Form birefringence of oxidized porous silicon

Abstract

A network of preferentially oriented pores is shown to induce anisotropy of linear and nonlinear optical properties of oxidized porous silicon (OPS) films. Although the x-ray diffraction indicates the presence of amorphous phase in OPS samples, the near-infrared and visible transmission measurements reveal a strong in-plane anisotropy exceeding that for the crystalline quartz. This anisotropy modifies dramatically polarization properties of the nonlinear optical properties resulting in a strong anisotropy of the third-harmonic signal generated from these films.