Two-color laser-plasma interactions for efficient production of non-thermal hot electrons

Efficient production of non-thermal hot electrons has been demonstrated experimentally by interactions of a plasma and two-color lasers with wavelengths of 527 and 1053 nm. The two-color-lasers and plasma interactions caused a 4.8 times enhancement of the temperature of the hot electrons and a 2.7 times enhancement of energy conversion from the lasers to the hot electrons compared with that obtained with only a 527 nm laser. These experimental results can be explained by a staging electron acceleration mechanism realized with a mixture of plasma waves excited by the two-color lasers. The primary 527 nm laser excites at least two electron plasma waves. Those have completely different phase velocities, therefore, staging acceleration cannot occur only with the 527 nm laser. The secondary 1053 nm laser excites other electron plasma waves, of which the phase velocities locate between those of the waves excited by the primary 527 nm laser. Some of the background thermal electrons can be heated contentiously to several hundred kilo-electronvolts by the electron plasma waves excited by the two-color lasers.