WO2021093259A1

WO2021093259A1 - Arbitrary singularity beam order detection device and method

Info

Publication number: WO2021093259A1
Application number: PCT/CN2020/083790
Authority: WO
Inventors: 李瑛�; 王穗玲; 贺炎亮; 陈学钰; 谢智强; 刘俊敏; 苏明样; 陈书青; 赵改清; 高艳霞; 范滇元
Original assignee: 深圳大学
Priority date: 2019-11-14
Filing date: 2020-04-08
Publication date: 2021-05-20
Also published as: CN110836726A

Abstract

An arbitrary singularity beam order detection device and method. The device comprises: a singularity beam generating module for generating singularity light having arbitrary topological charge and polarization order of orthogonal linear polarization components; a reference beam generating module for generating reference light linearly polarized along a preset angle; a polarization separation and interference module for performing separation and mutual interference of horizontal polarization components and vertical polarization components of the incident singularity light and the reference light; and a light intensity detection module for detecting interference light intensity distribution. By performing separation and mutual interference of the horizontal polarization components and the vertical polarization components on beams of an arbitrary polarization state, accurate detection of the topological charge and polarization order of an arbitrary singularity beam is implemented by analyzing interference fringes, and the present invention has the advantages of high detection efficiency and a wide application range. Further disclosed is an arbitrary singularity beam order detection method.

Description

Device and method for detecting arbitrary singular point beam order

Technical field

The invention relates to the technical field of information optics, and in particular to a device and method for detecting arbitrary singular point beam orders, which is suitable for detecting the topological charge and polarization order of arbitrary singular point beams.

Background technique

The structured beam has attracted widespread attention due to its spatially varying field distribution. Vortex Beam (VB) and Cylindrical Vector Beam (CVB) that carry Orbital Angular Momentum (OAM) are two typical singularity beams that have been extensively studied. They have phase singularity and polarization singularity. point. They all have a circular intensity distribution and dark spots due to the central singularity. Due to their unique optical characteristics, vortex light and cylindrical vector light have been widely used in various applications ranging from optical communication, optical manipulation, optical imaging to quantum information processing.

Generally, a beam with both phase singularity and polarization singularity can also provide more freedom for beam manipulation. These beams are also called Cylindrical Vector Vortex Beam (CVVB), which has attracted widespread attention in the field of optical manipulation. Researchers have proposed many methods for generating singular light beams. However, in addition to generating high-quality singular point beams, it is also important to effectively identify its topological charge and polarization order. Since the spatial field distribution of the singularity beam is different from each other, the detection methods for its topological charge and polarization order should also be different. Usually, the interferometry is used to determine the topological charge of VB, and the analyzer is widely used to detect the polarization order of CVB and CVVB. However, there is still a lack of a universal and effective method for detecting the topological charge and polarization order of any singularity beam.

Therefore, in view of the above-mentioned shortcomings, the prior art still needs to be improved and developed.

Summary of the invention

The technical problem to be solved by the present invention is to provide a device and method for detecting any singular point beam order in view of the above-mentioned defects of the prior art, which utilizes polarization-sensitive blazed grating to detect incident singular point light and reference light (incident 45 ° Linear polarization singularity light and 45° linear polarization reference light) separate the horizontal and vertical polarization components and interfere with each other. By analyzing the interference fringes generated after the aperture of the blazed grating, the vortex beam topological charge detection is realized. The whole system The optical path structure is relatively simple and reasonable, the detection phenomenon is intuitive and easy to read, and it is easy to operate in reality and takes a short time. It can not only accurately measure the topological charge value, but also the polarization order.

The technical solutions adopted by the present invention to solve the technical problems are as follows:

An arbitrary singular point beam order detection device, wherein the arbitrary singular point beam order detection device includes:

A singular point beam generating module for generating singular point light with any topological charge and polarization order of orthogonal linear polarization components;

A reference beam generating module for generating reference light linearly polarized along a preset angle;

A polarization separation interference module for separating and interfering with the horizontal polarization component and the vertical polarization component of the incident singular point light and the reference light;

Light intensity detection module for detecting interference light intensity distribution.

The arbitrary singular point beam order detection device, wherein the singular point beam generating module includes:

A light source used to generate a Gaussian beam;

A polarizer arranged behind the light source for adjusting the polarization of the Gaussian beam;

Singular point light generating device used to change the polarization direction and phase;

A first polarizer arranged behind the singular point light generating device and used for changing the polarization direction of the singular point light.

In the device for detecting arbitrary singularity beam orders, wherein the reference beam generating module includes:

A beam splitting device arranged behind the polarizer for splitting the Gaussian beam after being adjusted by the polarizer into two beams;

A first turning device arranged under the beam splitting device and used for changing the direction of the light path;

A second polarizer arranged behind the first turning device for changing the polarization direction;

A second turning device arranged behind the second polarizer for changing the direction of the light path;

A beam combining device arranged behind the first polarizer and above the second turning device and used for combining the singular point light with the adjusted polarization state and the reference light.

The arbitrary singular point beam order detection device, wherein the beam splitting device is used to divide the Gaussian beam after being adjusted by the polarizer into two beams, one beam is used to generate the singular point light, and the other is used to Generating the reference light;

The singular point light generating device is arranged behind the beam splitting device.

The arbitrary singularity beam order detection device, wherein the polarization separation interference module includes a blazed grating for reflecting back the horizontal and vertical polarization components of the incident beam at different reflection angles, so that the different polarization components are spatially separated;

The blazed grating is arranged behind the beam combining device.

The arbitrary singular point beam order detection device, wherein the light intensity detection module includes a light intensity detection device for recording interference fringe information;

The light intensity detection device is arranged under the blazed grating.

The arbitrary singular point beam order detection device, wherein the light source is a laser with a wavelength of 1550 nm;

The polarizer is a Glan prism;

The beam splitting device is a polarization beam splitter;

The singularity light generating device is a metasurface;

The first polarizer and the second polarizer are a quarter glass plate and a half wave plate, respectively;

The first steering device and the second steering device are both flat mirrors;

The beam combining device is a polarization beam combiner;

The blazed grating is a reflective phase type spatial light modulator;

The light intensity detection device is a CCD camera.

The arbitrary singular point beam order detection device, wherein the singular point light and the reference light are incident on the blazed grating coaxially.

An arbitrary singular point beam order detection method based on the arbitrary singular point beam order detection device, wherein the arbitrary singular point beam order detection method includes the following steps:

Step A, two sub-beams with strong coherence are generated through the light source, the polarizer and the beam splitting device, which are the first sub-beam and the second sub-beam respectively;

Step B: After the first sub-beam passes through the singular point light generating device and the first polarizer, a 45° linearly polarized singular point light is generated;

Step C, after the second sub-beam passes through the first turning device, the second polarizer and the second turning device, a 45° linearly polarized reference light is generated;

Step D, the 45° linearly polarized singular point light and the 45° linearly polarized reference light are projected onto the polarization-sensitive blazed grating after passing through the beam combining device to realize the separation and interference of the horizontal and vertical polarization components;

Step E: Read the interference pattern by the light intensity detection device, and obtain the topological charge and polarization order information of the singular point beam carried in the interference pattern through analysis.

The arbitrary singular point beam order detection method, wherein after passing through the polarization-sensitive blazed grating, the vertical polarization component of the beam is reflected at the same reflection angle as the incident angle, and the horizontal polarization component of the beam is diffracted at a reflection angle greater than the incident angle .

Beneficial effects: The present invention provides an arbitrary singular point beam order detection device and method. The device includes: a singular point for generating singular point light with an arbitrary topological charge and polarization order of orthogonal linear polarization components A beam generating module; a reference beam generating module for generating reference light linearly polarized along a preset angle; for separating and interfering with the horizontal polarization component and vertical polarization component of the incident singular point light and the reference light The polarization separation interference module; the light intensity detection module used to detect the interference light intensity distribution. The present invention separates and interferes with the horizontal polarization component and vertical polarization component of the beam of any polarization state, and realizes the accurate detection of the topological charge and polarization order of any singular point beam by analyzing the interference fringes, and has high detection efficiency, The advantages of a wide range of applications.

Description of the drawings

Fig. 1 is a schematic structural diagram of a preferred embodiment of a detection device for arbitrary singular point beam orders of the present invention.

2 is a schematic diagram of the specific structure of each module (that is, the entire optical path structure) of the preferred embodiment of an arbitrary singular point beam order detection device of the present invention.

Fig. 3 is a flowchart of a preferred embodiment of the method for detecting arbitrary singularity beam orders according to the present invention.

Fig. 4 is a schematic diagram of a device for generating vortex light in the method for detecting any singular point beam order of the present invention.

Fig. 5 is a schematic diagram of a device for generating cylindrical vector vortex light in the method for detecting any singular point beam order of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer and clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention.

Please refer to FIG. 1. FIG. 1 is a schematic structural diagram of a preferred embodiment of an arbitrary singular point beam order detection device of the present invention.

As shown in FIG. 1, an arbitrary singular point beam order detection device provided by an embodiment of the present invention includes:

A singular point beam generating module for generating singular point light with an arbitrary topological charge and polarization order of orthogonal linear polarization components; a reference beam generating module for generating reference light linearly polarized along a preset angle; A polarization separation interference module that separates and interferes with the horizontal polarization component and vertical polarization component of the incident singular point light and the reference light; and a light intensity detection module for detecting the interference light intensity distribution.

Specifically, as shown in FIG. 2, the singular point beam generating module includes: a light source 1 for generating a Gaussian beam; a polarizer 2 arranged behind the light source 1 for adjusting the polarization of the Gaussian beam; A singular point light generating device 4 for changing the polarization direction and phase; a first polarizer 5 arranged behind the singular point light generating device 4 and used for changing the polarization direction of the singular point light.

The reference beam generating module includes: a beam splitting device 3 arranged behind the polarizer 2 for splitting the Gaussian beam after being adjusted by the polarizer 2 into two beams; arranged below the beam splitting device 3 , The first turning device 8 for changing the direction of the light path; the second polarizer 9 arranged behind the first turning device 8 for changing the polarization direction; and the second polarizer 9 arranged behind the second polarizer 9 for changing A second turning device 10 in the direction of the light path; arranged behind the first polarizer 5 and above the second turning device 10, for combining the polarization state of the singular point light and the reference light Device 6.

Wherein, the beam splitting device 3 is used to divide the Gaussian beam after being adjusted by the polarizer into two beams, one beam is used to generate the singular point light, and the singular point light beam refers to a phase singularity or a polarization singularity The beam includes phase singularity light and polarization singularity light. The light intensity of the beam center is zero because the phase or polarization cannot be determined. The macroscopic appearance is a dark spot in the center of the beam, and the cross section of the beam is a hollow donut shape; one beam is used In order to generate the reference light, it is used to interfere with the singular point beam to form an auxiliary beam of specific interference fringes. Commonly used reference beams include Gaussian plane light and Gaussian spherical light. Phase singular point beams with known topological charges can also be used As the reference light, the Gaussian plane light with linear polarization along 45° is preferred here (it should be known that the unprocessed laser beam can be regarded as the Gaussian plane light without a specific polarization state); the two interfering beams must meet the coherence Conditions (in short, the laser is a short pulse generated by a molecular energy level transition, and only the light of the same pulse can be coherent), so it can only be split from the same laser; the singular point light generating device 4 is set at all The beam splitting device 3 is behind.

The polarization separation interference module includes a blazed grating 7 that is used to reflect the horizontal and vertical polarization components of the incident beam at different reflection angles to spatially separate the different polarization components. The blazed grating 7 has polarization-sensitive characteristics; The blazed grating 7 is arranged behind the beam combining device 6.

The light intensity detection module includes a light intensity detection device 11 for recording interference fringe information; the light intensity detection device 11 is arranged under the blazed grating 7.

Further, the light source 1 is a laser with a wavelength of 1550 nm, which is used to generate a continuous Gaussian laser beam.

The polarizer 2 is a Glan prism for adjusting the polarization state of the Gaussian beam to horizontal polarization.

The beam splitting device 3 is a polarization beam splitter for splitting the optical path.

The singular point light generating device 4 is a metasurface for generating cylindrical vector light (CVB) of any topological charge and polarization order. The metasurface is an array composed of a scattering structure of subwavelength anisotropic materials, which can be The ultra-thin artificial microstructure that regulates the polarization, phase, amplitude and even the propagation direction of the beam; it is not limited to the metasurface, but can also be replaced by a phase-type spatial light modulator, a spiral phase plate, etc.

The first polarizer 5 and the second polarizer 9 are a quarter glass plate and a half wave plate, respectively, wherein the first polarizer 5 is a quarter glass with a fast axis rotated to 45° The second polarizer 9 is a half-wave plate whose fast axis rotates to 45° and is used to adjust the polarization state of the reference beam to 45° linear polarization.

The first steering device 8 and the second steering device 10 are both flat mirrors for adjusting the transmission direction of the reference light.

The beam combining device 6 is a polarization beam combiner for combining light paths.

The blazed grating 7 is a reflective phase type spatial light modulator and the blazed grating information is loaded by a computer to realize the separation and interference of the horizontal polarization and vertical polarization components of the incident light; the blazed grating is not limited to the reflective phase type spatial light. The modulator loading can also be replaced by a specially designed actual grating; the singular point light and the reference light are incident on the blazed grating coaxially.

The light intensity detection device 11 is a 1550nm CCD camera, which is used to detect and record interference fringes.

Further, based on the arbitrary singular point beam order detection device provided in the above embodiments, the present invention also provides an arbitrary singular point beam order detection method, please refer to FIG. 3, which is the arbitrary singular point beam order detection method of the present invention A flowchart of a preferred embodiment of the method.

According to the optical path structure of the arbitrary singular point beam order detection device in the present invention, the specific implementation process is as follows:

Step S100, through the light source 1, the polarizer 2 and the beam splitting device 3, strong coherence is generated (laser is a beam with good monochromaticity, and the two sub-beams generated by the same laser beam splitting belong to the same wave in time. Two sub-beams with a constant phase difference, random phase differences between different wave trains, and good coherence) are the first sub-beam and the second sub-beam respectively;

Step S200, after the first sub-beam passes through the singular point light generating device 4 and the first polarizer 5, a 45° linearly polarized singular point light is generated;

Step S300, after the second sub-beam passes through the first turning device 8, the second polarizer 9 and the second turning device 10, a 45° linearly polarized reference light is generated;

Step S400, the 45° linearly polarized singular point light and the 45° linearly polarized reference light are projected onto the polarization-sensitive blazed grating 7 after passing through the beam combining device 6, so as to realize the separation and interference of horizontal and vertical polarization components;

In step S500, step E, the interference pattern is read by the light intensity detection device 11, and the topological charge and polarization order information of the singular point beam carried in the interference pattern is obtained through analysis.

Wherein, after passing through the polarization-sensitive blazed grating 7, the vertical polarization component of the light beam is reflected at the same reflection angle as the incident angle, and the horizontal polarization component of the light beam is diffracted at a reflection angle greater than the incident angle.

Specifically, in this embodiment, the light source 1 generates a Gaussian laser beam, which is converted into horizontal linearly polarized light after passing through the polarizer 2, and is evenly divided into two sub-beams after passing through the beam splitting device 3, wherein the transmission direction remains unchanged After the first sub-beam of is passed through the singular point beam generating device 4, a circularly polarized cylindrical vector light with controllable topological charge and polarization order is generated.

The singular point beam generating device 4 described in this embodiment is preferably a metasurface, which is manufactured by etching a space-varying nanograting on a fused silica substrate with a femtosecond laser, and thus has space-varying birefringence. The required polarization distribution can be adjusted by adjusting the groove. The local direction and geometric parameters are realized.

At this time, the emitted circular polarization cylinder vector light can be simply mathematically described as follows:

Where l is the topological charge, θ is the azimuth angle,

Is the initial phase, m is the polarization order, and i is the unit length in the imaginary field, which is equivalent to 1 in the real field, and the square of i is equal to -1. After passing through the first polarizer 5, the two orthogonal circular polarization components of the CVB are converted into two orthogonal linear polarization components, namely:

On the other hand, the second sub-beam generated by the beam splitter 3 is deflected by the first turning device 8, and then enters the second polarizer 9 and is adjusted to be linearly polarized light along 45°. The second steering device 10 and the beam combining device 6 realize coaxial transmission with the CVB.

Then, the CVB transmitted coaxially enters the polarization-sensitive blazed grating 7 together with the reference beam. The phase SLM can only modulate the horizontal polarization component of the incident light and is a polarization sensitive element. Therefore, by loading the blazed grating information on the SLM, the horizontally polarized light can be diffracted and the vertically polarized light beam can be reflected. By cleverly designing the period of the blazed grating, the reflected vertically polarized light and the diffracted horizontally polarized light can be spatially separated. Blazed grating can be expressed as follows:

2d sinαcos(α-β)=nλ,n=1,2,3..., (3)

Where d is the grating constant, α is the blaze angle, β is the incident angle, λ is the wavelength of the incident light, and n takes any positive integer.

After being modulated by the polarization-sensitive blazed grating 7, the linearly polarized Gaussian reference light and the horizontal and vertical polarization components of the linearly polarized CVB are separated from each other and interfere. In order to make full use of the SLM performance, the incident angle is controlled below 6°, the reflection angle of the vertical polarization component is equal to the incident angle, and the blaze angle of the blazed grating is about 20°. The light intensity detection device 11 is used to photograph the second polarizer 9 for reception, and the topological charge of the vortex light is used to determine the topological charge. After obtaining the topological charges of the horizontal and vertical polarization components (h, v respectively), the topological charge l and the polarization order m of any singular point beam can be calculated by the following formula:

The device and method for detecting any singular point beam order described in this embodiment successfully realize the separation of the horizontal polarization component and the vertical polarization component of the coaxial singular point light and the reference beam through the polarization-sensitive blazed grating, and use the same polarization component The interference fringe distribution realizes the detection of CVB topological charge and polarization order.

Finally, the detection of the interference light intensity distribution is realized. The interference light intensity distribution changes with the selection of the reference beam. When the reference light is a plane light, the interference pattern is a parallel fringe branched from the center, and the number of branches is related to the topological charge to be measured. The bifurcation direction is related to the positive and negative of the topological charge to be measured; when the reference light is a spherical light, the interference pattern is a spiral stripe with a central bifurcation, the number of spiral arms is related to the topological charge to be measured, and the spiral direction is related to the topological charge to be measured. Positive and negative are related; when the reference light is a phase singularity light with a known topological charge, the interference pattern is petal-like. The specific number and shape of the petals are related to the topological charge of the reference light and the light to be measured, and specific analysis is required.

It is worth noting that the present invention can not only realize the order detection of the CVB beam, but when the linearly polarized Gaussian beam passes through the singular point beam generating device 4, any singular point beam including VB, CVB, CVVB and other beams can be generated.

Figure 4 is a diagram of the VB generating device. The linearly polarized Gaussian beam is converted into a left-handed circular Gaussian beam after passing through a quarter glass with an angle of 45° between the fast axis and the optical axis. After passing through the metasurface, it will produce Right-handed circular offset VB with positive topological charges.

Figure 5 is a diagram of the CVVB generating device. CVVB can be generated by cascading two metasurfaces. First, the linearly polarized Gaussian beam passes through a quarter glass with a 45° angle between the fast axis and the optical axis, and then is converted into a left-handed circularly polarized Gaussian beam. After passing through the metasurface, the circularly polarized VB is obtained. The quarter behind the metasurface A glass slide converts it into linearly polarized VB, which is further modulated by another metasurface, and finally CVVB can be produced.

The present invention can detect the topological charge and polarization order of any singular point beam by using the device for detecting any singular point beam order. The detection method is to effectively measure the topological charge and polarization order of any singular point beam. The polarization order provides a new way.

In summary, the present invention provides an arbitrary singular point beam order detection device and method. The device includes: a device for generating singular point light with orthogonal linear polarization components with arbitrary topological charges and polarization orders. A singular point beam generating module; a reference beam generating module for generating reference light linearly polarized along a preset angle; used to separate and separate the incident singular point light and the horizontal polarization component and vertical polarization component of the reference light Polarization separation interference module for mutual interference; light intensity detection module for detecting interference light intensity distribution. The present invention separates and interferes with the horizontal polarization component and vertical polarization component of the beam of any polarization state, and realizes the accurate detection of the topological charge and polarization order of any singular point beam by analyzing the interference fringes, and has high detection efficiency, The advantages of a wide range of applications.

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 based on the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims

An arbitrary singular point beam order detection device, characterized in that the arbitrary singular point beam order detection device comprises:

A singular point beam generating module for generating singular point light with any topological charge and polarization order of orthogonal linear polarization components;

A reference beam generating module for generating reference light linearly polarized along a preset angle;

A polarization separation interference module for separating and interfering with the horizontal polarization component and the vertical polarization component of the incident singular point light and the reference light;

Light intensity detection module for detecting interference light intensity distribution.
2. The arbitrary singular point beam order detection device according to claim 1, wherein the singular point beam generating module comprises:

A light source used to generate a Gaussian beam;

A polarizer arranged behind the light source for adjusting the polarization of the Gaussian beam;

Singular point light generating device used to change the polarization direction and phase;

A first polarizer arranged behind the singular point light generating device and used for changing the polarization direction of the singular point light.
The device for detecting arbitrary singularity beam orders according to claim 2, wherein the reference beam generating module comprises:

A beam splitting device arranged behind the polarizer for splitting the Gaussian beam after being adjusted by the polarizer into two beams;

A first turning device arranged under the beam splitting device and used for changing the direction of the light path;

A second polarizer arranged behind the first turning device for changing the polarization direction;

A second turning device arranged behind the second polarizer for changing the direction of the light path;

A beam combining device arranged behind the first polarizer and above the second turning device and used for combining the singular point light with the adjusted polarization state and the reference light.
The arbitrary singular point beam order detection device according to claim 3, wherein the beam splitting device is used to split the Gaussian beam after being adjusted by the polarizer into two beams, and one beam is used to generate the odd beam. Point light, one beam is used to generate the reference light;

The singular point light generating device is arranged behind the beam splitting device.
The arbitrary singularity beam order detection device according to claim 3, wherein the polarization separation interference module includes a device for reflecting the horizontal and vertical polarization components of the incident beam at different reflection angles, so that the different polarization components are reflected back. Spatially separated blazed grating;

The blazed grating is arranged behind the beam combining device.
The arbitrary singular point beam order detection device according to claim 5, wherein the light intensity detection module comprises a light intensity detection device for recording interference fringe information;

The light intensity detection device is arranged under the blazed grating.
The arbitrary singular point beam order detection device according to claim 6, wherein the light source is a laser with a wavelength of 1550 nm;

The polarizer is a Glan prism;

The beam splitting device is a polarization beam splitter;

The singularity light generating device is a metasurface;

The first polarizer and the second polarizer are a quarter glass plate and a half wave plate, respectively;

The first steering device and the second steering device are both flat mirrors;

The beam combining device is a polarization beam combiner;

The blazed grating is a reflective phase type spatial light modulator;

The light intensity detection device is a CCD camera.
7. The arbitrary singular point beam order detection device according to claim 6, wherein the singular point light and the reference light are incident on the blazed grating coaxially.
An arbitrary singular point beam order detection method based on the arbitrary singular point beam order detection device of any one of claims 1-8, characterized in that the arbitrary singular point beam order detection method comprises the following steps:

Step A, two sub-beams with strong coherence are generated through the light source, the polarizer and the beam splitting device, which are the first sub-beam and the second sub-beam respectively;

Step B: After the first sub-beam passes through the singular point light generating device and the first polarizer, a 45° linearly polarized singular point light is generated;

Step C: After the second sub-beam passes through the first turning device, the second polarizer and the second turning device, a 45° linearly polarized reference light is generated;

Step D, the 45° linearly polarized singular point light and the 45° linearly polarized reference light are projected onto the polarization-sensitive blazed grating after passing through the beam combining device to realize the separation and interference of the horizontal and vertical polarization components;

Step E: Read the interference pattern by the light intensity detection device, and obtain the topological charge and polarization order information of the singular point beam carried in the interference pattern through analysis.
The method for detecting arbitrary singularity beam orders according to claim 9, wherein after passing the polarization-sensitive blazed grating, the vertical polarization component of the beam is reflected at the same reflection angle as the incident angle, and the horizontal polarization component of the beam is more The angle of incidence is diffracted by the angle of reflection.