SPECTROSCOPIC DETECTION OF METHANE BY USE OF GUIDED-WAVE DIODE-PUMPEDDIFFERENCE-FREQUENCY-GENERATION

We report spectroscopic gas detection by the use of mid-infrared diffe rence-frequency mixing of two diode lasers in a channel waveguide. The waveguide was fabricated by annealed proton exchange in periodically poled lithium niobate. We generated 3.43-3.73-mu m tunable radiation i n a single waveguide at room temperature by mixing diode lasers near 7 80 and 1010 nn. High-resolution spectra of methane were obtained in 2 s with electronically controlled frequency scans of 45 GHz. The use of highly efficient waveguide frequency converters pumped by fiber-coupl ed diode lasers will permit construction of compact, solid-state, room -temperature mid-infrared sources for use in trace-gas detection. (C) 1998 Optical Society of America OCIS codes: 130.2790, 130.3730, 190.26 20, 300.6260, 300.6390, 280.3420.