ИСТИНА

(Invited talk) High power femtosecond laser pulse propagation in gases leads to filament formation [1], [2]. High intensity in the filament provides the development of a number of nonlinear effects including four-wave mixing (FWM) [3]. FWM appears when high power pulse with carrier frequency w0, which forms the filament, propagates together with the seed pulse with the frequency w1 leading to signal pulse ( w2) generation. w2 = w0 + w0 - w1. (1) Generation of signal pulses in THz [3] spectral ranges has been experimentally observed, though the spatial and temporal properties of generated radiation have not been studied numerically in details. So the purpose of this work was to study temporal and spatial structures of THz signal radiation and its evolution during propagation. In our numerical simulations we use unidirectional pulse propagation equation [4] for electric field evolution. Spatial structure of THz radiation generated according (1) with l0 = 800 nm, l1 = 400 nm appears to have rings (fig. 1), as it was experimentally shown in [5]. THz pulse has only few electric field oscillations at the beginning of filamentation, but also becomes more complicated during propagation. [1] Chin S. L. et al., Canadian journal of physics 23(9), 863-905 (2005). [2] Couairon A. et al., Physics reports 441(2), 47-189 (2007). [3] Balakin A. V. et al., JOSA B 27(1), 16-26, (2010). [4] Kolesik M. et al., Physical Review E 70(3), 036604 (2004). [5] Klarskov P. et al. New Journal of Physics 15(7), 075012 (2013)