利用阿基米德螺旋纳米缝产生散斑涡旋

Generation of speckle vortices by Archimedes′ spiral nano-slit

为了研究散斑场的性质,设计了一个利用阿基米德螺旋纳米缝产生散斑涡旋的实验方案。在实验中,把阿基米德螺旋纳米缝的全息图输入到纯相位反射式液晶空间光调制器中。准直的平面光照射到液晶空间光调制器上,经阿基米德螺旋纳米缝调制后所产生的衍射光场由CCD相机捕获。数值模拟和实验结果表明,利用阿基米德螺旋纳米缝可以产生单位拓扑荷散斑涡旋。阿基米德螺旋纳米微缝结构可以应用到光学捕获和光学成像等领域。

In order to study the nature of the speckle field,an experimental scheme to generate speckle vortices which based on the Archimedes′ spiral nano-slit is proposed.First,we theoretically analyze the expression of the light field produced by the plane light perpendicular to the diffraction screen where the Archimedes spiral is located.Then,the light field distribution image is obtained by numerical simulation.In the experiment,the hologram of the Archimedes′ spiral nano-slit is displayed on the screen of a phase-only reflective liquid crystal spatial light modulator(LC-SLM).The collimated plane beam is illuminated on the screen of the LC-SLM,and the diffracted light field generated by the Archimedes′ spiral nano-slit is captured by the CCD camera.In the experiment,the diffracted light field passing through the Archimedes′ spiral nano-slit is interfered with the oblique incident plane light,and the interference fringe appears bifurcation.The bifurcation of the interferograms indicates the presence of the speckle vortices with a unit topological charge in the speckle field.The experimental results are consistent with the numerical results.Numerical simulations and experimental results show that the unit topological charge optical vortex can be generated by using Archimedes′ spiral nano-slit.The Archimedes′ spiral nano-slit structure may provide potential applications in optical capture,optical imaging and so on.