Polariton standing-wave structure as a test of boundary conditions for theories of spatial dispersion

Abstract

The reflectivity of $p$-polarized light ($\overrightarrow{\mathrm{E}}$ is in the plane of incidence) by a dielectric slab exhibiting spatial dispersion, when calculated theoretically in two limiting cases of internal specular reflection, has marked structure at frequencies corresponding to longitudinal polariton standing waves in the one case and transverse polariton standing waves in the other. This provides a possible experimental test of the approximate nature of the vacuum-crystal-vacuum polarizability and it also allows one to measure optically the polariton dispersion curve, either longitudinal or transverse. Application is made to the $A\mathrm{}(n=1\mathrm{})\mathrm{}$ exciton of CdS.