Аннотация:Laser pulse interaction with gas jet targets provides a lot of interesting effects resulting in generation of intense electromagnetic radiations in a wide frequency band. Below, two important examples of such processes will be considered using 2D particle-in-cell simulation. The first one is formation of relativistic electron mirrors from gas jets by accelerating laser pulses and generation of coherent ultrashort XUV pulses through Thomson backscattering of a probe laser pulse off such mirrors. The second example considers generation of intense infrared and terahertz radiation by strong nonlinear currents generated in plasma during wakefield formation.An idea for synchronous acceleration of electrons from a nanofilm with a longitudinal component of the Lorentz force of a superintense nonadiabatic laser pulse was considered in [1,2]. The same physical mechanism can work for the gas targets. If the target is thin enough and its density is moderate then full evacuation of electrons from a gas plasma near the laser beam axis takes place and a relativistic electron mirror is formed. For thick targets, relativistic boundary of the gas plasma can be produced providing for effective Thomson backscattering of a probe laser pulse. Parameters of produces relativistic electron mirrors and generated coherent ultrashort XUV pulses are studied.Emission of intense infrared and terahertz radiation by laser generated wakefield in inhomogeneous plasma is also studied. The main frequency of radiation in this case is defined by a plasma frequency so the terahertz and infrared bands can be covered by this source. Characteristics of generated radiation are found, the role of plasma inhomogeneity is elucidated. This work was partially supported by the Russian Foundation for Basic Research project 19-52-45035-Ind-a.