Trapping of Electromagnetic Wave by Nonstationary Plasma Layer

We report the phenomenon of transient excitation of guided modes by a plane electromagnetic wave obliquely incident on a plasma layer with electron density growing rapidly in time. It has been shown that two frequency down-shifted guided modes of the layer propagating in opposite directions are excited. Their amplitudes are calculated and the conditions for the effective excitation of one of the waves are found. The fundamental electromagnetic phenomenon of wave trapping may have important applications for integrated optics and microelectronics, providing a new way of input of infrared and (sub)millimeter radiation into open planar waveguides.