Angular dependence of optical second-harmonic generation at a Ge(111) surface

Abstract

The variation of the second-harmonic signal with the incident angle is studied for both isotropic and anisotropic contributions, which arise from a lack of inversion symmetry along the surface normal and in the surface plane, respectively. For Ge(111) the angular dependence of the different contributions is in good agreement with theoretical predictions. The results show that accurate determination of surface and bulk contributions from angular-dependence data is difficult for materials with high dielectric constants, such as Ge. From a comparison of intensity ratios of (111) and (001) crystal faces, we determined that surface and bulk terms make comparable contributions to the second-harmonic signal of Ge(111) at the chosen excitation wavelength.