详细研究了贝塞尔-高斯光束被无光阑透镜聚焦后的焦开关效应.推导出了轴上最大光强位置满足的一元三次方程和相对跃迁量公式,并用数值计算对理论结果作了说明.研究表明,当光束参数大于√2时,聚焦贝塞尔-高斯光束会有焦开关现象出现.相对跃迁量随着光束参数的增大而增大,轴上归一化光强最小值随着光束参数的增大而减小,并且当光束参数大于3.9时,轴上归一化光强最小值为零.

The focal switch effect of Bessel-Gaussian beams focused by a thin lens without aperture is studied in detail.The third-order algebraic equation determining the position of the axial maximum intensity and the formula of the relative transition height are derived. Numerical calculation results are presented to illustrate the theoretical predictions. It is shown that, if the beam parameter is bigger than √2, the focal switch of Bessel-Gaussian beams can appear. The relative transition height increases with increasing the beam parameter. The normalized axial minimum intensity decreases with increasing the beam parameter, and the normalized axial minimum intensity is zero, as the beam parameter is bigger than 3.9.