Tunable mid-infrared radiation (3.45–3.75 µm) with a power level of 0.14 µW is generated by quasi-phase-matched difference-frequency mixing of a Nd:YAG laser and a tunable-diode laser (near 1.5 µm) in multigrating periodically poled KTiOAsO<sub>4</sub> . The wavelength and temperature bandwidths are ≈65 nm cm and ≈62°C, respectively. The temperature-tuning slope of the phase-matched idler wavelength, -0.94 nm/°C, is almost twice that of periodically poled KTiOPO<sub>4</sub> . We use the measurements to derive a mid-infrared-corrected Sellmeier equation for the Z axis of KTiOAsO<sub>4</sub>. The generated mid-infrared radiation is applied to sensitive high-resolution spectroscopy of the ν<sub>3</sub> band of methane.
© 2000 Optical Society of America
K. Fradkin-Kashi, A. Arie, P. Urenski, and G. Rosenman, "Mid-infrared difference–frequency generation in periodically poled KTiOAsO4 and application to gas sensing," Opt. Lett. 25, 743-745 (2000)