Domain inversion in c-cut KTiOPO4 was produced by scanning an electron beam on the −c face. The domain reversal occurred through the 1 mm thickness of the sample. Second-harmonic conversion efficiency of 7×10−5 was measured for a fifth-order grating by focusing the beam to a 7 μm spot in a 500-μm-long domain-inverted KTP crystal. This efficiency is close to the theoretical value of 9×10−5. The measured phase matching bandwidth was 1.9 nm, which is in agreement with the theoretical value of 1.5 nm indicating that the domain-inverted grating is reasonably uniform over its entire length.

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We report a technique for periodic poling of KTiOPO4 (KTP). In this approach, we exploit the observation that Rb-exchanged regions of KTP resist electric field poling under conditions that produce domain inversion in unexchanged KTP. Thus, a pattern of Rb-exchanged regions can be transformed into a corresponding pattern of domain inverted regions by application of a uniform electric field. We applied this technique to in situ poling of segmented waveguides and report quasiphase matched second-harmonic generation in these devices.

Type-II second-harmonic generation was investigated in channel waveguides fabricated in potassium titanyl phosphate (KTiOPO4) crystals by ion exchange. The birefringence of the guided-wave structure was used to provide phasematching. A green (509 nm) output power of 0.25 mW was produced by frequency doubling the 1018-nm output of a titanium:sapphire laser; this power is 200 times greater than what would be obtained in the corresponding bulk interaction. Phasematching for second-harmonic generation was found to have broad tolerances with respect to temperature and wavelength. Blue light at 483 nm was produced by sum-frequency mixing of 1064-nm and 883-nm light.

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