Applications of Fibre Amplifiers and Lasers in Spectroscopy

Applications of near-IR fibre amplifiers and fibre lasers in gas spectroscopy are reviewed. Examples are given where fibre amplifiers may be employed to boost the optical power, for example, in photoacoustic spectroscopy or when splitting a single laser output over multiple fibre optic paths in tomographic imaging. The use of mode-locked fibre lasers for the generation of high-performance frequency combs is discussed and examples given of the state-of-the-art in compact, field-deployable erbium fibre laser combs. The method of dual comb spectroscopy is explained and illustrated with applications in the monitoring of atmospheric trace gases, pollution and exhaust emissions. Several techniques are considered for enhancing sensitivity by means of a high-finesse fibre laser cavity, such as by fibre ring-down spectroscopy or through use of the amplified spontaneous emission present within the laser cavity. Intra-cavity laser absorption spectroscopy, where the fibre laser’s spectral distribution is monitored during the transient period, is discussed in detail with examples given of its potential application for the simultaneous measurement of several gas species in various environments.