Spectral and temporal harmonic studies of laser-produced plasmas

Abstract

Studies of emission corresponding to the second (3w0) and three-halves (3/2w0) harmonics are reported from laser produced plasmas. These plasmas were produced by means of a neodymium laser with an irradiance up to 2.10 16 W/cm-2, in pulses of nominally 100ps duration. The spectral resolution of these harmonics from a range of targets has enabled various theories tobe verified and the location of the interaction identified. Acomputer code has been used to account for refraction of the emerging radiation in the plasma density profile. The expansion velocity and temporal variation of this profile has also been taken into account. Temporal resolution of the 2Wo and 3/2-Wo spectra has shown both harmonics to occur in pulses of less than the instrumental resolution limit which was ~10ps. This result gives some indication of the timescale for growth and saturation of parametrically excited instabilities.