Vector beam tuning with axisymmetric dielectric micro helical cone

Abstract

Here, we present a novel structure named as axisymmetric dielectric microhelical cone, which combines axisymmetric dielectric microhelical structure and a conic structure to produce localized vector vortex nanofocused optical field. The intensity distribution, Poynting vector, and phase distributions of the electric fields generated by the structure are simulated with the three-dimensional finite-difference time-domain method. The simulation results indicate that special electric field with different localized vortex effects generated when the structure is illuminated by different polarization states and the off-axis focused light spots can be tuned by changing the numbers of symmetry axes N. We also experimentally prove that it can generate a shaped beam similar to the beam generated by the axisymmetric dielectric microhelical cone structure, which can keep well by imposing the phase masks of the structure onto a spatial light modulator. The localized vector vortex beam generated by the structure has potential application in optical tweezers.