A crossed focused vortex beam with application to cold molecules

We report the generation of a crossed, focused, optical vortex beam by using a pair of hybrid holograms, which combine the vortex phase and lens phase onto a spatial light modulator. We study the intensity distributions of the vortex beam in free propagation space, and the relationship of its dark spot size with the incident Gaussian beam's waist, the lens's focal length, and its orbital angular momentum. Our results show that the crossed, focused, vortex beam's dark spot size can be as small as 16.3μm and adjustable by the quantum number of the orbital angular momentum, and can be used to increase the density of trapped molecules. Furthermore, we calculate the optical potential of the blue-detuned, crossed vortex beam for MgF molecules. It is applicable to cool and trap neutral molecules by intensity-gradient-induced Sisyphus cooling, as the intensity gradient of such vortex beam is extremely high near the focal point.     

非线性晶体产生的空心光束中大尺寸粒子囚禁与导引

提出了一种基于非线性ZnSe晶体产生的空心光束与光泳力的大尺寸粒子二维囚禁与一维导引、三维囚禁方案.理论上分析并计算了单个非线性ZnSe晶体产生的空心光束内粒子受到的横向与纵向光泳力,纵向光泳力的大小同粒子尺寸与光束尺寸比例的四次方成正比,与空心光束功率成正比,方向与光束传播方向一致.粒子尺寸与空心光束尺寸越接近时,横向光泳力的大小越大.结果表明该光泳力可以实现对大尺寸粒子的二维囚禁,同时可对粒子进行长距离(米量级)一维定向导引;理论上分析并计算了基于双非线性ZnSe晶体产生的局域空心光束内粒子所受横向与纵向光泳力情况,光泳力与系统参数的依赖关系与单个非线性晶体产生的空心光束中的粒子受力情况类似,不同的是该条件下纵向光泳力指向光束中心.结果表明该局域空心光束可以实现大尺寸粒子的三维有效囚禁.基于非线性ZnSe晶体产生的空心光束或者局域空心光束可以作为大尺寸粒子非接触式有效操控的工具,在现代光学以及生物医学中有潜在的应用.