Electromagnetic wave control device

Abstract

The electromagnetic wave control device includes an upper electrode layer, a lower electrode layer, a liquid crystal layer disposed between the upper electrode layer and the lower electrode layer, and a first metamaterial layer. The first metamaterial layer includes a first array including alignment unit structures. A first surface of the alignment unit structure is a surface of the alignment unit structure and faces away from the liquid crystal layer. The aspect ratio of the first surface of the alignment unit structure is greater than 1. The length of the first surface, the width of the first surface, and the distance between two adjacent alignment unit structures are in the range of 1 nm to 5000 nm. The metamaterial is combined with the liquid crystal material to configure an electromagnetic wave control device having both a liquid crystal alignment function and a phase adjustment control function.

Description

[Technical field]

[0001] This application relates to an electromagnetic wave control device, and in particular to an electromagnetic wave control device using a liquid crystal layer. do. [Background technology]

[0002] Liquid crystal materials are widely used in electromagnetic wave adjustment and control devices. Under the action of an external electric field, liquid crystal molecules are in a certain alignment state due to their anisotropic electric properties. At the same time, liquid crystal molecules exhibit different optical effects due to the anisotropic optical properties of the liquid crystal molecules. These characteristics of liquid crystal molecules can be used to implement flexible adjustment control for electromagnetic waves.

[0003] In the adjustment and control device based on liquid crystal material, the liquid crystal molecules need to be pre-aligned, and then the liquid crystal molecules are adjusted and controlled by applying an external driving voltage to control the electromagnetic wave. In the conventional adjustment control device, a thick liquid crystal layer material is selected to obtain a perfect 2π phase adjustment control. This is disadvantageous to the miniaturization and integration of the device, and results in a large driving voltage required by the device. In addition, in the conventional device, the liquid crystal molecules are aligned by using the conventional friction alignment method, which has the disadvantages of high loss and difficulty in controlling the uniformity of the product. For manufacturing a liquid crystal device with good photoelectric properties, factors such as the result of liquid crystal alignment and the thickness of the liquid crystal layer are important. Therefore, the present application provides a new electromagnetic wave control device to achieve good adjustment control for the electromagnetic wave while achieving alignment for the liquid crystal molecules. Summary of the Invention

[0004] The present application provides an electromagnetic wave control device, in which a metamaterial structure is combined with a liquid crystal material to enable the device to have both liquid crystal alignment capability and phase tuning control capability.

[0005] According to a first aspect, an electromagnetic wave control device is provided. The electromagnetic wave control device includes an upper electrode layer, a lower electrode layer, and a liquid crystal layer and a first metamaterial layer disposed between the upper electrode layer and the lower electrode layer. The first metamaterial layer includes a first array including alignment unit structures, and a first surface of the alignment unit structures has an aspect ratio greater than 1, and the first surface includes the Alignment The alignment unit structures are of a unit structure and have a surface facing away from the liquid crystal layer, and the length of the first surface, the width of the first surface, and the distance between two adjacent alignment unit structures are in the range of 1 nm to 5000 nm.

[0006] Therefore, in the electromagnetic wave control device in this embodiment of the present application, the array includes alignment unit structures each having an aspect ratio greater than 1 and a sub-wavelength size to allow the electromagnetic wave to accumulate a specific phase delay when the liquid crystal molecules are aligned. This improves the phase adjustment control of the reflected or transmitted electromagnetic wave. Correspondingly, the thickness of the liquid crystal layer in the device can be reduced, and the performance of the liquid crystal device can be improved.

[0007] In relation to the first aspect, in some embodiments of the first aspect, the length of the first surface, the width of the first surface, and the spacing are in the range of λ / 1000 to λ, where λ is a wavelength of electromagnetic radiation incident on the first metamaterial layer, and the wavelength of the electromagnetic radiation is in the range of 100 nm to 2000 nm.

[0008] Therefore, for the electromagnetic wave control device in this embodiment of the present application, the size of the alignment unit structure is λ / 1000 with respect to the wavelength λ of the incident electromagnetic wave, so that the incident electromagnetic wave accumulates a specific phase delay and enables phase adjustment control of electromagnetic waves having different wavelengths to be performed.

[0009] In relation to the first aspect, in some embodiments thereof, the aspect ratio of the first surface is 1.5 or greater.

[0010] Therefore, for the electromagnetic wave control device in this embodiment of the present application, the array includes alignment unit structures each having an aspect ratio of 1.5 or more, allowing the liquid crystal molecules to be aligned along the long axis of the alignment unit structures. In this way, the alignment effect on the liquid crystal molecules is better. At the same time, the larger the aspect ratio of the alignment unit structures, the better the alignment effect on the liquid crystal molecules of the device.

[0011] In relation to the first aspect, in some embodiments of the first aspect, the first metamaterial layer is disposed on a lower surface of the liquid crystal layer.

[0012] In relation to the first aspect, in some embodiments of the first aspect, the device further includes a second metamaterial layer disposed on a top surface of the liquid crystal layer, the second metamaterial layer including a second array including alignment unit structures.

[0013] In relation to the first aspect, in some embodiments thereof, an alignment direction of the second array is perpendicular to an alignment direction of the first array.

[0014] Therefore, for the electromagnetic wave control device in this embodiment of the present application, two metamaterial layers with perpendicular alignment directions are disposed on the upper surface of the liquid crystal layer and on the lower surface of the liquid crystal layer, respectively, to enable the polarization direction of the linearly polarized electromagnetic wave to be twisted by about 90° after the linearly polarized electromagnetic wave is transmitted by the device. By utilizing the special optical waveguide characteristics of the liquid crystal molecules in this device, a liquid crystal device with a better extinction ratio can be manufactured.

[0015] In relation to the first aspect, in some embodiments thereof, an alignment direction of the second array is parallel to an alignment direction of the first array.

[0016] In relation to the first aspect, in some embodiments of the first aspect, the device further comprises a polyimide PI friction layer disposed on the top surface of the liquid crystal layer, and an alignment direction of the PI friction layer is perpendicular to an alignment direction of the first array.

[0017] Therefore, for the electromagnetic wave control device in this embodiment of the present application, the metamaterial layer and the PI friction layer are disposed on the upper surface of the liquid crystal layer and the lower surface of the liquid crystal layer, respectively, and the alignment direction of the metamaterial layer to the liquid crystal molecules and the alignment direction of the PI friction layer to the liquid crystal molecules are perpendicular to each other, allowing the polarization direction of the linearly polarized electromagnetic wave to be twisted by about 90° after the linearly polarized electromagnetic wave is transmitted by the device. The special light guiding property of the liquid crystal molecules in the device can be used to manufacture a liquid crystal device with a better extinction ratio.

[0018] In relation to the first aspect, in some embodiments of the first aspect, the device further comprises a third array including alignment unit structures. direction The alignment of the first array direction is perpendicular to

[0019] Therefore, for the electromagnetic wave control device in this embodiment of the present application, two arrays with perpendicular alignment directions can be reused to align liquid crystal molecules in two different directions in the same metamaterial layer. Compared with the traditional friction alignment and photoalignment techniques, the alignment direction of liquid crystal molecules can be flexibly controlled, and the integration of liquid crystal devices can be realized.

[0020] In relation to the first aspect, in some embodiments thereof, the alignment unit structure is a rectangular pillar.

[0021] Therefore, for the electromagnetic wave control device in this embodiment of the present application, the array includes rectangular column unit structures each having an aspect ratio of 1 or more, so that the device is easy to prepare. In addition, the shape of the rectangular column unit structures is regular, so that the liquid crystal molecules are aligned orderly on the surface of the metamaterial layer. This can promote the alignment of the liquid crystal molecules and improve the working efficiency of the device.

[0022] In relation to the first aspect, in some embodiments thereof, the alignment unit structure is a wedge-shaped pillar.

[0023] In relation to the first aspect, in some embodiments of the first aspect, the alignment unit structure is a triangular prism. The first surface is a side surface of the triangular prism. The ratio of the height of the triangular prism to the side length of the base triangle is greater than 1.

[0024] In relation to the first aspect, in some embodiments of the first aspect, the alignment unit structure is an elliptical cylinder. The first surface is a base surface of the elliptical cylinder. A ratio of a major axis of the base surface of the elliptical cylinder to a minor axis of the base surface of the elliptical cylinder is greater than 1.

[0025] In relation to the first aspect, in some embodiments of the first aspect, the alignment unit structure is an ellipsoid. The first surface is a projection surface of the ellipsoid. A ratio of a major axis of the projection surface of the ellipsoid to a minor axis of the projection surface of the ellipsoid is greater than 1.

[0026] Therefore, for the electromagnetic wave control device in this embodiment of the present application, the shape of the alignment unit structure is not limited. The alignment of the liquid crystal molecules can be implemented as long as the aspect ratio of the alignment unit structure on the projection surface is greater than 1, so that the array including the alignment unit structure is easier to prepare.

[0027] In relation to the first aspect, in some embodiments thereof, the material of the alignment unit structures is a metal.

[0028] In relation to the first aspect, in some embodiments thereof, the material of the alignment unit structures is a dielectric material.

[0029] In relation to the first aspect, in some embodiments of the first aspect, the device further comprises a spacer layer, the metamaterial layer being disposed on a surface of the spacer layer.

[0030] Therefore, for the electromagnetic wave control device in this embodiment of the present application, a metamaterial layer is disposed on the surface of the spacer layer to improve the efficiency of the alignment device, so that the alignment device is easier to prepare and the placement and alignment on the liquid crystal molecules can be better performed.

[0031] In relation to the first aspect, in some embodiments of the first aspect, the spatial light modulator is a transmissive spatial light modulator.

[0032] In relation to the first aspect, in some embodiments thereof, the spatial light modulator is a reflective spatial light modulator.

[0033] Therefore, for the device provided in this application, metamaterials are combined with liquid crystal materials to construct an electromagnetic wave control device with both liquid crystal alignment and phase adjustment control capabilities. Based on the above device, alignment on liquid crystal molecules can be implemented by using a simple metamaterial structure. This overcomes the drawbacks of traditional friction alignment, such as large loss and difficult control, and realizes flexible placement and alignment on liquid crystal molecules. In addition, the array includes alignment unit structures, each with a subwavelength size, so that the electromagnetic wave can accumulate a specific phase delay in the transmission process of the electromagnetic wave. This enhances the phase adjustment control of the reflected or transmitted electromagnetic wave. Accordingly, the thickness of the liquid crystal layer in the device can be reduced, the performance of the liquid crystal device can be improved, and the integration degree of the liquid crystal device can be improved. [Brief description of the drawings]

[0034] [Figure 1] FIG. 1 is a schematic diagram of an electromagnetic wave control device applicable to one embodiment of the present application. [Diagram 2] FIG. 2 is a schematic diagram of several alignment unit structures applicable to one embodiment of the present application. [Diagram 3] FIG. 3 is a schematic diagram of an alignment unit structure applicable to one embodiment of the present application. [Figure 4] FIG. 4 is a schematic diagram of an alignment unit structure applicable to one embodiment of the present application. [Diagram 5] FIG. 5 is a schematic diagram of an alignment unit structure applicable to one embodiment of the present application. [Figure 6] FIG. 6 is a schematic diagram of the structure of an electromagnetic wave control device applicable to one embodiment of the present application. [Figure 7] FIG. 7 is a schematic diagram of the structure of an electromagnetic wave control device applicable to one embodiment of the present application. [Figure 8] FIG. 8 is an electron microscope photograph of an alignment unit structure applicable to one embodiment of the present application. [Figure 9] FIG. 9 is a diagram showing the liquid crystal alignment effect of the electromagnetic wave control device under a polarizing microscope, which is applicable to one embodiment of the present application. [Figure 10] FIG. 10 is a schematic diagram of a structure of a transmissive spatial light modulator applicable to one embodiment of the present application. [Figure 11] FIG. 11 is a schematic diagram relating to the electromagnetic wave transmittance of a transmissive spatial light modulator applicable to one embodiment of the present application. [Figure 12] FIG. 12 is a schematic diagram of a phase adjustment control performed by a transmissive spatial light modulator on an electromagnetic wave, applicable to one embodiment of the present application. [Figure 13] FIG. 13 is a schematic diagram showing the structure of a reflective spatial light modulator applied to an embodiment of the present invention. [Figure 14] FIG. 14 is a schematic diagram of a reusable and tunable metasurface structure applicable to one embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] In an embodiment of the present application, a metamaterial structure is combined with a liquid crystal material to perform tuning control on electromagnetic waves. As an artificial microstructure with subwavelength size, the metamaterial structure can assist the liquid crystal material to perform flexible tuning control on electromagnetic waves. At the same time, the liquid crystal device constructed by using metamaterials helps to promote the miniaturization and integration of products. In addition, by using photolithography technology, the metamaterial layer can be integrated on a photonic chip, which facilitates the large-scale manufacturing and processing of the device.

[0036] Specifically, in an embodiment of the present application, nanounit structures with a certain length-width ratio are arranged in order as one metamaterial layer to form a "groove"-shaped alignment layer to perform an alignment function for liquid crystal molecules. In addition, the sequentially aligned nanounit structures exhibit a structure similar to an antenna array, and the metamaterial structure can control the polarization, phase, amplitude and dispersion properties of electromagnetic waves based on the resonance feature of the nanoantenna array. Therefore, for the device provided in this application, the metamaterial is combined with a liquid crystal material to build an electromagnetic wave control device with both liquid crystal alignment ability and phase tuning control ability.

[0037] The following describes the technical solution of the present application with reference to the accompanying drawings. It is clear that the described embodiments are only some, but not all, of the embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0038] FIG. 1 is a schematic diagram of an electromagnetic wave control device 100 applicable to one embodiment of the present application. FIG. 1(a) is a cross-sectional view of the device 100 without a driving voltage. As shown in FIG. 1(a), the device 100 includes a lower electrode layer (including a substrate 101 and an electrode array 102 on a surface of the substrate 101) and an upper electrode layer 107. A liquid crystal layer 105 exists between the upper electrode layer and the lower electrode layer, and includes liquid crystal molecules 106 and a metamaterial layer 104 including a plurality of unit structures. Optionally, the device 100 may further include a spacer layer 103 configured to optimize structural efficiency. The metamaterial layer 104 may be disposed on a surface of the spacer layer 103. Alternatively, the device 100 may not include the spacer layer 103. This is not limited in the present application.

[0039] FIG. 1C shows a top view of the metamaterial layer 104 in FIG. 1A. The metamaterial layer 104 includes an array of well-ordered aligned unit structures. The device 100 is illustrated in FIG. 1 by using rectangular column unit structures as an example. The rectangular column unit structures have a certain aspect ratio, so that the metamaterial layer 104 exhibits a micro-"groove" structure. The liquid crystal molecules can lie down in the micro-"grooves" formed by the rectangular column unit structures. Thus, in the liquid crystal layer 105, the liquid crystal molecules on the surface of the electrodes are aligned with the major axis of the rectangular column unit structures. The upper and lower electrodes layer The liquid crystal molecules between them tend to align in parallel due to the action of van der Waals forces.

[0040] Different voltages are applied between the upper and lower electrode layers, allowing the liquid crystal molecules in the device 100 to rotate in the yz plane. The material of the electrode layers can be indium tin oxide (ITO) or another conductive material, which is not limited in this application.

[0041] FIG. 1B is a cross-sectional view of the device 100 when a driving voltage is applied. FIG. 1D is a top view of the metamaterial layer 104 of FIG. 1B. From FIG. 1B and FIG. 1D, it can be seen that by applying a driving voltage, the liquid crystal molecules rotate on the yz plane perpendicular to the metamaterial layer. When a sufficient voltage is applied, the liquid crystal molecules tend to be aligned parallel to the electric field direction under the attractive force of the electrostatic field, in other words, the long axis direction of the liquid crystal molecules is perpendicular to the xy plane. In this case, the liquid crystal molecules cannot adjust and control the polarization direction of the incident light.

[0042] FIG. 2( a ) is a schematic diagram of several alignment unit structures in a metamaterial layer 104 .

[0043] Specifically, in FIG. 2A, the aspect ratio of the first surface of each aligned unit structure 201 is greater than 1. The first surface is the surface of the unit structure 201, and faces away from the liquid crystal layer. As shown in FIG. 2A, the first surface of the aligned unit structure 201 may be the lower surface of a rectangular pillar. As shown in FIG. 2A, a plurality of rectangular pillar unit structures 201 are regularly aligned. W indicates the width of the rectangular pillar unit structure, and L indicates the length of the rectangular pillar unit structure. In order to enable the metamaterial layer 104 to present a "groove" parallel to the y-axis direction on the xy plane, the aspect ratio L / W of each rectangular pillar unit structure 201 needs to be greater than 1, so that the liquid crystal molecules 202 are aligned in the "groove" direction. In this way, the alignment of the liquid crystal molecules 202 is achieved. The rectangular pillar unit structures 201 need to have a geometric size of sub-wavelength size, which is smaller than the incident wavelength on the surface of the structure. When the aspect ratio L / W of the unit structure is sufficiently large, a strip-shaped rectangular pillar 203 may exist, as shown in FIG. 2(b).

[0044] An array including alignment unit structures each having an aspect ratio of 1 in the x-axis direction has the same period as an array including alignment unit structures each having an aspect ratio of 1 in the y-axis direction. Therefore, isotropic optical properties are exhibited. However, in this embodiment of the present application, the aspect ratio of the alignment unit structures 201 in the metamaterial layer 104 is greater than 1, and the alignment unit structures are not symmetric. Therefore, the array including the alignment unit structures is anisotropic, and performs an alignment function for the liquid crystal molecules. To achieve better alignment results, the aspect ratio of the alignment unit structures 201 may be 1.5 or more. The larger the aspect ratio of the alignment unit structures 201, the better the alignment effect for the liquid crystal molecules.

[0045] Therefore, for the electromagnetic wave control device in this embodiment of the present application, the array includes alignment unit structures each having an aspect ratio greater than 1, allowing the liquid crystal molecules to be aligned in the long axis direction of the alignment unit structures. In this way, the purpose of aligning the liquid crystal molecules is achieved. The device has a simple structure and is easy to prepare, can better control the alignment of the liquid crystal molecules, and can reduce the wear of the alignment layer, and can better implement alignment for the liquid crystal molecules.

[0046] 2(a), the length L of the first surface of the alignment unit structure 201, the width W of the first surface of the alignment unit structure 201, and the interval between two adjacent alignment unit structures 201 are all in the range of 1 nm to 5000 nm. In this case, the electromagnetic wave reflected or transmitted by the metamaterial layer 104 acquires a certain phase delay.

[0047] More specifically, the length L of the first surface, the width W of the first surface, and the interval between two adjacent alignment unit structures 201 are all in the range of λ / 100 to λ, where λ is the wavelength of the electromagnetic wave incident on the device. The wavelength range of the electromagnetic wave can be in the range of 100 nm to 5000 nm. Furthermore, the wavelength range of the electromagnetic wave can be in the range of 100 nm to 2000 nm. It should be understood that for electromagnetic waves of different wavelength ranges, alignment unit structures of different sizes can be selected for the device in this embodiment of the present application. The size of the alignment unit structure needs to be related to the wavelength of the electromagnetic wave that needs to be adjusted and controlled. In addition to the electromagnetic wave in the range of 100 nm to 2000 nm, the device provided in this embodiment of the present application can further be configured to adjust and control electromagnetic waves having another wavelength, for example, terahertz band or radio band. This is not limited in the present application.

[0048] It should be understood that the phase delay acquired by the electromagnetic wave reflected or transmitted by the metamaterial layer 104 may exist in the following cases: Since the array including the alignment unit structures 201 exhibits a structure similar to an antenna array, resonance occurs in the electromagnetic wave incident on the surface of the array. The electromagnetic wave incident on the device is reflected or transmitted by the array including the alignment unit structures to acquire a specific resonant phase. Alternatively, since the alignment unit structures 201 are sub-wavelength sized structures, there is a specific optical path difference between the electromagnetic wave reflected or transmitted by the metamaterial layer 104 and the incident electromagnetic wave, so that the reflected or transmitted electromagnetic wave acquires a transmission phase. Alternatively, since the size of the alignment unit structures 201 in the x-axis direction is different from the size of the alignment unit structures 201 in the y-axis direction, and there is anisotropy in the regulation and control of left-handed or right-handed polarized electromagnetic waves, the incident electromagnetic wave acquires a geometric phase.

[0049] It should be understood that the phase delay acquired by the reflected or transmitted electromagnetic wave is related to factors such as the size of the alignment unit structures 201 and the equivalent refractive index of the liquid crystal layer. Due to the phase delay created in the metamaterial layer 104, the phase accumulated in transmitting the electromagnetic wave by the electromagnetic wave transmitting device 100 can be increased. On the one hand, with the same thickness of liquid crystal material, the phase delay created by the metamaterial layer 104 allows the device 100 to generate deep phase modulation. On the other hand, due to the phase delay accumulated in the metamaterial layer, a thinner liquid crystal material can be used to perform 2π phase modulation on the electromagnetic wave. As the material thickness of the liquid crystal layer decreases, the driving voltage required to tune and control the electromagnetic wave can be reduced. As a result, the heating between the upper and lower electrodes can be reduced, and the crosstalk between adjacent alignment unit structures can be reduced. This reduces the pixel size of the liquid crystal device and improves the resolution of the device.

[0050] Therefore, in the electromagnetic wave control device in this embodiment of the present application, the array includes alignment unit structures each having an aspect ratio greater than 1 and a subwavelength size, allowing the electromagnetic wave to accumulate a specific phase delay based on the alignment in the liquid crystal molecules. This can enhance the adjustment control of the phase of the reflected or transmitted electromagnetic wave. Therefore, the thickness of the liquid crystal layer in the device can be reduced and the performance of the liquid crystal device can be improved.

[0051] It should be understood that in addition to the rectangular pillar unit structure shown in FIG. 2, the alignment unit structure may alternatively be another geometric structure having a specific aspect ratio. In an optional embodiment, the alignment unit structure may be a wedge-shaped pillar 301 shown in FIG. 3(a). The aspect ratio L / W of the first surface of each wedge-shaped pillar 301 should also be greater than 1. The first surface of the wedge-shaped pillar 301 is the surface facing away from the liquid crystal layer. As shown in FIG. 3(a), the first surface may be a side surface of the wedge-shaped pillar 301.

[0052] Alternatively, the alignment unit structure may be a triangular prism 302 as shown in Fig. 3(b). As shown in Fig. 3(b), the first surface of the triangular prism 302 is the surface facing away from the liquid crystal layer. For example, the first surface may be any side surface of the triangular prism 302. The ratio of the height of the triangular prism 302 to the side length of the base triangle of the triangular prism 302 is greater than 1.

[0053] As shown in Fig. 4, the alignment unit structure may alternatively be an elliptical cylinder 401. As shown in Fig. 4, a first surface of the elliptical cylinder 401 is a surface facing away from the liquid crystal layer. For example, the first surface may be a bottom surface of the elliptical cylinder 401. As shown in (b) of Fig. 4, a ratio L / W of the major axis of the bottom surface of the elliptical cylinder 401 to the minor axis of the bottom surface of the elliptical cylinder 401 is greater than 1.

[0054] In addition to some cases shown in FIG. 2 to FIG. 4, the alignment unit structure may alternatively be another structure with an irregular shape. When the aspect ratio of the alignment unit structure on the projection plane of the alignment unit structure is greater than 1, alignment can also be performed on the liquid crystal molecules in the liquid crystal layer. For example, the unit structure in the metamaterial layer 104 may be an ellipsoid 501 shown in FIG. 5. As shown in FIG. 5(b), the first surface of the ellipsoid 501 may be the projection plane of the ellipsoid and on the surface facing away from the liquid crystal layer. The ratio L / W of the major axis of the projection plane of the ellipsoid 501 to the minor axis of the projection plane of the ellipsoid 501 is greater than 1. In addition to the ellipsoid shown in FIG. 5, the alignment unit structure may alternatively be another structure with an irregular shape, for example, a spindle-shaped structure, a dumbbell-shaped structure, or a football-shaped structure. This is not limited in the present application.

[0055] It should be understood that the material of the alignment unit structure can be a low-loss dielectric material, such as silicon dioxide (SiO2), titanium dioxide (TiO2), silicon nitride (SiNx), aluminum oxide (Al2O3), silicon (Si), etc. The material of the alignment unit structure can alternatively be a metal material, such as gold (Au), silver (Ag), aluminum (Al), copper (Cu), or platinum (Pt). This is not limited in the present application.

[0056] The electromagnetic wave control device in this embodiment of the present application may alternatively use the three arrangement schemes shown in FIG.

[0057] A possible device structure is shown in Fig. 6(a) and includes an upper electrode layer 601, a lower electrode layer 602, and a liquid crystal layer 603 disposed between the upper electrode layer 601 and the lower electrode layer 602, and a first metamaterial layer 604. The metamaterial layer 604 may be disposed on a lower surface of the liquid crystal layer 603, for example, on a surface of the lower electrode layer 602. It should be understood that the first metamaterial layer 604 includes a first array including alignment unit structures. The alignment unit structures may be any structure shown in Figs. 2 to 5.

[0058] Another possible device structure is shown in FIG. 6(b), which includes an upper electrode layer 601, a lower electrode layer 602, a liquid crystal layer 603, a first metamaterial layer 604, and a second Metamaterials The liquid crystal layer includes a first metamaterial layer 604 disposed on a lower surface of the liquid crystal layer. A second metamaterial layer 605 is disposed on an upper surface of the liquid crystal layer, for example, the second metamaterial layer 605 is disposed on a surface of the upper electrode layer 601.

[0059] Another possible device structure is shown in FIG. 6(c) and includes an upper electrode layer 601, a lower electrode layer 602, a liquid crystal layer 603, a first metamaterial layer 604, and a polyimide (PI) friction layer 606. The first metamaterial layer 604 is disposed on the lower surface of the liquid crystal layer. The PI friction layer 606 is disposed on the upper surface of the liquid crystal layer 603, for example, on the surface of the upper electrode layer 601. Optionally, in the device shown in FIG. 6(c), the PI friction layer 606 can alternatively be disposed on the lower surface of the liquid crystal layer 603. The first metamaterial layer 604 can be disposed on the upper surface of the liquid crystal layer.

[0060] It should be further noted that in the electromagnetic wave control device shown in FIG. 6B, the alignment direction of the first metamaterial layer 604 and the alignment direction of the second metamaterial layer 605 may be parallel to each other. Optionally, there may alternatively be a certain included angle, for example 45°, between the alignment direction of the metamaterial layer 605 and the alignment direction of the metamaterial layer 604. Optionally, the alignment direction of the metamaterial layer 605 and the alignment direction of the metamaterial layer 604 may be perpendicular to each other. As shown in FIG. 7A, the first metamaterial layer 604 disposed on the surface of the lower electrode layer includes a first array including alignment unit structures. The second metamaterial layer 605 disposed on the upper electrode layer includes a second array including alignment unit structures. The alignment direction of the first array is perpendicular to the alignment direction of the second array. The liquid crystal molecules between the upper electrode layer and the lower electrode layer tend to be aligned parallel due to the action of van der Waals forces. However, since the alignment direction of the metamaterial layer 605 relative to the liquid crystal molecules is perpendicular to the alignment direction of the metamaterial layer 604 relative to the liquid crystal molecules, the alignment direction of the liquid crystal molecules near the upper electrode is perpendicular to the alignment direction of the liquid crystal molecules near the lower electrode. In this case, the liquid crystal molecules are aligned in a direction of 0° (the included angle between the upper electrode layer and the x-axis direction) from the upper electrode layer, and are gradually and uniformly twisted in a direction of -90° relative to the lower electrode. For example, the liquid crystal molecules are twisted clockwise by 90° one by one. The layer of liquid crystal molecules twisted in the alignment manner shown in FIG. 7(a) has the properties of an optical waveguide. When linearly polarized light with a polarization direction parallel to the x-axis direction propagates through the liquid crystal layer to the surface of the lower electrode layer, the polarization direction rotates by 90°. FIG. 7(b) is a schematic diagram of the alignment of liquid crystal molecules when a driving voltage is applied. In this case, the liquid crystal molecules tend to align parallel to the direction of the electric field, i.e., the long axis direction of the liquid crystal molecules is perpendicular to the xy plane, and the liquid crystal molecules cannot adjust and control the polarization direction of the incident light.

[0061] Therefore, for the electromagnetic wave control device in this embodiment of the present application, two metamaterial layers whose alignment directions are perpendicular are disposed in the upper electrode layer and the lower electrode layer, respectively, so that the polarization direction of the linearly polarized electromagnetic wave is twisted by about 90° after the linearly polarized electromagnetic wave is transmitted by the device. In order to manufacture a liquid crystal device with a better extinction rate, the special optical waveguide characteristics of the liquid crystal molecules in the device can be used.

[0062] Similar to the structure of FIG. 6B, the alignment direction of the first metamaterial layer 604 may also be parallel or perpendicular to the alignment direction of the PI friction layer 606 of FIG. 6C, or may form a certain included angle. In addition, to further configure a liquid crystal device with a better extinction ratio, the liquid crystal molecules may implement an optical waveguide structure similar to the optical waveguide structure shown in FIG. 7A.

[0063] In addition to the several structures shown in FIG. 6, the alignment device may alternatively use another similar arrangement method, which is not limited in this application. For example, in FIG. 6(b), the first metamaterial layer 604 and the second metamaterial layer 605 may use different alignment unit structures.

[0064] In any implementation, in the electromagnetic wave control device in this embodiment of the present application, the first metamaterial layer may alternatively include both the first array including the alignment unit structures and the third array including the alignment unit structures, and the alignment of the third array direction The first array is aligned direction To achieve alignment of liquid crystal molecules in two directions in the same metamaterial layer, two arrays with mutually perpendicular alignment directions are reused.

[0065] Similarly, the first metamaterial layer may further include a fourth array in another alignment direction. The first metamaterial layer may further include arrays in several alignment directions at the same time, and each array may use different alignment unit structures. This is not limited in this embodiment of the present application.

[0066] Therefore, for the electromagnetic wave control device in this embodiment of the present application, two arrays with perpendicular alignment directions can be reused to implement alignment of liquid crystal molecules in two different directions in the same metamaterial layer. Compared with the traditional friction alignment and photoalignment techniques, the alignment direction of liquid crystal molecules can be flexibly controlled, and the integration of liquid crystal devices can be realized.

[0067] In the following, the experimental results of the electromagnetic wave control device in this embodiment of the present application are described using the device 100 in FIG. 1 as an example. The unit structure used in the experiment is a rectangular column unit structure, and the material is gold. FIG. 8 is an electron microscope photograph of the structure of the unit structure with aspect ratios L / W of 1:1, 2:1, 3:1, 4:1, and 5:1. FIG. 9 shows the experimental results of the alignment effect of the unit structure with five aspect ratios of liquid crystal molecules. Two polarizers P1 and P2 are respectively disposed on the upper surface of the upper cover plate 106 of the device 100 and on the lower surface of the substrate layer 101 of the device 100. The polarizer P1 on the upper cover plate 106 exists in a polarization direction P. After the natural light from the light source passes through the polarizer, only linearly polarized light parallel to the polarization direction P is left. The polarization direction of the polarizer P2 on the lower surface of the substrate layer 101 is A. Only linearly polarized light whose polarization direction is parallel to A can be completely transmitted by P2. Linearly polarized light with another polarization direction can be partially transmitted by P2. Linearly polarized light whose polarization direction is perpendicular to A cannot be transmitted by P2. After natural light from a light source passes through P1 and P2, when A is perpendicular to P, the light ray cannot be transmitted by P2 and P2 cannot transmit the light. When A is parallel to P, the light ray is transmitted by P2 and P2 can transmit the light completely. FIG. 9 is a diagram showing the alignment effect of the device 100 on the liquid crystal molecules when A is perpendicular to P and when A is parallel to P. Under a polarizing microscope, the alignment effect in the power-off state (OFF) is compared with that in the power-on state (ON).

[0068] As shown in FIG. 9, when P is perpendicular to A, the power supply is turned off, and weak light is transmitted by P2. This indicates that the liquid crystal molecules change the polarization direction of the light beam. When the power supply is turned on, the liquid crystal molecules are aligned in the direction of the electric field, and the polarization direction of the light beam cannot be adjusted and controlled, and the light transmission phenomenon disappears. The larger the aspect ratio of the rectangular pillar, the more significant the contrast of the light transmission phenomenon. The experimental results show that the array including the unit structures can achieve alignment on the liquid crystal molecules. Similarly, when P is parallel to A, the power supply is turned off, and the light beam cannot be completely transmitted by P2, and there is an extinction phenomenon. This indicates that the liquid crystal molecules change the polarization direction of the light beam. When the power supply is turned on, the liquid crystal molecules are aligned in the direction of the electric field, and the polarization direction of the light beam cannot be adjusted and controlled, and the extinction phenomenon disappears. The larger the aspect ratio of the rectangular pillar, the more significant the contrast of the extinction phenomenon. It is also shown that the array including the unit structures can achieve alignment on the liquid crystal molecules. In addition, a larger aspect ratio L / W of the unit structure shows a better alignment effect on the liquid crystal molecules. To achieve a better alignment result, the aspect ratio L / W of the unit structure may be 5 or more.

[0069] In order to further optimize the adjustment control function of the device 100 to the incident light, in the device 100 shown in FIG. 1, a spacer layer 103 can be added to optimize the device efficiency. The material of the spacer layer 103 can be a low-loss and low-refractive index material, such as SiO2. Alternatively, the device 100 can not include the spacer layer 103. This is not limited in the present application.

[0070] The electromagnetic wave control device in this embodiment of the present application is a projection display liquid crystal on silicon (LCOS) module and Wavelength Selective Switch (wavelength-selective switch, WSS )andIt should be understood that the electromagnetic wave control device in this embodiment of the present application may be a spatial light modulator (SLM), and may perform temporal or spatial transformation or modulation on characteristics such as phase, amplitude, and intensity of a light wave under the control of a control signal. The control signal may be an optical signal or an electrical signal. The spatial light modulator may alternatively include multiple independent units, and the independent units are spatially arranged in a one-dimensional or two-dimensional array. Each unit may independently receive the control of the control signal, and may change the optical properties of each unit based on the signal to modulate an incident light beam.

[0071] FIG. 10 is a diagram showing a configuration of a transmissive spatial light modulator applicable to one embodiment of the present application. As shown in FIG. 10(a), the spatial light modulator structure 1000 is a polarization-dependent phase transmissive spatial light modulator based on a metasurface, and includes an upper glass layer 1001 and a lower glass layer 1001. The upper glass layer 1001 and the lower glass layer 1001 are plated with ITO electrodes, respectively, to form an external circuit 1002. A matrix control layer is disposed between the upper glass layer 1001 and the lower glass layer 1001, and includes a metamaterial layer and a liquid crystal layer. The metamaterial layer may include an alignment unit structure 1004 similar to the metamaterial layer 104 in FIG. 1(a). The liquid crystal molecules 1003 of the liquid crystal layer are aligned in the long axis direction (i.e., the y-axis direction) of the alignment unit structure 1004. To improve the efficiency of the structure, a spacer layer may be added between the lower electrode and the alignment unit structure 1004 instead.

[0072] It should be understood that Fig. 10 merely shows a possible example of a transmissive spatial light modulator structure. The metamaterial layer may include any array including the alignment unit structures in Figs. 2 to 5. This is not limited in this application. In addition, the transmissive spatial light modulator structure 1000 may use any arrangement method shown in Fig. 6. This is not limited in this application.

[0073] By changing the external applied voltage, the liquid crystal molecules 1003 in the spatial light modulator structure can rotate at different angles in the yz plane to change the equivalent refractive index of the liquid crystal layer in different directions. Thus, the spatial light modulator generates different electromagnetic responses to the incident light beam and performs tuning control on the incident light beam.

[0074] As shown in FIG. 10(a), there is a gap between the lower electrodes. Therefore, the matrix control layer can be divided into a plurality of adjustment and control matrix units. Independent voltage control can be implemented between the adjustment and control matrix units. FIG. 10(b) is a schematic diagram of one adjustment and control matrix unit. Each adjustment and control matrix unit can include at least one rectangular nanopillar. FIG. 10(c) is a top view of three adjustment and control matrix units shown in FIG. 10(a). Different voltages are applied to each adjustment and control matrix unit to control the liquid crystal molecules 1003 to exhibit different rotation angles. Therefore, different adjustment and control matrix units have different phase adjustment control effects on incident light with the same wavelength. The phase delay generated in the metamaterial layer can be used as a spatial light modulator. structure 1000 can perform phase adjustment control on the incident light and can perform adjustment control on the exit angle of the incident light.

[0075] spaceIn the optical modulator structure 1000, the thickness of the matrix control layer between the upper electrode 1002 and the lower electrode 1002 is 1.5 μm. In each adjustment control matrix unit, the length of the electrode in the x-axis direction is 690 nm, and the width in the y-axis direction is 345 nm. Each TiO2 rectangular nanopillar is 250 nm high in the z-axis direction, 225 nm long in the y-axis direction, and 150 nm wide in the x-axis direction. The alignment unit structure 904 is a TiO2 rectangular nanopillar. Each adjustment control matrix unit includes two TiO2 rectangular nanopillars.

[0076] In FIG. 10A, three combinations of adjustment control matrix units are shown. In the three adjustment control matrix units, the included angle θ between the liquid crystal molecule and the y axis is LC From left to right, θ is 90°, 45°, and 0°. The light that passes through the spatial light modulator is deflected to the right. LC The three adjustment control matrix units with rotation angles of 90°, 45°, and 0° can be regarded as a periodic structure. In one periodic structure, the rotation angles of the liquid crystal molecules in the adjacent adjustment control matrix units change drastically, and the maximum deflection angle φ of the emitted light can be 11.7°. Similarly, the rotation angle θ of the liquid crystal molecules LC is adjusted to 0°, 45°, and 90° from left to right, the emitted light is deflected to the left, and the maximum deflection angle is -11.7°. Therefore, the deflection angle of the emitted light can be adjusted and controlled within the range of ±11.7°.

[0077] It should be understood that the materials associated with the spatial light modulator structure 1000 are dielectric materials, and most of the incident light is not absorbed in the range of 600 nm to 700 nm. The TiO2 material used in the alignment unit structure 1004 can alternatively be replaced with another material that has no resistive losses and a high refractive index. Then, the geometric structure of the rectangular nanopillars is adjusted, and the adjustment control matrix unit The same functionality can be implemented if the periodic structure of is adjusted and controlled.

[0078] FIG. 11(a) shows the θ LC 11A is a distribution diagram of the electric field component Ey in the xz plane in a periodic structure including liquid crystal control units of 0°, 45°, and 90° from left to right. The dashed lines in FIG. 11A are equipotential lines of the electric field distribution, and the direction indicated by the arrow is the polarization direction of the emitted light after passing through the liquid crystal layer. FIG. 11B is a diagram related to the transmittance corresponding to different diffraction orders of the spatial light modulator 900. The incident light is a transverse electric wave (TE wave). The incident light is θ LC When passing through the liquid crystal control unit with angles of 0°, 45°, and 90°, the transmittance of the +1-order diffractive light of the incident light reaches 0.43, which is better than the transmittance of phase transmission spatial light modulators of other structures in the prior art.

[0079] The rectangular nanopillar unit structure 1004 enables the liquid crystal molecules to have a better alignment effect. In the absence of voltage, the liquid crystal molecules are aligned along the long axis direction of the rectangular nanopillar, i.e., the y-axis direction.

[0080] FIG. 12(a) shows the θ LC 12 is a distribution diagram of the electric field component Ey in the xz plane in a periodic structure including liquid crystal control units of 90°, 45°, and 0° from left to right. FIG. 12(b) shows the phase change when incident light (TE wave) of a different wavelength passes through the periodic structure. As shown in FIG. 12(b), the dashed line in the figure shows the phase change of the outgoing light when the incident wavelength is 634 nm. θ LC When θ = 0°, the liquid crystal molecules are aligned along the long axis of the rectangular nanopillars, and the phase change of the outgoing light is the largest. Therefore, when the polarization direction of the incident light is along the long axis of the rectangular nanopillars, the spatial light modulator has a good phase adjustment control effect on the outgoing light. LC= 90°, the liquid crystal molecules are aligned in a direction perpendicular to the long axis direction of the rectangular nanopillars, e.g., the z-axis direction, and the phase change of the outgoing light is small. Therefore, when the polarization direction of the incident light is perpendicular to the long axis direction of the rectangular nanopillars, the spatial light modulator has a weak phase adjustment control effect on the outgoing light.

[0081] Therefore, for the transmissive spatial light modulator in this embodiment of the present application, the liquid crystal molecules are aligned based on the metamaterial layer containing the alignment unit structures. In addition, the phase delay accumulated in the metamaterial layer can be utilized to generate deep phase modulation in the spatial light modulator or reduce the thickness of the liquid crystal layer. By changing the externally applied voltage to control the rotation angle of the liquid crystal molecules, the outgoing direction and phase of the transmitted light can be adjusted and controlled. Compared with other types of liquid crystal spatial light modulators, the transmissive spatial light modulator based on the metamaterial layer has a simple structure and is easier to prepare and optimize the structure of the liquid crystal spatial light modulator.

[0082] FIG. 13 is a diagram of another reflective spatial light modulator structure applicable to one embodiment of the present application. FIG. 13(a) is a side cross-sectional view of the reflective spatial light modulator structure. As shown in FIG. 13(a), the spatial light modulator structure 1300 is a polarization-dependent phase reflective spatial light modulator based on a metamaterial layer, and includes a top cover plate 1306, a liquid crystal layer 1304, liquid crystal molecules 1305, a metamaterial layer 1303, a spacer layer 1302, and a liquid crystal on silicon (LCoS) driving backplane 1301. The top cover plate 1306 includes an electrode. The electrode can be a conductive layer made of a material such as ITO or zinc oxide (ZnO).

[0083] It should be understood that Fig. 13 merely shows a possible example of a reflective spatial light modulator structure. The metamaterial layer may include an array including the alignment unit structures in Figs. 2 to 5. This is not limited in this application. In addition, the transmissive spatial light modulator structure 1300 may use any of the arrangement schemes shown in Fig. 6. This is not limited in this application.

[0084] Similar to the structure of the spatial light modulator 1000 in Figure 10, the LCoS driving backplane can apply different magnitudes of voltages to the liquid crystal layer 1304, resulting in the liquid crystal molecules being arranged with different rotation angles, thus changing the response of the spatial light modulator structure to the incident light with the same wavelength, so as to achieve the purpose of adjusting and controlling the phase of the outgoing light.

[0085] FIG. 13(b) shows a partial top view of the metamaterial layer 1303 of the spatial light modulator structure 1300. In the metamaterial layer 1303, the unit structures are rectangular pillars arranged in an orderly manner. In addition, the aspect ratio of the rectangular pillars is greater than 1. That is, the rectangular pillars are longer in the y-axis direction and shorter in the x-axis direction. The rectangular pillar unit structures form micro “grooves” on the lower surface of the liquid crystal layer. Under the cooperative action of van der Waals forces, the liquid crystal molecules of the liquid crystal layer 1304 are aligned along the long axis direction of the rectangular pillars, i.e., along the y-axis direction. Thus, the metamaterial layer 1303 can perform a liquid crystal alignment function in the spatial light modulator 1300. When a driving voltage is applied, the long axis direction of the liquid crystal molecules rotates around the x-axis until the long axis direction of the liquid crystal molecules is perpendicular to the xy plane. Similar to the spatial light modulator 1000 in FIG. 10, when the polarization direction of the incident light is along the long axis of the rectangular nanopillar (ie, the y-axis direction), the spatial light modulator has a good phase adjustment control effect on the outgoing light.

[0086] Therefore, for the reflective spatial light modulator in this embodiment of the present application, the liquid crystal molecules are aligned based on the metamaterial layer containing the alignment unit structures. By changing the externally applied voltage to control the rotation angle of the liquid crystal molecules, the output direction and phase of the light beam can be adjusted and controlled. In addition, by utilizing the phase delay accumulated in the metamaterial layer or by reducing the thickness of the liquid crystal layer, deep phase modulation can be generated in the spatial light modulator. In addition, by changing the externally applied voltage to control the rotation angle of the liquid crystal molecules, the output direction and phase of the transmitted light can be adjusted and controlled. Compared with another type of liquid crystal spatial light modulator, the transmissive spatial light modulator based on the metamaterial layer has a simple structure and is easier to prepare and optimize the structure of the liquid crystal spatial light modulator.

[0087] FIG. 14 shows a reusable and adjustable metasurface structure 1400 applicable to one embodiment of the present application. FIG. 14 is a partial top view of the metasurface. An array including two alignment unit structures 1401 with orthogonal alignment directions is disposed on the left and right substrate layers, respectively. In the left substrate layer, the long axis direction of the rectangular pillar is parallel to the x-axis, and the liquid crystal molecules are aligned parallel to the x-axis direction. In the right substrate layer, the long axis direction of the rectangular pillar is parallel to the y-axis, and the liquid crystal molecules are aligned parallel to the y-axis direction. Under the action of the liquid crystal molecules in the two alignment directions, the polarization direction of the light incident on the left side of the substrate layer is deflected parallel to the x-axis direction, and the polarization direction of the light incident on the right side of the substrate layer is deflected parallel to the y-axis direction. At the same time, the metasurface can also perform phase modulation of the incident light.

[0088] Therefore, for the metasurface structure in this embodiment of the present application, dual-polarization direction modulation can be implemented on the same chip, and the phase modulation of the light beam can be further implemented. The metasurface structure cooperates with the polarization beam splitter to reduce the polarization conversion element and realize better integration.

[0089] The above description is merely a specific embodiment of the present application, and is not intended to limit the scope of protection of the present application. Any variation or replacement that is easily conceived by a person skilled in the art within the technical scope disclosed in this application shall fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the scope of protection of the claims.

Claims

1. An electromagnetic wave control device, An upper electrode layer; A lower electrode layer; a liquid crystal layer and a first metamaterial layer disposed between the upper electrode layer and the lower electrode layer; The first metamaterial layer includes a first array including aligned unit structures; The aspect ratio of the first surface of the alignment unit structure is greater than 1; The first surface is a surface of the alignment unit structure and faces away from the liquid crystal layer; and The length of the first surface, the width of the first surface, and the distance between two adjacent alignment unit structures are in the range of 1 nm to 5000 nm. a first metamaterial layer; and Including, The alignment of the liquid crystal molecules is achieved by penetrating into the gap between adjacent alignment unit structures. Device.

2. the length of the first surface, the width of the first surface, and the spacing are in the range of λ / 1000 to λ, where λ is a wavelength of an electromagnetic wave incident on the first metamaterial layer; and The wavelength of the electromagnetic wave is in the range of 100 nm to 2000 nm.

2. The apparatus of claim 1.

3. the aspect ratio of the first surface is greater than or equal to 1.5; 3. Apparatus according to claim 1 or 2.

4. The first metamaterial layer is disposed on a lower surface of the liquid crystal layer.

4. Apparatus according to any one of claims 1 to 3.

5. The apparatus further comprises: a second metamaterial layer; the second metamaterial layer is disposed on an upper surface of the liquid crystal layer; and The second metamaterial layer includes a second array including aligned unit structures. A second metamaterial layer; and The apparatus of claim 4 , comprising:

6. The alignment direction of the second array is perpendicular to the alignment direction of the first array.

6. The apparatus of claim 5.

7. The alignment direction of the second array is parallel to the alignment direction of the first array.

6. The apparatus of claim 5.

8. The apparatus further comprises: Polyimide PI friction layer, The PI friction layer is disposed on the upper surface of the liquid crystal layer, and The alignment direction of the PI friction layer is perpendicular to the alignment direction of the first array. A polyimide PI friction layer; The apparatus of claim 4 , comprising:

9. The first metamaterial layer further comprises: a third array including an alignment unit structure; The alignment direction of the third array is perpendicular to the alignment direction of the first array. A third array; and 9. The apparatus according to claim 1 , comprising:

10. The apparatus further comprises: a spacer layer, The first metamaterial layer is disposed on a surface of the spacer layer. A spacer layer; and 10. The apparatus of claim 1 , further comprising:

11. The alignment unit structure is a rectangular pillar.

11. Apparatus according to any one of claims 1 to 10.

12. The alignment unit structure is a wedge-shaped pillar.

11. Apparatus according to any one of claims 1 to 10.

13. the alignment unit structure is a triangular prism, the first surface is a side surface of the triangular prism, and The ratio of the height of the triangular prism to the side length of the base triangle is greater than 1; 11. Apparatus according to any one of claims 1 to 10.

14. The alignment unit structure is an elliptical cylinder, the first surface is a base surface of the elliptical cylinder; and a ratio of a major axis of the base of the elliptical cylinder to a minor axis of the base of the elliptical cylinder is greater than 1; 11. Apparatus according to any one of claims 1 to 10.

15. The alignment unit structure is an ellipsoid, the first surface is a projection of the ellipsoid; and a ratio of a major axis of the projection surface of the ellipsoid to a minor axis of the projection surface of the ellipsoid is greater than 1; 11. Apparatus according to any one of claims 1 to 10.

16. The material of the alignment unit structure is a metal.

16. Apparatus according to any one of claims 1 to 15.

17. The material of the alignment unit structure is a dielectric material.

16. Apparatus according to any one of claims 1 to 15.

18. The apparatus is configured to control the electromagnetic waves reflected by the first metamaterial layer.

18. Apparatus according to any one of claims 1 to 17.

19. The device is configured to control the electromagnetic waves transmitted by the first metamaterial layer.

18. Apparatus according to any one of claims 1 to 17.

Images