Frequency-shift of self-trapped light

Abstract

A decrease in the frequency of self-trapped light by as much as a factor of two has been observed in computer simulations of several physical situations. The frequency shift is due to a decrease in the resonant frequency of the plasma cavity as it deepens and expands shortly after the light becomes trapped. Three examples are presented: a model problem in an initially uniform plasma, trapping of laser light in cavities at critical density, and modulational instability and self-trapping of Raman-scattered light at quarter-critical density in a nonuniform, expanding plasma. This effect is essential in the analysis of the evolution and stability of such cavities, and such large frequency changes limit the applicability of models using a nonlinear Schrödinger equation to represent the high-frequency fields.