Abstract

Difference frequency generation (DFG) of tunable IR radiation by mixing two high-power single-frequency cw lasers in AgGaS₂ or AgGaSe₂ provides a very attractive tunable-frequency laser source for high-resolution spectroscopy beyond 4 pm. This paper reports on the development of tunable IR laser spectrometer technology in the 4- to 18-μm spectral region that exploits recent progress in the growth technology of IR optical materials and new tunable cw pump sources. The recent commercial availability of AgGaS₂ and AgGaSe₂ crystals with excellent optical transmission characteristics of 0.5–10 μm and 0.9–18 μm, respectively, and long in teraction lengths of ≥40 mm makes it possible to generate tunable cw radiation at the 100-μW level. Experiments are described that use two cw dye/Ti–sapphire lasers covering the range from 590 to 900 nm, and a 45-mm-long AgGaS₂ crystal cut for 90° phase matching. A schematic of the essential components of the difference frequency spectrometer is shown in Fig. 1. Wavelength, linewidths, output power, and temperature characteristics are reported. Precise computer control of wavelength scanning, wavelength calibration, and data acquisition have been implemented, based on both hardware and software techniques developed for color-center and diode laser spectrometers in our laboratory. Software is also available with the Autoscan version of Coherent Model 899-29 dye/Ti-sapphire ring laser)

© 1992 Optical Society of America