Аннотация:Laser pulse propagating in an underdense plasma produces a wakefield which
can be used for acceleration of trapped electrons. Also, during the wakefield formation,
strong nonlinear currents are generated in plasma. Emission of intense
electromagnetic radiation by these nonlinear currents is studied by 2D particlein-
cell simulation. It is shown that, depending on parameters of the laser pulse
and plasma, waves of different frequencies can be generated and they propagate
with different angles with respect to the laser axis. In simulations, relatively
long pulses (containing many periods) of radiation with single, double and triple
plasma frequency were observed so the terahertz and infrared bands can be covered
by this source. The influence of a plasma density modulation on the process
of emission of plasma frequency harmonics is also investigated. In this case, the
amplitude of the generated radiation can be considerably increased. Characteristics
of radiation generated during laser wakefield propagation in plasma such
as polarization, frequency, amplitude, etc. are studied and spectral densities for
different harmonics of the plasma frequency are found. It is shown that the amplitude
of the radiation can be about 20 GV/m and efficiency of generation can
achieve a percent. Also, an analytical model is considered for generation of terahertz
or infrared radiation produced with a wakefield formed by a high-intensity
laser pulse in a gas medium.
This work was partially supported by the Russian Foundation for Basic Research
project 19-52-45035-Ind-a.