Methane gas sensor based on a novel dual‐path multipass cell

Abstract We have developed a novel dual‐path multipass cell (DP‐MPC) for trace gas detection. The sealed Herriott cell, measuring 16 × 16 × 41.5 cm, has two input/output coupling holes. By adjusting the mirror position and incident angle of the beam, optical paths of 105 and 37.5 m can be obtained, respectively. To test its performance, we setup a methane (CH 4 ) concentration detection system by combining the DP‐MPC with a 1.65 μm distributed feedback laser and carried out a methane gas detection experiment. The Allan variance analysis showed that the limit of detection for the two optical paths were 6 and 30 ppb, respectively.