Application of paired powerful laser diodes for detection and reconnaissance of atmospheric methane

Abstract

Differential absorption lidar (DIAL) feasible to detect methane is developed on a pair of powerful pulsed (10μJ) laser diodes emitting on 1,56μm -1,66μm wavelengths. Methane is a potent greenhouse gas that is responsible for the present enhancement of the greenhouse effect. The spectral range of wavelengths utilized by the laser diodes matches an intensive second overtone of the methane molecule pure of interfering spectra of the other major atmospheric gases. Spectroscopic applications of the powerful laser diodes were generally limited by their broad laser line. Though spectrally unresolved, multiple resonance absorption lines modulate the laser radiation propagating in the atmosphere. The intensity of integral absorption is assessed combining the linestrengths taken from HITRAN database with the laser spectral line. The resultant absorption spectrum is immune to pressure variation, while the dependence on temperature is found to be within 10% error. The reported DIAL technique utilizes the advantage of simple operation within lidar ranges of 0.5- 5km prospective for reconnaissance of atmospheric methane and climatic monitoring.