High-contrast grating polarizer with adjustable polarization characteristics

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 for invention patent bearing application number 202310727896.2 and titled "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 certain 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 utilize the polarization properties of the polarizer to effectively suppress the scattering and reflection of ambient light, the related technology uses mechanical means to switch the polarizer, but this method is expensive, has a slow response speed and is unreliable. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above deficiencies or shortcomings of the related art, it is desirable to provide a high contrast grating polarizer with tunable polarization properties, which can be changed by electronic switching, and 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 located on the transparent substrate; a switching layer having an electrically tunable refractive index; a first electrode layer; and a second electrode layer, wherein 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 comprising 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 below the plasmonic metallic antenna structure layer.

[0009] Optionally, in some embodiments of the present disclosure, the first electrode layer is located on top of 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 top of 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 transverse 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 transverse direction of the transparent substrate, the plasmonic metal antenna structure layer has a periodic structure in the transverse 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 transverse directions of the transparent substrate. Effect of the Invention

[0016] According to the above technical solutions, the embodiments of the present disclosure have the following advantages: An embodiment of the present disclosure provides a high-contrast grating polarizer with adjustable polarization characteristics. By combining a plasmonic metal antenna structure layer with a switching layer whose refractive index can be electrically tuned, the refractive index of the switching layer can be changed by an electrical tuning method such as an electric field or a magnetic field, thereby affecting the transmittance and reflectance of the opposite polarized light, and changing 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 examples, taken in conjunction with the drawings in which: [Brief description of the drawings]

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

[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 are described below clearly and completely with reference to the drawings, but it is clear that the described embodiments are only some embodiments of the present disclosure, and are not all embodiments. All other embodiments that a person skilled in the art can obtain based on the embodiments of the present disclosure without performing creative labor belong to 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 are used to distinguish between similar subject matter. It should be understood that data so used may be interchanged as appropriate to enable the described embodiments of the disclosure to be performed in orders other than those illustrated or described herein.

[0021] Furthermore, the terms "comprise" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusion, e.g., a process, method, system, product, or apparatus that includes a series of steps or modules need not be limited to the steps or modules explicitly listed, 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 description, 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, a plasmonic metal antenna structure layer 12, a switching layer 13 with an electrically tunable refractive index, a first electrode layer 14, and a second electrode layer 15, which are located on the transparent substrate 11. The plasmonic metal antenna structure layer 12 is a high contrast grating (HCG) and a plasmonic metal antenna structure 122 offset from the high contrast grating 121, where the high contrast grating 121 can transmit light of a first polarization direction and the plasmonic metal antenna structure 122 can reflect light of a second polarization direction, the first and second polarization directions being opposite to each other, for example, the polarization can include, but is not limited to, S-polarized light, P-polarized light, circular polarization, elliptical polarization, etc., and the polarization characteristics can include, but are not limited to, polarization direction, transmittance, extinction ratio, polarization type, etc., and the transmitted light is mainly linearly polarized parallel to the high contrast grating bars while the reflected light is mainly polarized perpendicular to the high contrast grating bars.

[0024] Optionally, in the embodiments of the present disclosure, the transparent substrate 11 may be made of one or more materials that are substantially transparent at the working wavelength of the polarizer. For example, the working wavelength includes, but is 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 material includes, but is not limited to, SiO2 (silica), Al2O3 (alumina), or Si (silicon), or the transparent substrate 11 may be various types of glass substrates, amorphous substrates, polycrystalline substrates, crystalline substrates, and the like. The high contrast grating 121 includes, but is not limited to, a semiconductor grating or a dielectric grating, and is 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. A 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 the polarized light is parallel to the long axis of the liquid crystal, the incident light is subjected to an extraordinary refractive index n e When the polarization is perpendicular to the long axis of the liquid crystal, the incident light normally has a refractive index of n o The liquid crystal molecules can be reoriented by electric or magnetic fields, changing their effective birefringence accordingly. Thus, incident light experiences a 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] Further, for example, as shown in FIG. 4 to FIG. 5, FIG. 4(a) is a schematic diagram of P-polarized light incident on a high-contrast grating polarizer to which no external voltage is applied, and P-polarized light refers to light whose electric field direction is perpendicular to the grating. In this case, since the electric field direction of light is perpendicular, the light strongly interacts with the metal, especially the two side walls, and the electric field cannot penetrate the metal and is reflected. In this case, both side walls reflect the electric field, and the two electric fields interfere with each other, and the cavity functions as an antenna resonator. FIG. 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, and as can be seen from the figure, the light is reflected and cannot penetrate this structure. Meanwhile, FIG. 5(a) is a schematic diagram of P-polarized light incident on a high-contrast grating polarizer to which an external voltage is applied, and the liquid crystal is oriented in the same direction due to the action of the voltage applied from the outside, and as a result, the refractive index of the surrounding environment is changed. Even though the interaction between light and metal is strong, most of the light escapes the grating due to the phase mismatch, and high transmittance is shown. 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 FIG. 6 to FIG. 7, FIG. 6(a) is a schematic diagram of S-polarized light incident on a high-contrast grating polarizer to which no external voltage is applied, and S-polarized light refers to light whose electric field direction is parallel to the grating. In this case, when light interacts with a high-contrast grating, a specific period, duty cycle, and grating thickness are designed, so that the reflection phase from the top of the grating and the reflection phase from the bottom of the grating are different, and thus, under specific design conditions, the effect of light reflection is suppressed. In addition, since the electric field direction of light is parallel to the grating and most of what is between the gratings is air, the effect of metal on light is extremely small, and most S-polarized light passes through this structure. FIG. 6(b) shows a schematic diagram of an electric field simulation of S-polarized light with θ of 0 degrees according to an embodiment of the present disclosure, and as can be seen from the figure, light passes through the grating. On the other hand, Fig. 7(a) is a schematic diagram of S-polarized light incident on a high-contrast grating polarizer with an external voltage applied, and the liquid crystals are oriented in the same direction under the action of the externally applied voltage, which results in a change in the refractive index of the surrounding environment, but most of the S-polarized light is also transmitted through the structure. Fig. 7(b) shows a schematic diagram of an electric field simulation of S-polarized light with θ of 0 degrees according to an embodiment of the present disclosure, and as can be seen, 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 figures, 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 refractive index may be essentially isotropic or essentially anisotropic, and the change in 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 refractive index may be continuous or may change abruptly, and the electrical bias may be applied stepwise or abruptly, so the polarization characteristics can be switched gradually or abruptly. Here, as a 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 an 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 the embodiments of the present disclosure, the high contrast grating polarizer 10 may have a periodic structure or a non-periodic structure. 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 FIG. 12 to FIG. 15, the plasmonic metal antenna structure layer 12 has a periodic structure in both the longitudinal direction and the lateral direction 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 this structure can be used for a linear polarizer or a beam splitter. Alternatively, the plasmonic metal antenna structure layer 12 has a periodic structure in the short direction of the transparent substrate 11 and a non-periodic structure in the long direction of the transparent substrate 11, or the plasmonic metal antenna structure layer 12 has a non-periodic structure in both the long and short directions of the transparent substrate 11 (for example, Figs. 14 and 15), and 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 usually 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. As an example, a two-dimensional grating structure with chiral symmetry is one of the preferred embodiments, where the polarizer is usually used as a circular polarizer. As another example, combining the characteristics of two gratings is a preferred embodiment for controlling elliptical polarization. Also, for light incident from a large viewing angle, high efficiency is obtained in either the transmission or reflection direction of the grating, so it is preferable for the polarizer grating to have a period less than a certain value related to the wavelength of light, so that there are no diffraction losses.

[0030] Exemplarily, 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 metal antenna structure 122 (e.g., FIG. 1, etc.), or the electrically tunable refractive index switching layer 13 is located below the plasmonic metal antenna structure layer 12. Such a configuration allows the optical properties of the high contrast grating polarizer 10 to be effectively switched, 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 a part of the plasmonic metal antenna structure 122. For example, the transparent conductive film includes, but is not limited to, ITO (indium tin oxide) glass, FTO (fluorine doped tin oxide) glass, etc., while the part of the plasmonic metal antenna structure 122 may be an Au (gold) contact electrode. In addition, a protective glass 16 may be further provided on the first electrode layer 14 (for example, FIG. 19), which can effectively protect the high contrast grating polarizer 10 and extend its service life.

[0033] Further, for example, the plasmonic metal antenna structure 122 is 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 is at the bottom, left sidewall, and right sidewall of the high contrast grating gap (e.g., FIG. 1), the plasmonic metal antenna structure 122 is at the bottom and left sidewall of the high contrast grating gap (e.g., FIG. 20), the plasmonic metal antenna structure 122 is at the bottom and right sidewall of the high contrast grating gap (e.g., FIG. 21), or the plasmonic metal antenna structure 122 is 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 adhesive strength 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 is provided between the transparent substrate 11 and the plasmonic metal antenna structure 122 and / or between the high contrast grating 121 and the plasmonic metal antenna structure 122, respectively, to improve the adhesion of the metal surface. 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 a method 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, which improves 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 a method such as ALD, PECVD, CVD, or PVD.

[0038] It should be noted that (a) in the embodiments of the present disclosure, the metal adjacent to the sidewall of one grating, the metal adjacent to the sidewall of the other grating, the metal at the bottom of the grating gap, and the metal at the top of the grating may have different thicknesses. In polarizers with plasmonic metal antenna structures 122 at the bottom, left side, and right side of the 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. There may be slits between the metal and the high contrast grating 121 and / or between the metal and the transparent substrate 11, and the slits should be less than 30 nm. Furthermore, there may be discontinuities in the metal layer, i.e., holes, and the size of such discontinuities should be less than the distance between the two gratings.

[0039] (b) In order to improve the manufacturability, reliability and performance of the high contrast grating polarizer 10, the embodiments of the present disclosure may add various structures and layers, while maintaining the basic features of the present disclosure, and such configurations should be considered as part of the present disclosure. Examples of such layers include the following layers: 1) A layer that is advantageous for adhering each assembly of the present disclosure. In one embodiment, a thin dielectric layer may be present between the substrate and the grating of the polarizer to improve adhesion of the grating to the substrate. In a preferred embodiment of a polarizer operating in a transmission mode, such a layer is a transparent dielectric. In another embodiment, this thin layer may improve adhesion between the metal part of the polarizer and the grating part. In a preferred embodiment, such a layer is a metal layer. 2) A layer that contributes 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 precisely limiting the depth and shape of the grating. 3) A layer for reliability or protection. In one embodiment, this thin auxiliary layer separates the material having the switchable refractive index from the grating and the metal part of the polarizer, improving the reliability of the device. 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 part of the polarizer serves as part of one electrode, and a transparent ITO glass serves as part of the other electrode. In another preferred embodiment, the grating and metal part of the polarizer are separated from the LC by a thin auxiliary layer, thereby improving reliability, and the electrodes are arranged laterally, or two transparent electrodes are 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. If the polarizer operates as a light transmitting device, a transparent electrode is a particularly preferred embodiment. If the polarizer is designed to primarily reflect light, at least one non-transparent electrode can be used.

[0041] In a high-contrast grating polarizer with adjustable polarization characteristics according to an embodiment of the present disclosure, a plasmonic metal antenna structure layer is combined with a switching layer whose refractive index can be electrically tuned, so that the refractive index of the switching layer can be changed by an electrical tuning method such as an electric field or a magnetic field, thereby affecting the transmittance and reflectance of the opposite 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 describe 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, it should be understood that those skilled in the art can modify the technical solutions described in the above embodiments or equally replace some of the technical features thereof. These modifications or replacements do not deviate the essence of the corresponding technical solution from 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 characteristics, comprising: A transparent substrate; a plasmonic metal antenna structure layer located on the transparent substrate, a switching layer having an electrically tunable refractive index, a first electrode layer, and a second electrode layer; A high contrast grating polarizer, characterized in that the plasmonic metal antenna structure layer includes a high contrast grating and a plasmonic metal antenna structure offset from the high contrast grating, the high contrast grating includes a semiconductor grating or a dielectric grating, the high contrast grating transmits light of a first polarization direction, the plasmonic metal antenna structure reflects light of a second polarization direction, and the first polarization direction and the second polarization direction are opposite to each other.

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

3. The high contrast grating polarizer of any one of claims 1 to 2, characterized in that the refractive index electrically tunable switching layer is located between the high contrast grating and the plasmonic metal antenna structure, or the refractive index electrically tunable switching layer is located below the plasmonic metal antenna structure layer.

4. 3. The high contrast grating polarizer of claim 1, wherein the first electrode layer is located on top of the electrically tunable refractive index switching layer and the second electrode layer is connected to the plasmonic metal antenna structure; the first electrode layer is located on top of 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.

5. 5. The high contrast grating polarizer of claim 4 , 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.

6. The high contrast grating polarizer of any one of claims 1 to 2, characterized in that 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.

7. The high contrast grating polarizer of any one of claims 1 to 2, characterized in that the plasmonic metallic antenna structures are located at at least one of the top, left sidewall, and right sidewall of each high contrast grating bar.

8. The high contrast grating polarizer of any one of claims 1 to 2, characterized in that a protective layer is provided between the plasmonic metal antenna structure layer and the switching layer whose refractive index is electrically tunable.

9. The protective layer is a SiN layer, an Al ２ O ３ layer, and SiO ２ 9. The high contrast grating polarizer of claim 8, comprising any one of the layers.

10. 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 transverse 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 transverse direction of the transparent substrate, the plasmonic metal antenna structure layer has a periodic structure in the transverse 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 transverse directions of the transparent substrate.

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