Second-Order Nonlinear Guided Wave Interactions

A general study of three-wave nonlinear mixing in the presence of longitudinal variations in phase-matching conditions is presented. The efficiency of second-harmonic generation and optical parametric amplification is quantified using a normalized set of equations and a polynomial description of the wave-vector mismatch as a function of the longitudinal coordinate. These modeling results are used to estimate the impact of spatial variations in wave-vector mismatch experimentally obtained for five partially deuterated potassium dihydrogen phosphate crystals. The longitudinal inhomogeneities in the properties of crystals of similar quality are not expected to have a significant impact on their use for second-harmonic generation and optical parametric amplification, but the efficiency of nonlinear processes in crystals with larger variations could decrease. 

Impact of longitudinal phase-matching variations on three-wave nonlinear interactions

A theoretical study is made of the influence of a longitudinal optical inhomogeneity of a nonlinear crystal on the value and spectral dependence of the gain, which is calculated numerically for arbitrary parameters of the inhomogeneity. An analytic dependence of the gain in the inhomogeneity parameters is obtained in the two most typical cases of a weak inhomogeneity (linear and step) in nonlinear LiNbO3 crystals. A study is made of the influence of an inhomogeneity on the width and shape of the parametric gain profile. The results are used to formulate requirements in respect of the inhomogeneity parameters of nonlinear crystals suitable for optical parametric oscillators. A report is given of an experimental study of the dependence of the average power of a singly resonant parametric oscillator on the inhomogeneity parameter of an LiNbO3 crystal. The experimental results confirm the theoretical predictions.

M A Kashintsev

Papers

Influence of the longitudinal inhomogeneity of the refractive index of a nonlinear crystal on the parametric gain