High-order harmonic generation by relativistic lasers in aMaxwellian distributed plasma

High-order harmonic generation by relativistic lasers in plasmas with initial velocity distribution has been studied. It is shown that, different from previous models, because of the random thermal motion of electrons, the initially Maxwellian distributed plasma will make the harmonic spectrum more smooth, i.e., it increases the higher-order harmonic power but decreases the lower-order harmonic power. This effect is beneficial for the generation of higherorder harmonics．