Electro-optically, widely tunable optical parametric oscillator based on periodically poled lithium niobate

We report fast and wide wavelength tuning of a ns-optical parametric oscillator (OPO) based on a periodically poled lithium niobate crystal (PPLN) with a three-segment structure. An ultra-broad parametric gain was accomplished by appropriately choosing the pump wavelength and the poling period for group velocity matching between the signal and the idler. While the first segment of the PPLN generated ultra-broad signal and idler bands, the third segment amplified selected portions of the spectra, which could be controlled electro-optically by applying a dc electric field in the middle single-domain segment. A ns-laser pumped singly resonant OPO was built, whose signal wavelength was tuned from 1.373 to 1 . 749 μm (corresponding idler tuning range from 2.863 to 1 . 972 μm) by varying the electric field from -6.5 to ＋5.0 kV/mm. The electro-optic tuning provided a fast wavelength selection method for the OPO within the wide infrared spectral range.