Extending the depth of focus with high NA lens axicon

Based on vectorial Debye theory, tight focusing of x-polarized beam with high NA lens axicon is studied. The high NA lens axicon utilizes spherical aberration to duplicate the performance of an axicon and to create an extended focal line. The intensity distribution in the focal region is illustrated by numerical calculations. We show that the high NA lens axicon system can generates a sub wavelength beam (0.826λ) with depth of focus around 10λ.     

Tight focusing of partially coherent radially polarized beam with high NA lens axicon

Tight focusing of radially polarized partially coherent vortex beam over a high numerical aperture lens axicon system is introduced and its propagation properties are studied based on vectorial Debye theory. The effect of propagation parameters on the intensity distribution, the polarization property and the coherent property of the beam is illustrated analytically and numerically. It is shown that the correlation length and maximal NA angle has a significant influence on the intensity profile.     

Focusing properties of hyperbolic-cosine-Gaussian beams combining a helical axicon

Focus shape plays an important role in many optical systems, and has attracted much attention. In this article, the focusing properties of hyperbolic-cosine-Gaussian (cosh-Gaussian) beams through a helical axicon were investigated theoretically. Results show that intensity distribution in focal region can be altered considerably by the decentered parameter of cosh-Gaussian beam, axicon parameter and topological charge of the helical axicon. Many novel focal pattern may occur, including annular focus, rectangular focal shape, multiple-peak focal pattern. And in order to show the possible applications of these alter focal pattern, some optical gradient force distributions were also calculated and illuminated.     

Generalization and propagation of spiraling Bessel beams with a helical axicon

A generalized type of spiral Bessel beam has been demonstrated by using a spatially displaced helical axicon (HA).The topological charge of the spiraling Bessel beams is determined by the order of the input Laguerre-Gaussian (LG) beam and the topological charge of the HA.The obtained spiraling Bessel beams have an LG type of modulation along their propagation direction and exhibit annihilation-reconstruction properties.Theoretical analysis is presented,including that of the stability,propagation distance,topological charge,and spiraling dynamic characteristics.The mathematical and numerical results show that the propagation distance and helical revolution of the spiraling Bessel beams can be controlled through choosing appropriate radius of the HA.     

轴锥镜光强分布的角谱衍射数值分析法

针对理论上推导轴锥镜的衍射光场分布解析式较为困难,且用菲涅耳衍射理论分析时存在近轴近似及不能适用于近场衍射光场分析的问题,采用了严格遵从标量衍射亥姆霍兹方程的角谱衍射波前重建方法,对轴锥镜在单色和准单色高斯光波照射下的横向和轴向衍射光强分布特性,以及在单色均匀平面光波照射下的轴向衍射光强分布进行了数值计算和分析。结果表明,轴锥镜后单色光衍射光强分布在几何光束重叠的菱形区域内为近似无衍射贝塞尔光强分布,轴上光强沿光轴方向呈振荡变化,轴上光强分布规律与入射光波的垂轴横向光强分布有关;入射光的准单色性使得贝塞尔衍射条纹对比度略下降、轴上光强沿光轴方向振荡程度减小,但分布规律与单色光一致。     

Spheric long-focal-depth lens

Spheric lens designed by nonlinear phase fitting method is proposed to duplicate the performance of logarithmic axicon, which can obtain a beam with long-focal-depth, small focal spot and side lobe. Moreover, the spheric lens is easier and less expensive for manufacture than logarithmic or aspherical elements. Based on this method, a simple lens is designed for the plasma diagnostic system in inertial confinement fusion. It is verified through Fresnel diffraction integral and an initial experiment that the performance of the lens can satisfy the requirements of the plasma measurements.     

双轴棱锥产生长距离近似无衍射光的新技术

提出了一种利用会聚透镜、轴棱锥等简单光学元件产生长距离近似无衍射光的新技术. 分别利用几何光学和衍射理论分析了该方法产生长距离近似无衍射光束的原理, 通过软件模拟了长距离近似无衍射光束的形成过程,得出了该光束在不同距离处的横向光强分布. 模拟结果显示该光束在较长距离处的横向光强分布满足Bessel分布. 从实验上获得了传播距离长达80 m、中心光斑发散角约为0.12 mrad的近似无衍射光束, 相比于国外学者最近的研究成果(Belyi et al. 2010 Opt. Exp. 18 1966)将传播距离延长了50多米,而光束发散角压缩了22倍.实验中, 对光束沿光轴传播时在不同距离处的光斑进行了拍摄,所得实验结果与理论分析基本符合.     

产生不同类型局域空心光束的可拆式组合轴棱锥

提出一种产生尺寸可调局域空心光束的新型光学元件——可拆式组合轴棱锥,这种新型光学元件是在传统轴棱锥的中部沿其轴线方向贯通开设一圆孔,在圆孔内嵌设一第二轴棱锥组成。通过更换不同底角的第二轴棱锥(或第一轴棱锥),可形成不同尺寸的单个局域空心光束或周期性局域空心光束。从几何光学出发分析了产生局域空心光束的原理,计算了局域空心光束的相关参量。由衍射积分理论分析和模拟了新型光学元件的光强分布特性。几何光学和衍射理论所得分析结果基本吻合。     

axicon透镜焦点光斑的点列图计算

介绍应用几何光学点列图仿真平行光斜入射于axicon透镜后的焦点光斑的程序设计方案，给出并讨论了点列图计算结果。     

半凸旋转棱镜对光束变换

本文对半凸旋转棱镜对光束变换进行了详细的理论分析，定量计算了变换光束的空间强度分布。结果表明经半凸旋转棱镜变换产生的光束具有“无衍射”性质