超短脉冲贝塞尔-高斯光束在自由空间的传输特性

 使用复解析信号法研究了束宽与频率无关的超短脉冲贝塞尔-高斯光束在自由空间的传输特性。研究表明：在无衍射长度内，超短脉冲贝塞尔-高斯光束的横向光强分布几乎不变并集中在传输轴附近，轴上脉冲随传输距离增加而展宽。在无衍射长度外，横向光强分布显著扩展。随传输距离增加，轴上光谱蓝移先增加，达到极大值后逐渐减小，最后在远场趋于一渐近值。对单周期的超短脉冲贝塞尔-高斯光束的轴上光谱蓝移先增加，达到极大值0.50 fs^-1。然后逐渐减小，在远场蓝移趋于渐近值0.16 fs^-1。

Propagation properties of ultrashort pulsed Bessel-Gauss beams in free space

Using a complex analytical signal representation, the free-space propagation properties of ultrashort pulsed Bessel-Gauss beams whose waist width is independent of frequency are studied. It is found that within the diffraction-free range the transversal intensity distribution of ultrashort pulsed Bessel-Gauss beams remains nearly unchanged, and the on-axis temporal pulse forms broaden along the propagation. Beyond this range, there is a remarkable spreading of the transversal intensity. With the increase of the propagation distance, the on-axis blue shift increases firstly, then gradually decreases after reaching its maximum, and finally approaches an asymptotic value. For example, for a single-cycle ultrashort pulsed Bessel-Gauss beam, the onaxis blue shift increases and reaches a maximum value of 0.50 fs^-1, then decreases gradually, and finally approaches an asymptotc value of O. 16 fs^-1 in the far field.