Nonparaxial propagation of a super-Lorentz-Gauss SLGmode beam

Based on the vectorial Rayleigh-Sommerfeld integral formulae,this paper derives the analytical nonparaxial propagation equation of a super-Lorentz-Gauss (SLG) SLG 01 mode beam in free space.The far field expression and the scalar paraxial result are treated with special cases of the general formulae.According to the obtained analytical representation,the nonparaxial propagation properties of the SLG 01 mode beam are illustrated and analysed with numerical examples.This research provides an approach to investigate the propagation of the SLG 01 mode beam within the framework of the nonparaxial regime.     

Far-field divergence of a vectorial plane wave diffracted by a circular aperture from the vectorial structure

Based on the vectorial structure of an electromagnetic wave, the analytical and concise expressions for the TE and TM terms of a vectorial plane wave diffracted by a circular aperture are derived in the far-field. The expressions of the energy flux distributions of the TE term, the TM term and the diffracted plane wave are also presented. The ratios of the power of the TE and TM terms to that of the diffracted plane wave are examined in the far-field. In addition, the far-field divergence angles of the TE term, the TM term and the diffracted plane wave, which are related to the energy flux distribution, are investigated. The different energy flux distributions of the TE and TM terms result in the discrepancy of their divergence angles. The influences of the linearly polarized angle and the radius of the circular aperture on the far-field divergence angles of the TE term, the TM term and the diffracted plane wave are discussed in detail. This research may promote the recognition of the optical propagation through a circular aperture.vspace1mm     

Near-field characteristics of highly non-paraxial subwavelength optical fields with hybrid states of polarization

The vectorial structure of an optical field with hybrid states of polarization(So P) in the near-field is studied by using the angular spectrum method of an electromagnetic beam. Physical images of the longitudinal components of evanescent waves are illustrated and compared with those of the transverse components from the vectorial structure. Our results indicate that the relative weight integrated over the transverse plane of the evanescent wave depends strongly on the number of the polarization topological charges. The shapes of the intensity profiles of the longitudinal components are different from those of the transverse components, and it can be manipulated by changing the initial So P of the field cross-section. The longitudinal component of evanescent wave dominates the near-field region. In addition, it also leads to three-dimensional shape variations of the optical field and the optical spin angular momentum flux density distributions.     

Orbital angular momentum density and spiral spectra of Lorentz–Gauss vortex beams passing through a single slit

Based on the Hermite–Gaussian expansion of the Lorentz distribution and the complex Gaussian expansion of the aperture function, an analytical expression of the Lorentz–Gauss vortex beam with one topological charge passing through a single slit is derived. By using the obtained analytical expressions, the properties of the Lorentz–Gauss vortex beam passing through a single slit are numerically demonstrated. According to the intensity distribution or the phase distribution of the Lorentz–Gauss vortex beam, one can judge whether the topological charge is positive or negative. The effects of the topological charge and three beam parameters on the orbital angular momentum density as well as the spiral spectra are systematically investigated respectively. The optimal choice for measuring the topological charge of the diffracted Lorentz–Gauss vortex beam is to make the single slit width wider than the waist of the Gaussian part.     

高斯光束经圆形光阑衍射的远场发散特性

线偏振高斯光束经圆形光阑衍射后,其远场可表示成互相正交的横电(TE)项和横磁(TM)项之和。利用TE项和TM项的远场能流分布,导出了高斯衍射光束的TE项和TM项远场功率的解析表达式,由此可度量TE项和TM项在远场占总功率的比例。基于能流二阶矩的定义,给出了高斯衍射光束、TE项和TM项远场发散角的解析式以及三者远场发散角间的关系通式,重点分析了f参数和截取参数对远场发散角的影响。结果表明:随着f参数的增大,远场发散角先增大后趋向于各自的饱和值。截取参数对远场发散角的影响与f参数相关,当f参数较大时,截取参数对远场发散角的影响不明显;当f参数适中时,随着截取参数的增大,远场发散角先减小后趋向于各自的最小值;但当f参数较小时,高斯衍射光束和TM项二者的远场发散角出现一定的波动性。     

半导体激光器的M2因子可以小于1

根据Porras的非傍轴矢量矩理论,对双异质结半导体激光器的光束质量进行了研究.结果表明,在有源层厚度d_a远小于波长λ的条件下,半导体激光器的M²因子可以小于1,并且没有下限.     

关于M21激光束的分析

对实验上和理论上出现的Ｍ＾２〈１激光束作了综述,并进行了分析与研究,发现真正可行、实用的Ｍ＾２〈１激光束只有由点光源经尾部控制衍射在中央输出经轴上相博士干叠加成新谓的余弦－高斯光束。     

Structural polarization properties of vector Gaussian beam in the far field

Based on the vector angular spectrum representation of optical beam and the method of stationary phase, the analytical TE and TM terms of vector Gaussian beam have been presented in the far field. By using the local polarization matrix, the polarization properties of the TE and TM terms in the far field are investigated, and it is found that the degree of their polarization is only determined by the spatial location. When the source is completely polarized, the TE and TM terms are both completely polarized in the far field. When the source is completely unpolarized, the TE and TM terms in the far field are partially polarized. The whole beam is also partially polarized except on the propagating axis. Moreover, the degrees of polarization of TE and TM terms are both larger than that of the whole beam.[第一段]     

任意线偏振高斯光束的非傍轴传输

运用非傍轴光束传输的矢量矩理论，对任意线偏振高斯光束的非傍轴传输进行了系统的研究，给出了定量计算偏振对束腰、横向远场发散角和光束传输因子贡献的解析通式. 并对高度非傍轴和傍轴两种极端情形，简化了相应的计算式. 在高斯光源线度趋向于零的极限情形下，两个横向的最大发散角均为90°，与偏振态无关. 在高度非傍轴情形下，可以通过所给出的解析通式设计高斯光源的半宽度与激射光波长之比值以及线偏振态来达到所期望的光束传输特性. 对于傍轴情形，不同偏振对束腰和横向远场发散角稍有影响，但这种影响一般可以忽略不计；而光束传输因子却始终保持不变，与偏振态无关. 若介于这两种极端情形之间，则可以根据高斯光源的半宽度之值和所期望的计算精度，确定解析式中级数的项数进而确定任意线偏振高斯光束的非傍轴传输特性. 关键词： 高斯光束 非傍轴传输 偏振 二阶矩     

Exotic interactions between solitons of the （2＋1）-dimensional asymmetric Nizhnik-Novikov-Veselov system

Starting from the extended tanh-function method (ETM) based on the mapping method, the variable separation solutions of the (2+1)-dimensional asymmetric Nizhnik--Novikov--Veselov (ANNV) system are derived. By further study, we find that these variable separation solutions are seemingly independent of but actually dependent on each other. Based on the variable separation solution and by choosing appropriate functions, some novel and interesting interactions between special solitons, such as bell-like compacton, peakon-like compacton and compacton-like semi-foldon, are investigated.