Generation of multiple focal spot using phase modulated radially polarized TEM11 * mode beam

Abstract

We propose a new approach for generating multiple focal spots segment of sub wavelength size, by tight focusing of phase modulated double ring shaped radially polarized beam. The focusing properties are investigated theoretically by vector diffraction theory. We proposed to design of binary phase plate (BPP) which can tune the phase of the incident RTEM11 * mode radially polarized Laguerre –Gaussian beams (R-TEM11*) beam in such way to generate a focal segment with four and three numbers of focal spots repectively. We also observed that by properly tuning the pupil to beam ratio(β) of the incident R-TEM11* beam, the generated four or three focal spot segment can be tuned to a focal segment of two focal spot.