ИСТИНА

The formation of so-called light bullets (LBs) in the result of simultaneous laser beam self-focusing and pulse selfcompression in transparent dielectrics is a bright phenomenon in femtosecond filamentation. A necessary condition for implementing this regime is the existence of anomalous group-velocity dispersion. Light bullet is a short-lived robust object comprising one-two optical periods of high density laser energy [1]. The formation of each LB in a sequence is accompanied by ‘ejection’ of an equal amount of supercontinuum energy in the visible range. The LB energy is transformed into the supercontinuum energy in the entire spectral range; this process is the main channel of LB degradation [2,3]. We present the results of experimental and numerical investigation of LB dynamics in femtosecond filament. Strictly periodic oscillations of LBs intensity and diameter were firstly recorded under mid-IR femtosecond pulse filamentation. Measurements were performed on the base of a periodic colour-centre (CC) structures induced in an isotropic LiF crystal by a single LB, formed in the single-filamentation mode by a femtosecond mid-IR (2600–350 nm) laser pulse with a power slightly exceeding the critical power for self-focusing. hese structures with a diameter close to the light wavelength are formed by an LB in the entire range of its existence (about 1 mm long). The period of changes in the CC density and diameter of induced structures is about 30 mcm and increases with decreasing radiation wavelength. Based on numerical simulation data, it is shown that the observed CC structure is formed due to the periodic oscillations of the maximum light field amplitude in an LB with a width of 1.5 optical oscillations during its propagation in a dispersive medium which are by-turn due to the difference between the LB envelope group velocity and the light-wave phase velocity. The numerical simulation data are in agreement with the experimental results [4,5]. References [1] E O Smetanina, A E Dormidonov and V P Kandidov, Laser Phys. 22, 1189 (2012) [2] S V Chekalin, A E Dokukina, A E Dormidonov, V O Kompanets, E O Smetanina and V P Kandidov,J. Phys. B 48, 094008 (2015) [3] S V Chekalin, V O Kompanets, A E Dokukina, A E Dormidonov, E O Smetanina and V P Kandidov, Quantum Electron. 45, 401 (2015) [4] A V Kuznetsov, V O Kompanets, A E Dormidonov, S V Chekalin, S A Shlenov and V P Kandidov, Quantum Electron. 46, 379 (2016) [5] S V Chekalin, V O Kompanets, A V Kuznetsov, A E Dormidonov and V P Kandidov, Laser Phys. Lett. 13, 065401 (2016)