A hyperbolic geometric phase lens with dual focal lines

Abstract

This invention relates to a hyperbolic geometric phase lens with dual focal lines. It utilizes micro-nano fabrication technology to construct the microstructure of the hyperbolic geometric phase diffraction lens, ensuring it conforms to the phase distribution of a hyperbolic function. By exhibiting the optical characteristics of a hyperbolic lens through geometric phase, it focuses left-handed and right-handed circularly polarized light onto two mutually perpendicular lines, thus achieving a planar hyperbolic lens with dual focal line characteristics. Compared to existing technologies, this invention can focus left-handed and right-handed circularly polarized light onto two mutually perpendicular directions. By setting different focal length parameters for the two perpendicular directions, the fabricated device can also focus beams of different circularly polarized states onto focal lines at different distances, with the two focal lines formed being mutually perpendicular. Utilizing the device's different responses to different circularly polarized states, and the diffraction pattern presenting two distinctly different perpendicular intersecting lines concentrated in the central region, the polarization state of the original incident light can be analytically determined.

Description

Technical Field

[0001] This invention relates to the field of lens technology, and in particular to a hyperbolic geometric phase lens with dual focal lines. Background Technology

[0002] Traditional cholesteric liquid crystals are limited by their monochiral helical structure and can only modulate monochiral circularly polarized light, unable to achieve simultaneous modulation of bichiral circularly polarized light.

[0003] CN114690479A discloses a liquid crystal geometric phase device and its fabrication method and detection device. This liquid crystal geometric phase device includes a first substrate, a second substrate, and a chiral coexisting liquid crystal layer located between the first and second substrates. The chiral coexisting liquid crystal layer comprises a liquid crystal layer in which a first oriented cholesteric liquid crystal and a second oriented cholesteric liquid crystal coexist. A first alignment layer is disposed on the side of the first substrate facing the second substrate, and a second alignment layer is disposed on the side of the second substrate facing the first substrate. The technical solution of this invention, by forming a uniformly distributed chiral coexisting system with the first and second oriented cholesteric liquid crystals, can overcome the limitations of traditional cholesteric liquid crystals in terms of selective geometric phase modulation, achieving simultaneous reflection and geometric phase modulation of chiral circularly polarized light.

[0004] This scheme achieves simultaneous modulation of bipolar circularly polarized light through two rotating liquid crystal layers. However, traditional liquid crystal geometric phase lenses are typically circularly symmetrical, capable of focusing circularly polarized light of a specific rotation into a point and defocusing circularly polarized light of the opposite rotation into a circular spot. For a liquid crystal geometric phase cylindrical lens with one-dimensional phase variation, it can only focus circularly polarized light of a specific rotation into a line and defocus circularly polarized light of the opposite rotation into a narrow ellipse.

[0005] The two types of lenses described above have a focusing effect on one type of circularly polarized light and an opposite defocusing effect on the other type of circularly polarized light. Currently, there is no liquid crystal geometric phase lens that can simultaneously focus left-handed and right-handed circularly polarized light. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art and provide a hyperbolic geometric phase lens with focusing characteristics and a double focal line.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A hyperbolic geometric phase lens with dual focal lines, wherein the phase distribution of the hyperbolic geometric phase lens satisfies:

[0009] Γ(x,y)=π[x 2 / (f x λ)-y 2 / (f y λ)]+Γ0

[0010] In the formula, Γ(x,y) is the phase distribution function in the xy plane perpendicular to the direction of light propagation, and the x-axis and y-axis are two mutually perpendicular directions. x And is f y Γ0 represents the focal length along the z-axis of the light propagation direction when focusing along the x-axis and y-axis, respectively; λ is the incident light wavelength; π in radians corresponds to an angle of 180°; and Γ0 is the initial phase, which is a constant.

[0011] Furthermore, the hyperbolic geometric phase lens includes an optical anisotropic layer, which is a liquid crystal layer with patterned planar orientation, or a geometric phase metal or dielectric metasurface layer with microstructure anisotropic response.

[0012] Furthermore, the optical anisotropic layer is a liquid crystal layer with patterned planar orientation, and the hyperbolic geometric phase lens includes a first substrate, a first optical alignment layer and a liquid crystal layer arranged sequentially from bottom to top;

[0013] The first optical alignment layer is located on the upper surface of the first substrate and is parallel to the upper surface of the first substrate;

[0014] The first optical alignment layer has a microstructure, and the orientation azimuth distribution of the microstructure satisfies:

[0015] α(x,y)=π[x 2 / (2f x λ)-y 2 / (2f y λ)]+Γ0 / 2

[0016] In the formula, α(x,y) is the distribution function of the orientation azimuth angle between the x-axis and the x-axis in the xy-plane, where the xy-plane is the upper surface of the first substrate, f x and f y Here, λ is the focal length parameter, λ is the incident light wavelength, π in radians corresponds to an angle of 180°, and Γ0 is the initial phase, which is a constant.

[0017] The liquid crystal layer is disposed parallel to the upper surface of the first light alignment layer, and the liquid crystal layer is a nematic liquid crystal or a chiral liquid crystal.

[0018] Furthermore, the hyperbolic geometric phase lens may also include a second substrate, which is disposed parallel to and above the liquid crystal layer.

[0019] Furthermore, the hyperbolic geometric phase lens may also include a second optical alignment layer located between the liquid crystal layer and the second substrate. The second optical alignment layer is aligned parallel to the plane of the second substrate, and a microstructure is provided on the second optical alignment layer. The orientation azimuth distribution of the microstructure is consistent with that of the first optical alignment layer.

[0020] Furthermore, the hyperbolic geometric phase lens also includes a trench alignment layer located between the liquid crystal layer and the second substrate, the trench alignment layer being aligned parallel to the plane of the second substrate;

[0021] The trench alignment layer is a trench structure created by friction or etching, and the trench extension direction of the trench alignment layer is the easy alignment direction of the liquid crystal layer.

[0022] Furthermore, the hyperbolic geometric phase lens also includes a vertical alignment layer located between the liquid crystal layer and the second substrate.

[0023] The vertical alignment layer is used to align the liquid crystal molecules of the liquid crystal layer perpendicular to the plane of the first substrate.

[0024] Furthermore, the first substrate and / or the second substrate are: a glass substrate or a flexible thin film substrate.

[0025] Furthermore, the liquid crystal layer is made of a liquid crystal material with birefringence; or it is made of a liquid crystal material with birefringence containing polymer monomers.

[0026] Furthermore, the optical anisotropic layer is a geometric phase metal or dielectric metasurface layer utilizing the anisotropic response of the microstructure. The hyperbolic geometric phase lens includes a first substrate on which raised metal or dielectric microstructures are provided. The microstructures exhibit optical anisotropy, and the geometric phase distribution induced by the microstructures satisfies Γ(x,y)=π[x 2 / (f x λ)-y 2 / (f y λ)]+Γ0.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] This invention utilizes micro-nano fabrication technology to create a compact, highly transparent, efficient, lightweight, and flexibly adjustable geometric phase device. The liquid crystal hyperbolic geometric phase lens based on patterned light alignment technology exhibits excellent device stability, electrically adjustable characteristics, and potential for mass production. Compared to ordinary cylindrical lenses, this invention provides differentiated responses to different circularly polarized light and possesses focusing characteristics for both left-handed and right-handed circularly polarized light, with the two focused states presenting two mutually perpendicular crosshairs—a feature impossible to achieve with parabolic phase distribution lenses.

[0029] Before the incident light passes through the device, it first passes through a quarter-wave plate that has been rotated by a certain angle or a liquid crystal wave plate with gradually increasing voltage. By recording and analyzing the evolution of the diffracted light, the polarization state of the original incident light can be determined. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a liquid crystal hyperbolic geometric phase lens structure provided in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of a metasurface hyperbolic geometric phase lens structure provided in an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the geometric phase distribution of a hyperbolic geometric phase lens, where the grayscale color corresponds to the numerical value of the geometric phase.

[0033] Figure 4 For the focal length parameter f x =f y The diffraction pattern of a hyperbolic geometric phase lens at the non-focal distance, the horizontal rays under left-handed circularly polarized light, the vertical rays under right-handed circularly polarized light, the cross rays on the cross section at the non-focal distance perpendicular to the direction of light propagation under linearly polarized light or under simultaneous left-handed and right-handed circularly polarized light, and the three-dimensional diagram of the light intensity distribution on the cross section.

[0034] Figure 5 For the focal length parameter f x =f y The diffraction pattern of a hyperbolic geometric phase lens at the focal length, the horizontal focal line under left-handed circularly polarized light, the vertical focal line under right-handed circularly polarized light, the cross focal line on the cross section perpendicular to the direction of light propagation at the non-focal length under linearly polarized light or under simultaneous left-handed and right-handed circularly polarized light, and a three-dimensional diagram of the light intensity distribution on the cross section.

[0035] Figure 6 To detect the polarization state of incident light using a hyperbolic geometric phase lens 100 and a liquid crystal 200 with a variable optical axis 201;

[0036] Figure 7 To detect the polarization state of incident light using a hyperbolic geometric phase lens 100 and a liquid crystal 200 whose phase delay is modulated by an AC voltage signal generator 202;

[0037] In the figure, 100. Hyperbolic geometric phase lens, 101. ITO glass substrate, 102. First alignment layer, 103. Second alignment layer, 104. Liquid crystal layer, 105. Substrate, 106. Metal or dielectric microstructure layer, 200. Liquid crystal waveplate with a single optical axis direction, 201. Liquid crystal optical axis, 202. AC voltage signal generator. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0039] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0040] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0041] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0042] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0043] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0044] The hyperbolic geometric phase lens with dual focal lines disclosed in this invention is a diffractive optical element. The hyperbolic geometric phase lens includes an optical anisotropic layer. The optical anisotropic layer can be a liquid crystal layer with patterned planar orientation, or it can be a geometric phase metal or dielectric metasurface layer with microstructure anisotropic response, thus forming a liquid crystal hyperbolic geometric phase lens and a metasurface hyperbolic geometric phase lens.

[0045] The geometric phase of a liquid crystal hyperbolic geometric phase lens is numerically equal to twice the orientation azimuth angle. Therefore, by constructing the orientation distribution of the orientation layer, the orientation of the liquid crystal can be driven to achieve an arbitrary geometric phase distribution.

[0046] The geometric phase interaction layer can exist independently, or it can be disposed in parallel on the first substrate, or it can be disposed in parallel between the first substrate and the second substrate.

[0047] Example 1

[0048] This embodiment provides a liquid crystal hyperbolic geometric phase lens, wherein the patterned orientation distribution of the liquid crystal hyperbolic geometric phase lens satisfies:

[0049] α(x,y)=π[x 2 / (2f x λ)-y 2 / (2f y λ)]+Γ0 / 2

[0050] Where α(x,y) is the distribution function of the orientation azimuth angle between the x-axis and the x-axis in the xy plane (substrate plane), f x and f y λ is the focal length parameter, λ is the incident light wavelength, and π in radians corresponds to an angle of 180°.

[0051] The resulting optical phenomenon is the formation of two thin focal lines perpendicular to each other when two circularly polarized lights are incident together.

[0052] Liquid crystal hyperbolic geometric phase lenses can be divided into two categories according to their working mode: active mode and passive mode.

[0053] I. Active Mode

[0054] The liquid crystal hyperbolic geometric phase lens in active mode, from bottom to top, specifically includes:

[0055] A first substrate having a transparent conductive layer, a first photoalignment layer disposed parallel to the upper surface of the first substrate, and a liquid crystal layer having a uniform thickness.

[0056] The first optical alignment layer is located on the upper surface of the first substrate and is parallel to the upper surface of the first substrate;

[0057] The first optical alignment layer has a microstructure, and the orientation azimuth distribution of the microstructure satisfies:

[0058] α(x,y)=π[x 2 / (2f x λ)-y 2 / (2f y λ)]+Γ0 / 2

[0059] In the formula, α(x,y) is the distribution function of the orientation azimuth angle between the x-axis and the x-axis in the xy plane, where the xy plane is the upper surface of the first substrate, and f x and f y Here, λ is the focal length parameter, λ is the incident light wavelength, π in radians corresponds to an angle of 180°, and Γ0 is the initial phase, which is a constant.

[0060] The liquid crystal layer is disposed parallel to the upper surface of the first optical alignment layer. It can be a nematic liquid crystal, corresponding to the optical characteristics of a transmissive geometric phase device, or a chiral liquid crystal, corresponding to the optical characteristics of a reflective geometric phase device.

[0061] Preferably, the above-mentioned liquid crystal hyperbolic geometric phase lens further includes a second substrate, which is disposed parallel to the liquid crystal layer above it.

[0062] A second light alignment layer is provided on the lower surface of the second substrate, which is oriented parallel to the plane of the second substrate. Microstructures are provided on the second light alignment layer, and the orientation azimuth distribution of the microstructures is consistent with that of the first light alignment layer; or, a trench alignment layer is provided on the lower surface of the second substrate, which is oriented parallel to the plane of the second substrate; or, a vertical alignment layer is provided on the lower surface of the second substrate; or, no alignment layer is provided on the lower surface of the second substrate.

[0063] The trench alignment layer has a trench structure generated by methods such as friction or etching, and the trench direction is the easy alignment direction of the liquid crystal;

[0064] The vertical alignment layer is used to align the liquid crystal molecules perpendicular to the plane of the first substrate.

[0065] II. Passive Mode

[0066] The liquid crystal hyperbolic geometric phase lens in passive mode, from bottom to top, specifically includes:

[0067] The first substrate has a patterned alignment layer disposed parallel to the upper surface of the first substrate and a liquid crystal layer containing polymer monomers of uniform thickness.

[0068] Alternatively, the first substrate may not be necessary. A liquid crystal layer containing polymer monomers with patterned orientation and photopolymerized curing can be formed into an independent solid optical film and peeled off from the first substrate.

[0069] Optionally, the first substrate and / or the second substrate may be a glass substrate or a flexible thin film substrate.

[0070] The liquid crystal layer is made of a liquid crystal material with birefringence; or, it is made of a liquid crystal material with birefringence containing polymer monomers.

[0071] Preferably, a transparent conductive layer is provided on the first substrate and the second substrate.

[0072] In this embodiment, the structure of the liquid crystal hyperbolic geometric phase lens 100 is as follows: Figure 1 As shown, it consists of two indium tin oxide (ITO) glass substrates 101 coated with alignment layers 102 and 103 and a liquid crystal layer 104 in the middle.

[0073] The glass substrate 101 is generally made of indium tin oxide conductive glass (ITO glass), and its electrodes are indium tin oxide coatings on the glass surface.

[0074] During the patterning alignment process, the distribution function of the alignment azimuth angle intersecting the x-axis in the xy plane (substrate plane) satisfies α(x,y)=π[x 2 / (2f x λ)-y 2 / (2f y λ)]+Γ0 / 2, where f x and f y λ is the focal length parameter, λ is the incident light wavelength, and π in radians corresponds to an angle of 180°.

[0075] In this example, f is taken. x =f y =10 mm, λ = 633 nm, yielding the expression for α in terms of x and y, which represents the distribution of the orientation angle in the plane. Mathematically, the geometric phase distribution is twice the distribution of the orientation azimuth angle. Gray levels represent the numerical values ​​of the geometric phase. A schematic diagram of the geometric phase distribution is shown below. Figure 3 As shown.

[0076] When collimated light of 633 nm is incident through this lens, the diffraction patterns obtained before and at the focal length are as follows: Figure 4 and Figure 5 As shown, the two intersecting focal lines are generated by the left-hand circular polarization component and the right-hand circular polarization component being focused by the hyperbolic geometric phase lens.

[0077] This invention utilizes the relationship between the orientation angle of liquid crystal molecules and the geometric phase. Through optical alignment technology, it achieves a fine structural arrangement of liquid crystal molecules in the plane of the lens liquid crystal layer, resulting in a hyperbolic geometric phase lens that can achieve differentiated left- and right-hand circular polarization responses and exhibits cross-focal convergence characteristics.

[0078] A liquid crystal waveplate with a single optical axis is placed in front of a hyperbolic phase lens. The optical axis direction is changed by rotating the liquid crystal waveplate, such as... Figure 6 As shown. Alternatively, a voltage can be applied to change the phase delay of the liquid crystal waveplate, such as... Figure 7 As shown, the polarization state of any incident light can be calculated and analyzed by utilizing the evolution of diffracted light behind a hyperbolic geometric phase lens.

[0079] Example 2

[0080] This embodiment provides a metasurface hyperbolic geometry phase lens, which operates in passive mode and specifically includes, from bottom to top:

[0081] A first substrate and a patterned metal or dielectric microstructure layer disposed parallel to the upper surface of the first substrate, the microstructure layer having optical anisotropy, the geometric phase distribution induced by the microstructure satisfying Γ(x,y)=π[x 2 / (f x λ)-y 2 / (f y λ)]+Γ0.

[0082] In this embodiment, the metasurface hyperbolic geometric phase lens structure is as follows: Figure 2 As shown, it consists of a substrate 105 and a metal or dielectric microstructure layer 106.

[0083] By utilizing the response characteristics of a hyperbolic phase lens to circularly polarized light, the polarization state of incident light can be conveniently detected by combining it with a liquid crystal waveplate that varies the optical axis or the phase retardation. A rotatable quarter-waveplate or a voltage-modulated phase retardation liquid crystal waveplate is inserted between the detection light and the hyperbolic phase lens. By changing the optical axis or phase retardation of the liquid crystal waveplate, the polarization state of the detection light is altered. Then, by observing and recording the evolution of the diffracted light from the hyperbolic phase lens, the polarization state of the detection light can be calculated and analyzed.

[0084] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A hyperbolic geometric phase lens with dual focal lines, characterized in that, The hyperbolic geometric phase lens includes an optical anisotropic layer, which is a liquid crystal layer with patterned planar orientation, or a geometric phase metal or dielectric metasurface layer with microstructure anisotropic response. The optical anisotropic layer is a liquid crystal layer with patterned planar orientation, and the hyperbolic geometric phase lens includes a first substrate, a first optical alignment layer and a liquid crystal layer arranged sequentially from bottom to top. The first optical alignment layer is located on the upper surface of the first substrate and is parallel to the upper surface of the first substrate; The first optical alignment layer has a microstructure, and the orientation azimuth distribution of the microstructure satisfies: α(x,y)=π[x 2 / (2f x l)-y 2 / (2f y l)]+Γ0 / 2 In the formula, α(x,y) is the distribution function of the orientation azimuth angle between the x-axis and the x-axis in the xy-plane, where the xy-plane is the upper surface of the first substrate, f x and f y Here, λ is the focal length parameter, λ is the incident light wavelength, π in radians corresponds to an angle of 180°, and Γ0 is the initial phase, which is a constant. The liquid crystal layer is disposed parallel to the upper surface of the first light alignment layer, and the liquid crystal layer is a nematic liquid crystal or a chiral liquid crystal. Alternatively, the optical anisotropic layer is a geometric phase metal or dielectric metasurface layer utilizing the anisotropic response of the microstructure. The hyperbolic geometric phase lens includes a first substrate on which raised metal or dielectric microstructures are provided. These microstructures exhibit optical anisotropy, and the geometric phase distribution induced by the microstructures satisfies the following: Γ(x,y)=π[x 2 / (f x l)-y 2 / (f y l)]+Γ0 In the formula, Γ(x,y) is the phase distribution function in the xy plane perpendicular to the direction of light propagation, and the x-axis and y-axis are two mutually perpendicular directions. x And is f y Γ0 represents the focal length along the z-axis of the light propagation direction when focusing along the x-axis and y-axis, respectively; λ is the incident light wavelength; π in radians corresponds to an angle of 180°; and Γ0 is the initial phase, which is a constant.

2. A hyperbolic geometric phase lens with dual focal lines according to claim 1, characterized in that, When the optical anisotropic layer is a liquid crystal layer, the hyperbolic geometric phase lens further includes a second substrate, which is disposed parallel to the liquid crystal layer above it.

3. A hyperbolic geometric phase lens with dual focal lines according to claim 2, characterized in that, When the optical anisotropic layer is a liquid crystal layer, the hyperbolic geometric phase lens further includes a second optical alignment layer, which is located between the liquid crystal layer and the second substrate. The second optical alignment layer is aligned parallel to the plane of the second substrate, and a microstructure is provided on the second optical alignment layer. The orientation azimuth distribution of the microstructure is consistent with that of the first optical alignment layer.

4. A hyperbolic geometric phase lens with dual focal lines according to claim 2, characterized in that, When the optical anisotropic layer is a liquid crystal layer, the hyperbolic geometric phase lens further includes a trench alignment layer, which is located between the liquid crystal layer and the second substrate, and the trench alignment layer is aligned parallel to the plane of the second substrate. The trench alignment layer is a trench structure created by friction or etching, and the trench extension direction of the trench alignment layer is the easy alignment direction of the liquid crystal layer.

5. A hyperbolic geometric phase lens with dual focal lines according to claim 2, characterized in that, When the optical anisotropic layer is a liquid crystal layer, the hyperbolic geometric phase lens further includes a vertical alignment layer located between the liquid crystal layer and the second substrate. The vertical alignment layer is used to align the liquid crystal molecules of the liquid crystal layer perpendicular to the plane of the first substrate.

6. A hyperbolic geometric phase lens with dual focal lines according to claim 2, characterized in that, When the optical anisotropic layer is a liquid crystal layer, the first substrate and / or the second substrate is a glass substrate or a flexible thin film substrate.

7. A hyperbolic geometric phase lens with dual focal lines according to claim 2, characterized in that, When the optical anisotropy layer is a liquid crystal layer, the liquid crystal layer is made of a liquid crystal material with birefringence; or it is made of a liquid crystal material with birefringence containing polymer monomers.

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