An optical element capable of producing long-distance bessel beams

Abstract

The invention discloses an optical element capable of generating a long-distance Bessel light beam. The optical element is a plane lens. The refractive index of the plane lens shows linear gradient change in the radial direction. The linear gradient change in the refractive index in the radial direction enables the plane lens to have the line focusing effect as an axicon, and an incidence light beam is subjected to line focusing to generate a Bessel light beam. The surface of the optical element is a plane and is wear-resistance, so that the problem of turning the optical element into a round-top axicon due to wearing is solved, and modulation of the refractive index and the thickness reduces processing requirements to the greatest extent. The non-diffracting distance of the Bessel light beam of linear change can be generated by changing parameters of the material thickness and the refractive index, and Bessel light beams of different non-diffracting distances can be formed by modulation. Therefore, the optical element provided by the invention is an optical element, which is simple, has high operability and is flexible and high in light beam quality, for generating Bessel light.

Description

Technical field [0001] The invention relates to an optical element capable of generating long-distance Bessel light beams, belonging to the field of optical transmission conversion and optical design. Background technique [0002] The Bessel beam is a special beam with unique properties in the transmission field, such as the central spot is extremely small, the central light intensity is extremely large, it does not diverge within a certain range, and it rebuilds itself when encountering obstacles. These characteristics of the Bessel beam make it applied in the fields of particle trapping, optical tension, optical imaging, optical guidance, high-precision orientation or collimation, etc. The research of Bessel beam has long become a hot spot in the field of beam transformation. [0003] An axicon is a conical axisymmetric optical element, because the axicon method is more operability, energy conversion efficiency is higher, and the beam quality is better. At present, axicons are of...

AI Technical Summary

Problems solved by technology

[0003] Axicon is a conical axisymmetric optical element, because the Bessel beam produced by the axicon method has stronger operability, higher energy conversion efficiency, and better beam quality. Currently, axicons are often used to generate Bessel beams. However, this The method has high requirements on the base angle of the axicon (under normal conditions, a 1° axicon can only produce an approximate Bessel light of 24.4 cm with a He-Ne laser at a 4 mm aperture), and due to processing limitations, it is difficult to make the base angle of the axicon is extremely small (0.5° is already very small), which limits the increase of the non-diffraction distance of the Bessel beam, which is greatly limited in practical applications (such as laser ranging)

Furthermore, the central cone angle of the axicon is extremely vulnerable to damage. After damage, it becomes a domed axicon, which will reduce the beam quality and affect the experimental results.

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