ИСТИНА

Generation of high-field infrared and terahertz radiation during interaction of a super-intense laser pulse with a complex nanodimensional target consisting of nanowires or nanofoils is studied. In the interaction, dense high-charge bunches of electrons are forced out of the target and accelerated in the laser field, generating intense electromagnetic radiation. Depending on the duration and shape of the laser pulse, three interaction modes can be realized. In the first mode, the laser pulse is smooth, and the electrons are only partially displaced from the target. In this case, characteristics of the low-frequency part of the generated radiation are determined by the laser and target parameters. In the second mode, the laser pulse has a large amplitude and a steep front (the amplitude of the first half-cycle is on the order of the maximum pulse amplitude), then, most of the electrons are displaced from the target at the initial moment of interaction. In this mode, unipolar and bipolar pulses with duration of dozens of laser periods can be generated. Changing the target geometry allows one to control the duration of the period and the number of the periods in the generated radiation. Finally, in the intermediate mode of short laser pulses with an insufficiently steep front, oscillations of the formed electron bunches may occur in the attracting field of ions, leading to radiation with a frequency several times lower than the laser one. Using numerical simulation, the characteristics of infrared and terahertz radiation in three interaction modes are found. The role of the target structure is elucidated.