空气中的3D +1 Lorentz型孤子
3D+1 Lorentz type soliton in air
摘要：
迄今为止，长程灯丝一直被认为是非线性焦点中等离子体产生的克尔聚焦和散焦之间的平衡。然而，在远场区难以应用上述对取向的解释。基本上有两个主要特征在这些距离上保持不变-超宽光谱和核心宽度，而稳定灯丝中的功率下降到自聚焦的临界值。在这样的功率下，等离子体和高阶克尔项太小而不能防止自聚焦。本文提出了一种新的孤子脉冲在远区稳定传输的机制，即激光脉冲的功率略高于临界功率，并且脉冲具有超宽的光谱。对于这样的脉冲，衍射不是傍轴的，并且初始对称的高斯脉冲在几个衍射长度处呈抛物线形式。稳定的孤子传输表现为宽带光脉冲的发散抛物型衍射和由光强分布引起的会聚非线性折射率之间的平衡。我们研究更精确的非线性三阶偏振，考虑到载波包络相位。这个额外的相位将三次谐波项转换为THz或GHz项，这取决于脉冲的频谱宽度。
英文摘要：
Up to now the long range filaments have been considered as a balance between Kerr focusing and defocusing by plasma generation in the nonlinear focus. However, it is difficult to apply the above explanation of filamentation in far-field zone. There are basically two main characteristics which remain the same at these distances - the super broad spectrum and the width of the core, while the power in a stable filament drops to the critical value for self-focusing. At such power the plasma and higher-order Kerr terms are too small to prevent self-focusing. We suggest here a new mechanism for stable soliton pulse propagation in far-away zone, where the power of the laser pulse is slightly above the critical one, and the pulse comprises super-broad spectra. For such pulses the diffraction is not paraxial and an initially symmetric Gaussian pulse takes parabolic form at several diffraction lengths . The stable soliton propagation appears as a balance between the divergent parabolic type diffraction of broadband optical pulses and the convergent nonlinear refractive index due to the intensity profile. We investigate more precisely the nonlinear third order polarization, using into account the carrier-to envelope phase. This additional phase transforms the third harmonic term to THz or GHz one, depending on the spectral width of the pulse.
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