Tight focusing of laser light using microlens array combined with radially polarised light converter

Abstract

ABSTRACT A facile method to prepare a liquid crystal polarisation conversion microlens array (LCPC MLA) is reported. One-step photolithography was used to form a microhole array patterned fluoropolymer poly (butenyl vinyl ether) (CYTOP) layer on the front and back side of a thin glass substrate. On the front side, LC droplets are radially aligned in the microholes, and a twisted radial arrangement texture is formed by the integration of another glass substrate coated with a parallel alignment layer to create the LCPC array. The MLA is located at the rear side of the thin glass substrate and each microlens centre is completely aligned with the centres of the LC droplets in the LCPC array. The LCPC array can convert linearly polarised light to radially polarised light and the MLA can focus the radially polarised light to a spot array. This tightly focused array has a high intensity and at each focused spot, a large component of the electric field is in the longitudinal direction. The LCPC MLA has a compact structure, good stability, and highly uniformity, and it shows potential for applications such as material processing, phase modulation, polarisation compensation, and polarisation imaging.