WO2020037813A1

WO2020037813A1 - Double-lug circular diffraction diaphragm and vortex optical topological charge number detection system and method

Info

Publication number: WO2020037813A1
Application number: PCT/CN2018/112176
Authority: WO
Inventors: 陈书青; 张安; 陈学钰; 谢智强; 王佩佩; 刘俊敏; 苏明样; 贺炎亮; 李瑛�
Original assignee: 深圳大学
Priority date: 2018-08-24
Filing date: 2018-10-26
Publication date: 2020-02-27
Also published as: CN109029745A; CN109029745B

Abstract

Disclosed by the present invention are a double-lug circular diffraction diaphragm and a vortex optical topological charge number detection system and detection method, the double-lug circular diffraction diaphragm comprising double-lug circular diffraction holes, wherein the double-lug circular diffraction hole is mainly formed by a lemniscate, a first arc and a second arc, the centers of the first arc and the second arc being located in the symmetric center of the lemniscate; the first arc is connected to the upper side of the lemniscate, the second arc is connected to the lower side of the lemniscate, and the ratio of the transverse length of the lemniscate to the radius of the first arc is (2.5-3.2): 1; and the double-lug circular diffraction holes are bilaterally symmetrical. According to the present invention, a vortex optical topological charge number may be measured by means of single aperture diffraction, so that the influence of the arrangement accuracy of multi-aperture mesopores on measurement precision is avoided. When a vortex light beam is adjusted to be coaxial with a double-lug circular aperture, the purpose of detecting the vortex optical topological charge number may still be achieved by diffraction light intensity distribution, even though a certain deviation exists. Therefore, the present technical solution has certain tolerance for detection operation error.

Description

Binocular circular diffraction diaphragm and vortex light topological charge number detection system and detection method

Technical field

The invention relates to the field of information optics, in particular to a binaural circular diffractive diaphragm and a vortex light topological charge number detection system and detection method.

Background technique

A vortex beam is a structured beam that carries orbital angular momentum. It has a special spiral wavefront structure and a fixed topological charge. This kind of light beam with spiral phase structure will form a ring with orbital angular momentum when focusing, instead of the ordinary spot, it is mainly caused by the phase singularity. In 1992, Allen et al. Pointed out that the spiral phase distribution of a vortex beam can be described by the exp (ilθ) phase function, with each photon carrying

Orbital angular momentum. Where l is the topological charge number θ of the vortex light is the azimuth, and

Is the Planck constant divided by 2π. In other words, each photon of a monochromatic vortex beam can theoretically carry both orbital angular momentum (OAM) and spin angular momentum (SAM), which affect the polarization and spatial distribution of vortex light, respectively. Recent studies have shown that vortex beams have great application value in the fields of optical tweezers, light capture, and quantum information technology research because of their ability to manipulate micro / nano particles. Especially in the field of quantum information technology research, due to the existence of infinite orthogonality between orbital angular momentum modes, the use of orbital angular momentum modes can effectively realize the transfer of information and greatly expand the capacity of transmitting information. In the study of vortex beams, orbital angular momentum is an important parameter for describing the characteristics of vortex beams. How to efficiently determine the magnitude of orbital angular momentum has become a top priority, and the magnitude of orbital angular momentum is the topological load through the vortex beam Reflected by the number l, the topological charge number l reflects the phase change law of the beam around the singular point. Therefore, it is of great research significance to explore a more efficient method to detect the topological charge of vortex beams.

In recent years, in the research of topological charge measurement, researchers have found several more effective measurement methods. In 2008, Gregarious C.G. Berkhout and Marco W. Beijersbergen et al. Proposed a porous method to measure the orbital angular momentum of vortex beams. In 2009, Wang Tao et al. Studied the single-slit diffraction characteristics of Laguerre-Gaussian beams based on Fresnel diffraction integral theory. In the same year, Guo Chengshan, Lu Leilei and others proposed the annular band Fourier transform method to measure the topological charge of vortex beams. In 2012, Yang Yuanjie and others used the cross-spectral density function method to measure the orbital angular momentum of partially coherent vortex light.

Although the above measurement methods can effectively determine the topological charge of vortex light, there are certain challenges in practical applications. For example, in the porous measurement method, the size of the topological charge is often related to the size and arrangement of the porous. The arrangement of sigma seriously affects its measurement accuracy. Although the ring-band Fourier measurement method and cross-spectrum density function method can accurately measure the topological charge, the experimental system structure is more complicated and is not suitable for practical applications.

Therefore, the existing technology needs to be improved and developed.

Summary of the Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a binaural circular diffractive diaphragm and a vortex light topological charge number detection system and a detection method, which aim to solve the existing topological charge of vortex light measurement in the field of information optics The method of numerical accuracy is not enough and the system structure is more complicated.

The technical solution of the present invention is as follows:

A binaural circular diffractive diaphragm includes a binaural circular diffractive aperture. The binaural circular diffractive aperture is mainly composed of a first circular arc and a first circular arc having a double twist line and a circle center located at the symmetrical center of the double twist line. Two arcs

Wherein, the first arc is connected to the upper side of the double button line, the second arc is connected to the lower side of the double button line, and the lateral length of the double button line is the same as the first circle. The ratio of the radii of the arcs is (2.5-3.2): 1; the binaural circular diffraction holes are bilaterally symmetrical.

In the binaural circular diffractive diaphragm, the radius of the second arc is not equal to the radius of the first arc, forming an up-and-down asymmetric structure.

In the binaural circular diffractive diaphragm, a ratio of a lateral length of the double twist line to a radius of the first arc is 31:11.

In the binaural circular diffraction diaphragm, a radius of the first arc is 0.55 mm, a radius of the second arc is 0.605 mm, and a lateral length of the double twist line is 1.55 mm.

A vortex light topology charge number detection system includes a vortex light generation module, a diaphragm diffraction module, and a light intensity detection module in order according to a beam propagation path. The diaphragm diffraction module is provided with the above-mentioned binaural circular diffraction. A diaphragm for diffracting a vortex beam incident on the diaphragm diffraction module.

According to the vortex light topology charge number detection system, according to a beam propagation path, the vortex light generation module includes a light source for generating a Gaussian beam, a polarizer for changing a polarization direction of light, and a light for changing light. A phase vortex light generating device and a diaphragm for screening vortex light, wherein the vortex light generating device is a reflective phase-type spatial light modulator, a spiral phase plate, or a metasurface.

In the vortex light topology charge number detection system, according to a beam propagation path, the diaphragm diffraction module includes a diffraction screen for diffracting, a polarizer for adjusting light polarization, and a Fourier for generating light. The transformed Fourier transform unit, wherein the diffraction screen is loaded with the binaural circular diffraction diaphragm.

According to the vortex light topology charge number detection system, according to a light beam propagation path, the light intensity detection module includes a light beam amplification system for expanding a beam and a light intensity photographing device for recording, wherein the light beam The magnification system is a combination of two confocal convex lenses or a beam expander.

In the vortex light topology charge number detection system, the focal lengths of the two confocal convex lenses are 25 mm and 75 mm, respectively, and the light intensity photographing device is a CCD detector.

A method for detecting the topological charge number of vortex light, which uses the binaural circular diffraction diaphragm as described above to diffract vortex light to obtain the far-field diffraction intensity distribution of the vortex light, and then detects the far-field diffraction intensity distribution.

Beneficial effect: The present invention provides a binaural circular diffractive diaphragm as described above, and the vortex light passes through the binaural circular hole to generate a special light intensity distribution, so as to detect the topological charge of the vortex beam. The invention can measure the topological charge of vortex light through diffraction of a single aperture, thereby avoiding the influence of the arrangement accuracy of multi-aperture mesopores on the measurement accuracy; and in adjusting the vortex beam to be coaxial with the binaural circular aperture At this time, even if there is a certain deviation, the diffracted light intensity distribution can still achieve the purpose of detecting the topological charge of the vortex light. When the center of the beam coincides with the center of the aperture, the phenomenon is most clear and obvious. Therefore, this technical solution allows the vortex beam to be rounded with both ears The apertures are not strictly aligned and have a certain tolerance for detection operation errors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a binaural circular diffraction aperture of the present invention.

FIG. 2 is a final external view of a binaural circular diffraction hole according to the present invention.

FIG. 3 is a schematic diagram of a module structure of a vortex optical topology charge number detection system according to the present invention.

FIG. 4 is a detailed schematic structural diagram of a vortex optical topological charge number detection system according to the present invention.

detailed description

The present invention provides a binaural circular diffractive diaphragm and a vortex light topological charge number detection system and detection method. In order to make the purpose, technical solution, and effect of the present invention clearer and clearer, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

It should be noted that the azimuth terms such as “upper side”, “lower side”, “left side”, and “right side” in the present invention are all based on FIG. 1, and specifically according to the different angles of the graphics, The description of the technical solution of the present invention will be different.

The structure of the binaural circular diffraction diaphragm provided by the present invention is shown in FIG. 1 and includes a binaural circular diffraction hole. The binaural circular diffraction hole is mainly composed of a double button line 1 and a circle center are located on the double button line. The symmetry center O is formed by a first arc 2 and a second arc 3.

Wherein, the first arc 2 is connected to the upper side of the double twisted line, the second arc 3 is connected to the lower side of the double twisted line 1, and the lateral length of the double twisted line 1 (2a ) And the radius Ra of the first arc 2 is (2.5-3.2): 1; the binaural circular diffraction apertures are bilaterally symmetrical, and the shape of the binaural circular diffraction apertures finally formed is shown in FIG. 2 .

Preferably, the radius Rb of the second arc 3 is not equal to the radius Ra of the first arc 2, and Rb can be made slightly larger or smaller than Ra, forming an up-and-down asymmetric structure, so that the diffraction pattern can distinguish the vortex beam. The positive and negative of the topological charge.

Preferably, a ratio of a lateral length of the double twisted line to a radius of the first arc is 31:11, and a better diffraction effect can be obtained. A preferred parameter of a binaural circular diffraction aperture is that the radius of the first arc is 0.55 mm, the radius of the second arc is 0.605 mm, and the lateral length of the double twisted line is 1.55 mm.

In the binaural circular diffractive diaphragm of the present invention, the vortex light passes through the binaural circular diffractive diaphragm to generate a special light intensity distribution, so as to detect the topological charge of the vortex beam. The invention can measure the topological charge of vortex light through diffraction of a single aperture, thereby avoiding the influence of the arrangement accuracy of multi-aperture mesopores on the measurement accuracy; and in adjusting the vortex beam to be coaxial with the binaural circular aperture At this time, even if there is a certain deviation, the diffracted light intensity distribution can still achieve the purpose of detecting the topological charge of the vortex light. When the center of the beam coincides with the center of the aperture, the phenomenon is most clear and obvious. Therefore, this technical solution allows the vortex beam to be rounded with both ears The apertures are not strictly aligned and have a certain tolerance for detection operation errors.

The present invention also provides a preferred embodiment of a vortex light topology charge number detection system, which is mainly used in the field of information optics. As shown in FIG. 3, according to the beam propagation path, a vortex light generation module 4 (for different topologies) is sequentially included. Generation of charge vortex light), diaphragm diffraction module 5 (for diffracting incident vortex light with different topological charges and forming a special light intensity distribution through Fourier transform) and light intensity detection module 6 (for Detecting the diffracted light intensity distribution), the diaphragm diffraction module is provided with the binaural circular diffraction diaphragm as described above for diffracting the vortex beam incident on the diaphragm diffraction module. In this system, the topological charge of the vortex beam can be judged only by the light intensity distribution after the beam is diffracted through the aperture. Fewer optical elements are used, and the measurement results are intuitive and easy to read, which is convenient for practical operation.

Specifically, as shown in FIG. 4, according to the beam propagation path, the vortex light generating module 4 includes: a light source 41 for generating a Gaussian beam, a polarizer 42 for changing a polarization direction of the light, and a phase for changing the light. The vortex light generating device 43 and the diaphragm 44 for screening vortex light, wherein the vortex light generating device 43 may be a reflective phase-type spatial light modulator, a spiral phase plate, or a metasurface. The light source may be a He-Ne laser with a wavelength of 632.5 nm, and the polarizing plate is a half-wave plate.

The diaphragm diffraction module 5 includes a diffraction screen 51 for diffracting, a polarizer 52 for adjusting the polarization of light, and a Fourier transform unit 53 for generating a Fourier transform. Loaded with the binaural circular diffractive diaphragm. Specifically, the polarizer may be a Glan prism, and the Fourier transform unit may be a convex lens having a focal length of 50 mm.

The light intensity detection module 6 includes: a beam magnification system 61 for expanding a beam and a light intensity photographing device 62 for recording, wherein the beam amplification system is a combination of two confocal convex lenses or a beam expanding mirror. Specifically, the focal lengths of the two confocal convex lenses may be set to 25 mm and 75 mm, respectively, and the light intensity photographing device may be a CCD detector.

The present invention also provides a method for detecting the topological charge of vortex light, which uses the binaural circular diffractive diaphragm as described above to diffract vortex light to obtain the far-field diffraction intensity distribution of the vortex light, and then diffracts the far-field light. The intensity distribution is detected. This method can measure the topological charge of vortex light through single aperture diffraction, and has a certain tolerance for detection operation errors.

The principle of the present invention will be further described in detail below with reference to FIG. 4.

The Gaussian light emitted from the light source 41 passes through the polarizing plate 42 to generate horizontally polarized light and enters the vortex light generating device 43 to generate multi-level vortex light, and then filters the zero-order vortex light through the diaphragm 44. At this time, the outgoing vortex beam can be approximated as:

among them

Laguerre-Gaussian (LG) vortex beam, where l is the topological charge, p is the radial parameter, r is the radial component, φ is the phase, w ₀ is the beam waist radius, and w (z) is at z Corset size,

To associate Laguerre polynomials, z _r is the Rayleigh distance, z is the beam transmission distance, k is the wave vector, the phase factor exp (-ilφ) indicates that the beam has a spiral structure, and i is an imaginary unit.

The generated vortex light is directly incident on the diffractive screen 51. A diffraction phenomenon occurs. The diffractive screen is provided with a binaural circular diffraction diaphragm. The binaural circular diffraction hole of the binaural circular diffraction diaphragm is composed of a double button line 1. The first arc 2 and the second arc 3 are both located at the center of symmetry O of the double twisted line. The amplitude transmittance function T (x, y) of the double twisted line and the amplitude transmittance function M (x, y) of the two arcs can be expressed as:

Among them, x, y represent the horizontal and vertical coordinates of the function, a is half of the horizontal length of the double button line, as shown in the label of Figure 1, cric represents the circular function, R _{a is} the radius of the first arc, and R _{b is the} second arc. Radius, the overall amplitude transmittance function after superposition can be expressed as:

In the above formula, t represents the amplitude transmittance function of the binaural circular hole, and ξ and η are the horizontal and vertical coordinates of the function. Substituting the binaural circular aperture amplitude transmittance function t (ξ, η) into the far-field diffraction intensity formula, the far-field diffraction intensity distribution of the vortex light passing through the binaural circular aperture can be obtained as:

In the above formula, I represents the diffraction intensity distribution function, x and y are the horizontal and vertical coordinates of the function, z is the beam transmission distance, i is the imaginary unit, k is the wave vector, and λ is the wavelength.

Denotes a Laguerre-Gaussian (LG) vortex beam, and F denotes a Fourier transform function.

Finally, the polarizer 52, the Fourier transform unit 53 and the beam magnification system 61 are used to adjust and receive it in the direct-incidence light-intensity photographing device 62. The diffraction pattern of the topological charge of vortex light is used to determine the topological charge. .

In summary, the present invention provides a binaural circular diffractive diaphragm and vortex light topological charge number detection system and detection method. The vortex light generates a special light intensity distribution after passing through the binaural circular hole of the present invention, and realizes Detection of Topological Charge of Vortex Beams. The invention can measure the topological charge of vortex light through diffraction of a single aperture, thereby avoiding the influence of the arrangement accuracy of multi-aperture mesopores on the measurement accuracy; and in adjusting the vortex beam to be coaxial with the binaural circular aperture At this time, even if there is a certain deviation, the diffracted light intensity distribution can still achieve the purpose of detecting the topological charge of the vortex light. When the center of the beam coincides with the center of the aperture, the phenomenon is most clear and obvious. Therefore, this technical solution allows the vortex beam to be rounded with both ears The apertures are not strictly aligned and have a certain tolerance for detection operation errors. At the same time, the present invention also provides a vortex light topological charge detection system based on the binaural circular diffractive diaphragm. The topological charge of the vortex beam can be determined only by the light intensity distribution after the beam is diffracted through the aperture. There are fewer optical components, and the measurement results are intuitive and easy to read, which is convenient for practical operation.

It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or changes can be made according to the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims

A binaural circular diffractive diaphragm, characterized in that it comprises a binaural circular diffraction aperture, said binaural circular diffraction aperture is mainly composed of a double button line and a circle center located at the first center of symmetry of the double button line. A circular arc and a second circular arc;

Wherein, the first arc is connected to the upper side of the double button line, the second arc is connected to the lower side of the double button line, and the lateral length of the double button line is the same as the first circle. The ratio of the radii of the arcs is (2.5-3.2): 1; the binaural circular diffraction holes are bilaterally symmetrical.
The binaural circular diffractive diaphragm according to claim 1, wherein a radius of the second arc is not equal to a radius of the first arc, forming an up-and-down asymmetric structure.
The binaural circular diffractive diaphragm according to claim 1, wherein a ratio of a lateral length of the double twist line to a radius of the first arc is 31:11.
The binaural circular diffractive diaphragm according to claim 3, wherein a radius of the first arc is 0.55 mm, a radius of the second arc is 0.605 mm, and a transverse direction of the double twist line is The length is 1.55mm.
A vortex light topology charge number detection system, characterized in that, according to a light beam propagation path, a vortex light generation module, a diaphragm diffraction module, and a light intensity detection module are sequentially included, and the diaphragm diffraction module is provided with claims 1-4 Any of the binaural circular diffraction diaphragms is used to diffract the vortex beam incident on the diaphragm diffraction module.
The vortex light topology charge number detection system according to claim 5, wherein the vortex light generation module comprises a light source for generating a Gaussian light beam and a polarizer for changing a polarization direction of the light according to a beam propagation path. A vortex light generating device for changing the phase of light and a diaphragm for screening the vortex light, wherein the vortex light generating device is a reflective phase-type spatial light modulator, a spiral phase plate, or a metasurface.
The vortex light topology charge number detection system according to claim 5, characterized in that, in accordance with the beam propagation path, the diaphragm diffraction module comprises a diffraction screen for generating diffraction, a polarizer for adjusting light polarization, and A Fourier transform unit for generating a Fourier transform, wherein the binaural circular diffraction diaphragm is loaded on the diffraction screen.
The vortex light topology charge number detection system according to claim 5, characterized in that, according to the beam propagation path, the light intensity detection module comprises: a beam amplification system for expanding a beam and a light intensity photographing device for recording Wherein, the beam magnification system is a combination of two confocal convex lenses or a beam expander.
The vortex light topology charge number detection system according to claim 8, wherein the focal lengths of the two confocal convex lenses are 25 mm and 75 mm, respectively, and the light intensity photographing device is a CCD detector.
A method for detecting the topological charge of vortex light, characterized in that the vortex light is diffracted by using the binaural circular diffraction diaphragm according to any one of claims 1-4, and the far-field diffraction intensity distribution of vortex light is obtained, and then The far-field diffraction intensity distribution is detected.