Multiplication of a Gaussian beam by a multisector binary phase plate into scalar vortex beams for laser microprocessing

Abstract

Subject of study. A method of multiplying Gaussian laser beams into scalar vortex beams using multisector binary phase plates for increased speed and productivity of laser microprocessing is studied. The purpose of the work is to apply the technology of structuring transparent dielectrics by a laser-induced microplasma for fabricating multisector binary phase plates on fused silica. Methodology of the work. Multisector binary phase plates on fused silica structures with 4, 6, and 10 sectors with phase levels of 0 and π for operation at a wavelength of 1.06 µm were fabricated using an experimental setup for implementing the laser-induced microplasma technology. Additional annealing was conducted in a furnace to clean the surface and reduce the roughness of the multisector binary phase plates in the area of laser-induced microplasma action. The fabricated multisector binary phase plates were tested by registering generated intensity distributions in the plane of increased contrast using a photosensitive camera and by ablation of steel samples. We measured the initial laser beam energy and multisector binary phase plate output energy to evaluate the energy conversion efficiency. Main results. The obtained results indicate that the fabricated multisector binary phase plates multiply a Gaussian beam into a series of diffraction-limited spots surrounding the region with zero intensity and the same intensity (standard deviation not larger than 1%), the same spot diameters (standard deviation not larger than 5%), and high energy conversion efficiency (approximately 92%). Practical significance. Such multisector binary phase plates fabricated by a laser-induced microplasma have a real prospect for use in the field of laser microprocessing of materials.