Uniform-light super lens and design method thereof

Abstract

The invention relates to a dodging super lens and a design method thereof, and belongs to the field of optical elements, and the design method comprises the following steps: carrying out the region division of the whole super lens and a target light field, and building the mapping relation between each region of the super lens and the target light field; aiming at the light source position, calculating to obtain a light ray position corresponding to each incident angle of the super lens, and calculating to obtain a light ray emergent angle required by each area of the super lens according to the mapping relation; calculating the phase gradient required by each position of the super lens according to the generalized Snell law; according to the distribution condition of the phase gradient, segmented integration is carried out on the phase gradient to obtain the phase distribution of the superlens of one subarea; selecting a proper super-lens period according to the phase distribution condition, and establishing a super-atom library, namely the relationship between different microstructure sizes and phase delay; and matching the phase distribution with the super-atom library to obtain the required dodging super-lens. The phase distribution of the whole super lens is obtained based on the regional design method, and finally the homogenization function of the emergent light of the light source can be achieved.

Description

Technical Field

[0001] The present invention belongs to the field of optical elements, and in particular relates to a light-homogenizing superlens and a design method thereof. Background Art

[0002] In the fields of security lighting, machine vision, display backlighting, etc., it is often necessary to homogenize the light emitted by the light source. Usually, the solution based on microlens array requires a lens group of multiple lenses to achieve the homogenization function, and the overall system size and weight are large; the design process based on free-form surface methods is complicated and has high requirements for processing conditions. These disadvantages limit the application scenarios of homogenization systems based on refractive lenses.

[0003] Due to its flexible beam control capability, the metalens provides the possibility for integrated light homogenization systems. However, the current light homogenization systems based on metalens still have problems. For example, the phase of light homogenization based on metalens array is difficult to generate stably, and the light homogenization metalens based on phase recovery method will produce speckle phenomenon due to phase singularity, affecting uniformity. Summary of the invention

[0004] The present application provides a light-homogenizing metalens and a design method thereof to at least solve the above technical problems existing in the prior art.

[0005] On the one hand, an embodiment of the present application provides a metalens light homogenization device, wherein the light homogenization metalens is composed of different superatoms in a specific arrangement, and the superatoms are composed of a substrate and a microstructure; the design method is as follows:

[0006] S1, dividing the entire superlens and the target light field into regions of the same number but different sizes;

[0007] S2. Establishing the mapping relationship between each area of ​​the metalens and the target light field according to the edge light principle and the energy conservation principle;

[0008] S3, calculating the light position corresponding to each incident angle of the metalens according to the light source position, and calculating the light exit angle required for each area of ​​the metalens according to the mapping relationship in S2;

[0009] S4, calculating the phase gradient required at each position of the metalens according to the generalized Snell's law;

[0010] S5, integrating the phase gradient piecewise according to its distribution to obtain a partitioned metalens phase distribution;

[0011] S6. Select an appropriate superlens period according to the phase distribution and establish a superatom library, that is, the relationship between different microstructure sizes and phase delays;

[0012] S7. Match the phase distribution obtained in S5 with the superatom library in S6 to obtain the desired light-homogenizing superlens.

[0013] In one possible implementation, the division method is equal luminous flux division or equal area division.

[0014] In one possible implementation, the light position in S3 is calculated by the following formula:

[0015] x0=z·tanθ in

[0016] x0 is the position where the light source is incident on the metalens substrate, z is the distance from the light source to the metalens, θ in is the angle of the incident light.

[0017] In one embodiment, light enters the metalens substrate and is refracted, which is described by the following law of refraction:

[0018] n mid sin(θ mid )-n in sin(θ in )=0

[0019] Among them, n mid With n in are the refractive index of the metalens substrate and the object side, θ mid is the angle of propagation in the metalens substrate.

[0020] In one embodiment, according to the calculated incident angle θ of the light on the metasurface mid and the required exit angle θ out , the generalized Snell's law is used to calculate the phase gradient required at each position of the metalens, and the calculation formula is:

[0021]

[0022] Where n out is the image space refractive index, k0 is the wave vector of the light in vacuum, is the phase gradient at position x.

[0023] In one possible implementation, the matching relationship in S7 is expressed by the following formula, and the entire metalens structure can be obtained by splicing each point with the smallest phase difference value:

[0024]

[0025] is the phase obtained by integration in S5, This is the phase delay that the atomic library in S6 can provide.

[0026] On the other hand, an embodiment of the present application provides a light-homogenizing superlens, which is composed of different superatoms in a specific arrangement, and the superatoms are composed of a substrate and a microstructure; the light-homogenizing superlens is designed by any of the above-mentioned design methods.

[0027] In one possible implementation, the material of the substrate is a material that is transparent to the designed wavelength band.

[0028] In one possible implementation, the designed band is visible light, near infrared or mid-infrared; in the visible light or near infrared band, the substrate material is PMMA, silicon dioxide or silicon nitride; in the mid-infrared band, the substrate material is fluoride glass, chalcogenide glass, germanium silicon glass.

[0029] Compared with the prior art, this application has the following advantages:

[0030] 1. The traditional method based on refractive lenses requires a large volume to achieve the beam homogenization effect, and the design and processing process are complicated; while the present application uses a super lens to achieve beam homogenization, which greatly reduces the required volume and simplifies the design and processing process.

[0031] 2. This application uses the energy conservation ray mapping method to establish the relationship between the phase gradients required at each position of the metalens.

[0032] 3. Currently, the phase of the uniform light based on the superlens array is difficult to generate stably, and the uniform light superlens based on the phase recovery method will produce speckle phenomenon due to the phase singularity, affecting the uniformity; the present application obtains the phase distribution of the entire superlens based on the method of regional design, and finally realizes the homogenization function of the light emitted by the light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 2 is a schematic diagram of the structure of the light-homogenizing superlens in the embodiment of the present application;

[0034] Figure 2 is a schematic diagram of the light mapping principle in an embodiment of the present application;

[0035] Figure 3 Schematic diagram of the light-homogenizing metalens ring in the embodiment of the present application;

[0036] Figure 4 is a schematic diagram of the superatom structure in the embodiment of the present application;

[0037] Figure 5 is the relationship between phase delay and nanocolumn diameter in the embodiment of the present application;

[0038] Figure 6 It is a schematic diagram of the uniform light effect in the embodiment of the present application. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0040] In the description of the present application, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0041] The present application discloses a design method for a light-homogenizing superlens, wherein the light-homogenizing superlens is composed of different superatoms in a specific arrangement, and the superatoms are composed of a substrate and a microstructure.

[0042] The specific design method is as follows:

[0043] S1, dividing the entire superlens and the target light field into regions of the same number but different sizes;

[0044] S2. Establishing the mapping relationship between each area of ​​the metalens and the target light field according to the edge light principle and the energy conservation principle;

[0045] S3, calculating the light position corresponding to each incident angle of the metalens according to the light source position, and calculating the light exit angle required for each area of ​​the metalens according to the mapping relationship in S2;

[0046] S4, calculating the phase gradient required at each position of the metalens according to the generalized Snell's law;

[0047] S5, integrating the phase gradient piecewise according to its distribution to obtain a partitioned metalens phase distribution;

[0048] S6. Select an appropriate superlens period according to the phase distribution and establish a superatom library, that is, the relationship between different microstructure sizes and phase delays;

[0049] S7. Match the phase distribution obtained in S5 with the superatom library in S6 to obtain the desired light-homogenizing superlens.

[0050] Example

[0051] A design method and effect of a uniform light super lens. The lens has a diameter of 3mm, an operating wavelength of 450nm, and a working distance of 1mm. It can homogenize a point light source with a Lambertian distribution at 3mm into a circular light spot with a diameter of 5mm. The schematic diagram is shown in Figure 1 As shown, the design steps include:

[0052] S1. First, the entire metalens and the target surface are divided into regions, the metalens surface is divided according to equal luminous flux, and the target surface is divided into equal areas;

[0053] S2. Establish the mapping relationship of light, such as Figure 2 As shown. The outgoing light from each angle of the light source will be distributed to a specific position on the target surface through the metalens. According to the mapping relationship, the required outgoing angle θ of each position of the metalens can be obtained. out .

[0054] S3. Calculate the incident position of the light, establish the relationship between the light source light exit angle and the exit angle after the metalens, and calculate the position of the light at each angle incident on the metasurface substrate according to the incident angle of the point light source. The following formula can be used for calculation:

[0055] x0=z·tanθ in

[0056] x0 is the position where the light source is incident on the metalens substrate, z is the distance from the light source to the metalens, θ in is the angle of the incident light. When the light enters the metalens substrate, it will be refracted. The law of refraction can be used to describe this process. The formula is:

[0057] n mid sin(θ mid )-n in sin(θ in )=0

[0058] Where n mid With n in are the refractive index of the metalens substrate and the object side, θ mid is the angle of propagation in the metalens substrate. Based on the refraction angle and the geometric relationship, the position x at which the light source incidents on the metasurface at a specific incident angle can be calculated.

[0059] S4. According to the calculated incident angle θ of the light on the metasurface mid and the required exit angle θ out , the generalized Snell's law is used to calculate the phase gradient required at each position of the metalens, and the calculation formula is:

[0060]

[0061] Where n out is the image space refractive index, k0 is the wave vector of the light in vacuum, is the phase gradient at position x.

[0062] S5. According to the distribution of the phase gradient, perform segmented integration to obtain the phase distribution of the metalens. In this embodiment, the metalens is divided into 5 ring zones for integration. The ring zone diagram is shown in FIG. Figure 3 shown.

[0063] S6. Select appropriate super-lens period according to phase distribution and establish super-atom library. Figure 4 The schematic diagram of the structure of the super atom is given. It is composed of a matrix unit substrate and a nanocolumn microstructure with a height of h. By changing the diameter d of the nanocolumn, different phase delays can be obtained to construct an atomic library. Figure 5 The relationship between the phase delay of some atomic pools and the diameter of the nanocolumn is given.

[0064] S7. Match the phase distribution obtained in S5 with the superatom library in S6 to obtain the desired superlens. The matching relationship can be expressed by the following formula.

[0065]

[0066] is the phase obtained by integration in S5, For the phase delay that the atomic library in S6 can provide, the entire superlens structure can be obtained by splicing each point with the smallest phase difference.

[0067] Figure 6 The final uniform light effect is given, the spot diameter can reach 5mm at 3mm, and the uniformity is >90%.

[0068] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A design method for a light homogenizing superlens, characterized in that: The light homogenizing superlens is composed of different superatoms in a specific arrangement, and the superatoms are composed of a substrate and a microstructure; the design method is as follows: S1, dividing the entire superlens and the target light field into regions of the same number but different sizes; S2. Establishing the mapping relationship between each area of ​​the metalens and the target light field according to the edge light principle and the energy conservation principle; S3, calculating the light position corresponding to each incident angle of the metalens according to the light source position, and calculating the light exit angle required for each area of ​​the metalens according to the mapping relationship in S2; S4, calculating the phase gradient required at each position of the metalens according to the generalized Snell's law; S5, integrating the phase gradient piecewise according to its distribution to obtain a partitioned metalens phase distribution; S6. Select an appropriate superlens period according to the phase distribution and establish a superatom library, that is, the relationship between different microstructure sizes and phase delays; S7. Match the phase distribution obtained in S5 with the superatom library in S6 to obtain the desired light-homogenizing superlens.

2. The design method according to claim 1, characterized in that: The division method is equal luminous flux division or equal area division.

3. The design method according to claim 1, characterized in that: The light position in S3 is calculated by the following formula: x0=z tanθ in x0 is the position where the light source is incident on the metalens substrate, z is the distance from the light source to the metalens, θ in is the angle of the incident light.

4. The design method according to claim 3, characterized in that: When light enters the metalens substrate, it will be refracted. The following law of refraction describes this process: n mid sin(θ mid )-n in sin(θ in )=0 Among them, n mid With n in are the refractive index of the metalens substrate and the object side, θ mid is the angle of propagation in the metalens substrate.

5. The design method according to claim 4, characterized in that: According to the calculated incident angle θ of the light on the metasurface mid and the required exit angle θ out , the generalized Snell's law is used to calculate the phase gradient required at each position of the metalens, and the calculation formula is: Where n out is the image space refractive index, k0 is the wave vector of the light in vacuum, is the phase gradient at position x.

6. The design method according to claim 1, characterized in that: The matching relationship in S7 is expressed by the following formula. The entire superlens structure can be obtained by splicing each point with the smallest phase difference: is the phase obtained by integration in S5, This is the phase delay that the atomic library in S6 can provide.

7. A light homogenizing superlens, characterized in that: The light-homogenizing superlens is composed of different superatoms in a specific arrangement, and the superatoms are composed of a substrate and a microstructure; the light-homogenizing superlens is designed by any one of the design methods of claims 1-6.

8. The light homogenizing superlens according to claim 7, characterized in that: The material of the substrate is a material that is transparent to the designed wavelength band.

9. The light homogenizing superlens according to claim 8, characterized in that: The designed wavelength band is visible light, near infrared or mid-infrared; In the visible or near-infrared band, the substrate material is PMMA, silicon dioxide or silicon nitride; In the mid-infrared band, the substrate materials are fluoride glass, chalcogenide glass, and germanium-silicon glass.

Images