Trace Ammonia (NH_3) Sensing using SLED and Multipass Gas Cell for Atmospheric Monitoring Application

摘要

A Super-luminescent diode (SLED) based sensor operating near 1.5 pm employing Direct Absorption Spectroscopy (DAS) as a detection technique for monitoring trace atmospheric Ammonia (NH_3) is reported. The sensor employs a broadband SLED source having a center wavelength at 1.55 μm, and a bandwidth of 40 nm attached with a 35 cm long Multipass cell which provides an optical path length upto 16 mt. The reference spectrum of NH_3 before and after passing 50 ppm of NH_3 in the multipass cell was analyzed and the decrease in the intensity in terms of ADC counts was found to be 21245. Also four absorption peaks of NH_3 near 1550 nm was observed and compared with the theoretically calculated peak absorption values. The minimum detectivity was found to be 38 ppm at 1527.20 nm and 34 ppm at 1531.65 nm transition peak respectively.