Frequency-locking and threshold current-lowering effects of a quantum cascade laser and an application in gas detection field*

In this paper, the frequency-locking and threshold current-lowering effects of a quantum cascade laser are studied and achieved. Combined with cavity-enhanced absorption spectroscopy, the noninvasive detection of H2 with a prepared concentration of 500 ppm in multiple dissolved gases is performed and evaluated. The high frequency selectivity of 0.0051 cm−1 at an acquisition time of 1 s allows the sensitive detection of the (1-0) S(1) band of H2 with a high accuracy of (96.53±0.29)% and shows that the detection limit to an absorption line of 4712.9046 cm−1 is approximately (17.26±0.63) ppm at an atmospheric pressure and a temperature of 20 °C.