Method for generating Bessel-like beams by growing microcones on fiber end faces

Abstract

The invention belongs to the technical field of beam conversion, in particular to a method for generating Bessel-like beams by growing microcones on the end faces of optical fibers. The invention includes: depositing a photopolymer liquid reagent on the end face of a single-mode fiber, coupling a green laser into the single-mode fiber through a lens, and reacting with the photopolymer liquid reagent deposited on the end face of the single-mode fiber to form a polymer microcone; After passing through the polymer microcone formed on the fiber end face, it transforms into a Bessel-like beam. The shape of the microcones is controlled by photopolymerization parameters such as green laser power, laser exposure time, and oxygen diffusion concentration. The working bandwidth of this microcone covers the entire visible light region and even the near-infrared band, and can have more than 30 concentric rings at most, and the generated Bessel-like beam has self-restoring properties. The method of the invention is efficient, low-cost, and convenient, and can be widely used in the fields of particle manipulation, optical imaging, nonlinear optics, photolithography, micro-manufacturing, and the like.

Description

technical field [0001] The invention belongs to the technical field of beam conversion, and in particular relates to a method for generating Bessel-like beams. Background technique [0002] The concept of a non-diffracting beam was proposed by Durnin in 1987, which is actually a zero-order Bessel beam, and Durnin pointed out that on any cross-section perpendicular to the propagation direction of the Bessel beam, the light intensity distribution of the Bessel beam Both have the form of zero-order Bessel functions of the first kind. The intensity distribution of the ideal Bessel beam cross-section appears as a central bright spot and a series of concentric rings, the intensity decreases from the inside to the outside, and the light intensity distribution does not change during the propagation process. Although the practically achievable Bessel-like beam has a limited non-diffraction-free propagation range, it also has self-recovery properties when encountering opaque obstacle...

AI Technical Summary

Problems solved by technology

The first is the selective chemical etching of optical fibers, which can create tapered lenses aligned with the fiber core and optimize the taper angle, but the required chemical process is time-consuming and has surface roughness issues

The second method is to use a focused ion beam (FIB), whereby the fiber core end face is conically shaped, however, FIB systems are expensive and produce Bessel-like beams inefficiently compared to other methods

The most convincing way at present is to use long-period gratings to excite the LP 0，m mode, it can produce a good Bessel-like beam, but the device can only work in a relatively narrow wavelength range

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