Light scattering from anisotropic block copolymer grains in a planar waveguide

A theory is presented to treat depolarized light scattering in a planar waveguide consisting of an ordered block copolymer thin film on a fused-silica substrate. In guided-wave depolarized light scattering (GWDLS), light is coupled into a transverse-magnetic mode of the film, which acts as a planar waveguide. Scattering of the incident light from randomly oriented, optically anisotropic grains results in the coupling of light into propagating transverse-electric (TE) modes in the sample. A dyadic Green's function approach is employed to derive a quantitative relationship between the total optical power of the scattered TE wave and the average size of the grains. The grain size thus calculated from GWDLS experiments is consistent with the position space results of atomic force microscopy.