Origin of optical anisotropies of nonpolar GaN surfaces

We investigate the origin of optical anisotropies of the nonpolar GaN (110) and (1010) surfaces. Using semiempirical tight-binding calculations, we an alyze in detail the main optical signature of each surface. The origin of t he optical spectra is discussed in terms of the main surface electronic sta tes and of the specific surface atomic rearrangement. Results of the surfac e dielectric function, and reflectance anisotropy spectra, are presented.