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0.16fs-1.

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 on-axis blue shift increases and reaches a maximum value of 0.50 fs^-1,then decreases gradually,and finally approaches an asymptotic value of 0.16 fs^-1 in the far field.