Abstract

Difference frequency generation was first used for molecular spectroscopy by Pine¹ using an argon ion laser as the fixed frequency source and a tunable dye laser feeding a lithium niobate crystal. It generated 2.2 to 4.2 micron smoothly tunable cw infrared with a resolution of 15 MHz and was demonstrated by detecting the absorption lines of water vapor, ammonia, methane, and nitrous oxide. We² and other colleagues³ have recently utilized the smoothly and continuously tunable advantages of Pine’s cw system with the modification of replacing the bulky and inefficient drive lasers with convenient room-temperature near-infrared diode lasers. This combination permits the design of portable trace-gas species detection systems without the use of cryogenically cooled lead salt lasers.

© 1996 Optical Society of America