) output power values up to 100mW will be targeted and the work will demonstrate R-DFB lasers in both germanosilicate and phosphosilicate fibres, each of which allows for different levels of Raman frequency shifts, at wavelengths applicable to LIDAR, high-spectral brightness and long coherence length applications incl., nonlinear optics applications, in particular four-wave-mixing (FWM), and spectroscopic sensing incl., trace sensing of targeted molecular species of importance for environmental monitoring. For ease of operation and integration, and for reduced complexity and cost, the work will also demonstrate direct laser diode-pumping of the developed R-DFB lasers. These lasers will help realise an increasingly important unmet need for low noise kHz linewidth sources in several wavelength bands where currently no such sources are available.