Sensitive gas detectors by nonlinear mixing in periodically-poled crystals of the KTiOPO4 family

Tunable mid-infrared radiation (3.1-3.75 mum) with a power level of up to 0.17 muW is generated by quasi-phase-matched difference frequency mixing of a Nd:YAG laser and a tunable diode laser (near 1.5 mum) in multi-grating periodically-poled crystals of the KTiOPO4 family. The measurements are used to explore the optical and nonlinear properties of these materials in the mid-infrared, e.g. temperature tuning coefficient, wavelength and temperature bandwidths and a mid-infrared-corrected dispersion equation for n(z). The generated mid-infrared radiation is applied to sensitive high-resolution spectroscopy of the v(3) -band of methane.