Optics of Nonlinear Crystals

Abstract

This chapter introduces the main concepts of the physics of nonlinear optical processes: three-wave interactions, phase matching and phase-matching angle, role of phase mismatch for the interaction of quasi-plane waves, group-velocity mismatch and interaction of ultrashort light pulses, optics of uniaxial and biaxial crystals, crystal symmetry and effective nonlinearity, “walk-off” angle, phase-matching bandwidths (angular, temperature, spectral), thermal effects, and so on. It presents the main material required for calculating of phase-matching angles and for an assessment (as a rule, in approximation of quasi-plane light waves) of frequency conversion efficiency in the case of generation of optical harmonics and combination (sum and difference) frequencies, and optical parametric oscillation in nonlinear optical crystals. For convenience, the so-called “effective lengths” are introduced for the corresponding processes: by comparing the nonlinear crystal’s length with the effective length of the corresponding process, we may conclude whether this process must be taken into account for the calculation of the conversion efficiency or not. The chapter contains many tables with the equations for calculating phase-matching and “walk-off” angles, bandwidths, effective nonlinearity and conversion efficiency.