Chow, JongWade, AndrewMow-Lowry, CRabeling, DavidLittler, IanMcClelland, DavidGray, Malcolm B2015-12-10October 259781424453351http://hdl.handle.net/1885/55784We present a new technique for cavity enhanced optical absorption spectrometry, employing a radio-frequency amplitude modulated laser to interrogate an optical cavity. It is capable of sensing molecular absorption at the fundamental laser shot noise limit, and is able to perform quantum noise limited gas sensing at atmospheric pressure. We implement this technique, for the first time, in a free space cavity, and demonstrate that the demodulated error signal can be used to measure losses in a resonator.Keywords: Amplitude-modulated laser; Error signal; Free space; Gas sensing; Laser shots; Molecular absorption; Noise limit; Optical absorption; Optical cavities; Radio frequencies; Amplitude modulation; Atmospheric pressure; Gas absorption; Light absorption; Sensor200910.1109/ICSENS.2009.53983182016-02-24