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Hu Y.,State Key Laboratory of Pulsed Power Laser Technology of China | Nie J.,State Key Laboratory of Pulsed Power Laser Technology of China | Sun K.,State Key Laboratory of Pulsed Power Laser Technology of China | Ye Q.,State Key Laboratory of Pulsed Power Laser Technology of China | Wang L.,State Key Laboratory of Pulsed Power Laser Technology of China
Optics Communications | Year: 2017

The spatiotemporal dynamics of femtosecond filamentation were investigated numerically to evaluate various intensity distributions of zero-order Mathieu beams without the phase alteration for adjacent lobes. The side filaments are formed due to constructive interferences of the light fields of the side lobes. For the beam with appropriate lobes, the whole length of filament can be extended. The diffraction-free characteristic can still be retained in the femtosecond filamentation area, even when ignoring the phase alternation of adjacent lobes. Thus, several high peak intensity spikes behind the continuous clamping segment were illuminated by the remaining energy of side filaments. For the spectrum, intensity distribution with a suitable number of lobes enhances the supercontinuum (SC) emission on both the blue and red sides. © 2017 Elsevier B.V.


Li Z.-M.,State Key Laboratory of Pulsed Power Laser Technology of China | Wang X.,Electronic Engineering Institute
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

An investigation of silicon melting occurring under femtosecond laser irradiation has been presented, The two-temperature model and photoionization model are introduced to calculate the free-carrier intensity's evolution with time. In both models, the electrons density's evolution under laser fluence 2 F0 = 0.2,0.3,0.5J/cm are performed. The maximum density reaching the threshold density for SPP excitation by these two model are discussed. For both single pulse and double pulse, according to the simulation data, the two temperature model have a more agreement with the experiment results. © 2017 SPIE.


Hu Y.,State Key Laboratory of Pulsed Power Laser Technology of China | Nie J.,State Key Laboratory of Pulsed Power Laser Technology of China | Sun K.,State Key Laboratory of Pulsed Power Laser Technology of China | Wang L.,State Key Laboratory of Pulsed Power Laser Technology of China
Optics Communications | Year: 2017

The spatial and temporal features of femtosecond laser filamentation, which are induced by a laser with power several times higher than the critical power, influenced by strong air turbulence at various propagation distances have been studied numerically. First, a strong turbulence occurring right before focal lens induces a few counter-balanced energy spikes which prevent the filament generation. Second, with the turbulence right before the filamentation, side filaments formed in the periphery towards the outside area leads the filament to be slightly short. Third, with the turbulence right after the lens, numerous energy spikes of the wave profile arise, but they will merge into one filament gradually, leading to a delayed filamentation onset and a shorter filamentation length. The deformation of temporal pulse shape become more sensitive and the supercontinuum (SC) can be weakened more significantly when strong turbulence takes place in air more previously. © 2016 Elsevier B.V.


Hu Y.,State Key Laboratory of Pulsed Power Laser Technology of China | Nie J.,State Key Laboratory of Pulsed Power Laser Technology of China | Ye Q.,State Key Laboratory of Pulsed Power Laser Technology of China | Bian J.,State Key Laboratory of Pulsed Power Laser Technology of China | And 2 more authors.
Optik | Year: 2016

Filamentation processes with different atmospheric pressure gradients are investigated numerically both in spatial and temporal regimes. The filamentation position and length are very sensitive to the pressure gradient. With the positive pressure gradient from low pressure to the standard pressure, the plasma density may still keep increasing with the intensity decreasing. The temporal profiles are also influenced by the pressure gradients dramatically. For supercontinuum (SC) emission, the red shift is dominated by the average atmospheric pressure while the blue shift is enhanced in the low pressure. Moreover, the positive pressure gradient is slightly good for the blue shift. © 2016 Elsevier GmbH

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