High-harmonic generation in plasmas from relativistic laser-electron scattering

Results are presented on the generation of high harmonics through the scattering of relativistic electrons from high-intensity laser light. The characteristic signatures of this process are found to be the emission of evenorder harmonics, linear dependence on the electron density, significant amount of harmonics with circular polarization, and small spatial extent of the source. The harmonics are emitted as a forward-directed beam with a divergence of 2°–3°. The measured spatial profile of the harmonics is in excellent agreement with calculations that assume that relativistic electrons play a significant part in the scattering process. © 2003 Optical Society of America OCIS codes: 190.4160, 320.7120.