EXTERNAL-CAVITY DIFFERENCE-FREQUENCY SOURCE NEAR 3.2-MU-M, BASED ON COMBINING A TUNABLE DIODE-LASER WITH A DIODE-PUMPED ND-YAG LASER IN AGGAS2

AgGaS2 has been used to generate more than 2 mu W of cw mid-infrared r adiation near 3.2 mu m by difference-frequency mixing of the outputs o f an extended-cavity diode laser near 795 nm (pump wave) an a compact diode-pumped Nd:YAG laser at 1064 nm (signal wave). An external ring e nhancement cavity was used to build up the signal power inside the non linear crystal by as much as 14.5 times. The novel mid-infrared source incorporating a single diode laser could be angle-tuned from 3.155 to 3.423 mu m (from 3170 to 2921 cm(-1)). This system was used to detect the Doppler-broadened fundamental upsilon(3)-asymmetric stretch vibra tion of methane (CH4) by both direct and wavelength-modulation absorpt ion spectroscopy.