Combined wavelength modulation and power amplification strategy for high-sensitivity off-axis integrated cavity output spectroscopy

We present a gas measurement method based on off-axis integrated cavity output spectroscopy (OA-ICOS). Specifically, this method utilized a distributed feedback laser operating in the near-infrared region (1651 nm) to measure methane gas through a combination of wavelength modulation and laser power amplification. Compared with the traditional unamplified OA-ICOS approach, the optical power-amplified wavelength modulation OA-ICOS (WM-OA-ICOS) technique improved the signal-to-noise ratio, measurement accuracy, and detection sensitivity by factors of more than 4.8, 3.7, and 6.4, respectively.