双环径向偏振涡旋光束经介质界面的深聚焦

Tight focusing of double-ring-shaped radially polarized vortex beam through dielectric interface

基于矢量德拜理论,研究了双环径向偏振涡旋光束经介质分界面的深聚焦特性。当选取适当的入射光束拦截比时(即透镜孔径半径与入射光束的束腰半径的比),在聚焦场中可以得到一个极小的局域空心光束。局域空心光束的大小不仅与透镜的数值孔径有关,还与聚焦场介质的折射率有关。另外,还研究了透镜的数值孔径、入射光束的拦截比以及探测深度对聚焦光束实际焦点位置的影响。通过对聚焦光束的实际焦点位置的计算发现:当选取一定的光束拦截比时,聚焦光束存在一个焦点开关。

Based on the vectorial Debye theory,the tight focusing of double-ring-shaped radially polarized vortex beams（DRS-RPVBs） through a dielectric interface is investigated.The investigation illustrates that when the interception ratio of the aperture radius to the incident beam waist radius is proper,a tiny bottle beam can be obtained in the focal region.The size of the bottle beam is dependent on the numerical aperture of the objective and the refractive index of the medium in the focal region.In addition,the influence of the numerical aperture,interception ratio and probe depth on the focal shift is investigated.And the calculation for the real focus location indicates that,for a proper interception ratio,there exists a jump in the location.