Experimental observation of specular optical activity

We report the first positive experimental observation of the optical activity effect on normal reflection. The experiment was performed along the optic axis in a gyrotropic semiconductor crystal of alpha-HgS, cinnabar, in a spectral region of strong absorption. Reflected light polarization azimuth rotation resulting from the reflection is of the order of 10 exp -4 rad, and has pronounced dependence on h(omega) - E sub g. (Author (revised))