Polarization Of Light Reflected On Real Crystal Surfaces. Zilbershtein A. & Solovev L., Inst. Precambrian Geol.& Geocron. Rus. Ac. Sci., St.Petersburg State University

The reflection of light on real crystal surfaces has been investigated. The reflected light is shown to be elliptically polarized (the incident light is linea- ry polarized due to surface gyrotropy for nongyrot- ropic crystals in particular. It was obtained that there are only 10 symmetry classes for crystal surf- aces: 1, 2, m, mm2, 4, 4mm, 3m, 3, 6, 6mm. Some of them (1, 2, m, mm2) are gyrotropic. (We have to no- te that gyrotropic surface can be for centrosymmetr- ic crystals too). The expression for reflected light amplitude (Ar) for polarization orthogonal to the polarization of incident light was obtained. For optically isotropic crystals and ones with "iso- tropic point" [1], the condition |Ar|>0 may be only for gyrotropic crystals and/or gyrotropic surfaces: Ar= -[2n*cosI*(cosR-1/cosR)*E]/[(N*N+1)*cosI*cosR+N(cosR*cosR+cosI*cosI)] (1), where the N is the refractive index of isotropic me- dia; the E is the amplitude of incident light; the R is the refractive angle; the I is the angle of inci- dent; n=Gij*Li*Lj/(2N), the {Gij} is the tensor of gyrotropy, Li & Lj are the directive cosinuses for wavevector.

It was obtained that for "m" surface symmetry and for incident wavevector parallel to [111], there are di- fferent values (n1 & n2) of the n for two crystal positions, which may be obtained by rotation of cry- stal on 180o around the normal to the surface: n1=(1/3N)*(G12+G23) and n2=(1/3N)*(G23-G12)

The theoretical results above may explain anisotropy (birefringence and double absorption) observed experimentally in super latices [2,3].

References:

[1].Zilbershtein A.& Solovev L. Optics & Spectroscopy v.43,N5,pp 536-539,1977;

[2].Ivchenko E., e.a. Exitons in semiconductors, Vilnius,1988;

[3].Voliotis V., e.a. ICSMM-6, Xi-an, 1992.