Single long linear flat-top, double and triple optical beams formation by an azimuthally polarized laser light using a seven-zone BPPF system

Abstract

This study explores the focusing of an azimuthally polarized laser beam with a double-ring shape as it propagates through a seven-zone Binary Phase Pupil Filtration (BPPF) system with a conventional lens, using the concept of vector diffraction. The key features of the focal region in a five-zone BPPF and a seven-zone BPPF system are analyzed and compared using mathematical findings. The commonly utilized long linear flat-top beam may be created by applying suitable angles to the seven-zone BPPF system for a conventional lens with a numerical aperture of 0.9. The intensity of the focus zones was significantly affected when the truncation parameter of the incoming polarized beams was adjusted from a lower to a higher value, generating double and triple focal ring segments. Consequently, it is a simple and novel method to adjust the spacing between focal holes, enabling the trapping of two focal segments simultaneously from the centre. This technique used in cell manipulation, molecular biology used to study the mechanical properties of DNA and proteins, and to investigate molecular motors and other biomolecules, optical engineering, optical microscopy, optical tweezers, lithography, optical micromanipulation, data storage, and beam shaping, etc.,