Tightly Focusing Properties of Radially Polarized Double Ring Shaped Beam through a Uniaxial Birefringent Crystal

The properties of radially polarized Double ring shaped beam tightly focused through a uniaxial birefringent crystal are studied numerically by the use vectorial diffraction theory for small birefringence. The intensity distribution of focal structure in the focal region can be shift along the longitudinal axis with increasing the birefringence value [Δn], and splitting of focal spot can be obtained by changing the pupil to beam ratio[β].and also splitting of single focal spot into double spot by changing the pupil to beam ratio[β].