Strong diffraction effects accompany the transmission of a laser beam through inhomogeneous plasma microstructures

In the study we thoroughly analyze diffraction effects accompanying the laser beam transmission through inhomogeneous plasma microstructures and simulate their diffraction patterns at the object output and in the near field. For this we solve the scalar Helmholtz wave equation in the first Rytov approximation and compute the diffraction spreading of the transmitted beam in free space. Diffraction effects are found to arise within the beam passage through inhomogeneous plasma microstructures even in the simplest approximations of the laser beam interaction with plasma. These effects become strong in the near-field region and significantly distort the patterns of plasma formations, as well as facilitate the appearance of various optical artifacts in the plasma images. By performing numerical simulations, we characterize in detail the features of the visualization of plasma formations in the field of a coherent laser beam registered by a lens system. The calculations are in good agreement with the experimental data. The study can find broad applications in the processing of the laser images of plasma microstructures registered by lens systems in the presence of strong diffraction effects.