CN102819110B - Novel axicon capable of generating multiple Bottle beams - Google Patents

Abstract

The invention discloses an axicon capable of generating multiple local hollow light beams. The axicon is based on the traditional axicon and the vicinity of the top is arranged in a spherical structure. The axicon of the present invention can produce multiple bottle beams through a single element, which not only has the advantages of simple element structure, high conversion efficiency, high optical damage threshold, and energy concentration, but also produces multiple bottle beams with energy concentration, which can improve the The strength of particle confinement. It provides a simple and effective new way to obtain multiple local hollow beams. It has guiding significance for particle manipulation such as particle trapping.

Description

Axicon that Generates Multiple Localized Hollow Beams

technical field

The invention relates to the field of optical design, in particular to a novel axicon capable of generating multiple Bottle beams (local hollow beams).

Background technique

Bottle beam is a special light beam with a dark field on the propagation axis, which is a closed area surrounded by surrounding high-intensity light. Because of this special property, Bottlebeam is used in many fields of optics, such as optical tweezers, laser catheters, optical wrenches, thick medium imaging, etc., and can also be used for particle trapping, playing an important role in life science and nanotechnology. It has been a hotspot of research in recent years.

At present, the methods for producing bottle beams mainly include Bessel beam focusing to produce a single bottle beam, two beams of Bessel beams coherently superimposed to produce a self-imaging bottle beam, a laser to directly output a bottle beam, and parallel light incident to a new type of axicon to directly generate a bottle beam, among which a new type of axicon is used The bottle beam structure is simple and easy to adjust. The gradient axicon and liquid axicon proposed by our research group have these advantages.

The confinement of particles by the local hollow beam is mainly achieved by the light intensity gradient in the dark region. The larger the light intensity gradient is, the stronger the confinement of particles is. In the existing methods for generating local hollow beams, the light intensity gradient of the local hollow beams produced is small, and the scattering force of trapped particles is weak.

Contents of the invention

The object of the present invention is to provide an axicon capable of generating multiple localized hollow beams, and the localized hollow beams generated by the axicon have the characteristic of strong scattering power of trapped particles.

In order to achieve the above object, the present invention adopts the following technical solutions:

An axicon that can generate multiple local hollow beams, including a base part and a top part arranged along the same axis line, the base part is a circular frustum with a base angle of γ, an upper base radius of R ₂ , and a lower base radius of R ₁ Shaped structure, wherein R ₂ < R ₁ ; the top part is a spherical crown structure with the upper bottom surface of the above-mentioned base part as the bottom surface and the radius of curvature is r, and the bottom surface of the above-mentioned top part coincides with the upper bottom surface of the above-mentioned base part. Together, the above radius of curvature

The above-mentioned base part and the above-mentioned top part are of an integral structure.

After adopting the above scheme, the axicon of the present invention, when parallel light is incident on the novel axicon of the present invention, can be divided into two parts according to the refraction effect of light in different regions of the axicon, and the first part is the region of 0<R< _R2 , this area forms a plano-convex lens, and the light passing through this area is converged at the focal point by the plano-convex lens; the second part is the area of R ₂ <R<R ₁ , at this time, the light can be equivalent to the situation of refraction through an axicon, A Bessel beam will be formed. The coherent superposition of the converging spherical waves and Bessel beams can generate multiple bottle beams.

The axicon of the present invention not only has the advantages of simple structure of the traditional axicon, high light damage threshold, and high energy conversion efficiency (almost up to 100%), but also the energy of the bottle beam produced is concentrated, and the scattering force of the trapped particles is strong, which is beneficial to the bottle The generation and application of beam has guiding significance.

Description of drawings

Fig. 1 is the structural representation of novel axicon of the present invention;

Fig. 2 is the refracted light path figure of parallel light incident axicon of the present invention;

Fig. 3 is the axial light intensity simulation diagram of a plurality of Bottle beams produced by the axicon of the present invention;

Fig. 4 is a cross-sectional light intensity simulation diagram of a plurality of Bottle beams produced by the axicon of the present invention.

Detailed ways

The structure and principle of the axicon of the present invention will be described in further detail below in conjunction with the accompanying drawings and examples.

The present invention can produce the axicon of a plurality of local hollow light beams, as shown in Figure 1, comprise the base part 1 and the top part 2 that are arranged along the same axis line, this base part 1 is that the base angle is γ, and the radius of the upper base is γ. R ₂ , a truncated conical structure with a lower base radius of R ₁ , wherein R ₂ <R ₁ ; the top part 2 is a spherical crown structure with the upper bottom of the base part 1 as the bottom surface and a curvature radius of r, and the top part 2 The bottom surface of the base part 1 coincides with the upper bottom surface of the base part 1, and the above-mentioned radius of curvature $r=\frac{R_1+R_2}{2\mathrm{\&gamma;}}.$

The axicon of the present invention can be processed on the basis of the traditional axicon. Take a traditional axicon with a base angle of γ and a base radius of R ₁ , take the axis as the center and R ₂ (R ₂ < R ₁ ) as the radius, grind the top of the axicon into a curvature radius of , so that a plano-convex lens is formed in the area of 0<R<R ₂ , and the part of R ₂ <R<R ₁ can be regarded as a traditional axicon.

From geometrical optics analysis, it can be seen that when the light beam is vertically incident on the axicon of the present invention, as shown in Figure 2, the light rays of the 0<R< _R2 part are focused at the focal point F by the plano-convex lens, and the _R2 <R< _R1 part The light rays are refracted by the axicon to form a Bessel beam between Z ₁ and Z ₂ . Adjusting the spherical curvature radius r according to the requirements can change the focal point F of the plano-convex lens, so that the focal point is in the middle of the non-diffraction area of the Bessel beam, that is From the geometric relationship, it can be known that The coherent superposition of the converging spherical waves and Bessel beams can form multiple bottle beams.

As an example, the parallel light source of the incident axicon of the present invention adopts He-Ne laser λ=632.8nm, and the axicon material in Fig. 1 adopts quartz glass n=1.45, bottom surface radius R ₁ =5mm, R ₂ =1.5mm, Base angle γ=2°, corresponding r=93.106mm. Fig. 3 is the axial light intensity distribution behind the axicon, and Fig. 4 is the cross-sectional distribution diagram of the light beam in two cycles, (a) z=200mm in this Fig. 4; (b) z=203mm; (c) z= 205.5 mm; (d) z=208.5 mm; (e) z=211.5 mm.

The axicon that can generate multiple bottle beams of the present invention has the advantage that multiple bottle beams can be obtained through a single element, which not only has the advantages of simple structure, high light conversion efficiency, and high optical damage threshold of the traditional axicon element, but also The energy concentration of the generated Bottle beam can increase the strength of particle confinement, which has special significance for particle manipulation such as particle confinement.

Claims (2)

1. An axicon capable of producing multiple local hollow beams, characterized in that: it includes a base portion and a top portion arranged along the same axis, the base portion has a base angle of γ, an upper base radius of R ₂ , and a lower base A frustum-shaped structure with a radius of R ₁ , wherein R ₂ < R ₁ ; the top part is a spherical crown structure with the upper bottom surface of the above-mentioned base part as the bottom surface and a radius of curvature r, and the bottom surface of the above-mentioned top part is in contact with the above-mentioned base part The upper and bottom surfaces of the two are coincidently compounded together, and the above-mentioned radius of curvature $r=\frac{R_1+R_2}{2\mathrm{\&gamma;}}.$ 2. The axicon capable of generating a plurality of localized hollow beams according to claim 1, characterized in that: the base part and the top part are of an integral structure.