Theoretical generation of arbitrarily homogeneously 3D spin-orientated optical needles and chains.

Abstract

The generation of homogeneously 3D spin-orientated optical needles and optical chains is investigated by focusing the annular collimated beam composed of radially polarized component and azimuthally polarized vortex components with aplanatic focusing systems. Using the Richards-Wolf vector diffraction theory, analytic expressions of focal electric fields and target spin-orientation are given. The results show that the spin-orientation is tunable by changing two parameters of the incident beam while keeping the mean size of the focal spot under 0.5λ. Spin-orientation homogeneity purity is introduced to evaluate spin-orientation homogeneity quantitatively and the results present that spin-orientation homogeneity purity is always beyond 0.996 when spin-orientation varies.