MIDINFRARED SPECTROSCOPIC DETECTION OF TRACE GASES USING GUIDED-WAVE DIFFERENCE-FREQUENCY-GENERATION

We report spectroscopic detection of methane and water vapor using mid -infrared difference-frequency generation of diode lasers in channel w aveguides at room temperature. Waveguides with two different designs w ere fabricated using annealed proton exchange in periodically poled li thium niobate. One waveguide produced tunable radiation between 3.33 m u m and 3.73 mu m and the other produced tunable radiation between 2.6 5 mu m and 2.90 mu m. High-resolution spectra of methane (at 6.7 kPa) and water vapor (in ambient air) were obtained using electronically co ntrolled frequency scans of up to 65 GHz. The use of diode lasers and highly efficient waveguide frequency converters in conjunction with fi ber coupling will permit construction of compact, solid-state, room-te mperature, mid-infrared sources for use in trace-gas detection.