Frequency tuning a mid-infrared optical parametric oscillator by the electro-optic effect

Controlled frequency tuning of an optical parametric oscillator is accomplished through the application of a dc electric field that perturbs the index ellipsoids for the pump, the signal, and the idler beams by means of the linear electro-optic (Pockels) effect. The changes in the refractive indices induce a dispersion-compensating wavelength tuning of the optical parametric oscillator signal and idler beams to maintain the birefringent phase-matching condition. Broadband wavelength tuning by the electro-optic effect in a mid-infrared lithium niobate optical parametric oscillator is demonstrated. A linear dependence of the wavelength shift on applied voltage is observed with an idler tuning range of up to ∼90 nm achieved electro-optically. Tuning rates in excess of 5 cm-1/(kV/cm) are obtained. All observations, including the dispersion in the tuning rate, are quantitatively described by a simple theory that uses no adjustable parameters.