Cavity-enhanced absorption spectroscopy with a mode-locked diode-pumped vertical external-cavity surface-emitting laser

We present a first demonstration of `mode-lockedʹ cavity-enhanced absorption spectroscopy (ML-CEAS) using a mode-locked diode-pumped, vertical external-cavity, surface-emitting semiconductor laser (DP-VECSEL). This laser, operating around 1.04 μm, was modeloked using a semiconductor saturable absorber mirror (SESAM) and provided an emission spectrum possessing a regular comb of modes with a broad and smooth envelope. Matching this comb with the comb of resonances of a high finesse cavity allowed efficient transmission of the laser spectrum by the cavity. Thanks to the enhancement of absorption by the cavity, on this transmitted spectrum we could observe weak absorption lines by a gas placed inside the cavity.