Fibre lasers for near-IR gas spectroscopy

We discuss the potential advantages of fibre lasers as sources for gas sensors in the near infrared. A number of challenges need to be met, particularly in regard to stable timing, application of high sensitivity detection techniques and operation over an extended range of wavelength. Conventional loop cavities suffer from instabilities due to mode hopping and polarisation drift. Some of these problems may be addressed through an alternative configuration using a short, polarisation-maintaining cavity and a Faraday rotator mirror (the sigma fibre laser). Initial experiments conducted on the sigma fibre laser have investigated the gain that can be achieved through double pass operation as compared with the prediction of a theoretical model which takes into account the effects of amplified spontaneous emission. Several fibre laser designs are proposed for potential application to gas spectroscopy systems