等衍射长度超短脉冲贝塞耳-高斯光束的传输特性

Propagation Properties of Ultrashort Pulsed Bessel-Gauss Beams with Constant Diffraction Length

使用复解析信号法,研究了衍射长度与频率无关的超短脉冲贝塞耳-高斯光束在自由空间中的传输,推导出了解析表达式并进行了理论和计算分析·结果表明:在无衍射长度内,等衍射长度超短脉冲贝塞耳-高斯光束的横向光强分布扩展很小·在无衍射长度之外,横向光强分布有显著扩展·但是,在无衍射长度内轴上脉冲波形仍有展宽·随传输距离增加轴上蓝移单调增加逐渐达到一渐近值·随横向距离增加轴外光谱移动由蓝移变为红移·

The complex analytical signal representation was applied to study the free-space propagation of ultrashort pulsed Bessel-Gauss beams with constant diffraction length. Closed-form expressions were derived and analyzed both theoretically and numerically. It is shown that within the diffraction-free range, the spreading of transversal intensity distributions of ultrashort pulsed Bessel-Gauss beams is small, whereas beyond this range a remarkable spreading appears. But, within the diffraction-free range there is still a broadening of on-axis pulse forms. With increasing propagation distance, the on-axis blue shift increases monotonously and then reaches gradually its asymptotic value. The off-axis spectral shift changes from the blue shift to the red one as the transversal distance increases.