Multisector binary phase plates on fused silica for generation of optical vortex beams superposition: Fabrication, characterization, and applications

Abstract

The paper describes the fabrication of multisector binary phase plates (MBPPs) on fused silica to generate the optical vortex beams (OVBs) superposition. Laser-induced microplasma plays the role of a spot tool for etching sectors which provides the required phase shifts – π and π/2 relative to non-etched sectors. We fabricated MBPPs with four, six, eight, ten and twenty sectors with 0 and π phase levels and plates with eight, ten and twelve sectors with 0 and π/2 phase levels. The depth of etched sectors was controlled by profilometry with vertical resolution ± 10 nm and diffraction-interference contrast optical microscopy. To evaluate the quality and depth of focusing, we analyzed the OVBs superposition with CCD camera. The OVBs superposition exists as spatially separated diffractive limited spots encircling over perimeter of the central area with the intensity reducing to zero. We also measured the efficiency of Gaussian beam conversion into the OVBs superposition for MBPPs of both types. MBPP was used in an optical setup with the nanosecond laser (the wavelength of 1060 nm) for simultaneous processing of steel plates.