Adiabatic frequency shifting of a surface wave guided by a time-varying plasma structure

The propagation of an electromagnetic wave along a planar waveguiding struc ture that contains gaseous/solid-state plasma slabs with time-varying free carrier density is considered in the case when the time scale of the densit y variation is much greater than the wave period (adiabatic approximation). Both ionization and deionization (recombination, attachment) processes are included. General relations describing frequency shifting and energy losse s of a guided wave are derived for an arbitrary open/closed waveguiding str ucture. Relations between the energy of the wave and its frequency conserve d during the process of plasma density variation (adiabatic invariants) are found. Detailed analyses are given for surface waves guided by the boundar y of a time-varying plasma half-space and a plasma slab. Slow variations of plasma density are shown to be energetically more efficient than fast vari ations. A new effect of reflection of the wave envelope that occurs without reflection of the fast oscillating carrier is pointed out. (C) 2000 Americ an Institute of Physics. [S1070-664X(00)01703-1].