Application of diode-laser-pumped difference-frequency generation to spectroscopic trace gas detection in the atmosphere.

摘要

The application of diode-laser-pumped tunable IR sources to trace gas detection in air is discussed. The design and technology issues of CW tunable mid-infrared difference-frequency generation are addressed. Feasibility experiments are reported in which the detection of CH{dollar}sb4{dollar}, and CO was performed at low pressure and in air using two laser sources near 3.2 {dollar}mu{dollar}m, and 4.7 {dollar}mu{dollar}m, respectively. They were based on difference-frequency mixing in AgGaS{dollar}sb2{dollar} at room temperature. Pump sources used were a diode-pumped Nd:YAG laser at 1064 nm, a laser diode at 693 nm, and a tunable fiber-coupled Ti:Sapphire laser near 795 nm, and 813 nm. Detection limits of 2.4 ppb*m/{dollar}rmsqrt{lcub}Hz{rcub}{dollar} for CO, and 9.0 ppb*m/{dollar}rmsqrt{lcub}Hz{rcub}{dollar} for CH{dollar}sb4{dollar} in air are estimated for 0.1 {dollar}mu{dollar}W of IR probe power based upon the performance of the sources and detector.