Mid-infrared difference–frequency generation in periodically poled KTiOAsO_4 and application to gas sensing

Tunable mid-infrared radiation (3.45-3.75 microm) with a power level of 0.14 microW is generated by quasi-phase-matched difference-frequency mixing of a Nd:YAG laser and a tunable-diode laser (near 1.5 microm) in multigrating periodically poled KTiOAsO(4) . The wavelength and temperature bandwidths are approximately 65 nm cm and approximately 62 degrees C, respectively. The temperature-tuning slope of the phase-matched idler wavelength, -0.94 nm/ degrees C, is almost twice that of periodically poled KTiOPO(4) . We use the measurements to derive a mid-infrared-corrected Sellmeier equation for the Z axis of KTiOAsO(4). The generated mid-infrared radiation is applied to sensitive high-resolution spectroscopy of the nu(3) band of methane.