Thermal oscillations of radiation harmonics generated by a laser plasma

It is shown that there is a set of oscillations with 0.5n(n + 1) periods against the background of a dependence of the efficiency of conversion of laser radiation into n≥2 harmonics that decays monotonically with increasing laser plasma temperature. The electron rest energy reduced by a factor (L / λ) >> 1 (L is the characteristic inhomogeneity scale of the plasma density, λ is the wavelength of the laser radiation) serves as the characteristic scale of the periods, which are an algebraic function of the harmonic number. In a hot laser plasma (T> 1 keV) with an inhomogeneity scale L = 50 μm exposed to the action of neodymium laser radiation, the flux density of the third harmonic oscillates with a period of the order of 0.5 keV.