CN117170004A - High-contrast grating polarizer with adjustable polarization characteristics - Google Patents
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Abstract
The disclosure provides a high-contrast grating polarizer with adjustable polarization characteristics, and relates to the technical field of photoelectric devices. The high contrast grating polarizer includes a transparent substrate; the plasma metal antenna structure layer comprises a high-contrast grating and plasma metal antenna structures which are arranged in a staggered mode with the high-contrast grating, wherein the high-contrast grating comprises a semiconductor grating or a dielectric grating and is used for transmitting light in a first polarization direction, the plasma metal antenna structure is used for reflecting light in a second polarization direction, and the first polarization direction and the second polarization direction are opposite. By adopting the high-contrast grating polarizer disclosed by the invention, the polarization characteristic of the polarizer can be changed in an electric tuning mode, the high-efficiency and convenient effects are achieved, and meanwhile, the response is sensitive and the reliability is high.
Description
Technical Field
The present disclosure relates generally to the field of optoelectronic device technology, and in particular, to a high contrast grating polarizer with adjustable polarization characteristics.
Background
A polarizer is a filter that allows light waves of a particular polarization to pass while blocking light waves of other polarization. Common commercial polarizers include linear polarizers, circular polarizers, etc., and are widely used in many optical instruments and equipment.
In order to effectively suppress scattered and reflected ambient light by utilizing the polarization characteristics of the polarizer, the related art switches the polarizer by a mechanical means, but this approach is costly, slow in response speed, and low in reliability.
Disclosure of Invention
In view of the above-mentioned drawbacks or shortcomings in the related art, it is desirable to provide a high-contrast grating polarizer with adjustable polarization characteristics, which can change the polarization characteristics of the polarizer by means of electronic switching, and which is efficient, convenient, and at the same time has high reliability.
The present disclosure provides a high contrast grating polarizer with tunable polarization characteristics, the high contrast grating polarizer comprising:
a transparent substrate;
the plasma metal antenna structure layer comprises a high-contrast grating and plasma metal antenna structures which are arranged in a staggered mode with the high-contrast grating, wherein the high-contrast grating comprises a semiconductor grating or a dielectric grating and is used for transmitting light in a first polarization direction, the plasma metal antenna structure is used for reflecting light in a second polarization direction, and the first polarization direction and the second polarization direction are opposite.
Optionally, in some embodiments of the disclosure, the refractive index electrically tunable switching layer comprises a liquid crystal layer.
Optionally, in some embodiments of the present disclosure, the refractive index electrically tunable switching layer is located between the high contrast grating and the plasmonic metal antenna structure; alternatively, the refractive index electrically tunable switching layer is located below the plasmonic metal antenna structure layer.
Optionally, in some embodiments of the present disclosure, the first electrode layer is located above the refractive index electrically tunable switching layer, and the second electrode layer is connected to the plasmonic metal antenna structure; alternatively, the first electrode layer is located above the refractive index electrically tunable switching layer, and the second electrode layer is located below the plasmonic metal antenna structure layer; alternatively, the first electrode layer is located on the left side of the refractive index electrically tunable switching layer, and the second electrode layer is located on the right side of the refractive index electrically tunable switching layer.
Optionally, in some embodiments of the present disclosure, the first electrode layer and the second electrode layer are both transparent conductive films; alternatively, the first electrode layer is the transparent conductive film, and the second electrode layer is part of the plasmonic metal antenna structure.
Optionally, in some embodiments of the present disclosure, the plasmonic metal antenna structure is located at least one of a bottom, a left sidewall, and a right sidewall of the high contrast grating gap.
Optionally, in some embodiments of the present disclosure, the plasmonic metal antenna structure is located at least one of a top, a left sidewall, and a right sidewall of each high contrast grating strip.
Optionally, in some embodiments of the present disclosure, a protective layer is disposed between the plasmonic metal antenna structure layer and the refractive index electrically tunable switching layer.
Optionally, in some embodiments of the present disclosure, the protective layer includes a SiN layer, al 2 O 3 Layer and SiO 2 Any one of the layers.
Optionally, in some embodiments of the present disclosure, the plasmonic metal antenna structure layer has a periodic structure along both a length direction and a width direction of the transparent substrate; alternatively, the plasmonic metal antenna structure layer has a periodic structure in a length direction along the transparent substrate and a non-periodic structure in a width direction along the transparent substrate; alternatively, the plasmonic metal antenna structure layer has a periodic structure in a width direction along the transparent substrate and a non-periodic structure in a length direction along the transparent substrate; alternatively, the plasmonic metal antenna structure layer has an aperiodic structure along both the length direction and the width direction of the transparent substrate.
From the above technical solutions, the embodiments of the present disclosure have the following advantages:
the embodiment of the disclosure provides a high-contrast grating polarizer with adjustable polarization characteristics, which combines a plasma metal antenna structure layer with a switching layer with an electrically tunable refractive index, so that the refractive index change of the switching layer can be caused by utilizing an electric tuning mode such as an electric field or a magnetic field, the transmissivity and the reflectivity of opposite polarized light are further influenced, the polarization characteristics of the polarizer are changed, and the high-contrast grating polarizer is efficient and convenient, and has sensitive response and high reliability.
Drawings
Other features, objects and advantages of the present disclosure will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the following drawings:
FIG. 1 is a schematic diagram of a first state cross-sectional structure of a first high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of a second state cross-sectional structure of a first high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 3 is a schematic three-dimensional structure of a first high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 4 is a schematic cross-sectional view of a P-polarized light incident on a high contrast grating polarizer with no external voltage applied and a schematic electric field simulation diagram according to an embodiment of the present disclosure;
FIG. 5 is a schematic cross-sectional view of a P-polarized light incident on a high contrast grating polarizer with an external voltage applied and a schematic simulation of an electric field according to an embodiment of the present disclosure;
FIG. 6 is a schematic cross-sectional view of S-polarized light incident on a high contrast grating polarizer with no external voltage applied and a schematic electric field simulation diagram according to an embodiment of the present disclosure;
FIG. 7 is a schematic cross-sectional view of S-polarized light incident on a high contrast grating polarizer with an external voltage applied and a schematic diagram of electric field simulation according to an embodiment of the present disclosure;
FIG. 8 is a schematic cross-sectional view of a high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 9 is a schematic cross-sectional view of a high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 10 is a schematic cross-sectional view of a third external voltage applied to a high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 11 is a schematic cross-sectional view of a fourth external voltage applied to a high contrast grating polarizer according to an embodiment of the present disclosure;
fig. 12 is a schematic cross-sectional structure of a first plasmonic metal antenna structure layer according to an embodiment of the disclosure;
fig. 13 is a schematic cross-sectional structure of a second plasmonic metal antenna structure layer provided in an embodiment of the disclosure;
fig. 14 is a schematic cross-sectional structure of a third plasmonic metal antenna structure layer provided in an embodiment of the disclosure;
fig. 15 is a schematic cross-sectional structure of a fourth plasmonic metal antenna structure layer provided in an embodiment of the disclosure;
FIG. 16 is a schematic cross-sectional view of a second high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 17 is a schematic cross-sectional view of a third high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 18 is a schematic cross-sectional view of a fourth high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 19 is a schematic cross-sectional view of a fifth high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 20 is a schematic cross-sectional view of a sixth high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 21 is a schematic cross-sectional view of a seventh high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 22 is a schematic cross-sectional view of an eighth high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 23 is a schematic cross-sectional view of a ninth high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 24 is a schematic cross-sectional view of a tenth high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 25 is a schematic cross-sectional view of an eleventh high contrast grating polarizer according to an embodiment of the present disclosure;
FIG. 26 is a schematic cross-sectional view of a twelfth high contrast grating polarizer provided by embodiments of the present disclosure;
FIG. 27 is a schematic cross-sectional view of a thirteenth high contrast grating polarizer provided by an embodiment of the present disclosure;
fig. 28 is a schematic cross-sectional structure of a fourteenth high-contrast grating polarizer according to an embodiment of the present disclosure.
Reference numerals:
10-high contrast grating polarizer with adjustable polarization characteristics, 11-transparent substrate, 12-plasma metal antenna structure layer, 121-high contrast grating, 122-plasma metal antenna structure, 13-refractive index electrically tunable switching layer, 14-first electrode layer, 15-second electrode layer, 16-protective glass, 17-protective layer.
Detailed Description
In order that those skilled in the art will better understand the present disclosure, a technical solution in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments in this disclosure, all other embodiments that a person of ordinary skill in the art would obtain without making any inventive effort are within the scope of protection of this disclosure.
The terms "first," "second," "third," "fourth" and the like in the description and in the claims and in the above-described figures, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the described embodiments of the disclosure may be capable of operation in sequences other than those illustrated or described herein.
Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or modules is not necessarily limited to those steps or modules that are expressly listed or inherent to such process, method, article, or apparatus.
For ease of understanding and explanation, the high contrast grating polarizers provided by embodiments of the present disclosure with tunable polarization characteristics are described in detail below with reference to fig. 1-28.
Please refer to fig. 1 to 3, which are schematic diagrams corresponding to different states or viewing angles of the high-contrast grating polarizer with adjustable polarization characteristics according to an embodiment of the present disclosure. The high contrast grating polarizer 10 comprises a transparent substrate 11, a plasmonic metal antenna structure layer 12 on the transparent substrate 11, a refractive index electrically tunable switching layer 13, a first electrode layer 14 and a second electrode layer 15, wherein the plasmonic metal antenna structure layer 12 may comprise a high contrast grating (High Contrast Grating, HCG) 121 and plasmonic metal antenna structures 122 interleaved with the high contrast grating 121, the high contrast grating 121 comprising but not limited to a semiconductor grating or a dielectric grating, the high contrast grating 121 being capable of transmitting light of a first polarization direction, the plasmonic metal antenna structures 122 being capable of reflecting light of a second polarization direction, whereas the first polarization direction and the second polarization direction are opposite, e.g. polarized light comprising but not limited to S-polarized light, P-polarized light, circularly polarized light, ellipsoi the like, polarization characteristics comprising but not limited to polarization direction, transmittance, extinction ratio, polarization type and the like, and the transmitted light being predominantly linear polarization parallel to the high contrast grating and the reflected light being predominantly polarization perpendicular to the high contrast grating.
Alternatively, the transparent substrate 11 in embodiments of the present disclosure may be made of one or more materials that are substantially transparent at the operating wavelength of the polarizer. For example, operating wavelengths 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), THz (terahertz), or the like; materials include, but are not limited to, siO 2 (silica), al 2 O 3 (aluminum oxide) or Si (silicon) or the like, or the transparent substrate 11 may be a glass substrate, an amorphous substrate, a polycrystalline substrate, a crystalline substrate or the like of various types. The high contrast grating 121 includes, but is not limited to, a semiconductor grating or a dielectric grating, such as Si (silicon), siN (silicon nitride), al 2 O 3 (alumina) or any other kind of non-conductive material. And, the plasmonic metal antenna structure 122 may be any kind of metal, such as Au (gold), ag (silver), al (aluminum), fe (iron), alloys, or other conductive materials.
Alternatively, the refractive index electrically tunable switching layer 13 in the embodiments of the present disclosure includes, but is not limited to, a Liquid Crystal (LC) layer, and the like. Liquid crystals are a state of matter whose properties are intermediate between conventional liquid and solid crystals. When rod-like molecules are aligned in a specific direction, LC may form a medium having anisotropic optical properties. When the polarized light is parallel to the long axis of the liquid crystal, the incident light corresponds to a very refractive index n e Whereas when the polarized light is perpendicular to the long axis of the liquid crystal, the incident light corresponds to the ordinary refractive index n o . The liquid crystal molecules may be reoriented by an electric or magnetic field and their effective birefringence changed accordingly. Thus, incident light experiences different phase delays as the applied electric or magnetic field changes. When the liquid crystal molecules are randomly oriented, the LC may form a medium having isotropic optical properties.
Further, as shown in fig. 4 to 5, for example, fig. 4 (a) is a schematic view of P-polarized light incident on a high contrast grating polarizer to which no external voltage is applied, the P-polarized light means that the electric field direction of the light is perpendicular to the grating. In this case, since the electric field direction of the light is vertical, the light will interact so much with the metal, in particular the two side walls, that the electric field cannot penetrate the metal, it will be reflected, and both side walls will reflect the electric field, which will interfere with each other, the cavity operating as an antenna resonator. As shown in fig. 4 (b), which is a schematic diagram of electric field simulation of P-polarized light with θ equal to 0 degrees according to an embodiment of the present disclosure, it can be seen that the light is reflected away and cannot pass through the structure. Whereas 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, the orientation of the liquid crystal follows one direction due to the applied voltage, resulting in a change in the refractive index of the surrounding environment. Even though the interaction of light with metal is large, most of the light will leak through the grating due to the phase mismatch and appear to be high in transmittance. As shown in fig. 5 (b), which is a schematic diagram of electric field simulation of P-polarized light with θ equal to 0 degrees according to an embodiment of the present disclosure, light passing through the grating can be seen from the figure.
For example, as shown in fig. 6 to 7, fig. 6 (a) is a schematic view of S-polarized light incident on a high contrast grating polarizer to which no external voltage is applied, and S-polarized light means that the electric field direction of the light is parallel to the grating. In this case, when light interacts with the high-contrast grating, the reflection phase from the top of the grating and the reflection phase from the bottom of the grating are made different by designing a specific period, duty ratio, and grating thickness, so that the effect of suppressing light reflection can be achieved under specific design conditions. Meanwhile, the electric field direction of the light is parallel to the gratings, and most of the light is air between the gratings, so that the influence of metal on the light is small, and most of S polarized light passes through the structure. As shown in fig. 6 (b), which is a schematic diagram of electric field simulation of S-polarized light with θ equal to 0 degrees according to an embodiment of the present disclosure, light passing through the grating can be seen. Whereas fig. 7 (a) is a schematic diagram of S-polarized light incident on a high contrast grating polarizer to which an external voltage is applied, the orientation of the liquid crystal follows a direction due to the applied voltage, resulting in a change in the refractive index of the surrounding environment, but most of the S-polarized light also passes through this structure. As shown in fig. 7 (b), which is a schematic diagram of electric field simulation of S-polarized light with θ equal to 0 degrees according to an embodiment of the present disclosure, light passing through the grating can be seen.
Further, as shown in fig. 8 to 11, for example, schematic diagrams of applying different external voltages to the high contrast grating polarizer are shown, respectively, wherein the relationship between the different external voltages is V0 < V1 < V2 < V3. It can be seen from the figure that when a higher voltage is added, more liquid crystal will follow the electric field direction. It should be noted that a continuous voltage, electric field, electric current, or magnetic field (or a combination thereof) is applied such that at least one material in the switching layer 13 of the high contrast grating polarizer 10 changes its refractive index. This change in refractive index may be isotropic in nature or anisotropic in nature, which may further change the material from having an isotropic to having an anisotropic refractive index, the liquid crystal exhibiting the latter. The change in refractive index may be continuous or abrupt and the electrical bias may be applied in a gradual or abrupt manner, so that the polarization characteristics may be switched in a gradual or abrupt manner. Wherein the taper comprises (1) effecting a gradual change in transmission of light of one polarization direction while transmission of light of an opposite polarization direction is largely maintained, (2) effecting a gradual change in reflection of light of one polarization direction while reflection of light of an opposite polarization direction is largely maintained, and (3) tuning the extinction ratio of the polarizer from a higher value to a lower value, and vice versa, and so forth; the abrupt modes include (1) a state in which light of one polarization state has high transmittance, a state in which light of the opposite polarization state has high transmittance, (2) a state in which light of one polarization state has high reflectance, a state in which light of the opposite polarization state has high reflectance, (3) a state in which light of one polarization state has high transmittance, a state in which light of both polarization states has substantially equal high transmittance, and (4) a state in which light of one polarization state has high reflectance, a state in which light of both polarization states has substantially equal high reflectance, and the like.
Alternatively, the high contrast grating polarizer 10 in embodiments of the present disclosure may be of periodic or non-periodic construction. And, in other embodiments of the present disclosure, the high contrast grating polarizer 10 may be a one-dimensional structure or a two-dimensional structure. As shown in fig. 12 to 15, for example, the plasmonic metal antenna structure layer 12 has a periodic structure (as in fig. 12) in both the length direction and the width direction along the transparent substrate 11, and such a structure can be used for a linear polarizer, a circular polarizer, an elliptical polarizer, and a beam splitter; alternatively, the plasmonic metal antenna structure layer 12 has a periodic structure in the length direction along the transparent substrate 11 and a non-periodic structure in the width direction along the transparent substrate 11 (as in fig. 13), and this structure can be used for linear polarizers and beam splitters; alternatively, the plasmonic metal antenna structure layer 12 has a periodic structure in the width direction along the transparent substrate 11 and a non-periodic structure in the length direction along the transparent substrate 11; alternatively, the plasmonic metal antenna structure layer 12 has an aperiodic structure (as in fig. 14 and 15) in both the length direction and the width direction of the transparent substrate 11, and such a structure can be used for a linear polarizer, a circular polarizer, an elliptical polarizer, and a beam splitter. It is noted that a one-dimensional grating structure or a two-dimensional grating structure with a certain preferred lateral direction is beneficial for applications where polarizers are commonly used as linear polarizers. In a preferred arrangement, the preferred lateral direction of the grating elements is perpendicular or parallel to the polarization of the incident light. As an example, a two-dimensional grating structure with chiral symmetry is a preferred embodiment, wherein a polarizer is typically used as a circular polarizer. As another example, a combination of two grating properties would be a preferred embodiment for controlling elliptically polarized light. In addition, for light incident from a large angle of view, in order to obtain high efficiency in the transmission direction or the reflection direction of the grating, the grating of the polarizer preferably has a period smaller than a specific value related to the wavelength of light to prevent diffraction loss.
Illustratively, various structures of the high contrast grating polarizer 10 in embodiments of the present disclosure are described in detail below. For example, the refractive index electrically tunable switching layer 13 is located between the high contrast grating 121 and the plasmonic metal antenna structure 122 (e.g., fig. 1, etc.); alternatively, the refractive index electrically tunable switching layer 13 is located below the plasmonic metal antenna structure layer 12. The advantage of this arrangement is that the optical characteristics of the high contrast grating polarizer 10 can be switched effectively, the sensitivity is high, and the reliability is improved.
For another example, the first electrode layer 14 is located above the refractive index electrically tunable switching layer 13, and the second electrode layer 15 is connected to the plasmonic metal antenna structure 122 (e.g., fig. 16, etc.); alternatively, the first electrode layer 14 is located above the refractive index electrically tunable switching layer 13, and the second electrode layer 15 is located below the plasmonic metal antenna structure layer 12 (as in fig. 17); alternatively, the first electrode layer 14 is located on the left side of the refractive index electrically tunable switching layer 13, and the second electrode layer 15 is located on the right side of the refractive index electrically tunable switching layer 13 (see fig. 18).
Alternatively, the first electrode layer 14 and the second electrode layer 15 are both transparent conductive films; alternatively, the first electrode layer 14 is a transparent conductive film and the second electrode layer 15 is part of a plasmonic metal antenna structure 122. Such as transparent conductive films including, but not limited to, ITO (indium tin oxide doped) glass, FTO (fluorine tin oxide doped) glass, etc., while a portion of the plasmonic metal antenna structure 122 may be an Au (gold) contact electrode. In addition, the first electrode layer 14 may be further provided with a protective glass 16 (as shown in fig. 19), thereby effectively protecting the high contrast grating polarizer 10 and prolonging the service life.
As another example, plasmonic metal antenna structure 122 is located at least one of the bottom, left side wall, and right side wall of the high contrast grating gap. For example, plasmonic metal antenna structure 122 is located at the bottom, left side wall, and right side wall of the high contrast grating gap (e.g., fig. 1, etc.); alternatively, the plasmonic metal antenna structure 122 is located at the bottom and left sidewalls of the high contrast grating gap (as in fig. 20); alternatively, the plasmonic metal antenna structure 122 is located at the bottom and right side walls of the high contrast grating gap (as in fig. 21); alternatively, the plasmonic metal antenna structure 122 is located at the bottom of the high contrast grating gap (as in fig. 22).
For another example, a plasmonic metal antenna structure 122 is located at least one of the top, left side wall, and right side wall of each high contrast grating strip. For example, a plasmonic metal antenna structure 122 is located on top of each high contrast grating strip (as in fig. 23); alternatively, plasmonic metal antenna structures 122 are located on top, left side wall, and right side wall of each high contrast grating strip (as in fig. 24); alternatively, plasmonic metal antenna structures 122 are located on the left and right sidewalls of each high contrast grating strip (as in fig. 25); alternatively, the plasmonic metal antenna structure 122 is located on the right side wall of each high contrast grating strip (as in fig. 26); alternatively, the plasmonic metal antenna structure 122 is located on the left side wall of each high contrast grating strip (see fig. 27).
Optionally, a first adhesive layer is provided between the transparent substrate 11 and the high-contrast grating 121 in the embodiment of the present disclosure, thereby enabling to enhance the adhesion of the high-contrast grating 121. Wherein the first bonding layer may comprise a SiN layer and Al 2 O 3 Layer and SiO 2 Any one of the layers. In actual production, the first adhesive layer may be deposited by ALD (Atomic Layer Deposition ), PECVD (Plasma Enhanced Chemical Vapor Deposition, plasma-enhanced chemical vapor deposition), CVD (Chemical Vapor Deposition ), or PVD (Physical Vapor Deposition, physical vapor deposition).
Optionally, a second adhesive layer is further disposed 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 in the embodiments of the present disclosure, so that adhesion of the metal surface can be enhanced. Wherein the second bonding layer may include any one of a Ti (titanium) layer, a Ge (germanium) layer, and an Al (aluminum) layer. In the actual production process, the second adhesive layer may be deposited by ALD, PECVD, CVD, PVD or sputtering, etc.
Optionally, as shown in fig. 28, a protective layer 17 is disposed between the plasmonic metal antenna structure layer 12 and the refractive index electrically tunable switching layer 13 in the embodiments of the present disclosure, thereby enabling improved manufacturability, reliability, and performance of the high contrast grating polarizer 10. Wherein the protective layer 17 may comprise a SiN layer, al 2 O 3 Layer and SiO 2 Any of the layers may be deposited by ALD, PECVD, CVD or PVD, etc.
It should be further noted that (a) 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 in embodiments of the present disclosure may have different thicknesses. In polarizers where the plasmonic metal antenna structure 122 is located at the bottom, left side wall, and right side wall of the high contrast grating gap, the ratio of the sidewall metal thickness divided by the bottom metal thickness may be greater than 0.2 and less than 3. There may be a gap between the metal and the high contrast grating 121 and/or between the metal and the transparent substrate 11, which should be less than 30nm. And where there may be discontinuities in the metal layer, i.e. air holes, the size of such discontinuities should be smaller than the distance between the two gratings.
(b) To enhance manufacturability, reliability, and performance of the high contrast grating polarizer 10, various structures and layers may be added by embodiments of the present disclosure without altering the basic features of the present disclosure, and such configurations should be considered as part of the present disclosure. Examples of such layers include (1) layers that help adhere the various components of the present disclosure. In one embodiment, a thin dielectric layer may be present between the substrate of the polarizer and the grating to improve the adhesion of the grating to the substrate. In a preferred embodiment of a polarizer operating in transmissive mode, such layer is a transparent dielectric. In another embodiment, the thin layer may enhance adhesion between the metal portion of the polarizer and the grating portion. In a preferred embodiment, such a layer is a metal layer. (2) A layer that contributes to manufacturability of the polarizer. In one embodiment, the auxiliary layer between the substrate and the grating acts as an etch stop layer, facilitating accurate definition of the grating depth and shape. (3) Enhancing reliability or layers for protection purposes. In one embodiment, a thin auxiliary layer separates the material with switchable refractive index from the grating and metal portions of the polarizer to enhance the reliability of the device. In a preferred embodiment LC is used as a material and the transparent electrode is realized by ITO or FTO glass, the glass substrate of such transparent electrode also serving as an auxiliary layer to protect and conceal LC inside the device.
(c) A variety of transparent conductive materials and films may be used to form part or all of the electrodes to achieve the high contrast grating polarizer 10. Preferred materials for such electrodes are ITO, FTO and nanostructured electrodes. In a preferred embodiment of the high contrast grating polarizer 10, the metallic portion of the polarizer is used as part of one electrode and the transparent ITO glass is used as part of the other electrode. In another preferred embodiment, the grating and metal portions of the polarizer are separated from the LC by a thin auxiliary layer to improve reliability, and either a lateral electrode configuration is used, or two transparent electrodes are used, one between the auxiliary layer and the LC and one on top of the LC. In a preferred embodiment, the top electrode is ITO glass. Transparent electrodes are particularly preferred embodiments when the polarizer is operated as a means for transmitting light. When the polarizer is designed to reflect light predominantly, at least one opaque electrode may be used.
According to the high-contrast grating polarizer with the adjustable polarization characteristic, the plasma metal antenna structure layer is combined with the switching layer with the electrically tunable refractive index, so that the refractive index change of the switching layer can be caused by utilizing an electric tuning mode such as an electric field or a magnetic field, the transmissivity and the reflectivity of opposite polarized light are affected, the polarization characteristic of the polarizer is changed, and the high-contrast grating polarizer is efficient and convenient, sensitive in response and high in reliability.
It should be noted that the above embodiments are merely for illustrating the technical solution of the disclosure, and are not limiting; although the present disclosure has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present disclosure.
Claims (10)
1. A high contrast grating polarizer with tunable polarization characteristics, the high contrast grating polarizer comprising:
a transparent substrate;
the plasma metal antenna structure layer comprises a high-contrast grating and plasma metal antenna structures which are arranged in a staggered mode with the high-contrast grating, wherein the high-contrast grating comprises a semiconductor grating or a dielectric grating and is used for transmitting light in a first polarization direction, the plasma metal antenna structure is used for reflecting light in a second polarization direction, and the first polarization direction and the second polarization direction are opposite.
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 1-2, wherein the refractive index electrically tunable switching layer is located between the high contrast grating and the plasmonic metal antenna structure; alternatively, the refractive index electrically tunable switching layer is located below the plasmonic metal antenna structure layer.
4. The high contrast grating polarizer of any one of claims 1-2, wherein the first electrode layer is located above the index of refraction electrically tunable switching layer, and the second electrode layer is connected to the plasmonic metal antenna structure; alternatively, the first electrode layer is located above the refractive index electrically tunable switching layer, and the second electrode layer is located below the plasmonic metal antenna structure layer; alternatively, the first electrode layer is located on the left side of the refractive index electrically tunable switching layer, and the second electrode layer is located on the right side of the refractive index electrically tunable switching layer.
5. The high contrast grating polarizer of claim 4, wherein the first electrode layer and the second electrode layer are both transparent conductive films; alternatively, 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 1-2, wherein the plasmonic metal antenna structure is located at least one of the bottom, left side wall, and right side wall of the high contrast grating gap.
7. The high contrast grating polarizer of any one of claims 1-2, wherein the plasmonic metal antenna structure is located at least one of a top, a left side wall, and a right side wall of each high contrast grating strip.
8. A high contrast grating polarizer according to any of claims 1-2, wherein a protective layer is provided between the plasmonic metal antenna structure layer and the refractive index electrically tunable switching layer.
9. The high contrast grating polarizer of claim 8, wherein the protective layer comprises a SiN layer, al 2 O 3 Layer and SiO 2 Any one of the layers.
10. The high contrast grating polarizer of any one of claims 1-2, wherein the plasmonic metal antenna structure layer has a periodic structure along both a length direction and a width direction of the transparent substrate; alternatively, the plasmonic metal antenna structure layer has a periodic structure in a length direction along the transparent substrate and a non-periodic structure in a width direction along the transparent substrate; alternatively, the plasmonic metal antenna structure layer has a periodic structure in a width direction along the transparent substrate and a non-periodic structure in a length direction along the transparent substrate; alternatively, the plasmonic metal antenna structure layer has an aperiodic structure along both the length direction and the width direction of the transparent substrate.
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