Lightsources employing quasiphasematched (QPM) nonlinear materials have demonstrated unique attributes for chemical sensing in the near- to mid-infrare spectral range (1 - 5 micrometers ). The advent of patterned-growth GaAs allows the first practical extension of QPM materials to operation in the long-wave IR (5 - 12 micrometers ). That wavelength range is particularly attractive for chemical sensing because it contains an atmospheric window, many molecular groups absorb there at distinct frequencies, and their absorptions tend to be strong relative to those in the near- and mid-IR. Here, the application of orientation-patterned GaAs (OPGaAs) for use in a continuous wave (cw) difference frequency spectrometer is described. The outputs of two external- cavity diode lasers operating in the 1.3 and 1.5 micrometers telecom bands are mixed in a OPGaAs crystal, producing tunable radiation at wavelengths near 8 micrometers . The application of the source to the measurement of a water vapor rovibrational absorption line is presented.

Date Published: 28 March 2002
PDF: 5 pages
Proc. SPIE 4634, Methods for Ultrasensitive Detection II, (28 March 2002); doi: 10.1117/12.463834

Published in SPIE Proceedings Vol. 4634:
Methods for Ultrasensitive Detection II
Charles W. Wilkerson Jr., Editor(s)