Abstract

Although it is well known that SH light can be generated in reflection front surfaces, the efficiencies are very small. Quasi-phasematching has been used to improve the SH conversion efficiency in both semiconductor¹ and insulator waveguides. In this paper we show that by modulating the linear and nonlinear optical properties of a material in the near- surface region, it is possible to achieve quasi-phase matching in the reflection geometry. Let w₁(z) and w₂(z) be the z-components of the incident and SH light wave vectors respectively, where tire z-axis is normal to the surface. For a homogeneous material, the SH field can become large only when w₂(z) - ww₁(z) = 0, corresponding to the conventional phase matching condition for copropagating SH and fundamental beams. However, in the reflection geometry shown in Fig. 1, the SH field at the surface can also become large if the ratio χ²(z)/w₂(z) has a modulated component of the form

© 1993 Optical Society of America