Low-profile metasurface reflectors

Abstract

The integrated optical structure includes a frequency-selective reflecting structure disposed between a decorative cover layer and an underlying metal layer. The underlying metal layer is configured to reflect and / or absorb radio frequency electromagnetic waves transmitted by the decorative cover layer and the frequency-selective reflecting structures. Each of the frequency-selective reflecting structures includes a frequency-selective surface layer having metal elements arranged on a multilayer stack and repeated across the frequency-selective surface layer to form an array. The integrated optical structure reflects collimated incident RF electromagnetic waves having a wavelength in the range of 1.0 mm to 10 cm and incident at an incident angle at a reflection angle different from the incident angle as collimated reflected waves. For normally incident light having a first visible wavelength, the frequency-selective reflecting structure has an optical transmittance greater than 50%.

Description

[Technical Field]

[0001] [Summary of the Invention] In some aspects of the present disclosure, an integrated optical structure is provided. The integrated optical structure includes at least one frequency-selective reflective structure disposed between a decorative cover layer and an underlying metal layer. The decorative cover layer is configured to display at least one of an image and information to a viewer. The underlying metal layer is configured to substantially reflect and / or substantially absorb radio frequency (RF) electromagnetic waves transmitted by the decorative cover layer and the at least one frequency-selective reflective structure. Each of the at least one frequency-selective reflective structure includes a frequency-selective surface (FSS) layer disposed on a multilayer stack, the FSS layer including metal elements repeated across the FSS layer to form an array of metal elements. The multilayer stack includes a plurality of alternating, distinct first dielectric layers and second adhesive layers. The integrated optical structure is configured to reflect substantially collimated incident RF electromagnetic waves having a free-space wavelength in the range of about 1.0 mm to about 20 cm and incident at an incident angle as substantially collimated reflected waves at a reflection angle different from the incident angle through either constructive or destructive interference. The at least one frequency selective reflecting structure has an optical transmittance of greater than about 50% for substantially normally incident light having a first visible wavelength within a visible wavelength range extending from about 420 nm to about 680 nm.

[0002] In some aspects of the present disclosure, a wireless system is provided. The wireless system includes first and second spaced-apart transceivers and any of the integrated optical structures described herein. Each of the spaced-apart first and second transceivers is configured to at least one of transmit and receive RF electromagnetic waves having a free-space wavelength. The integrated optical structure is configured to receive the RF electromagnetic waves transmitted by one of the first and second transceivers and reflect at least a portion of the received RF electromagnetic waves toward the other of the first and second transceivers. An angle of incidence of the received RF electromagnetic waves and an angle of reflection of the reflected RF electromagnetic waves differ by at least about 5 degrees.

[0003] In some aspects of the present disclosure, an integrated optical structure is provided. The integrated optical structure is configured to be mounted on a support and covered with a decorative cover layer configured to display at least one of an image and information to a viewer. The integrated optical structure includes a multilayer stack disposed between a frequency selective surface (FSS) layer configured to face the decorative cover layer and a wave reflecting layer configured to face the support. The FSS layer includes a plurality of discrete, spaced-apart, electrically insulated, conductive elements disposed along the width and length of the FSS layer (i.e., in a plane formed by the FSS layer). The multilayer stack includes at least two non-adhesive dielectric layers bonded to each other by at least one adhesive (100) layer. The integrated optical structure is configured to reflect, through either constructive or destructive interference, a substantially collimated incident RF electromagnetic wave having a free-space wavelength in the range of about 1.0 mm to about 300.0 cm and incident at an incident angle, as a substantially collimated reflected wave at a reflection angle different from the incident angle. When the integrated optical structure is attached to a support and covered with a decorative cover layer such that the FSS layer faces the decorative cover layer and the wave absorbing layer faces the support, the wave reflecting layer is configured to substantially reflect RF electromagnetic waves transmitted by the decorative cover layer, the FSS layer, and the multilayer stack. [Brief explanation of the drawings]

[0004] [Figure 1] FIG. 1 is a side view of a structure including an integrated optical structure according to one embodiment of the present disclosure. [Figure 2] 2A-2B provide diagrams of a frequency selective reflecting structure according to one embodiment of the present disclosure. [Figure 3] FIG. 3 is a side view of an integrated optical structure according to one embodiment of the present disclosure. [Figure 4A] FIG. 4A defines the angle of incidence of a light ray incident on an optical structure according to one embodiment of the present disclosure. [Figure 4B]FIG. 4B defines the angle of incidence of a light ray incident on an optical structure according to one embodiment of the present disclosure. [Figure 4C] FIG. 4C defines the angle of incidence of a light ray incident on an optical structure according to one embodiment of the present disclosure. [Figure 5] FIG. 5 is a top view of an underlying metal layer including a metal mesh layer according to one embodiment of the present disclosure. [Figure 6] 6A-6M define various types of images and information that may be displayed on a decorative cover layer according to one embodiment of the present disclosure. [Figure 7] FIG. 7 is a perspective view of the functional use of an integrated optical structure according to one embodiment of the present disclosure. [Figure 8] 8A-8J define the shapes and formats of components of an integrated optical structure according to one embodiment of the present disclosure. [Figure 9] FIG. 9 is a side view illustrating how metal elements of an integrated optical structure are partially embedded in adjacent layers according to one embodiment of the present disclosure. [Figure 10] FIG. 10 includes a side view of an integrated optical structure including a multi-layer stack according to another embodiment of the present disclosure. [Figure 11] FIG. 11 is a top view of a wireless system according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0005] In the following description, reference is made to the accompanying drawings included herein, in which various embodiments are shown by way of example. It should be noted that the drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. Accordingly, the following detailed description should not be taken in a limiting sense.

[0006] Demand for higher communication frequencies is rapidly increasing. Mobile and wireless communications are gradually migrating from sub-5 GHz frequencies (e.g., standard LTE, 5G NR FR1, and Wi-Fi 6 protocols) to deep microwave and millimeter-wave spectrum frequencies (e.g., 5G NR FR2, 6G for mobile and Wi-Fi 7, and Wi-Gig for wireless networks). Unfortunately, these higher frequencies are accompanied by reduced signal propagation efficiency due to free-space path loss (caused by a reduced receiver effective aperture size) and increased air absorption. Such degraded transmission and signal shadowing effects typically present in crowded urban indoor and outdoor environments require a significant increase in the number of powered components, such as active antenna nodes and repeaters. This is expensive both in terms of increased installation costs and increased power consumption.

[0007] Research has shown that passive, unpowered components such as metasurface-based (or equivalently, frequency-selective surface (FSS)-based) reflectarrays and diffuse reflectors can improve network coverage while conforming to the architectural profile of the environment. These reflectors are typically recommended for patching holes in network coverage, but they can also be used to redirect signals that may leak outside the designated network boundary. However, to have a noticeable effect on overall network quality, these solutions need to cover a large surface area (for individual reflectors, this means that the aperture size is comparable to, or at least not significantly smaller than, the antenna-to-reflector distance) and therefore need to be supplied in large quantities, preferably in the form of a low-cost, roll-based, flexible thin film with a low profile and without significant sacrifices in RF performance.

[0008] According to some aspects of the present disclosure, an integrated optical structure is configured to address these system requirements. In some embodiments, the integrated optical structure includes at least one frequency-selective reflective structure disposed between a decorative cover layer and an underlying metal layer. In some embodiments, the decorative cover layer may be configured to display at least one of an image and information (e.g., text, an image, a map, a logo, etc.) to a viewer. In some embodiments, the underlying metal layer may be configured to substantially reflect and / or substantially absorb radio frequency (RF) electromagnetic waves transmitted (i.e., allowed to pass) through the decorative cover layer and the at least one frequency-selective reflective structure. In some embodiments, each of the at least one frequency-selective reflective structure may include a frequency-selective surface (FSS) layer disposed on the multilayer stack, and the FSS layer may include metal elements that are repeated across the FSS layer (e.g., across an x-y plane defined by the FSS layer) to form an array of metal elements. In some embodiments, the multilayer stack may include a plurality of alternating, distinct first dielectric layers and second adhesive layers.

[0009] In some embodiments, the integrated optical structure is configured to reflect, by either constructive or destructive interference, a substantially collimated incident RF electromagnetic wave having a free-space wavelength ranging from about 1.0 mm to about 40 cm, or to about 20 cm, or to about 10 cm, incident at an incident angle q1, as a substantially collimated reflected wave at a reflection angle q2 different from the incident angle q1. In some embodiments, the difference between the incident angle and the reflection angle may be greater than about 5 degrees, greater than about 10 degrees, greater than about 15 degrees, greater than about 20 degrees, greater than about 25 degrees, greater than about 30 degrees, greater than about 35 degrees, greater than about 40 degrees, greater than about 45 degrees, or greater than about 50 degrees.

[0010] In some embodiments, for substantially normally incident light having a first visible wavelength within the visible wavelength range extending from about 420 nm to about 680 nm (e.g., 550 nm), the at least one frequency-selective reflecting structure has an optical transmittance of greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80%.

[0011] In some embodiments, the underlying metal layer is physically and electrically continuous across the integrated optical structure, and for substantially normally incident light having the first visible wavelength, the underlying metal layer may have an optical transmittance of less than about 20%, or less than about 15%, or less than about 10%, or less than about 5%, or less than about 1%, or less than about 0.5%.

[0012] In some embodiments, the underlying metal layer may be a metal mesh layer, the mesh including a plurality of metal traces connected to form a plurality of closed open areas, and the underlying metal layer may have an optical transmittance for substantially normally incident light having the first visible wavelength of greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80%.

[0013] In some embodiments, the integrated optical structure may have an optical transmittance of greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80% for substantially normally incident light having the first visible wavelength. In some embodiments, the decorative cover layer may have an optical transmittance of greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80% for substantially normally incident light having the first visible wavelength.

[0014] In some embodiments, any specular reflectance of substantially collimated incident RF electromagnetic radiation by the integrated optical structure can be less than about 90%, or less than about 80%, or less than about 70%, or less than about 60%, or less than about 50%, or less than about 40%, or less than about 30%, or less than about 20%, or less than about 15%, or less than about 10%, or less than about 8%, or less than about 6%, or less than about 4%, or less than about 2%, or less than about 1%, or less than about 0.5%, or less than about 0.1%. In some embodiments, the reflectivity of any substantially collimated incident RF electromagnetic wave by the integrated optical structure in a direction other than the direction of the substantially collimated reflected wave can be less than about 20%, or less than about 15%, or less than about 10%, or less than about 8%, or less than about 6%, or less than about 4%, or less than about 2%, or less than about 1%, or less than about 0.5%, or less than about 0.1%.

[0015] In some embodiments, at least the image displayed by the decorative cover layer may include one or more of blue, black, white, green, yellow, brown, red, and any other color at least partially visible to a viewer. In some embodiments, at least the image displayed by the decorative cover layer may include one or more of an image of an object, a solid color, a pattern, a landscape, a person, or an animal. In some embodiments, at least the image displayed by the decorative cover layer may include at least one of a logo, a map, a sign, or a symbol. In some embodiments, at least the information displayed by the decorative cover layer may include one or more of letters, words, and numbers.

[0016] In some embodiments, the at least one frequency-selective reflecting structure may include at least two frequency-selective reflecting structures. In some such embodiments, the metallic elements in the at least two frequency-selective reflecting structures are aligned with one another in a one-to-one correspondence. In some such embodiments, the metallic elements of the aligned metallic elements in the at least two frequency-selective reflecting structures are aligned with one another in a one-to-one correspondence.

[0017] In some embodiments, the metal elements of the group of metal elements form a regular array of metal elements. In some embodiments, the array of the group of metal elements is a regular array. In some embodiments, the regular array may be defined to include a regular (e.g., periodic) repetition of "unit cells," and the arrangement of the metal elements within the unit cells may themselves be irregular, random, aperiodic, or a combination thereof. In some embodiments, the arrangement of the metal elements within the unit cells may be linear or nonlinear (e.g., circular, elliptical, paraboloidal, or other nonlinear arrangement).

[0018] In some embodiments, the integrated optical structure can be configured to be attached to a support surface with the decorative cover layer facing away from the support surface. In some such embodiments, the support surface can be an exterior surface of a rigid support. In some such embodiments, the rigid support can be a wall, door, window, or other surface of a building. In some such embodiments, the wall can be a ceiling wall, floor wall, or side wall.

[0019] In some embodiments, the structure may include any of the integrated optical structures described herein attached to a rigid support with the decorative cover layer facing away from the rigid support. For example, in some embodiments, the rigid support may be a building wall (including a ceiling, floor, or sidewall), a door, or a window. In some embodiments, the integrated optical structure may be attached to the rigid support via an adhesive layer. In some such embodiments, the adhesive layer is a removable adhesive layer, such that the integrated optical structure and adhesive layer can be removed from the rigid support with little or no damage to the rigid support. In some such embodiments, the adhesive layer is a repositionable adhesive layer, such that after applying the repositionable adhesive layer to a first location on the rigid support, the repositionable adhesive layer can be moved to a different second location on the rigid support with little or no damage to the rigid support and the repositionable adhesive layer. In some such embodiments, applying pressure to the repositionable adhesive layer at the second location forms a substantially permanent bond between the integrated optical structure and the rigid support.

[0020] In some embodiments, the metal elements of the group of metal elements may comprise one or more of gold, silver, copper, aluminum, and titanium. In some embodiments, the shape of at least one metal element of the group of metal elements may be a disk, a cube, a rectangular parallelepiped, or a rectangular prism. In some embodiments, at least one metal element of the group of metal elements may be annular. In some such embodiments, the annular shape may be circular, elliptical, polygonal, curved, segmented linear, segmented curved, or other suitable shape. In some such embodiments, the average thickness of the annular wall may be between about 10 microns and about 2.5 cm. In some embodiments, the metal elements of the group of metal elements may have a thickness (e.g., in the z-axis of the integrated optical structure) ranging from about 10 nm to about 1 mm. In some embodiments, the metal elements of the group of metal elements may have a maximum lateral dimension (e.g., in the x-y plane of the integrated optical structure) ranging from about 10 nm to about 5 cm. In some embodiments, at least one metal element of the group of metal elements may be at least partially pressed into an adjacent layer such that the at least one metal element is at least partially embedded in the adjacent layer. In some such embodiments, the adjacent layer may be one of the first dielectric layers of a plurality of different alternating first dielectric layers and second adhesive layers.

[0021] In some embodiments, the second adhesive layer of the plurality of alternating different first dielectric layers and second adhesive layers may comprise one or more of a natural or synthetic rubber-based pressure-sensitive adhesive, an acrylic-based pressure-sensitive adhesive, a vinyl alkyl ether-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, a polyamide-based pressure-sensitive adhesive, a polyalphaolefin-based pressure-sensitive adhesive, a polyurethane-based pressure-sensitive adhesive, or a styrene-based block copolymer-based pressure-sensitive adhesive. In some embodiments, the second adhesive layer of the plurality of alternating different first dielectric layers and second adhesive layers may comprise one or more of an organic solvent-based adhesive, a water-based emulsion adhesive, a hot melt adhesive, and a radiation-curable adhesive. In some embodiments, the first dielectric layer may comprise one or more of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic-based polymers, butyric acid-based polymers, polycarbonate, polycarbonate copolymers, polyurethane, polyvinyl chloride (PVC), polyimide (PI), polyethersulfone, polyethylene, polypropylene, polylactic acid, fluoro-based polymers, copolymerized PET, polyvinylidene fluoride-based polymers, terpolymer-based polymers, tetrafluoroethylene-based polymers, hexafluoropropylene-based polymers, and vinylidene fluoride-based polymers.

[0022] In some embodiments, the decorative cover layer may include a plurality of conductive particles dispersed therein. In some such embodiments, the conductive particles may include one or more of aluminum, iron, nickel, silver, silica, silicates, alumina, glass, calcium carbonate, titanium dioxide, zinc oxide, copper oxide, and barium titanate. In some such embodiments, the conductive particles may have an average size of less than about 10% of the free-space wavelength.

[0023] According to some aspects of the present disclosure, a wireless system may include first and second spaced-apart transceivers and any embodiment of the integrated optical structure described herein. In some such embodiments, the spaced-apart first and second transceivers may be configured to at least one of transmit and receive RF electromagnetic waves having a free-space wavelength. In some such embodiments, the integrated optical structure may be configured to receive RF electromagnetic waves transmitted by one of the first and second transceivers and reflect at least a portion of the received RF electromagnetic waves toward the other of the first and second transceivers. In some such embodiments, an incident angle a1 of the received RF electromagnetic waves and a reflection angle a2 of the reflected RF electromagnetic waves may differ by at least about 5 degrees, or at least about 10 degrees, or at least about 15 degrees, or at least about 20 degrees, or at least about 25 degrees, or at least about 30 degrees, or at least about 35 degrees, or at least about 40 degrees, or at least about 45 degrees, or at least about 50 degrees. In some such embodiments, at least one of the first and second transceivers may include one or more of a signal transmission tower, a signal reception tower, a mobile communication device, a repeater, and an antenna.

[0024] In some embodiments, the integrated optical structure may include at least one flame-retardant material. In some such embodiments, the flame-retardant material may include at least one of ammonium polyphosphate, antimony trioxide, zinc boride, aluminum hydroxide, calcium carbonate, magnesium hydroxide, and polybrominated diphenyl ether. In some such embodiments, at least one of the decorative cover layers, at least one of the first dielectric layers, and at least one of the second adhesive layers may include at least a portion of the flame-retardant material.

[0025] In some embodiments, the underlying metal layer may be configured to primarily reflect RF electromagnetic radiation transmitted by the decorative cover layer and the at least one frequency-selective reflecting structure. In some such embodiments, the underlying metal layer may be configured to reflect at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95% of the RF electromagnetic radiation transmitted by the decorative cover layer and the at least one frequency-selective reflecting structure.

[0026] In some embodiments, the base metal layer may be configured to absorb up to 10%, or up to 8%, or up to 6%, or up to 4%, or up to 2%, or up to 1%, or up to 0.5% of the RF electromagnetic radiation transmitted by the decorative cover layer and the at least one frequency selective reflecting structure.

[0027] In some embodiments, the base metal layer may be configured to transmit up to 10%, or up to 8%, or up to 6%, or up to 4%, or up to 2%, or up to 1%, or up to 0.5% of the RF electromagnetic radiation transmitted by the decorative cover layer and the at least one frequency selective reflecting structure.

[0028] In some embodiments, the integrated optical structure may be configured to reflect at least 20%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95% of the substantially collimated incident RF electromagnetic radiation as a substantially collimated reflected wave. In some embodiments, the integrated optical structure may be configured to absorb up to 10%, or up to 8%, or up to 6%, or up to 4%, or up to 2%, or up to 1%, or up to 0.5% of the substantially collimated incident RF electromagnetic radiation. In some embodiments, the integrated optical structure may be configured to transmit up to 10%, or up to 8%, or up to 6%, or up to 4%, or up to 2%, or up to 1%, or up to 0.5% of the substantially collimated incident RF electromagnetic radiation.

[0029] According to some aspects of the present disclosure, an integrated optical structure configured to be mounted to a support (e.g., a sidewall, a ceiling, a floor, etc.) and covered with a decorative cover layer includes a multi-layer stack disposed between a frequency selective surface (FSS) layer and a wave reflecting layer. In some embodiments, the cover layer may be configured to display at least one of an image and information to a viewer. In some embodiments, the FSS layer may be configured to face the decorative cover layer, and the wave reflecting layer may be configured to face the support.

[0030] In some embodiments, the FSS layer may include a plurality of discrete, spaced apart, electrically isolated, conductive elements arranged along the width (e.g., x-axis) and length (e.g., y-axis) of the FSS layer. In some embodiments, the multilayer stack may include at least two non-adhesive dielectric layers bonded together by at least one adhesive layer.

[0031] In some embodiments, the integrated optical structure can be configured to reflect, through either constructive or destructive interference, substantially collimated incident RF electromagnetic waves, having a free-space wavelength in the range of about 1.0 mm to about 300.0 cm and incident at an incident angle q1, as substantially collimated reflected waves at a reflection angle q2 different from the incident angle. In some such embodiments, when the integrated optical structure is mounted on a support and covered with a decorative cover layer such that the FSS layer faces the decorative cover layer and the wave-absorbing layer faces the support, the wave-reflecting layer can be configured to substantially reflect RF electromagnetic waves transmitted by the decorative cover layer, the FSS layer, and the multilayer stack. In some embodiments, the integrated optical structure can be configured to reflect at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95% of the substantially collimated incident RF electromagnetic waves as substantially collimated reflected waves.

[0032] In some embodiments, the conductive elements may be regularly arranged along at least one of the width and length of the FSS layer. In some embodiments, the conductive elements may be metal elements. In some embodiments, the conductive elements may include one or more of indium tin oxide, zinc oxide, and a conductive polymer.

[0033] Turning to the drawings, FIG. 1 is a side view of a structure including one embodiment of an integrated optical structure according to the present disclosure. In some embodiments, structure 400 may include integrated optical structure 300 attached to rigid support 110. In some embodiments, the rigid support may be a wall (e.g., a ceiling wall, floor wall, or side wall) of a building, a door, or a window. In some embodiments, integrated optical structure 300 may be attached to support surface 111 of rigid support 110 via adhesive layer 130.

[0034] In some embodiments, the integrated optical structure 300 can include at least one, or at least two, or at least three, or at least five, or at least ten frequency-selective reflecting structures 200 disposed between the decorative cover layer 10 and the underlying metal layer 20. In some embodiments, the decorative cover layer 10 can be configured to display at least one of an image and information to a viewer 30 (see, e.g., FIGS. 6A-6M). In some embodiments, the underlying metal layer can be configured to substantially at least one of reflect and absorb radio frequency (RF) electromagnetic waves 40 transmitted (i.e., allowed to pass) by the decorative cover layer 10 and the at least one frequency-selective reflecting structure 200.

[0035] In some embodiments, each of the frequency selective reflecting structures 200 may include a frequency selective surface (FSS) layer 50 disposed on the multilayer stack 60. In some embodiments, the FSS layer 50 may include metal elements 71 that are repeated across the FSS layer 50 (e.g., in the xy plane defined in FIG. 1) to form an array of metal elements 71. Additional details regarding the arrangement of the metal elements are shown in FIGS. 2A and 2B.

[0036] In some embodiments, the multilayer stack 60 may include a plurality of alternating different first dielectric layers 90 and second adhesive layers 100. In some embodiments, each of the integrated optical structures 300 may be configured to reflect a substantially collimated incident RF electromagnetic wave having a free-space wavelength as a substantially collimated reflected wave at a reflection angle different from the angle of incidence through either constructive or destructive interference. In some embodiments, the at least one frequency-selective reflecting structure 200 may have an optical transmittance of greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80% for substantially normally incident light having a first visible wavelength within a visible wavelength range spanning from about 420 nm to about 680 nm (e.g., 550 nm).

[0037] In some embodiments, the integrated optical structure 300 may have a light transmittance of greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80% for substantially normally incident light 45 having the first visible wavelength. In some embodiments, the decorative cover layer may have a light transmittance of greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80% for substantially normally incident light 45 having the first visible wavelength.

[0038] 2A and 2B provide additional details regarding the embodiment of the frequency-selective reflecting structure 200 of FIG. 1, and may share the same numbered elements as FIG. 1, which are assumed to have the same function unless otherwise noted herein. FIG. 2A is a side schematic view of the frequency-selective reflecting structure 200, and FIG. 2B provides a top view showing one possible arrangement of the group 70 of metallic elements 71. In this embodiment, as shown in FIG. 2B, the metallic elements 71 are shown to have a circular annular shape. In some such embodiments, the average thickness of the annular wall 71w may be between about 10 microns and about 2.5 cm.

[0039] Figure 3 provides an additional side view of an embodiment of an integrated optical structure, such as the integrated optical structure 300 of Figure 1. As described elsewhere herein, in some embodiments, the integrated optical structure 300 may include at least two frequency-selective reflecting structures 200, for example, 200a, 200b, and 200c as shown in Figure 3. Each of the frequency-selective reflecting structures 200 includes a group 70 of metal elements 71, and the groups 70 of metal elements 71 in each of the frequency-selective reflecting structures 200 are aligned with one another in a one-to-one correspondence. For example, metal element 71a of metal element group 70a1 of frequency-selective reflecting structure 200a is aligned with metal element 71b of metal element group 70b1 of frequency-selective reflecting structure 200b and with metal element 71c of metal element group 70c1 of frequency-selective reflecting structure 200c in a one-to-one correspondence. A similar one-to-one correspondence may also apply to metal element groups 70a2, 70b2, 70c2 and metal element groups 70a3, 70b3, 70c3.

[0040] 4A-4C are provided primarily for discussion purposes and to define the angles of incidence of light rays incident on the optical structure. For example, FIG. 4A illustrates how a substantially collimated incident RF electromagnetic wave 41 having a free-space wavelength ranging from about 1.0 mm to about 40 cm, or to about 20 cm, or to about 10 cm, is incident on integrated optical structure 300 at an incident angle θ1 and is reflected as a substantially collimated reflected wave 42 at a reflection angle θ2 that is different from the incident angle θ1.

[0041] FIG. 4B shows that substantially normally incident light 43 (having a first visible wavelength within the visible wavelength range extending from about 420 nm to about 680 nm, as described elsewhere herein) is incident on the frequency selective reflecting structure 200a, which has a light transmittance of greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80%.

[0042] FIG. 4C illustrates substantially normally incident light 44 having a first visible wavelength incident on a physically and electrically continuous underlying metal layer 20, where the light 44 has an optical transmittance of less than about 20%, or less than about 15%, or less than about 10%, or less than about 5%, or less than about 1%, or less than about 0.5% (i.e., in some embodiments, the light 44 is substantially reflected by the underlying metal layer 20).

[0043] 5 is a top view of an embodiment of an underlying metal layer including a metal mesh layer. In this embodiment, the underlying metal layer (such as underlying metal layer 20 of FIG. 1) can be a metal mesh layer 20a having a plurality of metal traces 21 connected to form a plurality of closed open areas 22. In such mesh layer embodiments, the underlying metal layer 20a can have a light transmittance of greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80% for substantially normally incident light 44 having a first visible wavelength (see FIG. 4C).

[0044] 6A-6M provide additional details regarding various types of images and information that may be displayed on a decorative cover layer, such as decorative cover layer 10 of FIG. 1. The image displayed on decorative cover layer 10 (see FIG. 1) may be a single color (10a in FIG. 6A) or may include one or more of blue, black, white, green, yellow, brown, red, and any other color that is at least partially visible to a viewer. In some embodiments, the image displayed on decorative cover layer 10 may include one or more of an animal (10b in FIG. 6B), an object (10c in FIG. 6C), a pattern (10d in FIG. 6D), a landscape (10e in FIG. 6E), a person (10f in FIG. 6F), a logo (10g in FIG. 6G), a map (10h in FIG. 6H), a sign (10i in FIG. 6I), or a symbol (10j in FIG. 6J). In some embodiments, the information provided on decorative cover layer 10 may include one or more of letters (10k in FIG. 6K), words (10l in FIG. 6L), and numbers (10m in FIG. 6M). In some embodiments, decorative cover layer 10 may include any suitable combination of images and information.

[0045] FIG. 7 is a perspective view of an operational use of an embodiment of an integrated optical structure described herein. FIG. 7 shows the interior of a building 120. In operational use, the integrated optical structure 300 of FIG. 1 can be attached to a support surface 111 (e.g., an exterior surface) of a rigid support 110 (FIG. 1). For example, in some embodiments, the integrated optical structure 300a can be attached to a window 110c, the integrated optical structure 300b can be attached to a door 110b, and the integrated optical structure 300c can be attached to a wall 110a. In some embodiments, the wall 110a can include a ceiling (i.e., a ceiling wall) 110a2, a floor (i.e., a floor wall) 110a1, or a side wall 110a. In some embodiments, the integrated optical structure 300 is disposed between the support surface 111 and a decorative cover layer 10, with the decorative cover layer 10 facing away from the support surface 111 toward the interior of the building 120.

[0046] 8A-8J define additional shapes and formats of metal elements 71 of the integrated optical structure of FIG. 1. As discussed elsewhere herein, in some embodiments, at least one metal element 71 of metal element group 70 can be annular (i.e., a ring-shaped body, structure, or region). In some such embodiments, the annulus can be circular (72a in FIG. 8A). In some such embodiments, the annulus can be elliptical (72b in FIG. 8B). In some such embodiments, the annulus can be polygonal (72c in FIG. 8C). In some such embodiments, the annulus can be curvilinear (72d in FIG. 8D). In some such embodiments, the annulus can be segmented linear (72e in FIG. 8E). In some such embodiments, the annulus can be segmented curvilinear (72f in FIG. 8F). In some embodiments, the shape of at least one metal element 71 can be a disk (73a in FIG. 8G), a cube (73b in FIG. 8H), a rectangular parallelepiped (73c in FIG. 8I), or a rectangular prism (73d in FIG. 8J).

[0047] 9 is a side view illustrating how one or more metal elements 71 of integrated optical structure 300 (FIG. 1) may be partially embedded in adjacent layers. For example, as shown in FIG. 9, metal element 71d may be at least partially embedded (partially pressed into) adjacent dielectric layer 90a.

[0048] 10 includes a side view of another embodiment of an integrated optical structure including a multi-layer stack. Structure 400a includes an integrated optical structure 300d disposed between a decorative cover layer 10 and a support 110. In some embodiments, the integrated optical structure 300d may be attached to the support surface 111 of the support 110, with the decorative cover layer facing away from the support surface 111.

[0049] In some embodiments, the integrated optical structure 300d may include a multilayer stack 60a disposed between a frequency selective surface (FSS) layer 50 configured to face the decorative cover layer 10 and a wave reflecting layer 20 configured to face the support 110. In some embodiments, the FSS layer may include a plurality of discrete, spaced-apart, electrically isolated conductive elements 71 disposed along the width (e.g., the x-axis as defined in FIG. 10 ) and length (e.g., the y-axis in FIG. 10 ) of the FSS layer 50. In some embodiments, the conductive elements 71 may be regularly disposed along at least one of the width and length of the FSS layer 50. In some embodiments, the conductive elements 71 may include one or more of indium tin oxide, zinc oxide, and a conductive polymer.

[0050] In some embodiments, the multilayer stack 60a may include at least two non-adhesive dielectric layers 90b, 90c bonded to one another by at least one adhesive layer 100. In some embodiments, the integrated optical structure 300d may be configured to reflect substantially collimated incident RF electromagnetic waves having a free-space wavelength in the range of about 1.0 mm to about 300.0 cm and incident at an incident angle as substantially collimated reflected waves at a reflection angle different from the incident angle, through either constructive or destructive interference. In some embodiments, when the integrated optical structure 300d is attached to a support 110 and covered with a decorative cover layer 10 such that the FSS layer 50 faces the decorative cover layer 10 and the wave-reflecting layer 20 faces the support, the wave-reflecting layer 20 may be configured to substantially reflect RF electromagnetic waves transmitted through the decorative cover layer, the FSS layer, and the multilayer stack. In some embodiments, the integrated optical structure 300d may be configured to reflect at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95% of the substantially collimated incident RF electromagnetic radiation as substantially collimated reflected radiation.

[0051] In some embodiments, the integrated optical structure 300d may be attached to the support surface 111 of the rigid support 110 via an adhesive layer 130.

[0052] Finally, FIG. 11 is a top view of one embodiment of a wireless system according to the present disclosure. In some embodiments, the wireless system 500 may include a first transceiver 510 and a second transceiver 511 spaced apart and any embodiment of an integrated optical structure described herein, such as the integrated optical structure 300 of FIG. 1. In some embodiments, the first transceiver 510 and the second transceiver 511 may each be configured to at least one of transmit and receive RF electromagnetic waves 520, 522 having a free-space wavelength. In some embodiments, the integrated optical structure 300 may be configured to receive the RF electromagnetic waves 520, 522 transmitted by either the first transceiver 510 or the second transceiver 511 and reflect at least a portion of the received RF electromagnetic waves 520, 522 back to the other of the first transceiver 510 and the second transceiver 511. In some embodiments, the angle of incidence α1 of the received RF electromagnetic wave (e.g., wave 520) and the angle of reflection α2 of the reflected RF electromagnetic wave (e.g., wave 522) may differ by at least about 5 degrees, or at least about 10 degrees, or at least about 15 degrees, or at least about 20 degrees, or at least about 25 degrees, or at least about 30 degrees, or at least about 35 degrees, or at least about 40 degrees, or at least about 45 degrees, or at least about 50 degrees. In some embodiments, at least one of the first transceiver 510 and the second transceiver 511 may include one or more of the signal transmissions.

[0053] The term "about" shall be understood by those of ordinary skill in the art in the context in which it is used. In the context used and described herein, if the use of "about" as applied to a quantity expressing the size, amount, and physical properties of a feature is not clear to a person of ordinary skill in the art, "about" shall be understood to mean within 10% of the specified value. A quantity given as "about" may be the exact specified value. For example, in the context used and described herein, if it is not clear to a person of ordinary skill in the art, a quantity having a value of "about 1" means that the quantity has a value between 0.9 and 1.1, and may be 1.

[0054] The term "substantially" shall be understood by those skilled in the art in the context in which it is used. In the contexts used and described herein, if the use of "substantially equal" is not clear to those skilled in the art, "substantially equal" shall mean "about equal" as described above. In the contexts used and described herein, if the use of "substantially parallel" is not clear to those skilled in the art, "substantially parallel" shall mean within 30 degrees of parallel. Directions or surfaces described as being substantially parallel to each other may, in some embodiments, be within 20 degrees or within 10 degrees of parallel, or may be parallel or nominally parallel. In the contexts used and described herein, if the use of "substantially aligned" is not clear to those skilled in the art, "substantially aligned" shall mean aligned within 20% of the width of the objects being aligned. In some embodiments, objects described as being substantially aligned may be aligned within 10% or within 5% of the width of the objects being aligned.

[0055] The foregoing references, patents, and patent applications are incorporated herein by reference in their entirety and are incorporated in a consistent manner. In the event of any inconsistency or conflict between any portion of the incorporated references and this application, the information in the above description shall control.

[0056] Descriptions of elements in a figure should be understood to apply equally to corresponding elements in other figures, unless otherwise indicated. While specific embodiments have been shown and described herein, it will be understood by those skilled in the art that various alternative and / or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover adaptations or variations of the specific embodiments discussed herein. Accordingly, it is intended that the present disclosure be limited only by the claims and equivalents thereof. [Example]

[0057] Unless otherwise stated or apparent from the context, all parts, percentages, ratios, etc. in the examples and elsewhere in the specification are by weight.

[0058] Abbreviations used in this section are as follows: nm = nanometer, μm = micrometer, mm = millimeter, cm = centimeter, m = meter, ft = feet, in = inch, mil = thousandths of an inch, min = minute, °C = degrees Celsius, °F = degrees Fahrenheit, GHz = gigahertz, dB = decibel, Dk = dielectric constant, Df = dielectric loss tangent, BCM = billion cubic micrometers. Material abbreviations and material descriptions used in this section are provided in Table 1.

[0059] [Table 1] <Characteristics evaluation> The beam steering performance of the integrated optical structures (including the substrate, dielectric, frequency-selective surface, and attached decorative film, if used on the samples) in Examples EX-1 through EX-19 and Comparative Examples CE-1 through CE-3 was evaluated using a custom-built arc setup. The arc consisted of a semicircle with a radius of 0.8 m. Transmitter and receiver horn antennas were independently positioned at various angles along the arc to record the reflected beam intensity as a function of frequency. The transmitter and receiver horns were ERAVANT WR-28 standard gain horn antennas. They were connected to two ports of a vector network analyzer (Agilent Technologies E8364C).

[0060] The dielectric properties of the films in Table 1 were measured using a custom-made 24.7 GHz split-post dielectric resonator (SPDR) connected to a Keysight N5290A vector network analyzer (VNA) conforming to the IEC 61189-2-721 standard. The VNA's input and output ports were connected via coaxial cables to input and output loop probes coupled to two cylindrical dielectric posts spaced 0.4 mm apart within a conductive cylindrical cavity. The cavity's resonant frequency and Q-factor were measured both with and without the sample film, and numerical simulations were used to calculate the sample's permittivity (Dk) and dielectric loss tangent (Df). "Effective" in this case refers to a single Dk and Df value, even for multilayered films. This approach is justified when the film sample layer thickness is much smaller than the electromagnetic wavelength, which is true for the 24.7 GHz example presented. The lateral dimensions of the samples were 20 mm x 40 mm, and the average thickness was calculated from micrometer measurements across the electromagnetically active region of each sample.

[0061] For FILM R, the dielectric properties were measured before sputter-coating one side with Al. <Sample / Example> In Sample 1, the frequency selective surface was prepared on the side not coated with aluminum by Patterning Method A, described below. In Sample 2, the frequency selective surface was prepared by Patterning Method B, described below, using FILM P as the substrate. In Sample 3, the frequency selective surface was prepared by Patterning Method C, described below, and the substrate was prepared by laminating 24 μm thick aluminum foil, trade name 3540 ULTRA-CLEAN SUPREMIUM ALUMINUM FOIL, available from Traceable Products (Webster, TX), to the frequency selective surface with a hot roll laminator using 20 μm of PSA adhesive.

[0062] In Samples 1 and 2, the metaelements were circular or square, as shown in Table 2b. In Sample 3, the metaelement type was circular annular. The dimensions and spacing of the metaelements are listed in Table 2b for Samples 1 through 3. In all samples, the metaelements were arranged in a square lattice, and the lattice period shown in Table 2b indicates the center-to-center spacing between elements in the x and y directions.

[0063] For Samples 2 and 3, a frequency selective surface was prepared and laminated to the underlying metal layer as shown in Table 2a. The layers for Samples 2 and 3 were laminated using a PSA. <Patterning method A: Flexographic printing> A pattern of the desired metasurface antenna design was flexographically printed on the uncoated surface of Film R using water-based nanosilver ink (Novacentrix PFI-722 Conductive Silver Ink). The coated surface of Film R contained a 90-110 nm thick vacuum-coated conductive aluminum layer. The water-based nanosilver ink was applied at a rate of 2.5 BCM / in to prepare the metasurface antenna pattern shown in Table 2b. 2 (0.3875BCM / cm 2The ink was printed at a speed of 20 ft / min (6.1 m / min) using a 0.067 in (0.17 cm) thick anilox roll and a 0.067 in (0.17 cm) thick flexographic polymer printing plate (MacDermid LUX ITP60 Photopolymer plate) with a wet film thickness target of 0.25-1.0 μm. The printed substrate was then passed through an IR oven followed by an air impingement oven set at 280°F (138°C) to solidify the ink and sinter the silver nanoparticles. <Patterning Method B: Demetallization of Printed Patterns> A negative pattern of the metasurface antenna design shown in Table 2b was printed on polyester film using a gravure press with water-soluble ink. The printed surface was coated with a continuous layer of aluminum using a vapor deposition process. The vapor-deposited surface was then washed with water to remove the water-soluble printed pattern and aluminum in those areas, leaving the metasurface antenna pattern. The side of the film that had been demetallized with the pattern was coated with a corrosion protection layer. <Patterning Method C: Photolithography and Etching> The film substrate was prepared by sputter coating a tie layer and a copper seed layer onto optical-grade, heat-stabilized PET film. The patterned resonator structures shown in Table 2b were prepared by electrolytically plating the sputtered / seeded film substrate with 5 microns of copper. The exposed copper was vacuum-laminated with a layer of photoresist. The photoresist was exposed by laser direct imaging, and the unexposed areas were developed. The patterned photoresist served as a mask in a copper etching step using cupric chloride etchant, followed by an electroless tin finish plating.

[0064] [Table 2]

[0065] [Table 3] In Examples EX-1 to EX-19, integrated optical structures were prepared by laminating the decorative cover layers shown in Table 3 onto the frequency-selective surfaces of Samples 1 to 3. The characterization results for Examples EX-1 to EX-19 and Comparative Examples CE-1 to CE-3 are shown in Table 4.

[0066] [Table 4]

[0067] [Table 5]

Claims

1. An integrated optical structure, comprising at least one frequency-selective reflective structure disposed between a decorative cover layer and an underlying metal layer, the decorative cover layer configured to display at least one of an image and information to a viewer, the underlying metal layer configured to substantially at least one of reflect and absorb radio frequency (RF) electromagnetic waves transmitted by the decorative cover layer and the at least one frequency-selective reflective structure, each of the at least one frequency-selective reflective structure comprising: a frequency selective surface layer disposed on the multilayer stack, the frequency selective surface layer having metal elements repeated across the frequency selective surface layer to form the array of metal elements, the multilayer stack having a plurality of different alternating first dielectric layers and second adhesive layers; the integrated optical structure reflects, by either constructive or destructive interference, a substantially collimated incident RF electromagnetic wave having a free-space wavelength in a range of about 1.0 mm to about 10 cm and incident at an incident angle, as a substantially collimated reflected wave at a reflection angle different from the incident angle; the at least one frequency-selective reflecting structure has an optical transmittance of greater than about 50% for substantially normally incident light having a first visible wavelength within a visible wavelength range extending from about 420 nm to about 680 nm; Integrated optical structure.

2. 2. The integrated optical structure of claim 1, wherein the underlying metal layer is physically and electrically continuous throughout the integrated optical structure, and wherein the underlying metal layer has an optical transmittance of less than about 20% for substantially normally incident light having the first visible wavelength.

3. 10. The integrated optical structure of claim 1, having an optical transmission of greater than about 50% for substantially normally incident light having the first visible wavelength.

4. The integrated optical structure of claim 1 , wherein the decorative cover layer has a light transmittance of greater than about 50% for substantially normally incident light having the first visible wavelength.

5. 2. The integrated optical structure of claim 1, wherein the underlying metal layer is a metal mesh layer, the mesh including a plurality of metal traces connected to form a plurality of closed open areas, and the underlying metal layer has an optical transmittance of greater than about 50% for substantially normally incident light having the first visible wavelength.

6. 10. The integrated optical structure of claim 1, wherein the image displayed by the decorative cover layer includes at least one of blue, black, white, green, yellow, brown, red, and other colors that are at least partially visible to a viewer.

7. The integrated optical structure of claim 1 , wherein the image displayed by the decorative cover layer includes at least one of an image of an object, a solid color, a pattern, a landscape, a person, or an animal.

8. The integrated optical structure of claim 1 , wherein at least the image displayed by the decorative cover layer includes at least one of a logo, a map, a sign, and a symbol.

9. The integrated optical structure of claim 1 , wherein at least the information displayed by the decorative cover layer includes one or more of letters, words, and numbers.

10. The integrated optical structure of claim 1 , wherein the at least one frequency-selective reflecting structure comprises at least two frequency-selective reflecting structures.

11. 11. The integrated optical structure of claim 10, wherein the metallic elements in the at least two frequency selective reflecting structures are aligned with one another in one-to-one correspondence.

12. 12. The integrated optical structure of claim 11, wherein the metallic elements of the aligned metallic element groups in the at least two frequency selective reflecting structures are aligned with one another in one-to-one correspondence.

13. The integrated optical structure of claim 1 , wherein the metal elements of the group of metal elements form a regular array of metal elements.

14. The integrated optical structure of claim 1 , wherein the array of metallic elements is a regular array.

15. The integrated optical structure of claim 1 configured for attachment to a support surface with the decorative cover layer facing away from the support surface.

16. 16. The integrated optical structure of claim 15, wherein the support surface is an outer surface of a rigid support.

17. 17. The integrated optical structure of claim 16, wherein the rigid support is a wall, door, or window of a building.

18. 18. The integrated optical structure of claim 17, wherein the wall is one of a ceiling wall, a floor wall, or a side wall.

19. A structure comprising the integrated optical structure of claim 1 , wherein the integrated optical structure is attached to a rigid support and the decorative cover layer faces away from the rigid support.

20. 20. The structure of claim 19, wherein the rigid support is a wall, door, or window of a building.

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