Abstract

Although periodically poled crystals have shown great promise for non-linear applications, their use in widely tunable Optical Parametric Oscillators (OPO) is inherently limited by the Quasi Phase Matching method. A poled structure can generally accommodate only a narrow band of wavelengths. Tuning can be achieved either by sedately poling of different regions on the same crystal (discrete tuning), or controlling the crystal temperature. Since temperature tuning of a periodically poled KTiOPO₄ (PP-KTP) is quite small (about 7 Å/°C around 1 6 μm) we have used a fen shaped grating designⁱ to achieve wide band, continuous tuning. Two fan shaped periodic domain structures (Fig. 1) were fabricated by the low temperature electrical poling techniqueⁱⁱ in uncoated, flux grown, z-cut KTP plates, measuring 0 5mm thick and 30mm long. One fan structure had a half-angle (θ_H) of 2.25° while the half angle of the second fan was 4 5°. The period length varied between 36.9μm to 37.9μm across a 10mm width for the first structure and across 5mm. for the second structure. We found that the fan structures had no influence on the achieved domain quality.

© 2000 IEEE