Quarter-wave plate fast axis detection device based on optical metasurface

Abstract

This application discloses an optical detection device, comprising: a light source, a linear polarizer, a quarter-wave plate, an optical metasurface, and a light detection unit. The linear polarizer, quarter-wave plate, and metasurface are sequentially arranged along the propagation direction of the incident light. The metasurface comprises a transparent substrate layer and a dielectric nanocolumn layer. The fast axis of the quarter-wave plate has a first angle. When the first angle is a first characteristic angle, the light emitted from the quarter-wave plate is circularly polarized light. The light detection unit detects the optical power of the light emitted from the metasurface in a second angular direction, and obtains a second characteristic angle from the maximum optical power. The refraction angle is obtained from the wavelength of the incident light, the geometric parameters of the metasurface, and the refractive index of air. When the refraction angle is equal to the second characteristic angle, the first angle is the first characteristic angle. This device does not use a modulator or spectrometer, but only requires the pre-fabrication of the metasurface, which greatly reduces the device size and achieves miniaturization and integration.

Description

Technical Field

[0001] The present application relates to the fields of optical metasurfaces and micro-nano processing, and in particular to a quarter-wave plate fast-axis detection device based on an optical metasurface. Background Art

[0002] When circularly polarized light passes through chiral molecules, the molecules absorb left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light differently. This difference can be exploited to study the structural characteristics of biomacromolecules such as proteins and nucleic acids. Using circularly polarized weather radar to illuminate clouds and measure the proportion of left-handed and right-handed circularly polarized light in the scattered light can be used to study the shape characteristics of particles in the clouds and further determine whether the clouds contain hail, raindrops, snowflakes, and other information. Circularly polarized light is also widely used in polarization imaging, laser communications, and other fields. Optical quarter-wave plates, based on the principle of birefringence, are a versatile and convenient method for generating circularly polarized light. To obtain high-purity circularly polarized light, the angles between the quarter-wave plate's fast axis and the linear polarizer's transmission axis must be precisely controlled to maintain 135° and 45°, respectively. Therefore, accurate detection and calibration of the quarter-wave plate's fast axis are crucial. Traditional detection of the fast-axis position of a quarter-wave plate requires the use of photoelastic modulators, acousto-optic modulators, spectrometers, etc. These detection schemes increase the size of the detection device and make it difficult to achieve miniaturization and integration.

[0003] An optical metasurface is a periodic structure with subwavelength thickness. By changing the geometric parameters and materials of the metasurface units, the phase gradient required for optical devices can be artificially designed, achieving flexible control of the phase wavefront of light. In addition, the preparation of optical metasurfaces is compatible with semiconductor processing technology and has the advantages of being lightweight and miniaturized. Since the geometric phase sign introduced by the in-plane rotation of the metasurface units is opposite to that of LCP light and RCP light, the artificially designed geometric phase-based metasurface optical devices can conveniently realize the splitting and detection functions of circularly polarized light, thereby indirectly detecting the position of the fast axis of the quarter-wave plate in real time, which provides a way to miniaturize and integrate the detection device.

[0004] With respect to the technical problems in the prior art mentioned above that the quarter-wave plate fast axis detection device is large in size and difficult to be miniaturized and integrated, no effective solution has been proposed so far. Summary of the Invention

[0005] The present disclosure provides a quarter-wave plate fast-axis detection device based on an optical metasurface, which can solve the technical problems in the prior art of the quarter-wave plate fast-axis detection device being large in size and difficult to miniaturize and integrate.

[0006] According to one aspect of the present application, an optical detection device is provided, which includes: a light source, a linear polarizer, a quarter wave plate, an optical metasurface and a light detection unit, wherein the linear polarizer, the quarter wave plate and the optical metasurface are arranged in sequence along the propagation direction of the incident light, the axis of the linear polarizer coincides with the axis of the quarter wave plate, and constitutes the longitudinal axis of the detection device; the incident light emitted by the light source is incident on the linear polarizer along the longitudinal axis; the optical metasurface includes a transparent substrate layer and a dielectric nanocolumn layer, the transparent substrate layer faces the incident light, and the dielectric nanocolumn layer faces the back of the incident light, the center of the optical metasurface is on the longitudinal axis and the transparent substrate layer is perpendicular to the longitudinal axis; the transmission axis of the linear polarizer is fixed in the y direction; the incident light emitted by the light source passes through the linear polarizer and then enters the quarter wave plate; the fast axis of the quarter wave plate has a first angle, which is the angle facing the incident light. In the direction of the incident light, the fast axis of the quarter wave plate is rotated counterclockwise along the transmission axis of the linear polarizer; when the first angle is a first characteristic angle, the output light from the quarter wave plate is circularly polarized light; the output light from the quarter wave plate is incident on the transparent substrate layer side of the optical metasurface and is emitted from the dielectric nanocolumn layer side; the light detection unit is arranged on the side of the output light of the optical metasurface and the distance from the center of the optical metasurface remains unchanged, and is used to detect the optical power of the output light emitted from the optical metasurface in a second angle direction; a second characteristic angle is obtained, and the second characteristic angle is a second angle corresponding to when the optical power of the output light emitted from the optical metasurface has a maximum value; the refraction angle is obtained according to the wavelength of the incident light, the geometric parameters of the optical metasurface and the refractive index of air, and when the refraction angle is equal to the second characteristic angle, the first angle is the first characteristic angle.

[0007] Optionally, the optical metasurface is composed of optical metaunits periodically arranged along a specific direction, and each optical metaunit is composed of 8 metafunctional primitives; the metafunctional primitives in each optical metaunit are arranged along the +x direction, and each metafunctional primitive is rotated counterclockwise by an angle of π / 8 in turn, and the x, y, and z directions constitute a right-handed rectangular coordinate system.

[0008] Optionally, the metafunctional element is composed of a transparent substrate and a dielectric nanocolumn, wherein the dielectric nanocolumn is a cuboid vertically grown on the transparent substrate, and the cuboid has length dimensions L, W, and H in the x, y, and z directions, respectively; and the cuboid has a periodic dimension P in the x and y directions. x , P y The transparent substrate constitutes the transparent substrate layer of the optical metasurface, and the dielectric nanocolumns constitute the dielectric nanocolumn layer of the optical metasurface.

[0009] Optionally, the geometric parameter of the optical metasurface is the period length of the dielectric nanocolumns of the metafunctional element in the x-direction.

[0010] Optionally, the refraction angle is calculated by the following formula:

[0011]

[0012] where β + , β- are two refraction angles, β + >0,β - <0,λ d is the wavelength of the incident light, P x is the period length of the dielectric nanocolumns of the metafunctional unit in the x direction, n t is the refractive index of air.

[0013] Optionally, when the refraction angle is β + , and β + When the first characteristic angle is equal to the second characteristic angle, the first characteristic angle is 135°, the outgoing light from the quarter wave plate is left-handed circularly polarized light, and the outgoing light from the optical metasurface is right-handed circularly polarized light.

[0014] Optionally, when the refraction angle is β - , and β- is equal to the second characteristic angle, the first characteristic angle is 45°, the outgoing light from the quarter-wave plate is right-handed circularly polarized light, and the outgoing light from the optical metasurface is left-handed circularly polarized light.

[0015] Optionally, when the second characteristic angle is not equal to the refraction angle, the fast axis position of the quarter-wave plate is adjusted until the second characteristic angle is equal to the refraction angle, and the first angle at this time is the first characteristic angle.

[0016] Optionally, the light detection unit is an optical power meter, and the optical power meter is located on a guide rail. The guide rail is arc-shaped, and the center of the arc is located at the center of the optical metasurface.

[0017] Optionally, the light source is a broadband tunable laser light source.

[0018] Since the detection device disclosed in the present invention does not use an optical modulator or a spectrometer and only requires the pre-preparation of an optical metasurface, the volume of the detection device can be greatly reduced, thereby achieving miniaturization and integration of the detection device.

[0019] Furthermore, the detection device disclosed in the present invention can detect and calibrate the fast axis position of the quarter-wave plate in real time, and has the characteristics of high efficiency and automation.

[0020] Furthermore, the detection device disclosed in the present invention can obtain high-purity circularly polarized light, and the generated circularly polarized light is very stable.

[0021] Based on the detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Hereinafter, some specific embodiments of the present application will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the drawings:

[0023] Figure 1 is a schematic top view of an optical metasurface according to one embodiment of the present application.

[0024] Figure 2 1 is a structural diagram of a meta-functional element on an optical meta-surface according to an embodiment of the present application.

[0025] Figure 3 This is a schematic diagram of the principle of optical metasurface splitting incident light with different circular polarizations.

[0026] Figure 4 This is a flow chart for preparing optical metasurfaces.

[0027] Figure 5 1 is a structural diagram of a quarter-wave plate fast-axis detection device based on an optical metasurface according to one embodiment of the present application. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in the present disclosure may be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] In order to enable those skilled in the art to better understand the solutions of the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the embodiments described are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present disclosure.

[0030] It should be noted that the terms "first," "second," and the like in the specification and claims of the present disclosure and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate for the embodiments of the present disclosure described herein. In addition, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] In the description of the following embodiments, the word "optical" in "optical metasurface" and "optical metacell" is sometimes omitted and abbreviated to "metasurface" and "metacell", which is a common and well-known practice in the art.

[0033] Figure 1 This is a schematic top view of an optical metasurface. An optical metasurface consists of optical metaunits periodically arranged along a specific direction. Figure 1 In the figure, unit A is the optical meta-unit, which is periodically arranged along the x and y directions to form the following Figure 1 The optical metasurface shown. According to the generalized Snell refraction law:

[0034]

[0035] where θ i ,θ t They represent the angle of incidence and the angle of refraction, n i 、n t are the refractive indices of the incident and outgoing light environments, λ is the wavelength of the incident light, represents the gradient change of phase along the +x direction. By arranging optical meta-units with a certain phase gradient in the x direction, the refraction angle of the outgoing light in the x direction can be controlled. According to formula (1), the phase distribution required to control the refraction angle of the outgoing light is:

[0036]

[0037] In formula (2), the wavelength λ of the incident light is written as λ d , where Δx represents the deflection along the x direction, is the initial phase when x = 0. The spatial phase distribution required for the deflection of the outgoing light can be achieved through the geometric phase generated by the in-plane rotation of the meta-functional primitives in the meta-unit. Figure 1 In the figure, each optical meta-unit A is composed of 8 meta-functional primitives, which are arranged along the +x direction. The counterclockwise rotation angle is defined as positive. Along the +x direction, each meta-functional primitive is rotated counterclockwise by π / 8 compared with its adjacent meta-functional primitive on the left.

[0038] Figure 2 Figure 2 shows the structure of a metafunctional unit on an optical metasurface. The metafunctional unit consists of dielectric nanopillars 2 and a transparent substrate 1. Figure 2 The x and y directions in Figure 1 The x and y directions are the same. The dielectric nanopillars have a period length P in the x direction. x , with a period length P in the y direction y , P x and P y They can be the same or different. In this embodiment, they are selected to be the same. x With P y The length of the dielectric nanopillars 2 is between 300 and 800 nanometers. The dielectric nanopillars 2 are grown on substrate 1, with length (L), width (W), and height (H) respectively. H is between 600 and 1400 nanometers, and L and W are between 100 and 700 nanometers. The material of the metafunctional element can be selected based on the operating wavelength of the light source and quarter-wave plate. For visible light, dielectric materials such as titanium oxide and silicon nitride can be used, while for infrared light, silicon can be used.

[0039] Figure 3 This is a schematic diagram of the optical metasurface's beam splitting of incident light with different circular polarizations. The incident direction of light is the +z direction. A linear polarizer 3, a quarter-wave plate 4, and an optical metasurface 5 are arranged in sequence along the incident light direction. The transparent substrate of the optical metasurface 5 faces the incident light, while the dielectric nanopillars face away from the incident light. The axes of the linear polarizer 3 and the quarter-wave plate 4 coincide with the z-axis, the center of the optical metasurface 5 is on the z-axis, and the substrate is perpendicular to the z-axis. The transmission axis 6 of the linear polarizer 3 is fixed in the y-direction. When viewed from the angle facing the light, the angle of the quarter-wave plate 4's fast axis 7 rotated counterclockwise along the linear polarizer's transmission axis 6 is defined as a positive angle.

[0040] like Figure 3As shown in (a), when a beam of light 8 is incident on the linear polarizer 3 along the +z direction, the transmitted light 9 is linearly polarized along the y direction. When the linearly polarized light 9 passes through the quarter wave plate 4, it can be vector-decomposed into two beams of linear polarized light along the fast axis and the slow axis. When the angle between the fast axis 7 of the quarter wave plate and the transmission axis 6 of the linear polarizer is 135°, the amplitudes of the two beams of linear polarized light along the fast axis and the slow axis are the same, and the phase of the linear polarized light along the fast axis is ahead of the linear polarized light along the slow axis by Δφ=(2π / λ d )(n slow -n fast )L0=π / 2, where L0 is the thickness of the quarter wave plate 4, n slow 、n fast are the refractive indices in the slow axis and fast axis directions of the quarter wave plate, respectively. At this time, the transmitted light 10 emitted from the quarter wave plate 4 is left-handed circularly polarized light.

[0041] The left-handed circularly polarized light continues to be incident on the metasurface 5 along the +z direction. According to the geometric phase principle, after the circularly polarized light interacts with the metafunctional unit rotating counterclockwise at an angle of θ, the circular polarization state of the transmitted light is reversed and carries a geometric phase of 2σθ, where σ = ±1, σ = +1 indicates that the incident light is left-handed circularly polarized, and σ = -1 indicates that the incident light is right-handed circularly polarized. Therefore, the phase difference between adjacent metafunctional units is From formula (1), we can get:

[0042]

[0043] Among them, P x is the period length of the dielectric nanorods on the optical metasurface in the x direction. It can be seen that the refraction angle θ of the transmitted light 11 t >0, the transmitted light 11 is right-handed circularly polarized light, with an angle |θ t |Deflection in the +x direction.

[0044] like Figure 3 As shown in (b), the same light beam 8 is incident on the linear polarizer 3 along the +z direction, and the transmitted light 9 is horizontally polarized linear polarized light. When the angle between the fast axis 7 of the quarter wave plate 4 and the transmission axis 6 of the linear polarizer is 45°, the fast and slow axes of the quarter wave plate are at the same angle. Figure 3 When the angle in (a) is 135°, the positions of the fast and slow axes are swapped. At this time, the phase difference between the two linearly polarized beams along the fast and slow axes is Δφ=(2π / λ d )(n fast -n slow )L0=-π / 2, at this time, the transmitted light 10 emitted from the quarter-wave plate 4 is right-handed circularly polarized light. The right-handed circularly polarized light continues to be incident on the metasurface 5 along the +z direction, and is obtained from formula (1):

[0045]

[0046] It can be seen that the refraction angle θ of the transmitted light 11 is t <0, the transmitted light 11 is left-handed circularly polarized light, with an angle |θ t | deflects in the -x direction. Therefore, the above optical properties of the optical metasurface can be used to split incident light of different circular polarizations.

[0047] Figure 4 This is a diagram of the optical metasurface fabrication process. The fabrication process consists of eight steps:

[0048] S01. Select a transparent substrate 12 in the working band;

[0049] S02. A dielectric film 13 of a certain thickness is prepared on a transparent substrate 12 by chemical vapor deposition, electron beam evaporation, and the like;

[0050] S03 spin-coating an electronic glue or photoresist 14 on the dielectric film 13;

[0051] S04 using electron beam lithography or photolithography technology, the electronic glue or photoresist 14 is exposed to the desired pattern, and the exposed electronic glue or photoresist is removed by developing technology;

[0052] S05. Preparing a metal protective layer 15 on the surface of the wafer after removing the electronic glue or photoresist;

[0053] S06. Removing the unexposed electronic adhesive or photoresist and the metal protective layer thereon;

[0054] S07. Etching the dielectric film not covered by the metal protective layer using an etching process;

[0055] S08. Remove the metal protective layer to obtain the desired metasurface.

[0056] The photoresist used in the above preparation steps is a positive photoresist.

[0057] Figure 5 This is a structural diagram of a quarter-wave plate fast axis detection device based on an optical metasurface. The detection device includes a light source 15, a linear polarizer 3, a quarter-wave plate 4, an optical metasurface 5, a guide rail 16, and an optical power meter 17. The optical path of the tunable light source 15, the linear polarizer 3, the quarter-wave plate 4, and the optical metasurface 5 is arranged in the same manner as the optical path of the tunable light source 15, the linear polarizer 3, the quarter-wave plate 4, and the optical metasurface 5. Figure 3 The arrangement of the corresponding components is the same as in Figure 3Similarly, the incident direction of light is the +z direction. A linear polarizer 3, a quarter-wave plate 4, and an optical metasurface 5 are arranged in this order along the direction of the incident light. The transparent substrate of the optical metasurface 5 faces the incident light, while the dielectric nanopillars face away from the incident light. The axes of the linear polarizer 3 and the quarter-wave plate 4 coincide with the z-axis, the center of the optical metasurface 5 is on the z-axis, the substrate is perpendicular to the z-axis, and the incident light is incident along the +z direction. The transmission axis 6 of the linear polarizer 3 is fixed in the y-direction. When observed from the perspective facing the light, the angle of the fast axis 7 of the quarter-wave plate 4 rotated counterclockwise along the linear polarizer transmission axis 6 is defined as a positive angle. The orientation of the fast axis 7 of the quarter-wave plate is: rotated counterclockwise by an angle θ along the linear polarizer transmission axis 6. The guide rail 16 and the optical power meter 17 are arranged on the side of the optical metasurface 5 on which light is emitted. The track of the guide rail 16 is in an arc shape, and its center is located at the center of the optical metasurface 5. The optical power meter 17 is located on the guide rail 16 and can make a circular motion along the guide rail. The optical power meter 17 is used to detect the refraction angle θ t The optical power of the outgoing light is defined as θ deflected along the z-axis in the +x direction. t is a positive angle, θ deflected in the -x direction t A negative angle.

[0058] Light source 15 can be a tunable light source, preferably a broadband tunable laser light source. Light 8 emitted by the light source is incident along the +z direction and, after passing through the linear polarizer 3, becomes linearly polarized light 9 with a polarization direction along the y direction. Linearly polarized light 9, after passing through the quarter-wave plate 4, becomes elliptically polarized light 10. Transmitted light is circularly polarized only when θ = 45° or 135°. When θ = 45°, transmitted light 10 is right-handed circularly polarized light, and when θ = 135°, transmitted light 10 is left-handed circularly polarized light. This detection device detects in real time whether the fast axis position of the quarter-wave plate 4, i.e., the angle θ, is arranged at 45° or 135°. If the result is negative, it determines how to perform real-time calibration.

[0059] Arrange the initial position of the quarter-wave plate 4 so that the angle θ of its fast axis 7 rotated counterclockwise along the transmission axis 6 of the linear polarizer is 45° or 135°. The initial position of the fast axis of the quarter-wave plate 4 may or may not satisfy θ = 45° or 135° and needs to be calibrated. If θ = 135°, the transmitted light 10 is left-handed circularly polarized light. After entering the metasurface 5, the outgoing light 11 is right-handed circularly polarized light and deflected in the +x direction. Place the optical power meter 17 at θ t =β + The position of θ t =β + Scan the output light power in the +x and -x directions from the center. If the light power is in θ t =β + The position of the quarter-wave plate 4 has a maximum value, so the initial position of the fast axis is θ = 135°, where β +Solve the equation (3):

[0060]

[0061] If the maximum optical power corresponds to θ t Not in beta + Position, the initial position of the fast axis of the quarter wave plate 4 θ ≠ 135 °, which needs to be calibrated. At this time, the angle between the fast axis of the quarter wave plate 4 and the transmission axis 6 of the polarizer can be adjusted, and the above scanning process can be repeated until the optical power is within θ t =β + The fast axis of the quarter-wave plate 4 has reached its maximum value at this position, at which point the fast axis position of the quarter-wave plate 4 has been adjusted to θ = 135°. The fast axis direction of the quarter-wave plate 4 can be adjusted manually, or the quarter-wave plate 4 can be connected to a stepper motor to iteratively increase or decrease the step value Δθ.

[0062] Correspondingly, if θ = 45°, the transmitted light 10 is right-handed circularly polarized light. After entering the metasurface 5, the outgoing light 11 is left-handed circularly polarized light, which is deflected in the -x direction. The optical power meter 17 is placed at θ t =β - The position of θ t =β - Scan the output light power in the +x and -x directions from the center. If the light power is in θ t =β - The position of the quarter-wave plate 4 has a maximum value, so the initial position of the fast axis is θ = 45°, where β - Solve the equation (4):

[0063]

[0064] If the maximum optical power corresponds to θ t Not in beta - If the initial position of the fast axis of the quarter wave plate 4 is θ≠45°, calibration is required. At this time, the angle between the fast axis of the quarter wave plate 4 and the transmission axis 6 of the polarizer can be adjusted, and the above scanning detection process can be repeated until the optical power is within θ t =β - The position of the quarter-wave plate 4 reaches its maximum value. At this time, the fast axis position of the quarter-wave plate 4 has been adjusted to θ = 45°. The fast axis direction of the quarter-wave plate 4 can be adjusted manually, or the quarter-wave plate 4 can be connected to a stepper motor. The stepper motor drives the quarter-wave plate 4 to rotate, and the angle θ is adjusted by iteratively increasing or decreasing the step value Δθ.

[0065] The optical metasurface-based quarter-wave plate fast-axis detection device implemented in the present disclosure can detect and calibrate the fast-axis position of a quarter-wave plate in real time, thereby generating high-purity circularly polarized light of a specified handedness. This detection device does not utilize an optical modulator or spectrometer, requiring only prefabricated optical metasurfaces. This significantly reduces the size of the detection device, enabling its miniaturization and integration. Furthermore, this detection device detects and calibrates the fast-axis position of the quarter-wave plate in real time, offering high efficiency and automation, and the resulting circularly polarized light is highly stable.

[0066] Unless otherwise specifically stated, the relative arrangement of the parts and steps, the numerical expressions and the numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as being merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0067] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0068] In the description of the present disclosure, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present disclosure and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present disclosure; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0069] The above description is merely a preferred embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. An optical detection device, characterized in that: The detection device comprises: a light source (15), a linear polarizer (3), a quarter-wave plate (4), an optical metasurface (5) and a light detection unit, wherein the linear polarizer (3), the quarter-wave plate (4) and the optical metasurface (5) are arranged in sequence along the propagation direction of the incident light, the axes of the linear polarizer (3) and the quarter-wave plate (4) coincide with each other, forming a longitudinal axis z-axis of the detection device; the incident light (8) emitted by the light source (15) is incident on the linear polarizer (3) along the longitudinal axis; the optical metasurface (5) comprises a transparent substrate layer and a dielectric nanocolumn layer, wherein the transparent substrate layer faces the incident light and the dielectric nanocolumn layer faces away from the incident light, the center of the optical metasurface (5) is on the longitudinal axis and the transparent substrate layer is perpendicular to the longitudinal axis; The transmission axis (6) of the linear polarizer (3) is fixed in the y direction; the incident light (8) emitted by the light source (15) passes through the linear polarizer (3) and then enters the quarter-wave plate (4); the fast axis (7) of the quarter-wave plate (4) has a first angle, which is the angle of the fast axis (7) of the quarter-wave plate (4) rotated counterclockwise along the transmission axis (6) of the linear polarizer (3) in the direction facing the incident light; when the first angle is a first characteristic angle, the output light (10) emitted from the quarter-wave plate (4) is circularly polarized light; The output light (10) emitted from the quarter-wave plate (4) is incident on the transparent substrate layer side of the optical metasurface (5) and is emitted from the dielectric nanocolumn layer side; the light detection unit is arranged on the light output side of the optical metasurface (5) and the distance from the center of the optical metasurface (5) remains unchanged, and is used to detect the optical power of the output light (11) emitted from the optical metasurface (5) in a second angular direction; a second characteristic angle is obtained, and the second characteristic angle is a second angle corresponding to when the optical power of the output light (11) emitted from the optical metasurface (5) has a maximum value; Obtaining a refraction angle according to the wavelength of incident light, geometric parameters of the optical metasurface (5), and the refractive index of air, and when the refraction angle is equal to the second characteristic angle, the first angle is the first characteristic angle; The optical metasurface (5) is composed of optical metaunits periodically arranged along a specific direction, and each optical metaunit is composed of 8 metafunctional primitives; the metafunctional primitives in each optical metaunit are arranged along the +x direction, and each metafunctional primitive is rotated counterclockwise by an angle of π / 8 in sequence, and the x, y, and z directions form a right-handed rectangular coordinate system; The metafunctional element is composed of a transparent substrate (1) and a dielectric nanocolumn (2). The dielectric nanocolumn (2) is a cuboid vertically grown on the transparent substrate (1). The cuboid has length dimensions L, W, and H in the x, y, and z directions, respectively. The cuboid has a period length P in the x and y directions. x With P y The transparent substrate (1) constitutes a transparent substrate layer of the optical metasurface (5), and the dielectric nanocolumns (2) constitute a dielectric nanocolumn layer of the optical metasurface (5); The geometric parameter of the optical metasurface (5) is the period length of the dielectric nanocolumns (2) of the metafunctional element in the x-direction; The refraction angle is calculated by the following formula: where β + , β - are two refraction angles, β + >0,β - <0,λ d is the wavelength of the incident light, P x is the period length of the dielectric nanocolumn (2) of the metafunctional unit in the x direction, n t is the refractive index of air.

2. The optical detection device according to claim 1, characterized in that: When the refraction angle is β + , and β + When the first characteristic angle is equal to the second characteristic angle, the first characteristic angle is 135°, the outgoing light (10) emitted from the quarter-wave plate (4) is left-handed circularly polarized light, and the outgoing light (11) emitted from the optical metasurface (5) is right-handed circularly polarized light.

3. The optical detection device according to claim 1, wherein: When the refraction angle is β - , and β - When the first characteristic angle is equal to the second characteristic angle, the first characteristic angle is 45°, the outgoing light (10) emitted from the quarter-wave plate (4) is right-handed circularly polarized light, and the outgoing light (11) emitted from the optical metasurface (5) is left-handed circularly polarized light.

4. The optical detection device according to claim 1, wherein: When the refraction angle is not equal to the second characteristic angle, the fast axis (7) position of the quarter-wave plate (4) is adjusted until the refraction angle is equal to the second characteristic angle, and the first angle at this time is the first characteristic angle.

5. The optical detection device according to any one of claims 1 to 4, characterized in that: The light detection unit is an optical power meter (17), which is located on a guide rail (16). The guide rail (16) is in an arc shape, and its center is located at the center of the optical metasurface (5).

6. The optical detection device according to any one of claims 1 to 4, characterized in that: The light source (15) is a broadband tunable laser light source.

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