CN115933034A - Hyperbolic geometric phase lens with double focal lines - Google Patents

Abstract

The invention relates to a hyperbolic geometric phase lens with bifocal lines, which is characterized in that a micro-nano processing technology is utilized to perform microstructure construction on a hyperbolic geometric phase diffraction lens, so that the hyperbolic geometric phase diffraction lens meets the phase distribution of a hyperbolic function, and the optical characteristics of the hyperbolic lens are shown through the geometric phase, so that left-handed circularly polarized light and right-handed circularly polarized light are respectively focused on two mutually perpendicular lines, and the planar hyperbolic lens with bifocal line characteristics is realized. Compared with the prior art, the invention can focus the left-handed circularly polarized light and the right-handed circularly polarized light to two mutually vertical directions respectively, and the prepared device can also realize the effect of focusing light beams in different circular polarization states to different focal lines at different distances by setting different focal length parameters to the two vertical directions, and the two focal lines formed respectively are mutually vertical; the polarization state of the original incident light can be analyzed and judged by utilizing the characteristic that the device responds differently to different circular polarization states and the diffraction pattern is concentrated on two perpendicular intersecting lines with obvious difference in the central area.

Description

A Hyperbolic Geometric Phase Lens with Bifocal Lines

technical field

The invention relates to the field of lens technology, in particular to a hyperbolic geometric phase lens with bifocal lines.

Background technique

Traditional cholesteric liquid crystals are limited by the monochiral helical structure, and can only modulate monochiral circularly polarized light, but cannot simultaneously modulate bichiral circularly polarized light.

The invention with the publication number CN114690479A discloses a liquid crystal geometric phase device and its preparation method and detection device. The liquid crystal geometric phase device includes a first substrate, a second substrate and a substrate located between the first substrate and the second substrate. The two-handed coexistence liquid crystal layer, the two-handed coexistence liquid crystal layer includes the liquid crystal layer in which the first handed cholesteric liquid crystal and the second handed cholesteric liquid crystal coexist; the first substrate is provided with a first orientation toward the side of the second substrate layer, the side of the second substrate facing the first substrate is provided with a second alignment layer. According to the technical solution of the embodiment of the present invention, the first handed cholesteric liquid crystal and the second handed cholesteric liquid crystal form a uniformly distributed two-handed coexistence system, which can break through the optional selective geometric phase control of the traditional cholesteric liquid crystal, Simultaneous reflection and geometric phase modulation of bichiral circularly polarized light.

This scheme realizes the simultaneous modulation of bichiral circularly polarized light through two handed liquid crystal layers, but the traditional liquid crystal geometric phase lens is usually circularly symmetric, and can converge the circularly polarized light of a specific handedness into a point through focusing. The other kind of anti-rotation circularly polarized light expands into a circular spot through defocusing. For the liquid crystal geometric phase lenticular lens with one-dimensional phase change, it can only converge the circularly polarized light of a specific handedness into a line through focusing, and expand the circularly polarized light of the other opposite handedness into a narrow line through defocusing. ellipse.

The above two lenses have a focusing effect on one of the circularly polarized light, and have an opposite defocusing effect on the other circularly polarized light. At present, there is no liquid crystal geometric phase lens that can focus both left-handed and right-handed circularly polarized light at the same time. .

Contents of the invention

The object of the present invention is to provide a hyperbolic geometric phase lens with a bifocal line and a focusing characteristic in order to overcome the above defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

A hyperbolic geometric phase lens with bifocals, the phase distribution of the hyperbolic geometric phase lens satisfies:

Γ(x,y)=π[x ² /(f _x λ)-y ² /(f _y λ)]+Γ ₀

In the formula, Γ(x, y) is the phase distribution function in the xy plane perpendicular to the light propagation direction, the x-axis and the y-axis are two mutually perpendicular directions, f _x and f _y are respectively along the x-axis and y Focusing in the axial direction is the focal length on the z-axis of the light propagation direction, λ is the wavelength of the incident light, radian π corresponds to an angle of 180°, and Γ ₀ is the initial phase, which is a constant.

Further, the hyperbolic geometric phase lens includes an optically anisotropic layer, the optically anisotropic layer is a liquid crystal layer utilizing patterned planar alignment, or a geometric phase metal or dielectric superstructure utilizing microstructure anisotropy response. surface layer.

Further, the optically anisotropic effect layer is a liquid crystal layer aligned with a patterned plane, and the hyperbolic geometric phase lens includes a first substrate, a first photo-alignment layer, and a liquid crystal layer sequentially arranged from bottom to top;

The first photo-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 photo-alignment layer is provided with a microstructure, and the orientation azimuth angle distribution of the microstructure satisfies:

α(x,y)=π[x ² /(2f _x λ)-y ² /(2f _y λ)]+Γ ₀ /2

In the formula, α(x, y) is the distribution function of the orientation angle between the x-axis and the xy plane in the xy plane, the xy plane is the upper surface of the first substrate, f _x and f _y are focal length parameters, and λ is Incident light wavelength, radian π corresponds to an angle of 180°, Γ ₀ is the initial phase, which is a constant;

The liquid crystal layer is arranged parallel to the upper surface of the first photo-alignment layer, and the liquid crystal layer is a nematic liquid crystal or a chiral liquid crystal.

Further, the hyperbolic geometric phase lens may further include a second substrate, and the second substrate is arranged in parallel above the liquid crystal layer.

Further, the hyperbolic geometric phase lens may further include a second photo-alignment layer, the second photo-alignment layer is located between the liquid crystal layer and the second substrate, and the second photo-alignment layer is parallel to the second In the planar orientation of the substrate, a microstructure is provided on the second photo-alignment layer, and the orientation azimuth angle distribution of the micro-structure is consistent with that of the first photo-alignment layer.

Further, the hyperbolic geometric phase lens further includes a groove alignment layer, the groove alignment layer is located between the liquid crystal layer and the second substrate, and the groove alignment layer is parallel to the plane alignment of the second substrate ;

The groove alignment layer is a groove structure produced by rubbing or etching, and the groove extension direction of the groove alignment layer is the easy alignment direction of the liquid crystal layer.

Further, the hyperbolic geometric phase lens further includes a vertical alignment layer, and the vertical alignment layer is 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.

Further, the first substrate and/or the second substrate is: a glass substrate or a flexible film substrate.

Further, the liquid crystal layer is made of liquid crystal material with birefringence; or made of liquid crystal material with birefringence including polymer monomers.

Further, the optically anisotropic effect layer is a geometric phase metal or dielectric metasurface layer utilizing microstructure anisotropy response, and the hyperbolic geometric phase lens includes a first substrate on which protrusions are arranged. metal or dielectric microstructure, the microstructure has optical anisotropy, and the geometric phase distribution induced by the microstructure satisfies Γ(x,y)=π[x ² /(f _x λ)-y ² /(f _y λ)]+Γ ₀ .

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

The invention utilizes the micro-nano processing technology to manufacture a geometric phase device with compact structure, good light transmission, high efficiency, light weight, and flexible and adjustable parameters. The liquid crystal hyperbolic geometric phase lens based on patterned photo-alignment technology has good device stability, has electronically adjustable characteristics, and has the potential to be mass-produced. Compared with ordinary cylindrical lenses, the present invention has differential responses to different circularly polarized light, and has focusing characteristics for left-handed circularly polarized light or right-handed circularly polarized light, and the two focusing states present two mutually perpendicular cross focal lines , which cannot be achieved with a parabolic phase distribution lens.

Before the incident light passes through the device, it passes through a quarter-wave plate rotated by several angles or a liquid crystal wave plate with gradually increasing voltage applied. By recording and analyzing the evolution of the diffracted light, the original incident light can be analyzed and judged. polarization state.

Description of drawings

FIG. 1 is a schematic structural diagram of a liquid crystal hyperbolic geometric phase lens provided in an embodiment of the present invention;

Fig. 2 is a schematic structural diagram of a metasurface hyperbolic geometric phase lens provided in an embodiment of the present invention;

Fig. 3 is a schematic diagram of the geometric phase distribution of a hyperbolic geometric phase lens, and the color gray scale corresponds to the numerical value of the geometric phase;

Fig. 4 is the diffraction diagram of the hyperbolic geometric phase lens with focal length parameter f _x =f _y at the non-focal distance, the horizontal direction light under left-handed circularly polarized light irradiation, the vertical direction light under right-handed circularly polarized light irradiation, linearly polarized The cross-ray on the section perpendicular to the propagation direction of the light at the non-focal distance under the light irradiation or the left and right circularly polarized light at the same time, and the three-dimensional diagram of the light intensity distribution on the section;

Fig. 5 is the diffraction pattern of the hyperbolic geometric phase lens at the focal length of the focal length parameter f _x =f _y , the horizontal direction focal line under left-handed circularly polarized light irradiation, the vertical direction focal line under right-handed circularly polarized light irradiation, line The cross focal line on the section perpendicular to the propagation direction of the light at the non-focal distance under the irradiation of polarized light or the simultaneous irradiation of left and right circularly polarized light, and the three-dimensional diagram of the light intensity distribution on the section;

Fig. 6 is to utilize the hyperbolic geometric phase lens 100 and the liquid crystal plate 200 that changes the direction of the optical axis 201 to detect the polarization state of the incident light;

Fig. 7 is to utilize the hyperbolic geometric phase lens 100 and the liquid crystal plate 200 that modulates the phase retardation amount by the AC voltage signal generator 202 to detect the polarization state of the incident light;

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 wave plate with a single optical axis direction, 201. Liquid crystal optical axis, 202. AC voltage signal generator.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Accordingly, 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 represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

It should be noted that like numerals and letters denote similar items in the following figures, therefore, once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship that is usually placed when the product of the invention is used, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying References to devices or elements must have a particular orientation, be constructed, and operate in a particular orientation and therefore should not be construed as limiting the invention.

It should be noted that the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present application, "plurality" means two or more, unless otherwise specifically defined.

Furthermore, the terms "horizontal", "vertical" and the like do not imply that a component is absolutely level or overhanging, but may be slightly inclined. For example, "horizontal" only means that its direction is more horizontal than "vertical", and it does not mean that the structure must be completely horizontal, but can be slightly inclined.

The hyperbolic geometric phase lens with bifocal line disclosed by the present invention is a diffractive optical element, which includes a hyperbolic geometric phase lens and an optical anisotropy effect layer, and the optical anisotropy effect layer can be a liquid crystal with a patterned plane orientation layer, or it can also be a geometric phase metal or dielectric metasurface layer that utilizes the anisotropic response of the microstructure, that is, a liquid crystal hyperbolic geometric phase lens and a metasurface hyperbolic geometric phase lens are formed.

The geometric phase of the liquid crystal hyperbolic geometric phase lens is numerically equal to twice the orientation azimuth angle, so the distribution of any geometric phase can be realized by constructing the orientation distribution of the alignment layer and then driving the liquid crystal orientation.

The geometric phase effect layer can exist independently, or can also be arranged in parallel on the first substrate, or can also be arranged in parallel between the first substrate and the second substrate.

Example 1

This embodiment provides a liquid crystal hyperbolic geometric phase lens, and the patterned orientation distribution of the liquid crystal hyperbolic geometric phase lens satisfies:

α(x,y)=π[x ² /(2f _x λ)-y ² /(2f _y λ)]+Γ ₀ /2

Where α(x,y) is the distribution function of the orientation azimuth angle between the x-axis and the xy plane (substrate plane), f _x and f _y are the focal length parameters, λ is the wavelength of the incident light, and the radian π corresponds to an angle of 180° .

The presented optical phenomenon is to produce two thin focal lines perpendicular to each other under the common normal incidence of two kinds of circularly polarized light.

The liquid crystal hyperbolic geometric phase lens can be divided into active mode and passive mode according to the working mode.

1. Active mode

The liquid crystal hyperbolic geometric phase lens in active mode includes from bottom to top:

A first substrate with a transparent conductive layer, a first photo-alignment layer arranged parallel to the upper surface of the first substrate, and a liquid crystal layer with a uniform thickness.

The first photo-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 photo-alignment layer is provided with a microstructure, and the orientation azimuth distribution of the microstructure satisfies:

α(x,y)=π[x ² /(2f _x λ)-y ² /(2f _y λ)]+Γ ₀ /2

In the formula, α(x, y) is the distribution function of the orientation angle between the x-axis and the xy plane, the xy plane is the upper surface of the first substrate, f _x and f _y are the focal length parameters, and λ is the incident light Wavelength, radian π corresponds to an angle of 180°, Γ ₀ is the initial phase, which is a constant;

The liquid crystal layer is arranged parallel to the upper surface of the first photo-alignment layer, and 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.

Preferably, the liquid crystal hyperbolic geometric phase lens further includes a second substrate, and the second substrate is arranged in parallel above the liquid crystal layer.

A second photo-alignment layer oriented parallel to the plane of the second substrate is provided on the lower surface of the second substrate, a microstructure is provided on the second photo-alignment layer, and the orientation azimuth angle distribution of the microstructure is consistent with that of the first photo-alignment layer; Or, the lower surface of the second substrate is provided with a groove alignment layer oriented parallel to the plane of the second substrate; or, the lower surface of the second substrate is provided with a vertical alignment layer; or, the lower surface of the second substrate is not provided with have any orientation layers;

The trench alignment layer is provided with a trench structure produced by rubbing or etching, and the direction along the trench is the easy orientation direction of liquid crystal;

The vertical alignment layer is used to arrange the liquid crystal molecules perpendicular to the plane of the first substrate.

2. Passive mode

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

The first substrate, the patterned alignment layer arranged parallel to the upper surface of the first substrate, has a liquid crystal layer containing polymer monomers with a uniform thickness.

Alternatively, the first substrate may not be required, and the liquid crystal layer containing polymer monomers having a patterned orientation and cured by photopolymerization forms an independent solid optical film, which is peeled off from the first substrate.

Optionally, the first substrate and/or the second substrate is: a glass substrate or a flexible film substrate.

The liquid crystal layer is made of a birefringent liquid crystal material; or, is made of a birefringent liquid crystal material including a polymer monomer.

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

In this embodiment, the structure of the liquid crystal hyperbolic geometric phase lens 100 is shown in FIG. 1 , consisting of two indium tin oxide (ITO) glass substrates 101 coated with alignment layers 102 and 103 and a liquid crystal layer 104 in between.

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

During the patterned orientation process, the distribution function of the orientation azimuth angle between the x-axis in the xy plane (substrate plane) satisfies α(x,y)=π[x ² /(2f _x λ)-y ² /( 2f _y λ)]+Γ ₀ /2, where f _x and f _y are focal length parameters, λ is the wavelength of incident light, and radian π corresponds to an angle of 180°.

In this example, f _x = f _y = 10 millimeters, λ = 633 nanometers, and the expression of α with respect to x and y is obtained, which is the distribution of the orientation angle in the plane, and the geometric phase distribution is mathematically the distribution of the orientation and azimuth angles 2 times the relationship, the gray scale represents the value of the geometric phase, and the schematic diagram of the geometric phase distribution is shown in Figure 3.

When the collimated light of 633 nm is incident and passes through the lens, the diffraction patterns obtained before and at the focal length are shown in Figure 4 and Figure 5, and the two focal lines crossed are the left-handed circular polarization component and the right-handed circular polarization component respectively produced by focusing with a hyperbolic geometric phase lens.

The present invention utilizes the relationship between the orientation azimuth angle of the liquid crystal molecules and the geometric phase, realizes the fine structure arrangement of the liquid crystal molecules in the plane of the liquid crystal layer of the lens through the optical alignment technology, and obtains a method that can realize left-handed and right-handed circular polarization differentiation A hyperbolic geometric phase lens that is responsive and exhibits cross-focal-line converging characteristics.

A liquid crystal wave plate with a single optical axis direction is arranged in front of the hyperbolic geometric phase lens, and the optical axis direction is changed by rotating the liquid crystal wave plate, as shown in Figure 6. Or apply a voltage to change the phase retardation of the liquid crystal wave plate, as shown in Figure 7, the polarization state of any incident light can be calculated and analyzed by using the evolution of the diffracted light behind the hyperbolic geometric phase lens.

Example 2

This embodiment provides a metasurface hyperbolic geometric phase lens, the metasurface hyperbolic geometric phase lens is a passive mode according to the working mode, and specifically includes from bottom to top:

The first substrate and the patterned metal or dielectric microstructure layer arranged parallel to the upper surface of the first substrate, the microstructure layer has optical anisotropy, and the geometric phase distribution induced by the microstructure satisfies Γ(x,y)=π[x ² /(f _x λ)-y ² /(f _y λ)]+Γ ₀ .

In this embodiment, the metasurface hyperbolic geometric phase lens structure is shown in FIG. 2 , which consists of a substrate 105 and a metal or dielectric microstructure layer 106 .

Utilizing the response characteristics of the hyperbolic geometric phase lens to circularly polarized light, a liquid crystal wave plate that changes the direction of the optical axis or the amount of phase retardation can be combined to conveniently detect the polarization state of the incident light. Insert a rotatable quarter liquid crystal wave plate or a liquid crystal wave plate with voltage modulation phase retardation between the detection light and the hyperbolic geometric phase lens, and change the optical axis direction or phase retardation of the liquid crystal wave plate Detect the polarization state of the light, and then calculate and analyze the polarization state of the detected light by observing and recording the evolution of the diffracted light by the hyperbolic geometric phase lens.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to 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 experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (10)

1. A hyperbolic geometric phase lens having a bifocal line, wherein the phase profile of the hyperbolic geometric phase lens satisfies:

Γ(x,y)＝π[x ² /(f _x λ)-y ² /(f _y λ)]+Γ ₀

where Γ (x, y) is the phase distribution function in the xy plane perpendicular to the direction of light propagation, the x and y axes are two mutually perpendicular directions, f _x And is f _y Respectively the focal length on the z-axis in the light propagation direction when focusing along the x-axis and the y-axis, wherein lambda is the wavelength of incident light, and the radian pi corresponds to the angle of 180 DEG, gamma ₀ Is the initial phase and is constant.

2. The hyperbolic geometric phase lens of claim 1, comprising an optically anisotropic active layer, which is a liquid crystal layer oriented using patterned planes or a geometric phase metal or dielectric super surface layer using microstructure anisotropic response.

3. The hyperbolic geometric phase lens with the bifocal lines of claim 2, wherein the optically anisotropic active layer is a liquid crystal layer oriented by a patterned plane, and the hyperbolic geometric phase lens comprises a first substrate, a first photo-orientation layer and a liquid crystal layer which are sequentially arranged from bottom to top;

the first photo-alignment layer is positioned on the upper surface of the first substrate and is parallel to the upper surface of the first substrate;

the first light orientation layer is provided with a microstructure, and the orientation azimuth angle distribution of the microstructure satisfies the following conditions:

α(x,y)＝π[x ² /(2f _x λ)-y ² /(2f _y λ)]+Γ ₀ /2

wherein α (x, y) is a distribution function of an orientation azimuth included with the x-axis in an xy-plane which is an upper surface of the first substrate, f _x And f _y Is a focal length parameter, lambda is the wavelength of incident light, and radian pi corresponds to an angle of 180 DEG, gamma ₀ Is the initial phase, is constant;

the liquid crystal layer is arranged on the upper surface of the first optical orientation layer in parallel, and is nematic liquid crystal or chiral liquid crystal.

4. The hyperbolic geometric phase lens of claim 3, further comprising a second substrate disposed in parallel above the liquid crystal layer.

5. The hyperbolic geometric phase lens of claim 4, further comprising a second photo-alignment layer between the liquid crystal layer and a second substrate, the second photo-alignment layer being aligned parallel to the plane of the second substrate, the second photo-alignment layer having microstructures thereon, the microstructures having an azimuthal orientation distribution that is consistent with that of the first photo-alignment layer.

6. The hyperbolic geometric phase lens of claim 4, further comprising a trench alignment layer between the liquid crystal layer and a second substrate, the trench alignment layer being aligned parallel to a plane of the second substrate;

the groove orientation layer is of a groove structure generated by a friction or etching method, and the extending direction of the grooves of the groove orientation layer is the easy-to-orient direction of the liquid crystal layer.

7. The hyperbolic geometric phase lens of claim 4, further comprising a vertical alignment layer between the liquid crystal layer and the second substrate,

the vertical alignment layer is used for enabling liquid crystal molecules of the liquid crystal layer to be aligned perpendicular to the first substrate plane.

8. Hyperbolic geometric-phase lens according to claim 4, characterized in that the first and/or second substrate is: a glass substrate or a flexible film substrate.

9. Hyperbolic geometric phase lens according to claim 4, characterized in that said liquid crystal layer is made of a liquid crystal material with birefringence; or from a liquid crystal material with a birefringent effect comprising a polymeric monomer.

10. The hyperbolic geometric phase lens of claim 2, wherein the optically anisotropic active layer is a geometric phase metal or dielectric super-surface layer with microstructure anisotropic response, the hyperbolic geometric phase lens comprises a first substrate on which a raised metal or dielectric microstructure is disposed, the microstructure has optical anisotropy, and the microstructure-induced geometric phase distribution satisfies Γ (x, y) = π [ x ] x ² /(f _x λ)-y ² /(f _y λ)]+Γ ₀ 。

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