TIGHTLY FOCUSING PROPERTIES OF RADIALLY POLARIZED DOUGHNUT GAUSSIAN BEAM THROUGH A UNIAXIAL BIREFRINGENT CRYSTAL

Abstract

The properties of radially polarized doughnut shaped beam tightly focused through aC system is studied numerically by the use of vectorial diffraction theory for small birefringence condition. It is observed that many novel focal patterns such as sub wavelength scale focal spot, focal hole and flattop profiled focal spot evolved considerably when properly choosing the doughnut angle (θ0) of incident Doughnut Gaussian (DG) beam. We also observed that axial shifting of generated focal patterns is possible with increasing the birefringence value [Δn] of the uniaxial crystal. We expect such a possibility of tuning and shifting the generated focal patterns finds possible applications in optical trapping and manipulating of particles and in material processing.