Dial Sounder of Methane Insusceptible to Variable Humidity Based on Broadband Laser Diodes

Abstract

A novel differential absorption lidar method utilizing the spectral and energetic properties of pulsed, high-power, broadband laser diodes for remote sensing of methane is reported. The atmospheric gas content is retrieved using the derived calibration function, integrating multiple resonance lines of the selected CH4/Qyν3 second overtone absorption spectrum matched to a laser mode centred at optimal wavelength. The sensitivity of the lidar is effectively improved by multiplexation of the detected laser radiation in dual spectral channels eliminating the interference of the atmospheric water vapour.