Multi-laser sensor for simultaneous multi-gas measurements using off-axis cavity-enhanced absorption spectroscopy with an opposite two-way configuration

An opposite two-way off-axis cavity-enhanced absorption spectroscopy-based multi-gas sensor is reported. More than two lasers can be employed in the sensor for simultaneous detection of different gas species. An approximately two times improvement in magnitude of the 2 f signal and the signal-to-noise ratio is achieved because the concave spherical mirrors outside each end of the cavity and the narrow bandpass filters before the detectors can act as re-injection mirrors to re-inject the light into the cavity in the scheme. The performance of the sensor is demonstrated by simultaneous measurement of CO 2 and CH 4 in the atmosphere. This Letter highlights a new, to the best of our knowledge, strategy for simultaneous multi-gas measurement in a single integrated cavity by employing as many as four lasers.