Guan, YajieBandutunga, ChathuraGray, MalcolmChow, Jong2023-09-149-14 May 2978-1-943580-91-0http://hdl.handle.net/1885/299540We describe a new optical cavity-enhanced spectroscopy technique which uses a polarization analyzed readout for molecular absorption. It has a double-pass cavity configuration which serves as both a spatial as well as frequency mode self-cleaner. We demonstrate a quantum noise-equivalent absorption sensitivity of ~3x10-13 /vHz /cm, with a sample of carbon dioxide gas in a cavity of finesse ~2000.application/pdfen-AU© OSA 2021202110.1364/CLEO_AT.2021.AM4P.52022-07-31