Optical-Feedback Cavity-Enhanced Absorption Spectroscopy Using a Short-Cavity Vertical-External-Cavity Surface-Emitting Laser

We report first results on the coupling by optical-feedback of a vertical-external-cavity surface-emitting laser to a high finesse optical cavity to obtain high sensitivity absorption measurements around 2.3 μm. This was possible thanks to a mechanically stiff, short-cavity (0.3 mm) design of the laser cavity allowing broad tuning capabilities together with low frequency noise. With respect to other semiconductor laser sources, we achieved comparable sensitivity (base line noise 9 × 10^-10 cm^-1Hz^-1/2). The laser system has a small footprint and allows a large spectral coverage (about 50 cm^-1).