Creating adjustable uniform optical cages through polarization shaping in a low NA optical system.
We propose a method to generate uniform optical cages with adjustable number and position along the optical axis in a low numerical aperture (NA) optical system. The uniform optical cages are the superposition of multiple dark and bright spots, which are of x- and y-polarized electric fields with the neglected axial component obtained, respectively, by focusing a quasi-x-polarized vortex beam with topological charge 1 and a quasi-y-polarized beam. By adjusting the number and position of the dark and bright spots with reversal radiation theory, valuable optical cages with uniformity up to 1, such as multiple optical cages, optical chain, and optical tube, can be realized. Moreover, the influences of the axial field to the quality of optical cages are also investigated. Numerical results show that an effective optical cage with uniformity up to 0.695 can be achieved even with an NA close to 0.75. The generated optical cages may find valuable application in optical trapping of samples with a large scale, which are difficult to be trapped under a high NA focusing condition.
Xiaoyu
X
Weng
Luping
L
Du
Peng
P
Shi
Xiaocong
X
Yuan