Direct frequency comb cavity ringdown spectroscopy: Enhancing sensitivity and precision

We present a novel approach to cavity ringdown spectroscopy utilizing an optical frequency comb as the direct probe of the Fabry–Pérot cavity, coupled with a time-resolved Fourier transform spectrometer for parallel retrieval of ringdown events. Our method achieves a high spectral resolution over a broad range, enabling precision measurements of cavity losses and absorption line shapes with enhanced sensitivity. A critical advancement involves a stabilization technique ensuring complete extinction of comb light without compromising cavity stabilization. We demonstrate the capabilities of our system through precision spectroscopy of carbon monoxide rovibrational transitions perturbed by argon.