Development of an automated diode-laser-based multicomponent gas sensor

摘要

The implementation and application of a portable fiber-coupled trace-gas sensor for the detection of several trace gases, including CO_(2), CH_(4), and H_(2)CO, are reported. This particular sensor is based on a cw fiber-amplified near-infrared (distributed Bragg reflector) diode laser and an external cavity diode laser that are frequency converted in a periodically poled lithium niobate crystal to the mid-IR spectroscopic fingerprint region (3.3-4.4 μm). A continuous absorption spectrum of CH_(4) and H_(2)CO from 3.37 to 3.70 μm with a spectral resolution of 40 MHz (～0.0013 cm~(-1)) demonstrated the spectral performance that can be achieved by means of automated wavelength tuning and phase matching with stepper motor control. Autonomous long-term detection of ambient CO_(2) and CH_(4) over a 3- and 7-day period was also demonstrated.