Citation

Qiang G, Hua L, Dapeng F. J. Appl. Optics 2017; 38(4): 578-583.

Copyright

(Copyright © 2017, Ying yong guang xue bian ji bu)

DOI

10.5768/JAO201738.0103001

PMID

unavailable

Abstract

Laguerre-Gaussian (LG) vortex beam has orbital angular momentum (OAM). Recurrence propagation formulae of LG beam through optical system with aperture is analyzed in near field. Phase difference change of LG beam with different orders passing double slit is calculated. Forked diffraction grating on computer is employed to diffract fundamentalmode Gaussian beam, which gives rise to LG vortex beam with different orders. LG beam spot through aperture system and double slit interference pattern are captured via CCD camera. Experimental measurement of LG beam propagation characteristics is conducted in near field. Fork diffraction grating 4 mm×5 mm are displayed on SLM at 1 m distance laser, grating density is about 16 lines/mm. LG hollow beam is generated when size of LG dark spot is between 0.5 mm and 0.9 mm, and width of radius ratio is 0.2. Double slit width is 0.2 mm while double seam spacing is 0.5 mm, in this way clear interference fringes are obtained.

RESULTS can be used in optical communication information encoded optical vortex orbital angular momentum.


Keywords： Laguerre-Gaussian beams, twoslit interference, orbital angular momentum, measurement

拉盖尔-高斯（LaguerreGaussian，LG）光束具有轨道角动量，分析近场条件下LG光束通过含光阑光学系统传输的解析公式，对不同阶LG光束通过双缝时双缝间的相位差变化进行了计算。利用计算机生成叉形衍射光栅显示在空间光调制器上，基模高斯光束产生衍射，得到不同阶次LG涡旋光束，通过CCD采集LG空心光束的光斑及双缝干涉后的图样，实现对LG光束传输轨道角动量特性的实验测量。在确定光束束径下，分析了叉形衍射光栅密度、空心光束宽度半径比、双缝宽度等参数对双缝干涉条纹的影响, 在距离激光器1m处的SLM 上显示4 mm×5 mm 叉形衍射光栅，光栅密度约为16 lines/mm，可产生暗斑尺寸在0.5 mm~0.9 mm之间、宽度半径比为0.2的LG空心光束。LG光束通过双缝宽度0.2 mm，双缝间距0.5 mm的光栅，可以得到清晰的干涉条纹。研究结果为近场光通信中利用光学涡旋轨道角动量编码信息提供了理论依据。

关键词： LG光束 双缝干涉 轨道角动量 测量

Language: en