Annular focusing light spot realization method and realization device thereof

Abstract

The invention discloses an annular focusing light spot realization method. The method includes that a laser beam is expanded and collimated and then the expanded and collimated laser beam is converted into a linearly polarized laser beam; the laser beam phase modulation is carried out on the linearly polarized laser beam after the collimation and expansion by means of a reflective pure phase spatial light modulator; the linearly polarized light is imaged after the phase modulation to the rear aperture plane of a focusing object lens via a 4F imaging system; the object lens is used to focus the phase-modulated incident linearly polarized laser beam, a plurality of focal points are generated on the circumference in the focal plane area, and the azimuthal spacing between the focal points equal is equal; an annular light spot is generated when the circumference radius is reduced to a wavelength lambda, and the size of the annular light spot is continuously decreased when the circumference radius r changes until a solid light spot is formed; and when a plurality of phase modulation graphs are calculated, the change in the corresponding position movement of each graph is small, and the phase map of the spatial light modulator is updated so that the annular light spot moves continuously. The annular focusing light spot realization method realizes the non-vortex plane linearly polarized light focusing to generate the dynamic annular light spot which is accurate in position and size control.

Description

technical field [0001] The present invention relates to the field of optics, in particular to a method and device for realizing an annular focus spot. The laser beam is focused by a high numerical aperture objective lens to produce a special shape, and an annular focus with controllable position and changeable size on the focal plane is produced. spot. Background technique [0002] The laser beam is focused by a high numerical aperture objective lens, and its spot shape, position, phase distribution, intensity distribution, and polarization distribution are related to the amplitude distribution, polarization state, phase modulation of the incident laser beam, and the numerical aperture of the objective lens. Since the spot produced by laser focusing through the objective lens is related to many application fields, it has become a very important research field to study how to achieve the laser focusing spot required by various applications by changing the amplitude distributi...

AI Technical Summary

Problems solved by technology

But there is no way to focus the vortex linearly polarized beam to produce a circularly symmetrical ring spot

Moreover, the size of the annular spot can only be changed by changing the integer value of the topological charge, and this change is discontinuous

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