Observation of harmonics in the visible and ultraviolet created in C<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>-laser-produced plasmas

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-\ensuremath{\mu}m wavelength reveal the generation of harmonic spectral components up to the 46th order (\ensuremath{\sim}230 nm). These harmonics are of very short duration (200 ps), have a polarization parallel to that of the incident 10.6-\ensuremath{\mu}m 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.