High-contrast grating polarizer with adjustable polarization properties

Abstract

To provide a high-contrast grating polarizer with adjustable polarization characteristics.SOLUTION: A high-contrast grating polarizer comprises: a transparent substrate 11; a plasmonic metal antenna structure layer 12 located on the transparent substrate 11; a switching layer 13 capable of electrically tuning a refractive index; a first electrode layer 14, and a second electrode layer 15. The plasmonic metal antenna structure layer 12 includes a high-contrast grating 121, and a plasmonic metal antenna structure 122 provided at a position shifted from the high-contrast grating 121. The high-contrast grating 121 includes a semiconductor grating or a dielectric grating. The high-contrast grating 121 transmits light in a first polarization direction. The plasmonic metal antenna structure 122 reflects light in a second polarization direction. The first polarization direction and the second polarization direction are opposite to each other.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to a Chinese patent application bearing invention patent application number 202310727896.2 and entitled "High-contrast grating polarizer with adjustable polarization properties" filed with the State Intellectual Property Office of the People's Republic of China on June 16, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates generally to the technical field of optoelectronic devices, and more particularly to high-contrast grating polarizers with tunable polarization properties. [Background technology]

[0003] A polarizer is an optical filter that allows light waves of a specific polarization direction to pass and blocks light waves of other polarization directions. Common commercial polarizers include linear polarizers and circular polarizers, and are widely used in many optical instruments.

[0004] In order to effectively suppress the scattering and reflection of ambient light by utilizing the polarization properties of the polarizer, related technologies use mechanical means to switch the polarizer, but this method is expensive, has slow response speed, and is unreliable. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above-mentioned deficiencies or shortcomings of the related art, it is desirable to provide a high-contrast grating polarizer with tunable polarization properties that can be changed by electronic switching, and that is highly efficient, convenient, and reliable. [Means for solving the problem]

[0006] The present disclosure provides a high-contrast grating polarizer with adjustable polarization characteristics, comprising: a transparent substrate; a plasmonic metal antenna structure layer positioned on the transparent substrate; a switching layer with an electrically tunable refractive index; a first electrode layer; and a second electrode layer. The plasmonic metal antenna structure layer comprises a high-contrast grating and a plasmonic metal antenna structure offset from the high-contrast grating. The high-contrast grating comprises a semiconductor grating or a dielectric grating. The high-contrast grating transmits light of a first polarization direction, and the plasmonic metal antenna structure reflects light of a second polarization direction, the first polarization direction and the second polarization direction being opposite to each other.

[0007] Optionally, in some embodiments of the present disclosure, the refractive index electrically tunable switchable layer comprises a liquid crystal layer.

[0008] Optionally, in some embodiments of the present disclosure, the electrically tunable refractive index switching layer is located between the high-contrast grating and the plasmonic metallic antenna structure, or the electrically tunable refractive index switching layer is located between the high-contrast grating and the plasmonic metallic antenna structure layer. above Located in.

[0009] Optionally, in some embodiments of the present disclosure, the first electrode layer is located on the electrically tunable refractive index switching layer and the second electrode layer is connected to the plasmonic metal antenna structure, or the first electrode layer is located on the electrically tunable refractive index switching layer and the second electrode layer is located below the plasmonic metal antenna structure layer, or the first electrode layer is located to the left of the electrically tunable refractive index switching layer and the second electrode layer is located to the right of the electrically tunable refractive index switching layer.

[0010] Optionally, in some embodiments of the present disclosure, the first electrode layer and the second electrode layer are both transparent conductive films, or the first electrode layer is the transparent conductive film and the second electrode layer is part of the plasmonic metal antenna structure.

[0011] Optionally, in some embodiments of the present disclosure, the plasmonic metallic antenna structure is located at at least one of a bottom, a left sidewall, and a right sidewall of a gap of a high contrast grating.

[0012] Optionally, in some embodiments of the present disclosure, the plasmonic metallic antenna structure is located at at least one of the top, left sidewall, and right sidewall of each high contrast grating bar.

[0013] Optionally, in some embodiments of the present disclosure, a protective layer is provided between the plasmonic metallic antenna structure layer and the refractive index electrically tunable switching layer.

[0014] Optionally, in some embodiments of the present disclosure, the protective layer includes any one of a SiN layer, an Al2O3 layer, and a SiO2 layer.

[0015] Optionally, in some embodiments of the present disclosure, the plasmonic metal antenna structure layer has a periodic structure in both the longitudinal and lateral directions of the transparent substrate, or the plasmonic metal antenna structure layer has a periodic structure in the longitudinal direction of the transparent substrate and a non-periodic structure in the lateral direction of the transparent substrate, or the plasmonic metal antenna structure layer has a periodic structure in the lateral direction of the transparent substrate and a non-periodic structure in the longitudinal direction of the transparent substrate, or the plasmonic metal antenna structure layer has a non-periodic structure in both the longitudinal and lateral directions of the transparent substrate. [Effects of the Invention]

[0016] According to the above technical solutions, the embodiments of the present disclosure have the following advantages: The embodiments of the present disclosure provide a high-contrast grating polarizer with adjustable polarization characteristics, which combines a plasmonic metal antenna structure layer with a switching layer whose refractive index is electrically tunable, and changes the refractive index of the switching layer by an electrical tuning method such as an electric field or a magnetic field; Orthogonal This affects the transmittance and reflectance of polarized light and makes it possible to change the polarization characteristics of the polarizer, which is highly efficient, convenient, and has high response sensitivity and reliability.

[0017] Other features, objects, and advantages of the present disclosure will become more apparent from a reading of the following detailed description of non-limiting embodiments, taken in conjunction with the drawings, in which: [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a structural cross-sectional schematic diagram of a first high-contrast grating polarizer in a first state according to an embodiment of the present disclosure; FIG. [Figure 2] FIG. 2 is a structural cross-sectional schematic diagram of a first high-contrast grating polarizer in a second state according to an embodiment of the present disclosure. [Figure 3] 1 is a schematic diagram of the three-dimensional structure of a first high-contrast grating polarizer according to an embodiment of the present disclosure. FIG. [Figure 4(a)] 1 is a cross-sectional schematic diagram of a structure when P-polarized light is incident on a high-contrast grating polarizer with no external voltage applied, according to an embodiment of the present disclosure. FIG. [Figure 4(b)] FIG. 1B is a schematic diagram of a simulated electric field when P-polarized light is incident on a high-contrast grating polarizer with no external voltage applied, according to an embodiment of the present disclosure. [Figure 5(a)] 1 is a cross-sectional schematic diagram of a structure when P-polarized light is incident on a high-contrast grating polarizer with an external voltage applied, according to an embodiment of the present disclosure. FIG. [Figure 5(b)] 1A is a schematic diagram of a simulated electric field when P-polarized light is incident on a high-contrast grating polarizer with an external voltage applied, according to an embodiment of the present disclosure. FIG. [Figure 6(a)]1 is a cross-sectional schematic diagram of a high-contrast grating polarizer with no external voltage applied, according to an embodiment of the present disclosure, when S-polarized light is incident on the polarizer; FIG. [Figure 6(b)] FIG. 1B is a schematic diagram of a simulated electric field when S-polarized light is incident on a high-contrast grating polarizer with no external voltage applied, according to an embodiment of the present disclosure. [Figure 7(a)] 1 is a cross-sectional schematic diagram of a structure when S-polarized light is incident on a high-contrast grating polarizer with an external voltage applied, according to an embodiment of the present disclosure. FIG. [Figure 7(b)] FIG. 1B is a schematic diagram of a simulated electric field when S-polarized light is incident on a high-contrast grating polarizer with an external voltage applied, according to an embodiment of the present disclosure. [Figure 8] 1 is a cross-sectional schematic diagram of a high-contrast grating polarizer according to an embodiment of the present disclosure when a first external voltage is applied to the polarizer; [Figure 9] 1 is a cross-sectional schematic diagram of a high-contrast grating polarizer according to an embodiment of the present disclosure when a second external voltage is applied to the polarizer; [Figure 10] 10 is a cross-sectional schematic diagram of a high-contrast grating polarizer according to an embodiment of the present disclosure when a third external voltage is applied to the polarizer. FIG. [Figure 11] 10 is a cross-sectional schematic diagram of a high-contrast grating polarizer with a fourth external voltage applied thereto according to an embodiment of the present disclosure. FIG. [Figure 12] 1 is a schematic cross-sectional view of a first plasmonic metal antenna structure layer according to an embodiment of the present disclosure. FIG. [Figure 13] FIG. 10 is a schematic cross-sectional view of a second plasmonic metal antenna structure layer according to an embodiment of the present disclosure. [Figure 14] FIG. 10 is a schematic cross-sectional view of a third plasmonic metal antenna structure layer according to an embodiment of the present disclosure. [Figure 15] FIG. 10 is a schematic cross-sectional view of a fourth plasmonic metallic antenna structure layer according to an embodiment of the present disclosure. [Figure 16] 1 is a cross-sectional schematic diagram of a second high-contrast grating polarizer according to an embodiment of the present disclosure; FIG. [Figure 17] FIG. 10 is a cross-sectional schematic diagram of the structure of a third high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 18] FIG. 10 is a cross-sectional schematic diagram of the structure of a fourth high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 19] FIG. 10 is a cross-sectional schematic diagram of the structure of a fifth high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 20] FIG. 10 is a cross-sectional schematic diagram of the structure of a sixth high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 21] FIG. 10 is a cross-sectional schematic diagram of the structure of a seventh high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 22] FIG. 10 is a cross-sectional schematic diagram of the structure of an eighth high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 23] FIG. 10 is a cross-sectional schematic diagram of the structure of a ninth high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 24] FIG. 12 is a cross-sectional schematic diagram of the structure of the tenth high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 25] FIG. 11 is a schematic cross-sectional view of the structure of an eleventh high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 26] FIG. 12 is a cross-sectional schematic diagram of the structure of a twelfth high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 27] FIG. 13 is a cross-sectional schematic diagram of the structure of a thirteenth high-contrast grating polarizer according to an embodiment of the present disclosure. [Figure 28] FIG. 14 is a cross-sectional schematic diagram of the structure of a 14th high-contrast grating polarizer according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019] In order to allow those skilled in the art to better understand the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings, but it is clear that the described embodiments are only some embodiments of the present disclosure, and do not represent all embodiments. All other embodiments that a person skilled in the art can obtain based on the embodiments of the present disclosure without performing any creative work fall within the patent scope of the present disclosure.

[0020] The terms "first," "second," "third," "fourth," etc. (when present) in the specification and claims of this disclosure, as well as in the foregoing drawings, are not used to describe a particular order or priority, but rather to distinguish between similar objects. It should be understood that the data so used may be interchanged as appropriate to enable the described embodiments of the present disclosure to be performed in orders other than those illustrated or described herein.

[0021] Furthermore, the terms "comprise" and "have," and any variations thereof, are intended to cover non-exclusive inclusions; for example, a process, method, system, product, or apparatus that includes a series of steps or modules need not be limited to the explicitly listed steps or modules, but may include other steps or modules that are not explicitly listed or that are inherent to the process, method, product, or apparatus.

[0022] For ease of understanding and explanation, a high-contrast grating polarizer with adjustable polarization characteristics according to an embodiment of the present disclosure will be described in detail below with reference to FIGS.

[0023] 1 to 3 show schematic structural diagrams corresponding to various states and viewing angles of a high-contrast grating polarizer with adjustable polarization characteristics according to an embodiment of the present disclosure. The high-contrast grating polarizer 10 includes a transparent substrate 11, and a plasmonic metal antenna structure layer 12, an electrically tunable refractive index switching layer 13, a first electrode layer 14, and a second electrode layer 15, which are disposed on the transparent substrate 11. The plasmonic metal antenna structure layer 12 may include a high-contrast grating (HCG) 121 and a plasmonic metal antenna structure 122 offset from the high-contrast grating 121. The high-contrast grating 121 may include, but is not limited to, a semiconductor grating or a dielectric grating. The high-contrast grating 121 is capable of transmitting light of a first polarization direction, and the plasmonic metal antenna structure 122 is capable of reflecting light of a second polarization direction, and the first polarization direction and the second polarization direction are Orthogonal For example, the polarization may include, but is not limited to, S-polarized light, P-polarized light, circularly polarized light, and elliptically polarized light, and the polarization characteristics may include, but are not limited to, polarization direction, transmittance, extinction ratio, and polarization type, and the transmitted light is primarily linearly polarized light parallel to the high-contrast grating bars, while the reflected light is primarily polarized light perpendicular to the high-contrast grating bars.

[0024] Optionally, in embodiments of the present disclosure, the transparent substrate 11 may be made of one or more materials that are substantially transparent at the operating wavelength of the polarizer. For example, the operating wavelengths may include, but are not limited to, EUV (extreme ultraviolet), DUV (deep ultraviolet), UV (ultraviolet), VIS (visible), NIR (near infrared), MIR (mid infrared), FIR (far infrared), or THz (terahertz), and the materials may include, but are not limited to, SiO2 (silica), Al2O3 (alumina), or Si (silicon). Alternatively, the transparent substrate 11 may be various types of glass substrates, amorphous substrates, polycrystalline substrates, crystalline substrates, etc. The high-contrast grating 121 may include, but is not limited to, semiconductor gratings or dielectric gratings, and may be made of, for example, Si (silicon), SiN (silicon nitride), Al2O3 (alumina), or any other type of non-conductive material. Also, the plasmonic metallic antenna structure 122 may be any type of metal, such as Au (gold), Ag (silver), Al (aluminum), Fe (iron), alloys, or other conductive materials.

[0025] Optionally, in the embodiments of the present disclosure, the electrically tunable refractive index switching layer 13 may include, but is not limited to, a liquid crystal (LC) layer. Liquid crystal is a state of matter with properties intermediate between those of a conventional liquid and a solid crystal. When the rod-like molecules are aligned along a specific direction, LC becomes a medium with anisotropic optical properties. When polarized light is parallel to the long axis of the liquid crystal, the incident light is reflected by the extraordinary refractive index n e When the polarization is perpendicular to the long axis of the liquid crystal, the incident light has a normal refractive index n o The liquid crystal molecules can be reoriented by electric or magnetic fields, changing their effective birefringence accordingly. Thus, incident light experiences different phase retardation with changes in the applied electric or magnetic field. When the liquid crystal molecules are randomly oriented, the LC becomes a medium with isotropic optical properties.

[0026] Furthermore, as shown in Figures 4 and 5, for example, Figure 4(a) is a schematic diagram of P-polarized light incident on a high-contrast grating polarizer with no external voltage applied. P-polarized light refers to light whose electric field direction is perpendicular to the grating. In this case, because the electric field direction of the light is perpendicular, the light strongly interacts with the metal, particularly the two sidewalls, preventing the electric field from penetrating the metal and resulting in reflection. In this case, both sidewalls reflect the electric field, and these two electric fields interfere with each other, causing the cavity to function as an antenna resonator. Figure 4(b) shows a schematic diagram of an electric field simulation of P-polarized light with θ of 0 degrees according to an embodiment of the present disclosure. As can be seen from the figure, the light is reflected and cannot penetrate this structure. Meanwhile, Figure 5(a) is a schematic diagram of P-polarized light incident on a high-contrast grating polarizer with an external voltage applied. Due to the action of the externally applied voltage, the liquid crystals are oriented in the same direction, resulting in a change in the refractive index of the surrounding environment. Even though the interaction between light and metal is strong, most of the light escapes the grating due to the phase mismatch, resulting in high transmittance. Figure 5(b) shows a schematic diagram of the electric field simulation for P-polarized light with θ=0 degrees according to an embodiment of the present disclosure, and as can be seen, the light is transmitted through the grating.

[0027] For example, as shown in Figures 6 and 7, Figure 6(a) is a schematic diagram of S-polarized light incident on a high-contrast grating polarizer with no external voltage applied. S-polarized light refers to light whose electric field direction is parallel to the grating. In this case, when light interacts with the high-contrast grating, a specific period, duty cycle, and grating thickness can be designed to create a difference between the reflection phase from the top of the grating and the reflection phase from the bottom of the grating. Thus, under certain design conditions, the effect of light reflection can be suppressed. Furthermore, because the electric field direction of the light is parallel to the grating and most of the material between the gratings is air, the effect of metal on the light is extremely small, and most S-polarized light is transmitted through this structure. Figure 6(b) shows a schematic diagram of an electric field simulation of S-polarized light with θ = 0 degrees according to an embodiment of the present disclosure. As can be seen from the figure, the light is transmitted through the grating. On the other hand, Figure 7(a) is a schematic diagram of S-polarized light incident on a high-contrast grating polarizer with an external voltage applied. Under the action of the externally applied voltage, the liquid crystals are oriented in the same direction, which results in a change in the refractive index of the surrounding environment, but most S-polarized light is also transmitted through this structure. Figure 7(b) shows a schematic diagram of an electric field simulation of S-polarized light with θ = 0 degrees according to an embodiment of the present disclosure. As can be seen from the figure, the light is transmitted through the grating.

[0028] Furthermore, for example, FIGS. 8 to 11 each show a schematic diagram when various external voltages are applied to a high-contrast grating polarizer. Here, the relationship of each external voltage is V0 < V1 < V2 < V3. As can be seen from the figure, as the voltage increases, more liquid crystals tend to follow the direction of the electric field. When a continuous voltage, electric field, current or magnetic field (or a combination thereof) is applied, the refractive index of at least one material in the switching layer 13 of the high-contrast grating polarizer 10 can be known. Such a change in the refractive index may be essentially isotropic or essentially anisotropic. The change in the refractive index can further change the material from an isotropic refractive index to an anisotropic refractive index, and the liquid crystal is expressed as the latter. The change in the refractive index may be continuous or may change abruptly, and the electric bias may be applied stepwise or abruptly, so the polarization characteristics can be switched gradually or abruptly. Here, as the stepwise method, 1) gradually changing the transmission of light in one polarization direction while maintaining the transmission of light in the opposite polarization direction large, 2) gradually changing the reflection of light in one polarization direction while maintaining the reflection of light in the opposite polarization direction large, 3) synchronizing the extinction ratio of the polarizer from a high value to a low value, and vice versa, etc. are included. As the abrupt change method, 1) switching from a state where the transmittance of light in one polarization state is high to a state where the transmittance of light in the opposite polarization state is high, 2) switching from a state where the reflectance of light in one polarization state is high to a state where the reflectance of light in the opposite polarization state is high, 3) switching from a state where the transmittance of light in one polarization state is high to a state where the transmittances of light in both polarization states are substantially equal, 4) switching from a state where the reflectance of light in one polarization state is high to a state where the reflectances of light in both polarization states are substantially equal, etc. are included.

[0029] Optionally, in some embodiments of the present disclosure, the high-contrast grating polarizer 10 may have a periodic structure or a non-periodic structure. Furthermore, in some other embodiments of the present disclosure, the high-contrast grating polarizer 10 may have a one-dimensional structure or a two-dimensional structure. For example, as shown in FIGS. 12 to 15, the plasmonic metal antenna structure layer 12 has a periodic structure in both the longitudinal and lateral directions of the transparent substrate 11 (e.g., FIG. 12), and such a structure can be used for a linear polarizer, a circular polarizer, an elliptical polarizer, or a beam splitter. Alternatively, the plasmonic metal antenna structure layer 12 has a periodic structure in the longitudinal direction of the transparent substrate 11 and a non-periodic structure in the lateral direction of the transparent substrate 11 (e.g., FIG. 13), and such a structure can be used for a linear polarizer or a beam splitter. Alternatively, the plasmonic metal antenna structure layer 12 may have a periodic structure in the transverse direction of the transparent substrate 11 and an aperiodic structure in the longitudinal direction of the transparent substrate 11. Alternatively, the plasmonic metal antenna structure layer 12 may have aperiodic structures in both the longitudinal and transverse directions of the transparent substrate 11 (e.g., Figures 14 and 15). This structure can be used for a linear polarizer, a circular polarizer, an elliptical polarizer, or a beam splitter. Note that a one-dimensional grating structure or a two-dimensional grating structure with a specific preferred transverse direction is advantageous for applications where the polarizer is typically used as a linear polarizer. In a preferred configuration, the preferred transverse direction of the grating element is perpendicular or parallel to the polarization of the incident light. For example, a two-dimensional grating structure with chiral symmetry is one preferred embodiment, where the polarizer is typically used as a circular polarizer. As another example, combining the properties of two gratings is a preferred embodiment for controlling elliptical polarization. Furthermore, for light incident from a large viewing angle, high efficiency can be achieved in either the transmission or reflection direction of the grating, so that there are no diffraction losses, it is preferable that the polarizer grating has a period less than a certain value related to the wavelength of light.

[0030] For example, various structures of the high-contrast grating polarizer 10 in the embodiments of the present disclosure are described in detail below. For example, the electrically tunable refractive index switching layer 13 is located between the high-contrast grating 121 and the plasmonic metallic antenna structure 122. death, Alternatively, the refractive index of the electrically tunable switching layer 13 may be a plasmonic metal antenna structure layer 12. above Located in (For example, Figure 1) Such a configuration makes it possible to effectively switch the optical characteristics of the high contrast grating polarizer 10, and has the advantages of high sensitivity and improved reliability.

[0031] Also, for example, the first electrode layer 14 is located on the switching layer 13 whose refractive index is electrically tunable, and the second electrode layer 15 is connected to the plasmonic metal antenna structure 122 (e.g., Figure 16, etc.), or the first electrode layer 14 is located on the switching layer 13 whose refractive index is electrically tunable, and the second electrode layer 15 is located below the plasmonic metal antenna structure layer 12 (e.g., Figure 17), or the first electrode layer 14 is located on the left side of the switching layer 13 whose refractive index is electrically tunable, and the second electrode layer 15 is located on the right side of the switching layer 13 whose refractive index is electrically tunable (e.g., Figure 18).

[0032] Optionally, the first electrode layer 14 and the second electrode layer 15 are both transparent conductive films, or the first electrode layer 14 is a transparent conductive film and the second electrode layer 15 is part of the plasmonic metal antenna structure 122. For example, the transparent conductive film may be, but is not limited to, ITO (indium tin oxide) glass or FTO (fluorine doped tin oxide) glass, while the plasmonic metal antenna structure 122 may be part of an Au (gold) contact electrode. A protective glass 16 may also be provided on the first electrode layer 14 (e.g., FIG. 19 ), which effectively protects the high-contrast grating polarizer 10 and extends its service life.

[0033] Further, for example, the plasmonic metal antenna structure 122 may be located at at least one of the bottom, left sidewall, and right sidewall of the high-contrast grating gap. For example, the plasmonic metal antenna structure 122 may be located at the bottom, left sidewall, and right sidewall of the high-contrast grating gap (e.g., FIG. 1), the plasmonic metal antenna structure 122 may be located at the bottom and left sidewall of the high-contrast grating gap (e.g., FIG. 20), the plasmonic metal antenna structure 122 may be located at the bottom and right sidewall of the high-contrast grating gap (e.g., FIG. 21), or the plasmonic metal antenna structure 122 may be located at the bottom of the high-contrast grating gap (e.g., FIG. 22).

[0034] Also, for example, the plasmonic metal antenna structure 122 is located at at least one of the top, left sidewall, and right sidewall of each high-contrast grating bar. For example, the plasmonic metal antenna structure 122 is located at the top of each high-contrast grating bar (e.g., FIG. 23), the plasmonic metal antenna structure 122 is located at the top, left sidewall, and right sidewall of each high-contrast grating bar (e.g., FIG. 24), the plasmonic metal antenna structure 122 is located at the left sidewall and right sidewall of each high-contrast grating bar (e.g., FIG. 25), the plasmonic metal antenna structure 122 is located at the right sidewall of each high-contrast grating bar (e.g., FIG. 26), or the plasmonic metal antenna structure 122 is located at the left sidewall of each high-contrast grating bar (e.g., FIG. 27).

[0035] Optionally, in the embodiment of the present disclosure, a first adhesive layer is provided between the transparent substrate 11 and the high-contrast grating 121, thereby improving the adhesion of the high-contrast grating 121. Here, the first adhesive layer may include any one of a SiN layer, an Al2O3 layer, and a SiO2 layer. In actual production, the first adhesive layer may be deposited by methods such as atomic layer deposition (ALD), plasma-enhanced chemical vapor deposition (PECVD), chemical vapor deposition (CVD), or physical vapor deposition (PVD).

[0036] Optionally, in the embodiment of the present disclosure, a second adhesive layer may be provided between the transparent substrate 11 and the plasmonic metallic antenna structure 122 and / or between the high-contrast grating 121 and the plasmonic metallic antenna structure 122, thereby improving the adhesion of the metal surfaces. Here, the second adhesive layer may include any one of a Ti (titanium) layer, a Ge (germanium) layer, and an Al (aluminum) layer. In actual production, the second adhesive layer may be deposited by methods such as ALD, PECVD, CVD, PVD, or sputtering.

[0037] 28, in the embodiment of the present disclosure, a protective layer 17 is provided between the plasmonic metal antenna structure layer 12 and the electrically tunable refractive index switching layer 13, thereby improving the manufacturability, reliability, and performance of the high-contrast grating polarizer 10. Here, the protective layer 17 may include any one of a SiN layer, an Al2O3 layer, and a SiO2 layer, and may be deposited by methods such as ALD, PECVD, CVD, or PVD.

[0038] Note that (a) in the embodiments of the present disclosure, the metal adjacent to one grating sidewall, the metal adjacent to the other grating sidewall, the metal at the bottom of the grating gap, and the metal at the top of the grating may have different thicknesses. In polarizers where the plasmonic metallic antenna structures 122 are located at the bottom, left sidewall, and right sidewall of a high-contrast grating gap, the thickness of the metal at the sidewall divided by the thickness of the metal at the bottom may be greater than 0.2 and less than 3. Slits may exist between the metal and the high-contrast grating 121 and / or between the metal and the transparent substrate 11, and these slits should be less than 30 nm. Furthermore, discontinuities, i.e., holes, may exist in the metal layer, and the size of such discontinuities should be less than the distance between the two gratings.

[0039] (b) To improve the manufacturability, reliability, and performance of the high-contrast grating polarizer 10, embodiments of the present disclosure may include various additional structures and layers while maintaining the basic features of the present disclosure, and such structures and layers are to be considered part of the present disclosure. Examples of such layers include: 1) Layers advantageous for adhering the assemblies of the present disclosure. In one embodiment, a thin dielectric layer may be present between the polarizer substrate and the grating to enhance adhesion of the grating to the substrate. In preferred embodiments of polarizers operating in transmissive mode, such a layer is a transparent dielectric. In another embodiment, this thin layer may enhance adhesion between the metal portion of the polarizer and the grating. In a preferred embodiment, such a layer is a metal layer. 2) Layers that contribute to the manufacturability of the polarizer. In one embodiment, an auxiliary layer between the substrate and the grating serves as an etch stop layer and is advantageous for accurately defining the depth and shape of the grating. 3) Layers for reliability or protection. In one embodiment, this thin auxiliary layer separates the switchable refractive index material from the grating and metal portion of the polarizer, improving device reliability. In one preferred embodiment, LC is used as one of the materials, and the transparent electrode is implemented as ITO or FTO glass, and the glass substrate of such transparent electrode is also used as an auxiliary layer to protect or hide the LC inside the device.

[0040] (c) Various transparent conductive materials or thin films can be used to partially or completely form the electrodes to achieve a high-contrast grating polarizer 10. Preferred materials for such electrodes include ITO, FTO, and nanostructured electrodes. In one preferred embodiment of the high-contrast grating polarizer 10, the metal portion of the polarizer functions as part of one electrode, and a transparent ITO glass functions as part of the other electrode. In another preferred embodiment, the grating and metal portion of the polarizer are separated from the LC by a thin auxiliary layer, thereby improving reliability. Alternatively, the electrodes may be arranged laterally, or two transparent electrodes may be used, one between the auxiliary layer and the LC and the other on top of the LC. In a preferred embodiment, the top electrode is ITO glass. Transparent electrodes are particularly preferred when the polarizer operates as a light-transmitting device. If the polarizer is designed to primarily reflect light, at least one non-transparent electrode may be used.

[0041] In the high-contrast grating polarizer with adjustable polarization characteristics according to the embodiments of the present disclosure, a plasmonic metal antenna structure layer is combined with a switching layer whose refractive index can be electrically tuned. This allows the refractive index of the switching layer to be changed by an electrical tuning method such as an electric field or a magnetic field, thereby affecting the transmittance or reflectance of the oppositely polarized light and changing the polarization characteristics of the polarizer. This is highly efficient, convenient, and has high response sensitivity and reliability.

[0042] It should be noted that the above embodiments are only used to explain the technical solutions of the present disclosure and are not intended to limit the same. Although the present disclosure has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can be modified or some technical features can be equivalently substituted. These modifications or substitutions do not deviate from the essence of the corresponding technical solutions and the spirit and scope of the technical solutions of the embodiments of the present disclosure. [Explanation of symbols]

[0043] 10 High-contrast grating polarizer with adjustable polarization properties 11 Transparent substrate 12 Plasmonic metal antenna structure layer 121 High Contrast Grating 122 Plasmonic Metallic Antenna Structures 13 Switching layer with electrically tunable refractive index 14 1st electrode layer 15 Second electrode layer 16 Protective glass 17 Protective layer

Claims

1. A high-contrast grating polarizer with adjustable polarization properties, comprising: A transparent substrate; a plasmonic metal antenna structure layer, a refractive index electrically tunable switching layer, a first electrode layer, and a second electrode layer located on the transparent substrate; The first electrode layer and the second electrode layer are for applying an external voltage to the switching layer, the plasmonic metal antenna structure layer includes a high-contrast grating and a plasmonic metal antenna structure offset from the high-contrast grating, the switching layer is located between the high-contrast grating and the plasmonic metal antenna structure, or is located on the high-contrast grating and the plasmonic metal antenna structure, the high-contrast grating includes a semiconductor grating or a dielectric grating, and the high-contrast grating is used to switch the switching layer. a plasmonic metal antenna structure layer that transmits light polarized in a first polarization direction through the switching layer and reflects light polarized in a second polarization direction that is orthogonal to the first polarization direction through the switching layer; and the first electrode layer is located on the switching layer and the second electrode layer is connected to the plasmonic metal antenna structure layer, or the first electrode layer is located on the switching layer and the second electrode layer is located below the plasmonic metal antenna structure layer, or the first electrode layer is located to the left of the switching layer and the second electrode layer is located to the right of the switching layer.

2. 10. The high contrast grating polarizer of claim 1, wherein the refractive index electrically tunable switching layer comprises a liquid crystal layer.

3. 3. The high-contrast grating polarizer of claim 1, wherein the first electrode layer and the second electrode layer are both transparent conductive films, or the first electrode layer is the transparent conductive film and the second electrode layer is part of the plasmonic metal antenna structure.

4. 3. The high contrast grating polarizer of claim 1, wherein the plasmonic metallic antenna structure is located at at least one of the bottom, left sidewall, and right sidewall of the gap of the high contrast grating.

5. 3. The high contrast grating polarizer of claim 1, wherein the plasmonic metallic antenna structure is located on at least one of the top, left sidewall, and right sidewall of each high contrast grating bar.

6. 3. The high-contrast grating polarizer of claim 1, wherein a protective layer is provided between the plasmonic metal antenna structure layer and the refractive index electrically tunable switching layer.

7. The protective layer is a SiN layer, an Al ２ O ３ layer, and SiO ２ 7. The high contrast grating polarizer of claim 6, comprising any one of the layers.

8. The high-contrast grating polarizer according to any one of claims 1 to 2, characterized in that the plasmonic metal antenna structure layer has a periodic structure in both the longitudinal and lateral directions of the transparent substrate, the plasmonic metal antenna structure layer has a periodic structure in the longitudinal direction of the transparent substrate and a non-periodic structure in the lateral direction of the transparent substrate, the plasmonic metal antenna structure layer has a periodic structure in the lateral direction of the transparent substrate and a non-periodic structure in the longitudinal direction of the transparent substrate, or the plasmonic metal antenna structure layer has a non-periodic structure in both the longitudinal and lateral directions of the transparent substrate.

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