洛默尔-高斯光束在梯度折射率介质中的传输特性

Propagation Characteristics of Lommel-Gaussian Beams in a Gradient-Index Medium

基于梯度折射率介质,分析了洛默尔-高斯光束的强度包络和传输特性,给出了洛默尔-高斯光束的强度表达式。高斯腰斑取值越小,洛默尔-高斯光束的非零区域越小即高斯光束的截断作用越明显;半锥角取值越大,光束的空间尺度越小;拓扑荷数取值越大,光束中心的暗斑尺寸越大。非对称参数可以改变洛默尔-高斯光束的空间形态和对称特性,随着非对称参数幅值的增加,光强分布逐渐由圆对称改变为轴对称的双月结构,随着非对称参数幅角的增大,双月结构的对称轴呈现顺时针旋转的特性。洛默尔-高斯光束在梯度折射率介质中传输时,在一个传输周期内,光束的相对强度分布没有变化,只是光束尺度发生周期性聚焦变化,而在自由空间中,光束会很快演化为两个光斑。这些结果对研究洛默尔-高斯光束的实际应用具有一定参考价值。

The intensity envelopes and propagation characteristics of LommelGaussian beams are investigated numerically based on gradientindex medium.The intensity expression of LommelGaussian beams is provided.The zerofree region of LommelGaussian beams decreases with decreasing spot of Gaussian beams,that is,the truncation effect of beams is more obvious.The spatial scale decreases with increasing halfcone angles and the hollow region of beam center increases with increasing topological charges.The spatial distribution and symmetry can be modulated by changing the asymmetric parameters.The intensity distribution of beams gradually changes from circular symmetry to axialsymmetry doublecrescent pattern with increasing amplitude of asymmetric parameters and the symmetric axis of doublecrescent pattern is rotated clockwise with increasing argument of asymmetric parameters.When the LommelGaussian beams are propagating in a gradientindex medium,within a transmission cycle,the relative intensity distribution of beams has no change,only the beam scale has a periodic focus change.But in free space,the beam quickly evolves into two light spots.All results are helpful to study the application of LommelGaussian beams.