Abstract:We present a detailed characterization of the optical properties of the recently developed nonlinear material, orientation-patterned gallium phosphide (OP-GaP), by performing difference-frequency-generation experiments in the 2548-2782 nm wavelength range in the mid-infrared (mid-IR). Temperature and spectral acceptance bandwidth measurements have been performed to study the phase-matching characteristics of OP-GaP, and the dependence of nonlinear gain on the polarization of input incident fields has been investigated. The transmission of the OP-GaP crystal at the pump and signal wavelengths has been studied and found to be dependent on polarization as well as temperature. Further, we have observed a polarization-dependent spatial shift in the transmitted pump beam through the OP-GaP sample. We have also measured the damage threshold of the OP-GaP crystal to be 0.84 J/cm 2 at 1064 nm.

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We report on experimental demonstration of optical transient detection (OTD) based on photorefractive two-wave mixing of femtosecond pulses. The demonstrated technique also combines nonlinear-crystal-based OTD with up-conversion from infrared into the visible range. The approach enables measurement of phase changes of a dynamic signal in the infrared using GaP- or Si-based detectors while suppressing stationary background. Experimental results reveal existence of the relation between input phases in the infrared and output phases in the visible wavelength range. We further present experimental evidence of additional merits of up-converted transient phase analysis under noisy conditions, such as residual continuous-wave emission affecting the ultrashort pulses from the laser.

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