Polarization impedance measurement cavity enhanced laser absorption spectroscopy

We present a theoretical overview and experimental demonstration of a continuous-wave, cavity-enhanced optical absorption spectrometry method to detect molecular gas. This technique utilizes the two non-degenerate polarization modes of a birefringent cavity to obtain a zero background readout of the infra-cavity absorption. We use a double-pass equilateral triangle optical cavity design with additional feed-forward frequency noise correction to measure the R14e absorption line in the 30012 <- 00001 band of CO2 at 1572.655 nm. We demonstrate a shot noise equivalent absorption of 3 x 10(-13) cm(-1) Hz(-1/2). (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

This study presents a continuous-wave, cavity-enhanced optical absorption spectrometry method for detecting molecular gas, utilizing the two non-degenerate polarization modes of a birefringent cavity to achieve zero background readout of infra-cavity absorption. The experimental demonstration showed a shot noise equivalent absorption of 3 x 10(-13) cm(-1) Hz(-1/2) for measuring the R14e absorption line of CO2 at 1572.655 nm.