【摘要】 基于Porras提出的光传输的非傍轴矢量矩理论,推导出初始圆偏振的非傍轴矢量拉盖尔-高斯(LG)光束的特征参数,包括束宽、远场发散角和M2因子等的公式,并表示为级数求和形式.非傍轴矢量高斯光束公式作为特例给出.研究表明,基于二阶矩定义的束宽按双曲线规律传输,当w0/λ→0(w0为束宽,λ为波长)时,远场发散角θ趋于90°,大于非傍轴标量理论预示的值63.435°.非傍轴矢量LG光束的M2因子不仅与模指数p有关,而且还与w0/λ有关.最后,对非傍轴矢量LG光束和非傍轴标量LG光束的传输作了比较,结果表明在w0/λ较小时,矢量效应对远场发散角的影响十分显著.对θ→90°引起的问题和非傍轴矢量矩理论的适用范围,以及解决问题的可能途径作了分析和讨论.更多还原

【Abstract】 Based on the nonparaxial vectorial moment theory of light beam propagation proposed by Porras,the characteristic parameters,such as the beam width,far-field divergence angle and M2 factor of nonparaxial vectorial Laguerre-Gaussian （LG） beams with initial circular polarization,are derived and expressed in terms of a series sum. The nonparaxial vectorial Gaussian beam is treated as a special case of our result. It is shown that the second-order-moment based beam width propagates according to the hyperbolic law,and for w₀/λ→0 （w₀-waist width,λ-wavelength） the far-field divergence angle θ approaches 90°,which is larger than 63.435° predicated by the nonparaxial scalar theory. The M2 factor of nonparaxial vectorial LG beams depends not only on the mode index p,but also on the w₀/λ. Finally,comparison between the propagation of nonparaxial vectorial LG beams and that of nonparaxial scalar LG beams indicates that the far-field divergence angle is greatly influenced by the vectorial effect when w₀/λ is relatively small. The problem which results from θ→90° and the applicability of the nonparaxial vectorial moment theory as well as the possible method for solving the problem are discussed.更多还原