Enhanced selective reflection from a thin layer of a dilute gaseous medium

A theory of selective reflection and transmission is developed for a system consisting of a thin layer of a dilute atomic vapor sandwiched between two transparent solids with parallel interfaces. Strong effects of spatial dispersion due to the atomic motion and electronic quenching on gas-solid interfaces are accounted for. It is shown that both even and odd Doppler-free resonances may occur in selective reflection, depending upon the thickness of the vapor layer. It is also found that the amplitude of selective reflection is a result of the interference between reflections from the two boundaries of the vapor-solid interfaces and, hence, may be greatly enhanced under certain conditions.