Multiplex, continuous-wave spectroscopic sensing with a swept ringdown cavity and optical heterodyne detection

Abstract

Summary form only given. Cavity ringdown (CRD) absorption spectroscopy with continuous-wave (cw) tunable coherent sources is recognised as a convenient, sensitive and precise way to measure very weak optical absorption spectra. We have recently introduced several innovations in CRD technique, with one or more single-mode tunable diode laser (TDL) sources, a rapidly swept ringdown cavity, and a simple optical heterodyne detected (OHD) approach (based on the dynamics of coherent light reflected from such an active optical cavity).