Comparison of Wide-Band Electro-Optic Frequency Tuning in LiNbO3 and KNbO3 OPO's

Abstract

Typically, wavelength tuning in a birefringently phase-matched optical parametric oscillator (OPO) is accomplished by adjusting the angle of propagation in the nonlinear optical crystal. However, angle tuning is not the only way to alter the wavelength of an OPO; other physical mechanisms such as temperature, pressure or electric field1,2 that change the refractive indices (or more specifically, the birefringence) will induce a corresponding dispersion-compensating change in wavelength to maintain phase matching. Electro-optically tuning an OPO is particularly attractive since it is non-mechanical (does not involving any moving parts) and can be done rapidly. Previously, electro-optic tuning was used to compensate for the phase mismatch from self-heating in CD*A during second-harmonic generation.3 More recently, frequency stabilization in a doubly-resonant OPO configuration with KTP was accomplished using electro-optic tuning.4 Here, we describe the first demonstration of broadband wavelength tuning in an OPO via the electro-optic effect in LiNbO3. The method is then applied to KNbO3 since it has much larger electro-optic coefficients. A comparison of electro-optic tuning range and tuning rate for LiNbO3 and KNbO3 are also discussed.