A CW AGGAS2 DIFFERENCE-FREQUENCY SPECTROMETER WITH DIODE-LASERS AS PUMP SOURCES

A tunable high resolution cw difference frequency spectrometer applyin g the non-linear crystal AgGaS2 and two diode lasers as pump sources a nd experiments with this setup are presented. In contrast to the major ity of known applications of the difference frequency mixing with soli d state or gas lasers, we apply two single mode diode lasers with emis sion wavelengths of 690 nm and 805 nm, respectively. By fixing the emi ssion wavelength of one diode laser and tuning the wavelength of the s econd laser, by changing temperature or excitation current, we can cov er typically 0.87 cm(-1) (FWHM) in good agreement with recently publis hed data and theory. With an input power of 20 mW and 6 mW we achieved an output power in the nW-range. To demonstrate the capabilities of t he spectrometer we scanned CO and OCS absorption lines near 2107 cm(-1 ). From these experiments we deduce an overall signal-to-noise ratio o f 1000 : 1 and a spectral resolution better than 30 MHz. With such par ameters a trace gas detection of CO at sub-ppm level will be possible.