Band Theory of the Optical Activity of Crystals

The optical activity of crystals is investigated in terms of the crystal energy band theory. The ordinary optical activity is the spatial dispersion effect of light and is due to the ohmic current response caused by light field. The two sorts of contribution is specified, the matrix element term and the energy spectrum term. The latter term is directly related to the presence of k -linear terms is the energy dispersion E ( k ) at symmetry points in the Brillouin zone. The sum rule of the rotatory strength is derived and the Wannier exciton effect is discussed. The theory is applied to the optical rotatory dispersion of tellurium with the use of the known values of energy band parameters. The calculated dispersion curve is in good agreement with the experimental data. The optical rotatory dispersion of selenium is also discussed.