不同能量下环形高斯强激光光束在空气中的非线性传输

以线性传输模型为对比研究了不同初始能量的环形光束在空气中的非线性传输。结果显示，在传输初始阶段，非线性克尔效应减弱了线性空间啁啾导致的聚焦作用。线性聚焦使能量向光轴方向流动导致强光强核心，在光轴附近生成类高斯脉冲结构，增强了非线性自聚焦效应，导致光强急剧增加形成光丝。环形光束的初始能量的大小能够影响自聚焦焦距、光丝长度和光强通量。自聚焦焦距随着初始脉冲能量的增加而减小，但自聚焦焦距与初始功率的开方不成反比（这点与高斯光束不同）。光丝长度随着初始脉冲能量的增加而增加。轴上光强通量随初始脉冲能量的增加而增加。

Nonlinear Propagation of annular Gaussian beams with different energy in air

The annular Gaussian beams having different initial energies propagation in air are numerically studied by two models, the linear model and the nonlinear model. Numerical results show that (i) at the beginning of the propagation the nonlinear Kerr effect slightly suppresses the focusing caused by the spatial chirp, and (ii) the focusing caused by the spatial chirp generates a high intensity core making the beam shape near the axis similar to the Gaussian shape and this can enhance the Kerr self-focusing, and (iii) the initial energy of the annular beams can influence the nonlinear foci, filamentation length, and the fluence of the propagation. The nonlinear foci decrease with the initial energy, but the foci are not inversely proportional to the square root of the initial peak power, which is not the same as the Gaussian beam. The filamentation length increases with the initial input energy.