Optical properties of an ionic-crystal slab

Abstract

The macroscopic theory for the optical properties of an ionic-crystal slab is extended so as to allow for the possibility of exciting longitudinal-optical phonons. The resulting semimacroscopic method correctly reproduces the complex absorption structure which previous microscopic calculations have predicted to occur in the frequency range between ${\omega }_T$ and ${\omega }_L$, the frequencies of the long-wavelength transverse- and longitudinal-optical phonons. Calculated spectra for the case of extremely thin LiF films are presented and the influence of various physical parameters on the absorptance is discussed.