Study of fast electron jet produced from interaction of intense laser beam with solid target at oblique incidence

Fast electrons generated along target normal direction from the interaction of intense ultrashort Ti:sapphire laser pulses (lambda(0) = 800 nm) with planar copper target at 45 degrees incidence angle have been experimentally studied under different interaction conditions. Angular spread and energy spectrum of the fast electrons was measured for both p- and s-polarized laser irradiation at intensities in the range 4 x 10(16) - 4 x 10(17) W/cm(2) (for a fixed pulse duration of 45 fs) and for pulse duration in the range 45 fs-1.2 ps (for a fixed laser fluence of 1.8 x 10(4) J/cm(2)). The fast electrons were observed consistently along the target normal direction over the entire range of interaction conditions in the form of a collimated jet, within a half cone angle of 20 degrees. The fast electrons have continuous energy spectrum with effective temperature 290 keV and 160 keV, respectively, for p- and s-polarized 45 fs laser pulse irradiation at intensity 4 x 10(17) W/cm(2). Scaling laws for temperature of fast electrons with laser intensity and pulse duration were obtained. The experimental results have been explained on the basis of laser absorption and fast electron generation through the resonance absorption mechanism. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769175]