Portable fiber-coupled diode-laser-based sensor for multiple trace gas detection

Abstract

Tunable narrowband mid-infrared radiation from 3.25 to 4:4 mm is generated by a compact fiber-coupled, difference-frequency-based spectrosopic source. A 20-mW external cavity diode laser (with a tuning range from 814 to 870 nm) and a 50-mW distributed-Bragg-reflector diode-laser- seeded ytterbium-doped fiber amplifier operating at 1083 nm are difference-frequency mixed in a multi-grating, temperature-controlled periodically poled LiNbO3 crystal. A conversion efficiency of 0:44mW/(W₂cm) (corresponding to a power of ≈3 μW at 3:3 μm) represents the highest conversion efficiency reported for a portable device. Performance characteristics of such a sensor and its application to spectroscopic detection of CO2, N2O, H2CO, HCl, NO2, and CH4 will be reported in this work.