Laser-energy transfer and enhancement of plasma waves and electron beams by interfering high-intensity laser pulses.

The effects of interference due to crossed laser beams were studied experimentally in the high-intensity regime. Two ultrashort (400 fs), high-intensity (4 x 10(17) and 1.6 x 10(18) W/cm(2)) and 1 microm wavelength laser pulses were crossed in a plasma of density 4 x 10(19) cm(3). Energy was observed to be transferred from the higher-power to the lower-power pulse, increasing the amplitude of the plasma wave propagating in the direction of the latter. This results in increased electron self-trapping and plasma-wave acceleration gradient, which led to an increased number of hot electrons (by 300%) and hot-electron temperature (by 70%) and a decreased electron-beam divergence angle (by 45%), as compared with single-pulse illumination. Simulations reveal that increased stochastic heating of electrons may have also contributed to the electron-beam enhancement.