Optical feedback linear cavity enhanced absorption spectroscopy

A simple and universal technique for performing optical feedback cavity enhanced absorption spectroscopy with a linear Fabry-Perot cavity is presented. We demonstrate through both theoretical analysis and experiment that a diode laser can be sequentially stabilized to a series of cavity modes without any influence from the direct reflection if the feedback phase is appropriately controlled. With robust handling of the feedback phase and help from balanced detection, a detection limit of 1.3 x 10(-9) cm(-1) was achieved in an integration time of 30 s. The spectrometer performance enabled precision monitoring of atmospheric methane (CH4) concentrations over a time period of 72 h. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

The study presents a simple and universal technique for optical feedback cavity enhanced absorption spectroscopy using a linear Fabry-Perot cavity. By appropriately controlling the feedback phase, a diode laser can be stabilized to cavity modes without interference from direct reflection. With robust handling of the feedback phase and balanced detection, an impressive detection limit of 1.3 x 10(-9) cm(-1) was achieved within a short 30-second integration time, enabling precise monitoring of atmospheric methane concentrations over a 72-hour period.