Vector vortex light field polarization conversion device and construction method and system thereof

Abstract

The invention discloses a vector vortex light field polarization conversion device and a construction method and system thereof, and relates to the field of polarization conversion application, and the polarization conversion device comprises a substrate layer and a super-atom unit layer. The super atom unit layer is arranged on the substrate layer; the super-atom unit layer comprises a plurality of super-atom ring bands; the super-atomic girdle comprises a plurality of super-atomic units; the distances between the super-atom units are equal; the attribute of the super-atom unit is consistent with that of a 1 / 4 wave plate or a common wave plate; the super-atom unit layer is used for converting incident circularly polarized light into radial polarized light and angular polarized light carrying first-order orbital angular momentum. According to the vector vortex light field polarization conversion device constructed by using the super-atom units, the problem of low transmittance of a traditional vector vortex polarization conversion device is solved, and the construction process of the vector vortex light field polarization conversion device is simplified.

Description

Technical Field

[0001] The present application relates to the field of polarization conversion applications, and in particular to a vector vortex light field polarization conversion device and a construction method and system thereof. Background Art

[0002] Vector light fields have unique optical properties such as the directional distribution of the electric vector of light waves, and have been widely used in many fields such as optical imaging, optical sensing, optical tweezers and particle manipulation. Common vector light fields include polarized vortex light fields, vector vortex light fields, radially polarized light fields and azimuthally polarized light fields. Among them, the vector vortex light field is a special light field, which is characterized by the presence of a phase singularity at the center of the light beam, where the light intensity is zero and the light field is distributed in a ring shape. The orbital angular momentum carried by each photon in this light field can be transferred to the particle, driving the particle to rotate, thereby achieving the capture and translation of the particle.

[0003] Vector vortex polarization conversion is a technology that uses optical elements to control the polarization state of light, especially in the generation and control of optical vortices. An optical vortex is a special light field characterized by the presence of a phase singularity at the center of the light beam, which makes the light field present a ring distribution. Each photon in this vortex beam carries a certain orbital angular momentum, which can capture and translate particles, so it has a wide range of applications in biomedicine, quantum information processing and other fields.

[0004] Vector vortex polarization conversion devices can achieve precise control of the polarization state of light beams, generate vector beams with specific polarization distribution or vortex beams carrying orbital angular momentum, and are key components used in optical communications, optical information processing, quantum information science, and other fields. However, traditional vector vortex polarization conversion devices made of liquid crystal materials and anisotropic crystals (quartz and calcite, etc.) have low transmittance and complex manufacturing processes. Summary of the invention

[0005] The purpose of the present application is to provide a vector vortex light field polarization conversion device and a construction method and system thereof. The vector vortex polarization conversion device constructed using super-atomic units not only solves the problem of low transmittance of traditional vector vortex polarization conversion devices, but also simplifies the construction process of the vector vortex light field polarization conversion device.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a vector vortex light field polarization conversion device, comprising: a substrate layer and a super-atomic unit layer;

[0008] The super-atomic unit layer is arranged on the base layer; the super-atomic unit layer includes a plurality of super-atomic ring belts; the super-atomic ring belts include a plurality of super-atomic units; the spacing between the super-atomic units is equal; the super-atomic unit has the same properties as a 1 / 4 wave plate or a general wave plate; the general wave plate is a wave plate with set amplitude transmittance;

[0009] The super-atomic unit layer is used to convert incident circularly polarized light into radially polarized light and angularly polarized light carrying first-order orbital angular momentum.

[0010] Optionally, the spacing between the super-atom units is greater than 0 and smaller than the wavelength of the incident circularly polarized light.

[0011] In a second aspect, the present application provides a method for constructing a vector vortex light field polarization conversion device, wherein the method is used to construct the above-mentioned vector vortex light field polarization conversion device; the method comprises:

[0012] Determining the period and height of the super-atom unit according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atom unit;

[0013] Determine the number of superatomic ring belts and the number of superatomic units on each superatomic ring belt based on the side length of the substrate layer and the period of the superatomic unit;

[0014] Determining the distribution position of the super-atomic unit according to the number of the super-atomic ring bands and the period of the super-atomic unit;

[0015] Determining a rotation angle of the super-atom unit according to the distribution position of the super-atom unit;

[0016] The vector vortex light field polarization conversion device is constructed according to the size of the super-atomic unit, the distribution position of the super-atomic unit and the rotation angle of the super-atomic unit.

[0017] Optionally, determining the size of the super-atom unit according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atom unit specifically includes:

[0018] Incident linearly polarized light onto super-atomic units of different sizes, and obtaining the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atomic units of different sizes;

[0019] According to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atomic units of different sizes, determining the super-atomic units with the same amplitude transmittance and phase difference in the fast axis and slow axis directions as the super-atomic units in the super-atomic units of different sizes;

[0020] Get the size of the super-atom unit.

[0021] Optionally, based on the side length of the substrate layer and the period of the super-atomic unit, determining the number of super-atomic ring belts and the number of super-atomic units on each super-atomic ring belt comprises:

[0022] Acquire the side length of the base layer, and determine the number of the super-atom ring belts according to the side length of the base layer and the period of the super-atom unit;

[0023] The number of superatomic units on each superatomic ring belt is obtained according to the number of the superatomic ring belts.

[0024] Optionally, determining the rotation angle of the super-atomic unit according to the distribution position of the super-atomic unit specifically includes:

[0025] injecting circularly polarized light into the super-atom unit to obtain radially polarized light and angularly polarized light of the super-atom unit;

[0026] Determining the emission angles of the radially polarized light and the angularly polarized light according to the distribution positions;

[0027] The rotation angle of the super-atom unit is determined according to the emission angle.

[0028] Optionally, the calculation formula for the number of superatomic rings is:

[0029]

[0030] Where N is the number of superatomic rings; floor is rounded down; d is the side length of the base layer; and T is the spacing between superatomic units.

[0031] Optionally, the distribution position of the super-atomic unit specifically includes:

[0032] Establishing a coordinate system with the center of the super-atomic unit layer as the origin;

[0033] The center coordinates of the superatomic unit in the first quadrant of the coordinate system (x ij ,y ij )for:

[0034] (T / 2+T·j, T / 2+T·i);

[0035] Where i is the horizontal coordinate number of the superatomic unit; j is the vertical coordinate number of the superatomic unit; the value range of i and j is [0, N], N is the number of superatomic rings; T is the period of the superatomic unit;

[0036] The center coordinates of the superatomic unit in the second quadrant of the coordinate system (x ij ,y ij )for:

[0037] (-T / 2+T·j, T / 2+T·i);

[0038] Among them, the value range of i is [0, N]; the value range of j is [0, -N];

[0039] The center coordinates of the superatomic unit in the third quadrant of the coordinate system (x ij ,y ij )for:

[0040] (-T / 2+T·j, -T / 2+T·i);

[0041] The value range of i and j is [0, -N];

[0042] The center coordinates of the superatomic unit in the fourth quadrant of the coordinate system (x ij ,y ij )for:

[0043] (T / 2+T·j, -T / 2+T·i);

[0044] Among them, the value range of i is [0, -N]; the value range of j is [0, N].

[0045] Optionally, when the properties of the super-atom unit are consistent with those of the quarter-wave plate, the rotation angle of the super-atom unit is expressed as:

[0046] θ = β - α;

[0047] Among them, θ is the rotation angle; α is the intrinsic angle; β is the angle of the emitted light, x is the horizontal coordinate of the superatom; y is the vertical coordinate of the superatom;

[0048] When the properties of the super-atom unit are consistent with those of a general wave plate, the expression for the rotation angle of the super-atom unit is:

[0049] θ=β.

[0050] In a third aspect, the present application provides a vector vortex light field polarization conversion device construction system, characterized in that the vector vortex light field polarization conversion device construction system specifically includes:

[0051] A size determination module, used to determine the size of the super-atom unit according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atom unit;

[0052] A position determination module, used to determine the distribution position of the super-atom unit based on the side length of the substrate layer and the spacing between the super-atom units;

[0053] A rotation angle determination module, used to determine the rotation angle of the super-atom unit according to the distribution position of the super-atom unit;

[0054] The device construction module is used to construct a vector vortex light field polarization conversion device according to the size of the super-atomic unit, the distribution position of the super-atomic unit and the rotation angle of the super-atomic unit.

[0055] According to the specific embodiments provided in this application, this application has the following technical effects:

[0056] The present application provides a vector vortex light field polarization conversion device and a construction method and system thereof. The vector vortex light field polarization conversion device constructed based on super-atomic units can control the propagation and phase of light through precise regulation structure, thereby solving the problem of low transmittance of traditional vector vortex polarization conversion devices. In addition, since the vector vortex light field polarization conversion device includes a base layer and a super-atomic unit layer, the structure of the vector vortex light field polarization conversion device is simplified, thereby simplifying the construction process of the vector vortex light field polarization conversion device and improving the construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0058] Figure 1 A design diagram and a partial enlarged diagram of a vector vortex light field polarization conversion device provided in one embodiment of the present application;

[0059] Figure 2 A schematic diagram of a process for constructing a vector vortex light field polarization conversion device provided in one embodiment of the present application;

[0060] Figure 3 A design flow chart of a vector vortex light field polarization conversion device provided for an embodiment of the application;

[0061] Figure 4 A top view, a left top view or a right top view and a front view of an optimal super-atom unit size provided in an embodiment of the present application;

[0062] Figure 5 A schematic diagram of an optical characteristic curve of an optimal super-atom unit provided in one embodiment of the present application;

[0063] Figure 6A schematic diagram of the spatial distribution of super-atomic units, a schematic diagram of the light field intensity and polarization direction, and a schematic diagram of the phase distribution of a 1 / 4 wave plate super-atomic unit simulation model provided in an embodiment of the present application;

[0064] Figure 7 A simulation model of a quarter wave plate super-atom unit and a diagram showing the relationship between the rotation angle of a general wave plate and the emission angle of the emitted light provided in an embodiment of the present application;

[0065] Figure 8 A schematic diagram of the arrangement structure, a schematic diagram of the light field intensity and polarization direction, and a schematic diagram of the phase distribution for generating radial vortex beams and angular vortex beams through a 1 / 4 wave plate simulation model and a general wave plate simulation model provided in one embodiment of the present application;

[0066] Fig. 9 A schematic diagram of the light field intensity and polarization angle and a phase distribution diagram of a vector vortex light field polarization conversion device (a 1 / 4 wave plate simulation model and a general wave plate simulation model) at different wavelengths provided in one embodiment of the present application.

[0067] Reference numerals: superatomic unit—501; base layer—502. DETAILED DESCRIPTION

[0068] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0069] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0070] In an exemplary embodiment of the present application, a vector vortex light field polarization conversion device is provided, comprising: a substrate layer and a super-atom unit layer, such as Figure 1 shown.

[0071] The super-atom unit layer is arranged on the base layer. The super-atom unit layer includes a plurality of super-atom rings. The super-atom rings include a plurality of super-atom units. The spacing between the super-atom units is equal. The super-atom unit has the same properties as the 1 / 4 wave plate. Among them, the general wave plate is a wave plate with set amplitude transmittance. The above characteristics are as follows Figure 1 (a) The design diagram of the vector vortex light field polarization conversion device. Figure 1In (a), d is the side length of the substrate layer, T is the spacing between superatomic units or the width of the superatomic ring band. Four ring bands have been drawn in the figure, and N-4 is the number of ring bands that need to be established in the vector vortex light field polarization conversion device.

[0072] The superatomic unit layer is used to convert the incident circularly polarized light into radially polarized light and azimuthal polarized light carrying the first-order orbital angular momentum.

[0073] In an exemplary embodiment of the present application, the spacing between the provided super-atom units is greater than 0 and smaller than the wavelength of the incident circularly polarized light.

[0074] In an exemplary embodiment of the present application, the period T of the super-atom unit is 380 nm (the super-atom unit structure is a square, and the period of the super-atom unit is the spacing between the super-atom units).

[0075] In an exemplary embodiment of the present application, the base layer is a rectangular parallelepiped structure, and the material used for the base layer is silicon dioxide (SiO2). The super-atom unit is a rectangular parallelepiped structure, and the material used for the super-atom unit is amorphous silicon (α-Si).

[0076] The vector vortex light field polarization conversion device in the present application includes: a base layer and a super-atomic unit layer. The super-atomic unit layer is a metasurface (Metasurface), which includes multiple super-atomic units. The metasurface (Metasurface) is a two-dimensional device composed of micro-nano structures. The propagation and phase of light can be controlled by precise control structures. Compared with traditional polarization conversion devices, the metasurface has the advantages of smaller size, easier preparation, and more precise control. The present application combines the vector light field with the metasurface, and utilizes the advantages of miniaturization and easy integration of the metasurface to conveniently and flexibly generate vector light beams with different characteristics. Based on the transmission phase, geometric phase and the combination of the two, suitable materials are selected in different frequency bands and different functions to construct vector vortex light field polarization conversion devices.

[0077] In an exemplary embodiment of the present application, Figure 2 As shown, a method for constructing a vector vortex light field polarization conversion device is provided, which is used to construct the above-mentioned vector vortex light field polarization conversion device; the method for constructing a vector vortex light field polarization conversion device includes the following steps 101 to 104:

[0078] Step 101, determining the period and height of the super-atom unit according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atom unit.

[0079] Step 102, determining the number of superatomic ring belts and the number of superatomic units on each superatomic ring belt based on the side length of the base layer and the period of the superatomic unit;

[0080] Step 103, determining the distribution position of the super-atomic unit according to the number of super-atomic unit rings and the period of the super-atomic unit.

[0081] Step 104, determining the rotation angle of the super-atomic unit according to the distribution position of the super-atomic unit.

[0082] Step 105 , constructing a vector vortex light field polarization conversion device according to the period and height of the super-atomic unit, the distribution position of the super-atomic unit, and the rotation angle of the super-atomic unit.

[0083] By implementing the above steps 101 to 104, using the metasurface structure composed of meta-atomic units, and determining the period and height of the meta-atomic units, the distribution position of the meta-atomic units, and the rotation angle of the meta-atomic units, a vector vortex light field polarization conversion device is constructed, which not only solves the problem of low transmittance of traditional polarization conversion devices, but also simplifies the manufacturing process and improves manufacturing efficiency.

[0084] In an exemplary embodiment of the present application, the size of the super-atom unit is determined according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atom unit, that is, step 101 is replaced by the following steps 201 to 203:

[0085] Step 201 , incident linearly polarized light onto super-atomic units of different sizes, and obtaining amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atomic units of different sizes.

[0086] Step 202 , based on the amplitude transmittance and phase difference of superatomic units of different sizes in the fast and slow axis directions, determine the superatomic units with the same amplitude transmittance and phase difference in the fast and slow axis directions among the superatomic units of different sizes.

[0087] Step 203, obtaining the period and height of the super-atom unit.

[0088] By implementing the above steps 201 to 203 , the period and height of the super-atomic unit can be determined according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atomic unit.

[0089] In an exemplary embodiment of the present application, step 102 includes obtaining the side length of the substrate layer, and determining the number of superatomic bands according to the side length of the substrate layer and the period of the superatomic unit. The number of superatomic units on each superatomic band is obtained according to the number of superatomic bands. For example, the side length of the substrate layer is obtained, and the number of superatomic bands and the number of superatomic units on each superatomic band are determined according to the side length of the substrate layer and the period of the superatomic unit.

[0090] The calculation formula for the number of superatomic rings is:

[0091]

[0092] Where N is the number of superatomic belts; floor is rounded down; d is the side length of the base layer; T is the spacing between superatomic units. The number of superatomic units on each square belt (i.e., superatomic belt) is (2*N)^2-{2*(N-1)}^2.

[0093] As an optional implementation, in determining the distribution position of the superatomic unit according to the number of superatomic rings and the period of the superatomic unit, the process of determining the distribution position of the superatomic unit, that is, the coordinate of the atomic unit, includes:

[0094] A coordinate system is established with the center of the superatomic unit layer as the origin.

[0095] The coordinates of the center of the superatomic unit in the first quadrant of the coordinate system (x ij ,y ij )for:

[0096] (T / 2+T·j, T / 2+T·i).

[0097] Among them, i is the horizontal coordinate number of the superatomic unit; j is the vertical coordinate number of the superatomic unit; the value range of i and j is [0, N], N is the number of superatomic rings; T is the period of the superatomic unit.

[0098] The coordinates of the center of the superatomic unit in the second quadrant of the coordinate system (x ij ,y ij )for:

[0099] (-T / 2+T·j, T / 2+T·i).

[0100] Among them, the value range of i is [0, N]; the value range of j is [0, -N].

[0101] The coordinates of the center of the superatomic unit in the third quadrant of the coordinate system (x ij ,y ij )for:

[0102] (-T / 2+T·j, -T / 2+T·i).

[0103] The value range of i and j is [0, -N].

[0104] The coordinates of the center of the superatomic unit in the fourth quadrant of the coordinate system (x ij ,y ij )for:

[0105] (T / 2+T·j, -T / 2+T·i).

[0106] Among them, the value range of i is [0, -N]; the value range of j is [0, N].

[0107] In an exemplary embodiment of the present application, the rotation angle of the super-atomic unit is determined according to the distribution position of the super-atomic unit, that is, step 104 is replaced by the following steps 401 to 403:

[0108] Step 401 , incident circularly polarized light onto a super-atom unit to obtain radially polarized light and angularly polarized light of the super-atom unit.

[0109] Step 402: determining the emission angles of the radially polarized light and the angularly polarized light according to the distribution positions.

[0110] Step 403, determining the rotation angle of the super-atom unit according to the emission angle.

[0111] The specific positions of the exit angle and the incident angle, such as Figure 1 (b) Figure 1 (b) is a partial enlarged view of the vector vortex light field polarization conversion device, in which the fast axis and slow axis of the outgoing light beam and the coordinates (x, y) of the super-atom unit are marked. The outgoing angle is the angle between the oblique line between the fast axis and the slow axis and the x-axis. The rotation angle is the angle between the fast axis and the x-axis.

[0112] By implementing the above steps 401 and 403, the rotation angle of the super-atomic unit can be determined according to the distribution position of the super-atomic unit. When the properties of the super-atomic unit and the quarter-wave plate are consistent, the expression of the rotation angle of the obtained super-atomic unit is:

[0113] θ=β-α.

[0114] Among them, θ is the rotation angle; α is the intrinsic angle, which is a unique property of the wave plate with birefringence effect; β is the angle of the emitted light, x is the horizontal coordinate of the superatom; y is the vertical coordinate of the superatom.

[0115] When the properties of the super-atom unit are consistent with those of a general wave plate, the expression for the rotation angle of the super-atom unit is:

[0116] θ=β.

[0117] In an exemplary embodiment, the present application provides a method for constructing a vector vortex light field polarization conversion device in an actual process, such as Figure 3 As shown, the specific steps include:

[0118] S1, before starting, the finite difference time domain method (FDTD) is used to construct a 1 / 4 wave plate (α = 45°, ) and general wave plates (α=0°, const is a constant, that is, the general wave plate only constrains the amplitude transmittance and has no special requirements for the phase) polarization conversion devices with the same properties are the 1 / 4 wave plate super atom model and the general wave plate super atom model. Among them, the cross-sectional side length of the substrate layer of the 1 / 4 wave plate super atom model and the general wave plate super atom model is 380nm, the material is silicon dioxide (SiO2) with a refractive index of 1.457, and a super atom unit layer is set on the substrate, and the material of the super atom unit layer is amorphous silicon (α-Si). The general wave plate only constrains the amplitude transmittance and has no special requirements for the phase.

[0119] The Jones matrix expressions of the 1 / 4 wave plate superatom model and the general wave plate superatom model are:

[0120]

[0121] Where G is the Jones matrix; t is the amplitude transmittance; t f is the amplitude transmittance in the fast axis direction; t s is the amplitude transmittance in the slow axis direction; cosα is the ratio of the amplitude transmittance in the fast axis direction to the amplitude transmittance of the super-atom unit; sinα is the ratio of the amplitude transmittance in the slow axis direction to the amplitude transmittance of the super-atom unit; α is the intrinsic angle; is the phase difference between the slow axis phase and the fast axis phase; i is the imaginary unit; is an exponential function, which means that e Power.

[0122] Among them, the 1 / 4 wave plate property is that in the standard 1 / 4 wave plate, its phase difference The amplitude transmittance in the fast and slow axis directions is equal: t f =t s =1, α=45°, and The general wave plate properties are cosα→1 and sinα→0 (i.e., the amplitude transmittance of the general wave plate is set).

[0123] The finite-difference time-domain solutions (FDTD) in the finite element simulation software was used to simulate and verify the 1 / 4 wave plate super atom model and the general wave plate super atom model. First, a linear polarized light with an angle of 45° between the polarization direction and the positive direction of the axis was used to incident on the super atom unit model. A series of super atom libraries were created using the scanning function of the finite element simulation software. In the established super atom library, there is information such as the amplitude, phase, and intensity of the outgoing light beam of each super atom unit of different sizes (length, width, and height) under the condition of 45° linear polarized light incident. Based on the properties of the 1 / 4 wave plate (α = 45°, ) and general wave plate properties (α=0°, ) Search in the super-atom library to find the super-atom unit that satisfies the 1 / 4 wave plate attribute and the general wave plate attribute, and obtain the size of the super-atom unit that satisfies the 1 / 4 wave plate attribute and the general wave plate attribute, that is, the length L, width W and height H of the super-atom unit that satisfies the 1 / 4 wave plate attribute and the general wave plate attribute. If the length L, width W and height H of the super-atom unit that satisfies the 1 / 4 wave plate attribute and the general wave plate attribute are not found, continue searching.

[0124] S2, since general wave plates only perform polarization control on the fast axis direction, there is no need to verify their control characteristics. Therefore, it is only necessary to use finite element simulation software to verify the 1 / 4 wave plate super-atom unit model. During verification, linearly polarized light with an angle of 45° between the polarization direction and the positive direction of the x-axis was used to incident on the 1 / 4 wave plate super-atom unit model, and the wavelength of the light source was changed to scan it. The scanning wavelength range of the light source was 400nm~700nm, and the scanning wavelength interval was 20nm, so as to obtain a group of super-atom libraries of the 1 / 4 wave plate super-atom unit model; the angle of the light source in the vertical direction was changed again to scan, and the angle scanning range was 0°~60°, and the angle scanning interval was 1°, so as to obtain another group of super-atom libraries of the 1 / 4 wave plate type; since the super-atom library contains information such as the amplitude, phase and intensity of the outgoing light field of each super-atom unit under the condition of 45° linearly polarized light incidence, the phase difference between the two groups of super-atom libraries is analyzed, so that the super-atom unit meets the 1 / 4 wave plate properties under a wider bandwidth, and finally the optimal super-atom unit size is obtained, which can provide a suitable arrangement unit structure for subsequent simulation models.

[0125] The optimal superatomic unit size, such as Figure 4 As shown, Figure 4 (a) is a top view of the optimal super-atom unit size. Figure 4 (b) is the left top view or right view of the optimal super-atom unit size. Figure 4 (c) is a front view of the optimal super-atom unit size, where the super-atom unit 501 has a height of H=480nm, a length of L=168.71nm, a width of W=80nm, and a cross-sectional side length of the base layer 502 is d.

[0126] If the optimal super-atom unit size is not found, return to S1 to re-search the length L, width W and height H of the super-atom unit that satisfies the 1 / 4 wave plate properties and the general wave plate properties.

[0127] Figure 5 Schematic diagram of the optical characteristic curve of the optimal super-atom unit. Figure 5 (a) is the phase diagram of different light source tilt angles from 0° to 60°. Figure 5 (b) is the phase difference diagram for different light source tilt angles from 0° to 60°. Figure 5(c) is the phase diagram of the fast axis and slow axis of different light source wavelengths from 400nm to 700nm. Figure 5 (d) in the figure is the phase difference diagram of the fast axis and the slow axis at different light source wavelengths from 400nm to 700nm. Figure 5 It can be seen that in the angle range of 0° to 4°, the superatom conforms to the local 1 / 4 wave plate properties; in the wavelength range of 630nm to 640nm, the superatom conforms to the local 1 / 4 wave plate properties.

[0128] S3, based on the optimal super-atomic unit size obtained in S2, a 1 / 4 wave plate super-atomic unit simulation model is established using finite element simulation software. The side length d of the cross section of the substrate layer of the 1 / 4 wave plate super-atomic unit simulation model is 16μm, and it is composed of 40×40 super-atomic units made of amorphous silicon (α-Si). The super-atomic units are arranged on the substrate in an orderly manner according to central symmetry and two adjacent super-atomic units are 380nm apart (each super-atomic unit has no rotation). In the finite element simulation software, boundary conditions in the three directions of x, y and z are set in the three-dimensional coordinate system. The boundary conditions all use the perfect matching layer-advanced absorption boundary condition (Perfect Matched Layer, PML), which can absorb light waves leaving the simulation area. The incident light is right-handed circularly polarized light with a wavelength of λ=632.8nm, which is incident perpendicular to the substrate.

[0129] Figure 6 It is a schematic diagram of the spatial distribution of the super-atomic unit of the polarization conversion device of the present invention, a schematic diagram of the light field intensity and polarization direction, and a schematic diagram of the phase distribution;

[0130] like Figure 6 As shown, Figure 6 (a) is a schematic diagram of the spatial distribution of superatomic units in the 1 / 4 wave plate superatomic unit simulation model. Figure 6 (b) is a schematic diagram of the light field intensity and polarization direction of the 1 / 4 wave plate super atom unit simulation model. Figure 6 (c) is a schematic diagram of the phase distribution of the 1 / 4 wave plate super atom unit simulation model. Figure 6 It can be seen that when circularly polarized light is used as the incident light, the light field intensity of the outgoing light is relatively uniform, and the angle between the polarization direction of the outgoing light and the positive direction of the axis is about , indicating that the 1 / 4 wave plate super-atom unit simulation model can convert circularly polarized light into linearly polarized light, proving that the 1 / 4 wave plate super-atom unit simulation model has good 1 / 4 wave plate function.

[0131] S4, use right-handed or left-handed circularly polarized light to enter the 1 / 4 wave plate super-atomic unit simulation model to obtain radially polarized light and angularly polarized light, use finite element simulation software to perform a 360° rotation scan on the super-atomic unit in the 1 / 4 wave plate super-atomic unit simulation model (the scanning angle interval period is 1°), and obtain the relationship between the rotation angle θ and the output light angle β.

[0132] The expression of the Jones vector for right-handed circularly polarized light is as follows:

[0133]

[0134] J in is the Jones vector of the incident right-handed circularly polarized light; i is the imaginary unit.

[0135] The Jones vector expressions for radially polarized light and angularly polarized light are as follows:

[0136]

[0137] Where E RPB is the electric field of radially polarized light; E APB is the electric field of azimuthally polarized light; E out is the total electric field; β is the polarization angle of radial polarized light and angular polarized light, that is, the exit angle.

[0138] The expression of the Jones matrix of the outgoing light is as follows:

[0139]

[0140] Among them, J out is the Jones matrix of the outgoing light; R is the rotation matrix; θ is the rotation angle.

[0141] When the 1 / 4 wave plate super atom unit simulation model is used for polarization conversion, the Jones matrix of the outgoing light can be further expressed as:

[0142]

[0143] Where l is the orbital angular momentum. When l = 1, the incident light is right-handed circularly polarized light, and the outgoing light carries a phase of θ; when l = -1, the incident light is left-handed circularly polarized light, and the outgoing light carries a phase of -θ.

[0144] When a general wave plate is used for polarization conversion, cosθ is set close to 1 and sinθ is set close to 0. The Jones matrix of the outgoing light can be expressed as:

[0145]

[0146] It can be concluded from the above formula that both the 1 / 4 wave plate super-atom unit simulation model and the general wave plate can successfully realize the polarization conversion of the vector vortex light field.

[0147] According to the Jones matrix of the polarization-converted output light of the 1 / 4 wave plate superatom unit simulation model, the theoretical expression of the arrangement position and rotation orientation of each superatom can be obtained as follows:

[0148]

[0149] Where x is the horizontal coordinate with the super-atomic unit layer as the coordinate origin; y is the vertical coordinate with the super-atomic unit layer as the coordinate origin.

[0150] According to the Jones matrix of the outgoing light based on the polarization conversion of the general wave plate, the theoretical expression of the position and rotation orientation of each superatom arrangement can be obtained as follows:

[0151]

[0152] By using the theoretical expressions of the arrangement position and rotation orientation of each superatom obtained by using the Jones matrix of the outgoing light polarization converted according to the 1 / 4 wave plate superatom unit simulation model and the theoretical expressions of the arrangement position and rotation orientation of each superatom obtained by using the Jones matrix of the outgoing light polarization converted based on the general wave plate, the theoretical calculation verification is carried out, and the relationship between the tilt angle and the output angle can be obtained.

[0153] like Figure 7 As shown in the figure, the relationship between the rotation angle and the emission angle of the outgoing light of the 1 / 4 wave plate super atom unit simulation model and the general wave plate in S4 is given respectively. Figure 7 (a) is the relationship between the rotation angle of the 1 / 4 wave plate super atom unit simulation model and the output angle of the output light. Figure 7 (b) is a graph showing the relationship between the rotation angle of a general wave plate and the output angle of the output light, where the hollow dots are simulation results and the straight solid lines are theoretical calculation results. The two show good consistency, and the output angle of the output light is close to the rotation angle.

[0154] S5. According to the relationship between the rotation angle and the output angle of the super-atomic unit obtained in S4, a simulation model for the conversion of right-handed or left-handed circularly polarized light to vortex radial polarized light of l=-1 is established. Then each super-atomic unit is rotated 90° on the rotation angle of the radial polarization conversion device, and the phase is further delayed by π / 2 to establish a simulation model for the conversion of right-handed or left-handed circularly polarized light to vortex radial polarized light and vortex angular polarized light of l=-1 (1 / 4 wave plate simulation model and general wave plate simulation model). The cross-section of the polarization conversion device model is a square with a side length of 16μm, and it is composed of 40×40 super-atomic units in total; using finite element simulation software, the boundary conditions of x, y and z are set to use perfect matching layers, and the incident light is right-handed circularly polarized light with a wavelength of λ=632.8nm, which is incident perpendicular to the substrate. The schematic diagram of the arrangement structure of the radial vortex beam and the angular vortex beam, the schematic diagram of the light field intensity and polarization direction, and the schematic diagram of the phase distribution are generated by the 1 / 4 wave plate simulation model and the general wave plate simulation model, as shown in FIG. Figure 8 As shown, Figure 8 (a) is a schematic diagram of the arrangement structure of the radial vortex beam generated by the 1 / 4 wave plate simulation model. Figure 8 (b) is a schematic diagram of the light field intensity and polarization direction of the radial vortex beam generated by the 1 / 4 wave plate simulation model. Figure 8 (c) is a schematic diagram of the phase distribution of the radial vortex beam generated by the 1 / 4 wave plate simulation model. Figure 8 (d) is a schematic diagram of the arrangement structure of the angular vortex beam generated by the 1 / 4 wave plate simulation model. Figure 8 (e) is a schematic diagram of the light field intensity and polarization direction of the angular vortex beam generated by the 1 / 4 wave plate simulation model. Figure 8 (f) is a schematic diagram of the phase distribution of the angular vortex beam generated by the 1 / 4 wave plate simulation model. Figure 8 (g) is a schematic diagram of the arrangement structure of the radial vortex beam generated by the general wave plate simulation model. Figure 8 (h) is a schematic diagram of the light field intensity and polarization direction of a radial vortex beam generated by a general wave plate simulation model. Figure 8 (i) is a schematic diagram of the phase distribution of a radial vortex beam generated by a general wave plate simulation model. Figure 8 (j) is a schematic diagram of the arrangement structure of the angular vortex beam generated by the general wave plate simulation model. Figure 8 (k) is a schematic diagram of the light field intensity and polarization direction of the angular vortex beam generated by a general wave plate simulation model. Figure 8 (l) in FIG. 1 is a schematic diagram of the phase distribution of an angular vortex beam generated by a general wave plate simulation model. Figure 8It can be seen that the 1 / 4 wave plate simulation model and the general wave plate simulation model convert circularly polarized light into radial vortex beams and angular vortex beams, which proves that they can realize the polarization conversion and have the conversion function of radial vortex beams and angular vortex beams.

[0155] S6, end.

[0156] An embodiment of the present application provides a schematic diagram of the light field intensity and polarization angle at different wavelengths and a schematic diagram of the phase distribution of the vector vortex light field polarization conversion device (1 / 4 wave plate simulation model and general wave plate simulation model) constructed by the present application, such as Fig. 9 As shown, Fig. 9 (a) is a schematic diagram of the light field intensity and polarization angle of the 1 / 4 wave plate simulation model at a wavelength of 600nm. Fig. 9 (b) is a schematic diagram of the phase distribution of the 1 / 4 wave plate simulation model at a wavelength of 600nm. Fig. 9 (c) is a schematic diagram of the light field intensity and polarization angle of a general wave plate simulation model at a wavelength of 600nm. Fig. 9 (d) is a schematic diagram of the phase distribution of a general wave plate simulation model at a wavelength of 600nm. Fig. 9 (e) is a schematic diagram of the light field intensity and polarization angle of the 1 / 4 wave plate simulation model at a wavelength of 610nm. Fig. 9 (f) is a schematic diagram of the phase distribution of the 1 / 4 wave plate simulation model at a wavelength of 610nm. Fig. 9 (g) is a schematic diagram of the light field intensity and polarization angle of a general wave plate simulation model at a wavelength of 610nm. Fig. 9 (h) is a schematic diagram of the phase distribution of a general wave plate simulation model at a wavelength of 610nm. Fig. 9 (i) is a schematic diagram of the light field intensity and polarization angle of the 1 / 4 wave plate simulation model at a wavelength of 620nm. Fig. 9 (j) is a schematic diagram of the phase distribution of the 1 / 4 wave plate simulation model at a wavelength of 620nm. Fig. 9 (k) is a schematic diagram of the light field intensity and polarization angle of a general wave plate simulation model at a wavelength of 620nm. Fig. 9 (l) is a schematic diagram of the phase distribution of a general wave plate simulation model at a wavelength of 620nm. Fig. 9 (m) in the figure is a schematic diagram of the light field intensity and polarization angle of the 1 / 4 wave plate simulation model at a wavelength of 630nm. Fig. 9 (n) in the figure is a schematic diagram of the phase distribution of the 1 / 4 wave plate simulation model at a wavelength of 630nm. Fig. 9 (o) is a schematic diagram of the light field intensity and polarization angle of a general wave plate simulation model at a wavelength of 630nm. Fig. 9(p) in the figure is a schematic diagram of the phase distribution of a general wave plate simulation model at a wavelength of 630nm. Fig. 9 (q) in the figure is a schematic diagram of the light field intensity and polarization angle of the 1 / 4 wave plate simulation model at a wavelength of 640nm. Fig. 9 (r) in the figure is a schematic diagram of the phase distribution of the 1 / 4 wave plate simulation model at a wavelength of 640nm. Fig. 9 (s) is a schematic diagram of the light field intensity and polarization angle of a general wave plate simulation model at a wavelength of 640nm. Fig. 9 (t) in is a schematic diagram of the phase distribution of a general wave plate simulation model at a wavelength of 640nm. Fig. 9 It can be seen that the simulation model based on the 1 / 4 wave plate has good polarization conversion efficiency in the band, and the simulation model based on the general wave plate has good polarization conversion efficiency in the band.

[0157] In another exemplary embodiment of the present application, a vector vortex light field polarization conversion device construction system is provided, specifically comprising:

[0158] The size determination module is used to determine the size of the super-atom unit according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atom unit.

[0159] The position determination module is used to determine the distribution position of the super-atomic unit based on the side length of the substrate layer and the spacing between the super-atomic units.

[0160] The rotation angle determination module is used to determine the rotation angle of the super-atomic unit according to the distribution position of the super-atomic unit.

[0161] The device building module is used to construct a vector vortex light field polarization conversion device according to the size of the super-atomic unit, the distribution position of the super-atomic unit and the rotation angle of the super-atomic unit.

[0162] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0163] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A vector vortex light field polarization conversion device, characterized in that: The vector vortex light field polarization conversion device comprises: a substrate layer and a super-atom unit layer; The super-atomic unit layer is arranged on the base layer; the super-atomic unit layer includes a plurality of super-atomic ring belts; the super-atomic ring belts include a plurality of super-atomic units; the spacing between the super-atomic units is equal; the super-atomic unit has the same properties as a 1 / 4 wave plate or a general wave plate; the general wave plate is a wave plate with set amplitude transmittance; The super-atomic unit layer is used to convert incident circularly polarized light into radially polarized light and angularly polarized light carrying first-order orbital angular momentum.

2. The vector vortex light field polarization conversion device according to claim 1, characterized in that: The spacing between the super-atom units is greater than 0 and smaller than the wavelength of the incident circularly polarized light.

3. A method for constructing a vector vortex light field polarization conversion device, characterized in that: The method for constructing a vector vortex light field polarization conversion device is used to construct the vector vortex light field polarization conversion device according to claims 1-2; the method comprises: Determining the period and height of the super-atom unit according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atom unit; Determine the number of superatomic ring belts and the number of superatomic units on each superatomic ring belt based on the side length of the substrate layer and the period of the superatomic unit; Determining the distribution position of the super-atomic unit according to the number of the super-atomic ring bands and the period of the super-atomic unit; Determining a rotation angle of the super-atom unit according to the distribution position of the super-atom unit; The vector vortex light field polarization conversion device is constructed according to the size of the super-atomic unit, the distribution position of the super-atomic unit and the rotation angle of the super-atomic unit.

4. The method for constructing a vector vortex light field polarization conversion device according to claim 3, characterized in that: Determining the size of the super-atom unit according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atom unit specifically includes: Incident linearly polarized light onto super-atomic units of different sizes, and obtaining the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atomic units of different sizes; According to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atomic units of different sizes, determining the super-atomic units with the same amplitude transmittance and phase difference in the fast axis and slow axis directions as the super-atomic units in the super-atomic units of different sizes; Get the size of the super-atom unit.

5. The method for constructing a vector vortex light field polarization conversion device according to claim 3, characterized in that: Based on the side length of the base layer and the period of the superatomic unit, the number of superatomic ring belts and the number of superatomic units on each superatomic ring belt are determined, including: Acquire the side length of the base layer, and determine the number of the super-atom ring belts according to the side length of the base layer and the period of the super-atom unit; The number of superatomic units on each superatomic ring belt is obtained according to the number of the superatomic ring belts.

6. The method for constructing a vector vortex light field polarization conversion device according to claim 3, characterized in that: Determining the rotation angle of the super-atomic unit according to the distribution position of the super-atomic unit specifically includes: injecting circularly polarized light into the super-atom unit to obtain radially polarized light and angularly polarized light of the super-atom unit; Determining the emission angles of the radially polarized light and the angularly polarized light according to the distribution positions; The rotation angle of the super-atom unit is determined according to the emission angle.

7. The method for constructing a vector vortex light field polarization conversion device according to claim 5, characterized in that: The calculation formula for the number of the superatomic ring bands is: Where N is the number of superatomic rings; floor is rounded down; d is the side length of the base layer; and T is the spacing between superatomic units.

8. The method for constructing a vector vortex light field polarization conversion device according to claim 3, characterized in that: The distribution position of the super-atomic unit specifically includes: Establishing a coordinate system with the center of the super-atomic unit layer as the origin; The center coordinates of the superatomic unit in the first quadrant of the coordinate system (x ij ,y ij )for: (T / 2+T·j, T / 2+T·i); Where i is the horizontal coordinate number of the superatomic unit; j is the vertical coordinate number of the superatomic unit; the value range of i and j is [0, N], N is the number of superatomic rings; T is the period of the superatomic unit; The center coordinates of the superatomic unit in the second quadrant of the coordinate system (x ij ,y ij )for: (-T / 2+T·j, T / 2+T·i); Among them, the value range of i is [0, N]; the value range of j is [0, -N]; The center coordinates of the superatomic unit in the third quadrant of the coordinate system (x ij ,y ij )for: (-T / 2+T·j, -T / 2+T·i); The value range of i and j is [0, -N]; The center coordinates of the superatomic unit in the fourth quadrant of the coordinate system (x ij ,y ij )for: (T / 2+T·j, -T / 2+T·i); Among them, the value range of i is [0, -N]; the value range of j is [0, N].

9. The method for constructing a vector vortex light field polarization conversion device according to claim 3, characterized in that: When the properties of the super-atom unit are consistent with those of the quarter-wave plate, the expression for the rotation angle of the super-atom unit is: θ = β - α; Among them, θ is the rotation angle; α is the intrinsic angle; β is the angle of the emitted light, x is the horizontal coordinate of the superatom; y is the vertical coordinate of the superatom; When the properties of the super-atom unit are consistent with those of a general wave plate, the expression for the rotation angle of the super-atom unit is: θ=β.

10. A vector vortex light field polarization conversion device construction system, characterized in that: The vector vortex light field polarization conversion device construction system specifically includes: A size determination module, used to determine the size of the super-atom unit according to the amplitude transmittance and phase difference in the fast axis and slow axis directions of the super-atom unit; A position determination module, used to determine the distribution position of the super-atom unit based on the side length of the substrate layer and the spacing between the super-atom units; A rotation angle determination module, used to determine the rotation angle of the super-atom unit according to the distribution position of the super-atom unit; A device construction module is used to construct a vector vortex light field polarization conversion device according to the size of the super-atomic unit, the distribution position of the super-atomic unit and the rotation angle of the super-atomic unit.

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