High order harmonics generation via laser reflection at electron density peaks

Abstract

A novel regime of high frequency radiation generation via reflection at the electron density spikes in under- dense plasma is proposed. Intense driver laser pulse propagating in underdense plasma forms dense electron singularities near the front part of the bow waves, moving at relativistic velocity. By irradiating a source pulse counterpropagating to the electron density singularities, it is reflected and compressed, producing ultrashort coherent high order harmonics with frequency upshift.