Spectroscopic applications of QPM devices

Abstract

The development and application of a range of absorption spectrometers, which operate in the 3.2 - 4.6 μm spectral region, are presented. The sensors are based on difference frequency mixing two cw diode lasers in periodically poled LiNbO3 to generate narrow linewidth light (<60 MHz). Ruggedness and increased power is achieved by the use of fiber optics for beam delivery and inline fiber amplifiers. Species detected in air include H2CO, CO, CO2, CH4, H2O, HCl with sensitivities down to the parts-per-billion level with direct absorption detection or <100 ppt using 2-f modulation spectroscopy.