Frequency conversion and amplification by stimulated electromagnetic shock radiation (SESR)

Abstract

The coherent response of a polarizable medium to the radiation stimulated by the interaction of an incident coherent electromagnetic wave with a charged-particle beam, moving with greater than critical speed, results in intense electromagnetic radiation in the form of one or more shock fronts. The shock frequencies are shifted significantly from that of the incident wave and are tunable by parametric variation of the incident beams. The mechanism for this new effect (SESR) differs fundamentally from the laser mechanism. Production of intense quasi-coherent x-ray radiation by SESR obviates the need for x-ray mirrors and is not inhibited by the large spontaneous emission rates at these frequencies. Substantial fraction of the particle-beam energy can be converted into frequency-shifted radiation, with intensity larger than that of the incident wave, because of quadratic dependence on the interaction distance in the medium of the energy radiated into SESR, as compared to the linear dependence of Cerenkov radiative energy. Specific shock frequencies cross from below to above a given resonance frequency of the medium as the relevant two level populations become inverted. This dynamical dependence of the shock frequencies on the level populations provides the basis for new pumping and amplification mechanisms. An example of a possible SESR-based transducing-amplification system is described.