All-dielectric free-form polarizing structure

Abstract

This application provides a free-form polarization structure in an all-dielectric environment. The free-form polarization structure includes a substrate, a first elliptical polarization structure, a second elliptical polarization structure, a third elliptical polarization structure, and a circular polarization structure. The substrate surface includes a first region, a second region, a third region, and a fourth region. The first elliptical polarization structure is located on the substrate surface corresponding to the first region, and its shape is a first type Z-shape. The second elliptical polarization structure is located on the substrate surface corresponding to the second region, and its shape is a second type Z-shape. The third elliptical polarization structure is located on the substrate surface corresponding to the third region, and its third structure includes a first substructure and a second substructure spaced apart. The first substructure has a third type Z-shape, and the second substructure has a near-circular shape. The circular polarization structure is located on the substrate surface corresponding to the fourth region. This design ensures high polarization detection accuracy.

Description

Technical Field

[0001] This application relates to the field of imaging, and more specifically, to a polarization structure with a free-form shape in all dielectrics. Background Technology

[0002] Polarization imaging technology, as a novel multidimensional information acquisition technology, has broad application potential in fields such as photography, security, and national defense. Currently commonly used polarization imaging technologies include: time-division rotation imaging, aperture-division polarization imaging, amplitude-division polarization imaging, and focal plane polarization imaging. Time-division rotation imaging uses a rotating polarization filter to acquire multi-directional, multi-spectral information from a single detector over time, but its drawback is poor real-time performance. Aperture-division polarization imaging utilizes multiple independent imaging unit arrays to acquire multiple polarization image information in real time, but its disadvantage is large system size, making integration difficult. Amplitude-division polarization imaging uses prisms to separate light of different polarizations, acquiring different polarization image information in real time. Focal plane polarization imaging uses a micro-polarization array directly coupled to the detector's photosensitive element; different pixels on the imaging focal plane acquire corresponding polarization information, thus obtaining different polarization image information in real time.

[0003] Currently, in the commercial field, micro-polarization arrays, as the core component of focal plane polarization imaging technology, mainly utilize wire grating structures made of metal or dielectric materials to analyze different linear polarization states, thereby obtaining the linear polarization information of the image. To further obtain complete polarization information, the micro-polarization array must include a circular polarization analyzer. However, circular polarization analyzers designed using traditional metal spirals have low extinction ratios and high absorption losses, limiting their practical application. Some researchers have attempted to design focal plane full Stokes polarization imaging elements using metasurfaces, a novel artificial electromagnetic material, but their circular polarization extinction ratios are not high, and their operating bandwidth is narrow.

[0004] Therefore, there is an urgent need for a polarization element to improve the accuracy of polarization detection.

[0005] The information disclosed above in the background section is only intended to enhance the understanding of the background art of the art described herein. Therefore, the background art may contain certain information that does not constitute prior art known to those skilled in the art in this country. Summary of the Invention

[0006] The main objective of this application is to provide a polarization structure with a free-form shape in all dielectrics to solve the problem of low polarization detection accuracy in existing polarization devices.

[0007] According to one aspect of the present invention, a polarization structure with a completely free-form dielectric structure is provided. The polarization structure includes a substrate, a first elliptical polarization structure, a second elliptical polarization structure, a third elliptical polarization structure, and a circular polarization structure. The substrate surface includes a first region, a second region, a third region, and a fourth region. The first elliptical polarization structure is located on the substrate surface corresponding to the first region. The first elliptical polarization structure includes multiple first structures arranged in an array, and the shape of the first structures is a first type Z-shape. The second elliptical polarization structure is located on the substrate surface corresponding to the second region. The second elliptical polarization structure includes multiple second structures arranged in an array, and the shape of the second structures is a first type Z-shape. The shape is a second type Z-shape; the third elliptic polarization structure is located on the substrate surface corresponding to the third region, the third elliptic polarization structure includes multiple third structures, the multiple third structures are arranged in an array, the third structure includes a first substructure and a second substructure arranged at intervals, the shape of the first substructure is a third type Z-shape, the shape of the second substructure is a circular shape, the shapes of the first type Z-shape, the second type Z-shape and the third type Z-shape are different; the circular polarization structure is located on the substrate surface corresponding to the fourth region, the circular polarization structure includes multiple fourth structures, the multiple fourth structures are arranged in an array, the shape of the fourth structure includes a polarization part and two protrusions located on two opposite surfaces of the polarization part.

[0008] Optionally, the polarization structure further includes a protective layer that covers the surfaces of the substrate, the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure, and the circular polarization structure, wherein the surface of the protective layer away from the substrate is planar.

[0009] Optionally, the first structure, the second structure, and the third structure each include a first horizontal portion, a first connecting portion, and a second horizontal portion, wherein one end of the first connecting portion contacts one end of the first horizontal portion, and one end of the second horizontal portion contacts the other end of the first connecting portion.

[0010] Optionally, the edges of the first horizontal portion, the first connecting portion, and the second horizontal portion are not straight lines.

[0011] Optionally, the thickness of the end of the first horizontal portion and the second horizontal portion away from the first connecting portion in the first direction is a first value, and the thickness of the end of the first horizontal portion and the second horizontal portion near the first connecting portion in the first direction is a second value. The first value is less than the second value, and the first direction is a direction perpendicular to the thickness of the substrate.

[0012] Optionally, the extension directions of the two ends of the first connecting portion of the first type Z-shape, the second type Z-shape, and the third type Z-shape are all different.

[0013] Optionally, the thickness of the polarizing portion in the second direction is 210nm-220nm, and the thickness of the protrusion in the second direction is 70nm-75nm. The second direction is perpendicular to the thickness of the substrate and is perpendicular to the arrangement direction of the two protrusions.

[0014] Optionally, the first type of Z-shape, the second type of Z-shape, the third type of Z-shape, and the fourth structure are all centrally symmetric shapes.

[0015] Optionally, the materials of the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure, and the circular polarization structure are all silicon, and the material of the substrate is silicon dioxide.

[0016] Optionally, the thickness range of the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure, and the circular polarization structure is 450nm-550nm.

[0017] Optionally, the distance between any two adjacent first structures is the first distance, the distance between any two adjacent second structures is the second distance, the distance between any two third structures is the third distance, and the distance between any two fourth structures is the fourth distance. The range of the first distance, the second distance, the third distance, and the fourth distance is 550nm-650nm.

[0018] In this embodiment of the invention, the all-dielectric free-form polarization structure includes a substrate, a first elliptical polarization structure, a second elliptical polarization structure, a third elliptical polarization structure, and a circular polarization structure. The substrate surface includes a first region, a second region, a third region, and a fourth region. The first elliptical polarization structure is located on the substrate surface corresponding to the first region. The first elliptical polarization structure includes multiple first structures arranged in an array, and the shape of the first structure is a first type of Z-shape. The second elliptical polarization structure is located on the substrate surface corresponding to the second region. The second elliptical polarization structure includes multiple second structures arranged in an array, and the shape of the second structure is a second type of Z-shape. The third elliptic polarization structure is located on the substrate surface corresponding to the third region. The third elliptic polarization structure includes multiple third structures arranged in an array. Each third structure includes a first substructure and a second substructure arranged at intervals. The shape of the first substructure is a third type Z-shape, and the shape of the second substructure is a near-circular shape. The shapes of the first type Z-shape, the second type Z-shape, and the third type Z-shape are different. The circular polarization structure is located on the substrate surface corresponding to the fourth region. The circular polarization structure includes multiple fourth structures arranged in an array. The shape of each fourth structure includes a polarization portion and two protrusions located on two opposite surfaces of the polarization portion. Compared to the low polarization detection accuracy of existing polarization devices, the free-form polarization structure of this application, by setting a first elliptic polarization structure, a second elliptic polarization structure, a third elliptic polarization structure, and a circular polarization structure on the surface of the substrate, wherein the first elliptic polarization structure includes multiple arrays of the first structure, the second elliptic polarization structure includes multiple arrays of the second structure, the third elliptic polarization structure includes multiple arrays of the third structure, and the circular polarization structure includes multiple arrays of the fourth structure, wherein the first, second, and third structures have different Z-shaped patterns, making the formed polarization structure a free-form surface array, and enabling polarization detection of circular polarization and three different elliptic polarization states, i.e., realizing polarization detection of multiple polarization states, solves the problem of low polarization detection accuracy of existing polarization devices, and ensures high polarization detection accuracy of the polarization structure. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0020] Figure 1A top view schematic diagram of a polarization structure of all dielectric free form according to an embodiment of this application is shown;

[0021] Figure 2 A side view schematic diagram of a polarization structure of all-dielectric free form according to an embodiment of this application is shown;

[0022] Figure 3 A schematic diagram of the structure of a first elliptic polarization structure according to an embodiment of this application is shown;

[0023] Figure 4 A schematic diagram of the transmittance of a first elliptic polarization structure according to an embodiment of this application is shown.

[0024] Figure 5 A schematic diagram of the circular dichroism of a first elliptic polarization structure according to an embodiment of this application is shown;

[0025] Figure 6 A schematic diagram of the extinction ratio of a first elliptic polarization structure according to an embodiment of this application is shown;

[0026] Figure 7 A schematic diagram of the structure of a third elliptic polarization structure according to an embodiment of this application is shown;

[0027] Figure 8 A schematic diagram of the transmittance of a third elliptic polarization structure according to an embodiment of this application is shown.

[0028] Figure 9 A schematic diagram of the circular dichroism of a third elliptic polarization structure according to an embodiment of this application is shown;

[0029] Figure 10 A schematic diagram of the extinction ratio of a third elliptic polarization structure according to an embodiment of this application is shown;

[0030] Figure 11 A schematic diagram of the structure of a second elliptic polarization structure according to an embodiment of this application is shown;

[0031] Figure 12 A schematic diagram of the transmittance of a second elliptic polarization structure according to an embodiment of this application is shown.

[0032] Figure 13 A schematic diagram of the circular dichroism of a second elliptic polarization structure according to an embodiment of this application is shown;

[0033] Figure 14 A schematic diagram of the extinction ratio of a second elliptic polarization structure according to an embodiment of this application is shown;

[0034] Figure 15A schematic diagram of a fourth elliptic polarization structure according to an embodiment of this application is shown;

[0035] Figure 16 A schematic diagram of the transmittance of a fourth elliptic polarization structure according to an embodiment of this application is shown.

[0036] Figure 17 A schematic diagram of the circular dichroism of a fourth elliptic polarization structure according to an embodiment of this application is shown;

[0037] Figure 18 A schematic diagram of the extinction ratio of a fourth elliptic polarization structure according to an embodiment of this application is shown.

[0038] The above figures include the following reference numerals:

[0039] 10. Substrate; 20. First elliptic polarization structure; 30. Second elliptic polarization structure; 40. Third elliptic polarization structure; 50. Circular polarization structure; 60. Protective layer; 201. First structure; 301. Second structure; 401. Third structure; 402. First substructure; 403. Second substructure; 501. Fourth structure. Detailed Implementation

[0040] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0042] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0043] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element, or there may be an intermediate element present. Furthermore, in the specification and claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element, or "connected" to the other element via a third element.

[0044] As mentioned in the background section, existing polarization devices suffer from low polarization detection accuracy. To address this issue, a typical embodiment of this application provides a polarization structure with a completely free-form dielectric structure.

[0045] According to embodiments of this application, a polarization structure with a completely free dielectric form is provided, such as... Figure 1 as well as Figure 2 As shown, the polarization structure includes a substrate 10, a first elliptic polarization structure 20, a second elliptic polarization structure 30, a third elliptic polarization structure 40, and a circular polarization structure 50. The surface of the substrate 10 includes a first region, a second region, a third region, and a fourth region. The first elliptic polarization structure 20 is located on the surface of the substrate 10 corresponding to the first region. The first elliptic polarization structure 20 includes multiple first structures 201, arranged in an array. The shape of each first structure 201 is a first-type Z-shape. The second elliptic polarization structure 30 is located on the surface of the substrate 10 corresponding to the second region. The second elliptic polarization structure 30 includes multiple second structures 301, arranged in an array. The shape of structure 301 is a second type Z-shape; the third elliptic polarization structure 40 is located on the surface of the substrate 10 corresponding to the third region, and the third elliptic polarization structure 40 includes a plurality of third structures 401, which are arranged in an array. Each third structure 401 includes a first substructure 402 and a second substructure 403 spaced apart. The shape of the first substructure 402 is a third type Z-shape, and the shape of the second substructure 403 is a near-circular shape. The shapes of the first type Z-shape, the second type Z-shape, and the third type Z-shape are different; the circular polarization structure 50 is located on the surface of the substrate 10 corresponding to the fourth region, and the circular polarization structure 50 includes a plurality of fourth structures 501, which are arranged in an array, such as... Figure 15 As shown, the shape of the fourth structure 501 includes a polarizing portion and two protrusions located on two opposing surfaces of the polarizing portion.

[0046] The aforementioned all-dielectric free-form polarization structure includes a substrate, a first elliptical polarization structure, a second elliptical polarization structure, a third elliptical polarization structure, and a circular polarization structure. The substrate surface includes a first region, a second region, a third region, and a fourth region. The first elliptical polarization structure is located on the substrate surface corresponding to the first region. The first elliptical polarization structure includes multiple first structures arranged in an array, and the shape of each first structure is a first-type Z-shape. The second elliptical polarization structure is located on the substrate surface corresponding to the second region. The second elliptical polarization structure includes multiple second structures arranged in an array, and the shape of each second structure is a second-type Z-shape. The third elliptic polarization structure is located on the substrate surface corresponding to the third region. The third elliptic polarization structure includes multiple third structures arranged in an array. Each third structure includes a first substructure and a second substructure arranged at intervals. The shape of the first substructure is a third type Z-shape, and the shape of the second substructure is a near-circular shape. The shapes of the first type Z-shape, the second type Z-shape, and the third type Z-shape are different. The circular polarization structure is located on the substrate surface corresponding to the fourth region. The circular polarization structure includes multiple fourth structures arranged in an array. The shape of each fourth structure includes a polarization portion and two protrusions located on two opposing surfaces of the polarization portion. Compared to the low polarization detection accuracy of existing polarization devices, the free-form polarization structure of this application, by setting the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure, and the circular polarization structure on the surface of the substrate, wherein the first elliptic polarization structure includes multiple arrays of the first structure, the second elliptic polarization structure includes multiple arrays of the second structure, the third elliptic polarization structure includes multiple arrays of the third structure, and the circular polarization structure includes multiple arrays of the fourth structure, wherein the first, second, and third structures have different Z-shaped patterns, the resulting polarization structure is a free-form surface array, and can detect circular polarization and three different elliptic polarization states, that is, it realizes the detection of multiple polarization states, solves the problem of low polarization detection accuracy of existing polarization devices, and ensures high polarization detection accuracy of the above polarization structure.

[0047] It should be noted that the aforementioned all-dielectric free-form polarization structure is a free-form nanostructure optimized through a reverse design algorithm.

[0048] Specifically, by setting different target polarization states, an analyzer with a high extinction ratio for the target polarization state is optimized according to the algorithm. For different target polarization states, the objective function in the corresponding reverse design algorithm is set differently, resulting in different optimized free-form structures. In the optimization process, the degree of freedom of adjusting the structural parameters of the free-form structure is 3-4 orders of magnitude higher than that of the geometric structure in the prior art. This will be beneficial for the micro-polarization array structure that uses the above-mentioned all-dielectric free-form polarization structure to analyze any polarization state. Moreover, compared with the regular geometric structure nanounits in the prior art, the above-mentioned all-dielectric free-form polarization structure supports more optical modes, which also helps to realize the design of nanostructures for analyzing any polarization state.

[0049] In one specific embodiment, the aforementioned all-dielectric free-form polarization structure can achieve a circular polarization extinction ratio of up to 50dB and a transmittance of over 90% within a working bandwidth of 920nm-960nm, while the elliptic polarization extinction ratio can reach up to 40dB and the transmittance of over 95%. Furthermore, unlike the design of existing pixel-type all-Stokes polarization imaging elements, the aforementioned all-dielectric free-form polarization structure employs a combination of circular polarization and three elliptic polarizations, which helps to improve the accuracy of Stokes parametric reconstruction.

[0050] According to a specific embodiment of this application, such as Figure 2 As shown, the polarization structure further includes a protective layer 60, which covers the surfaces of the substrate 10, the first ellipsoidal polarization structure 20, the second ellipsoidal polarization structure 30, the third ellipsoidal polarization structure 40, and the circular polarization structure 50. The surface of the protective layer 60 away from the substrate 10 is planar. By providing the protective layer, the first ellipsoidal polarization structure, the second ellipsoidal polarization structure, the third ellipsoidal polarization structure, and the circular polarization structure are protected from damage, ensuring that the polarization detection performance of the all-dielectric free-form polarization structure can be achieved.

[0051] Specifically, the aforementioned protective layer includes SU8 adhesive.

[0052] To further ensure high polarization detection accuracy of the above polarization structure, according to another specific embodiment of this application, such as... Figure 3 , Figure 7 , Figure 11 as well as Figure 15As shown, the first structure 201, the second structure 301, and the third structure 401 respectively include a first horizontal portion, a first connecting portion, and a second horizontal portion, wherein one end of the first connecting portion contacts one end of the first horizontal portion; and one end of the second horizontal portion contacts the other end of the first connecting portion. Because the first structure, the second structure, and the third structure respectively include the first horizontal portion, the first connecting portion, and the second horizontal portion, the all-dielectric free-form polarization structure can achieve polarization detection of three different elliptic polarization states. This further ensures that the all-dielectric free-form polarization structure can achieve polarization detection of multiple polarization states, solving the problem of low polarization detection accuracy in existing polarization devices and further ensuring high polarization detection accuracy of the polarization structure.

[0053] According to another specific embodiment of this application, the edges of the first horizontal portion, the first connecting portion, and the second horizontal portion are not straight lines. Since the edges of the first horizontal portion, the first connecting portion, and the second horizontal portion are not straight lines, the first structure, the second structure, and the third structure formed by the first horizontal portion, the first connecting portion, and the second horizontal portion are all free-form. This allows the first elliptic polarization structure, the second elliptic polarization structure, and the third elliptic polarization structure formed by the first structure, the second structure, and the third structure to achieve high accuracy in polarization detection of different polarization states, further ensuring high polarization detection accuracy of the polarization structure.

[0054] According to a specific embodiment of this application, the thickness of the first horizontal portion and the end of the second horizontal portion away from the first connecting portion in the first direction is a first value, and the thickness of the end of the first horizontal portion and the end of the second horizontal portion near the first connecting portion in the first direction is a second value. The first value is less than the second value, and the first direction is a direction perpendicular to the thickness of the substrate.

[0055] According to another specific embodiment of this application, the extension directions of the two ends of the first connecting portion of the first type Z-pattern, the second type Z-pattern, and the third type Z-pattern are all different. Since the extension directions of the two ends of the first connecting portion of the first type Z-pattern, the second type Z-pattern, and the third type Z-pattern are all different, that is, the rotation angles of the first type Z-pattern, the second type Z-pattern, and the third type Z-pattern are different, it further ensures that the polarization structure with the free-form shape of the entire dielectric can achieve polarization detection of different polarization states, and further ensures that the polarization detection accuracy of the polarization structure is high.

[0056] According to another specific embodiment of this application, the thickness range of the polarization portion in the second direction is 210nm-220nm, the thickness range of the protrusion in the second direction is 70nm-75nm, the second direction is perpendicular to the thickness of the substrate, and the second direction is perpendicular to the arrangement direction of the two protrusions.

[0057] Specifically, such as Figure 3 As shown, Figure 3 The sizes of the first structure at different locations are as follows: P = 600 nm, L1 = 84 nm, L2 = 82 nm, L3 = 88 nm, W1 = 120 nm, W2 = 101 nm, V1 = 76 nm, V2 = 79 nm. Figure 7 For the different positions of the third structure mentioned above, P = 600 nm, M1 = 322 nm, M2 = 91 nm, M3 = 95 nm, M4 = 122 nm, N1 = 157 nm, N2 = 120 nm. Figure 11 For the different positions of the second structure described above, P = 600 nm, E1 = 133 nm, E2 = 372 nm, E3 = 132 nm, and F1 = 120 nm. Figure 15 The sizes of the fourth structure at different positions are P = 600 nm, X1 = 74 nm, X2 = 217 nm, X3 = 72 nm, and Y1 = 545 nm.

[0058] in addition, Figure 4 A schematic diagram of the transmittance of the first elliptic polarization structure is shown. Figure 5 A schematic diagram of the circular dichroism of the first elliptic polarization structure is shown. Figure 6 A schematic diagram of the extinction ratio of the first elliptic polarization structure is shown. Figure 8 A schematic diagram of the transmittance of the third elliptic polarization structure is shown. Figure 9 A schematic diagram of the circular dichroism of the third elliptic polarization structure is shown. Figure 10 A schematic diagram of the extinction ratio of the third elliptic polarization structure is shown. Figure 12 A schematic diagram of the transmittance of the second elliptic polarization structure is shown. Figure 13 A schematic diagram of the circular dichroism of the second elliptic polarization structure is shown. Figure 14 A schematic diagram of the extinction ratio of the second elliptic polarization structure is shown. Figure 16 A schematic diagram of the transmittance of the fourth elliptic polarization structure is shown. Figure 17 A schematic diagram of the circular dichroism of the fourth elliptic polarization structure is shown. Figure 18A schematic diagram of the extinction ratio of the fourth elliptic polarization structure is shown. As can be seen from the figure, the above-mentioned free-form polarization structure of all dielectrics can achieve a maximum circular polarization extinction ratio of 50dB and a transmittance of over 90% within a working bandwidth of 920nm-960nm. At the same time, the maximum elliptic polarization extinction ratio can reach 40dB and the transmittance is over 95%.

[0059] According to a specific embodiment of this application, the first type of Z-shape, the second type of Z-shape, the third type of Z-shape, and the fourth structure are all centrally symmetric shapes.

[0060] According to another specific embodiment of this application, the materials of the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure and the circular polarization structure respectively include silicon, and the material of the substrate includes silicon dioxide.

[0061] Specifically, the aforementioned all-dielectric free-form polarization structure is made of dielectric material. For different operating wavelengths, appropriate low-loss dielectric materials can be selected for design, thereby ensuring that the transmittance of the aforementioned all-dielectric free-form polarization structure is much higher than that of the metal structure in the prior art. Secondly, compared with the dielectric micro-polarization devices implemented by the forward design method in the prior art, we construct the corresponding objective function by setting the extinction ratio and transmittance and other device performance indicators corresponding to different polarization states. We then optimize the objective function using the inverse design algorithm based on adjoint optics simulation, and finally design the aforementioned all-dielectric free-form polarization structure with high extinction ratio and high transmittance for specific ellipsoidal states.

[0062] According to another specific embodiment of this application, the thickness range of the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure and the circular polarization structure is 450nm-550nm.

[0063] According to a specific embodiment of this application, the distance between any two adjacent first structures is the first distance, the distance between any two adjacent second structures is the second distance, the distance between any two third structures is the third distance, and the distance between any two fourth structures is the fourth distance. The range of the first distance, the second distance, the third distance, and the fourth distance is 550nm-650nm.

[0064] In one specific embodiment, the range of the first distance, the second distance, the third distance, and the fourth distance is not limited to 550nm-650nm, but can be determined according to the actual size of the imaging pixels on the detector.

[0065] Specifically, in the all-Stokes parametric measurement method, different combinations of polarization states affect the accuracy of the final measurement result. When noise generated in the photoelectric conversion device in the measurement system affects the accuracy of the measurement, the above-mentioned free-form polarization structure of the all-dielectric system, by optimizing the combination of four polarization states, minimizes the impact of noise on the measurement. Through theoretical calculations, the optimal polarization state is designed to be the combination of polarization states corresponding to the vertices of the inscribed regular tetrahedron on the Poincaré sphere. By selecting one right-handed circular polarization and three ellipsoidal polarizations as the polarization state combination, other combinations of polarization states, such as the combination of three linear polarizations and one circular polarization commonly used in traditional polarization measurements, can also achieve the function of all-Stokes parametric measurement, but they are not the optimal combination of polarization states. The polarization state combination of the inscribed regular tetrahedron in the inscribed Poincaré sphere of the above-mentioned free-form polarization structure of the all-dielectric system (one circular polarization state plus three polarization states with specific Poincaré sphere parameters: χ = -9.7356; χ = -9.7356; The measurement accuracy is less affected by system noise (χ = -9.735 elliptic polarization state).

[0066] In the prior art, due to the limitations of forward design, it is difficult to find an elliptic polarization state microanalyzer that meets specific requirements. Therefore, the prior art often adopts a design with circular polarization plus three linear polarization states. However, the above-mentioned free-form polarization structure of the all-dielectric type in this application optimizes the nanostructure with the extinction ratio and transmittance of the target polarization state as initial conditions through reverse design. It can accurately find the free-form nanounit structure that realizes elliptic polarization state detection. Therefore, the optimal combination can be used to construct a highly efficient focal plane polarization imaging device.

[0067] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0068] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0069] The aforementioned all-dielectric free-form polarization structure of this application includes a substrate, a first elliptical polarization structure, a second elliptical polarization structure, a third elliptical polarization structure, and a circular polarization structure. The substrate surface includes a first region, a second region, a third region, and a fourth region. The first elliptical polarization structure is located on the substrate surface corresponding to the first region. The first elliptical polarization structure includes multiple first structures arranged in an array, and the shape of the first structure is a first-type Z-shape. The second elliptical polarization structure is located on the substrate surface corresponding to the second region. The second elliptical polarization structure includes multiple second structures arranged in an array, and the shape of the second structure is a second-type Z-shape. The aforementioned third elliptic polarization structure is located on the substrate surface corresponding to the aforementioned third region. The aforementioned third elliptic polarization structure includes multiple third structures, which are arranged in an array. Each third structure includes a first substructure and a second substructure arranged at intervals. The shape of the first substructure is a third type Z-shape, and the shape of the second substructure is a near-circular shape. The shapes of the first type Z-shape, the second type Z-shape, and the third type Z-shape are different. The aforementioned circular polarization structure is located on the substrate surface corresponding to the aforementioned fourth region. The aforementioned circular polarization structure includes multiple fourth structures, which are arranged in an array. The shape of each fourth structure includes a polarization portion and two protrusions located on two opposing surfaces of the polarization portion. Compared to the low polarization detection accuracy of existing polarization devices, the free-form polarization structure of this application, by setting the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure, and the circular polarization structure on the surface of the substrate, wherein the first elliptic polarization structure includes multiple arrays of the first structure, the second elliptic polarization structure includes multiple arrays of the second structure, the third elliptic polarization structure includes multiple arrays of the third structure, and the circular polarization structure includes multiple arrays of the fourth structure, wherein the first, second, and third structures have different Z-shaped patterns, the resulting polarization structure is a free-form surface array, and can detect circular polarization and three different elliptic polarization states, that is, it realizes the detection of multiple polarization states, solves the problem of low polarization detection accuracy of existing polarization devices, and ensures high polarization detection accuracy of the above polarization structure.

[0070] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A polarization structure with a completely free-form dielectric shape, characterized in that, The polarization structure includes: A substrate, the surface of which includes a first region, a second region, a third region, and a fourth region; A first elliptic polarization structure is located on the substrate surface corresponding to the first region. The first elliptic polarization structure includes a plurality of first structures, which are arranged in an array. The shape of the first structure is a first type Z pattern. A second elliptic polarization structure is located on the substrate surface corresponding to the second region. The second elliptic polarization structure includes a plurality of second structures, which are arranged in an array. The shape of the second structure is a second type Z pattern. A third elliptic polarization structure is located on the substrate surface corresponding to the third region. The third elliptic polarization structure includes multiple third structures, which are arranged in an array. Each third structure includes a first substructure and a second substructure arranged at intervals. The shape of the first substructure is a third type Z-shape, and the shape of the second substructure is a circle-like shape. The shapes of the first type Z-shape, the second type Z-shape, and the third type Z-shape are different. A circular polarization structure is located on the substrate surface corresponding to the fourth region. The circular polarization structure includes a plurality of fourth structures, which are arranged in an array. Each fourth structure includes a polarization portion and two protrusions located on two opposing surfaces of the polarization portion.

2. The polarization structure with a completely free-form dielectric shape according to claim 1, characterized in that, The polarization structure further includes: A protective layer covers the surfaces of the substrate, the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure, and the circular polarization structure, wherein the surface of the protective layer away from the substrate is planar.

3. The polarization structure with a completely free-form dielectric shape according to claim 1, characterized in that, The first structure, the second structure, and the third structure each include: First horizontal section; A first connecting portion, one end of which contacts one end of the first horizontal portion; The second horizontal portion has one end in contact with the other end of the first connecting portion.

4. The polarization structure with a free-form all-dielectric shape according to claim 3, characterized in that, The edges of the first horizontal portion, the first connecting portion, and the second horizontal portion are not straight lines.

5. The polarization structure with a completely free-form dielectric shape according to claim 3, characterized in that, The thickness of the first horizontal portion and the end of the second horizontal portion away from the first connecting portion in the first direction is a first value, and the thickness of the end of the first horizontal portion and the end of the second horizontal portion near the first connecting portion in the first direction is a second value. The first value is less than the second value, and the first direction is a direction perpendicular to the thickness of the substrate.

6. The polarization structure with a completely free-form dielectric shape according to claim 3, characterized in that, The extension directions of the two ends of the first connecting portion of the first type Z-shape, the second type Z-shape, and the third type Z-shape are all different.

7. The polarization structure with a completely free-form dielectric shape according to any one of claims 1 to 6, characterized in that, The polarizing portion has a thickness range of 210nm-220nm in the second direction, and the protrusion has a thickness range of 70nm-75nm in the second direction. The second direction is perpendicular to the thickness of the substrate and is perpendicular to the arrangement direction of the two protrusions.

8. The polarization structure with a completely free-form dielectric shape according to any one of claims 1 to 6, characterized in that, The first type of Z-shape, the second type of Z-shape, the third type of Z-shape, and the fourth structure are all centrally symmetric shapes.

9. The polarization structure with a completely free-form dielectric shape according to any one of claims 1 to 6, characterized in that, The materials of the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure, and the circular polarization structure are all silicon, and the material of the substrate is silicon dioxide.

10. The polarization structure with a free-form all-dielectric shape according to claim 1, characterized in that, The thickness range of the first elliptic polarization structure, the second elliptic polarization structure, the third elliptic polarization structure, and the circular polarization structure is 450nm-550nm.

11. The polarization structure with a free-form all-dielectric shape according to claim 1, characterized in that, The distance between any two adjacent first structures is the first distance, the distance between any two adjacent second structures is the second distance, the distance between any two third structures is the third distance, and the distance between any two fourth structures is the fourth distance. The range of the first distance, the second distance, the third distance, and the fourth distance is 550nm-650nm.

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