Observation of harmonics in the visible and ultraviolet created in CO2-laser-produced plasmas

Abstract

Experimental studies of inertially confined plasmas irradiated with C${\mathrm{O}}_2$ laser intensities greater than ${10}^{15}$ W/${\mathrm{cm}}^2$ at 10.6-μm wavelength reveal the generation of harmonic spectral components up to the 46th order (∼230 nm). These harmonics are of very short duration (<200 ps), have a polarization parallel to that of the incident 10.6-μm electric field, and exhibit a conversion efficiency approximately independent of the harmonic order up to a maximum order. The plasma-physics phenomena responsible for the high-harmonic emission are examined. The data and theory are consistent with the presence of self-focusing.