Electrically controlled dynamic optical components including super-surfaces

Abstract

An optical assembly (1) comprising a planar metasurface (2) arranged on a surface of a first substrate (3) and a top layer (4) arranged above the metasurface (2) in a height direction Z, wherein the metasurface (2) comprises an array (9) of scattering structures (5, 5a, 5b), wherein the array (9) is a repeating pattern of unit cells (7), wherein the unit cells (7) comprise at least two different scattering structures, wherein an optical property of the metasurface (2) is controllable by a control signal, wherein a first scattering structure (5, 5a) at least partially contacts a layer of a first substance (6a) having a first refractive index, and a second scattering structure (5, 5b) at least partially contacts a layer of a second substance (6b), the second substance being different from the first substance (6a) and providing a variable refractive index according to the control signal.

Description

Technical Field

[0001] The present invention relates to an optical component including a metasurface, the optical component including the surface of a first substrate and a top layer arranged in the height direction Z above the metasurface. Background Technology

[0002] The propagation of a beam of light or electromagnetic radiation can be determined entirely by its phase and its amplitude profile on a given two-dimensional surface. Optical devices or components are used to manipulate such beams. While amplitude and phase manipulation can be considered typical, phase manipulation is preferred to avoid undesirable losses. The propagation of a beam is manipulated by introducing a specific phase profile onto the beam. Such optical devices can be lenses, prisms, mirrors, or holographic elements. Such manipulation can be achieved through variations in the thickness of the optical device.

[0003] Optical metasurfaces have been found to be suitable replacements for traditional optical components in many optical systems. A metasurface is a (primarily planar) structure that can modulate the local properties of a light beam. Typically, a metasurface is an artificial nanostructure interface that manipulates light through spatially arranged superatoms. These superatoms are often composed of plasmonic or dielectric nanoantennas, which can directly alter the properties of light, such as phase, amplitude, and polarization.

[0004] Traditional optics manipulate light solely through refraction and propagation. Optical metasurfaces, on the other hand, are subwavelength patterned layers that interact strongly with light, altering the properties of light across their subwavelength thickness through scattering via small nanostructures. Therefore, optical metasurfaces offer a novel approach to light manipulation, including spectral selectivity, wavefront control, and polarization control. Furthermore, optical systems incorporating optical metasurfaces can be significantly smaller than conventional optics. Metasurfaces provide high-resolution control over the phase profile of light beams. Specifically, metasurfaces are advantageous for holographic applications and beam shaping.

[0005] The manipulation of light is achieved through nanostructures that resonantly capture light and re-emit it with defined phase, polarization, morphology, and spectrum. This enables light wave sculpting with unprecedented precision. OMs share some similarities with frequency-selective surfaces and high-contrast gratings. However, they have undergone tremendous advancements in complexity and functionality over the past decade.

[0006] An electrically tunable metasurface is known from US2018 / 0321518 A1. It comprises a mirror, a conductive layer, and a dielectric layer. The conductive layer and the dielectric layer are in direct contact, thereby defining a conductor-dielectric interface. Multiple subwavelength antenna elements are arranged on the dielectric layer and configured to establish a potential difference between the subwavelength antenna elements and the mirror. By combining the geometry and material composition of each of the subwavelength antenna elements, the conductive layer, and the dielectric layer, the propagation characteristics of the incident electromagnetic wave can be tuned using the electrically tunable metasurface.

[0007] A drawback of existing optical metasurfaces is that their optical properties are fixed, or their optical reconfigurability is greatly limited. Improved optical reconfigurability is needed because it allows control over certain properties and functions of optical metasurfaces. Summary of the Invention

[0008] The object of this invention is to provide an optical component and optical device that overcomes the aforementioned drawbacks. It is desirable to integrate such an optical component into an optical device. Furthermore, a method for manufacturing such an optical component should be provided.

[0009] The optical component and method according to the present invention solve this problem. Further detailed description provides preferred embodiments.

[0010] According to the present invention, an optical component includes a metasurface disposed on a (preferably planar) surface of a first substrate and a top layer disposed above the metasurface along a height direction. The metasurface includes an array of scattering structures. The array is a repeating pattern of unit cells, wherein each unit cell includes at least two different scattering structures. The optical properties of the metasurface can be controlled by a control signal, wherein a first scattering structure at least partially contacts a layer of a first material having a first refractive index, and a second scattering structure at least partially contacts a layer of a second material, which is different from the first material and provides a variable refractive index according to the control signal. Therefore, the refractive index of the second material can be selectively modified by the control signal. Because the second material is different from the first material, the refractive index in each unit cell is locally different between the region where the first scattering structure is present and the region where the second scattering structure is located.

[0011] Preferably, the second substance comprises a polymer. It has been found that conformational changes in polymers are particularly suitable for altering the refractive index of such substances. Preferably, the second substance comprises conductive and / or electrochromic polymers, as these polymers provide large differences in refractive index in different states. Preferably, the polymer can transition between oxidized and reduced states. Typically, the oxidized and reduced states of a polymer provide a large difference in refractive index. Furthermore, it is preferred that the polymer can electrochemically transition between oxidized and reduced states. Electrochemical transitions have been found to be very rapid compared to other techniques. Preferably, the polymer comprises conjugated double bonds and / or conjugated p-orbitals, as the applied charge can be transported along the conjugated system and is therefore stable. Polymers comprising multiple aromatic rings are particularly preferred, as aromatic rings stabilize the charge even better. Polyaniline (substituted or preferably unsubstituted) has been found to be particularly suitable due to its high stability, low cost, worldwide availability, and ease of synthesis.

[0012] Preferably, in the case of incident radiation, the first scattering structure and the second scattering structure produce a propagation phase difference. Advantageously, each unit cell comprising the two scattering structures can be addressed by a control signal.

[0013] In a preferred embodiment, the scattering structure comprises a metal. Metals have been found particularly suitable because they can serve as antennas for control signals. To avoid oxidation, noble metals are preferred. Therefore, the metal is preferably selected from the group consisting of ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, rhenium, copper, and gold. The scattering structure is preferably composed primarily of one or more of these metals. "Composed of" should be understood to mean that one or more of these metals of at least industrial grade purity are the sole components of these structures. Impurities are acceptable, but no other substances are added. However, it is generally desirable that the properties of the scattering structures are more or less identical. This can be achieved in a preferred embodiment, wherein the scattering structure comprises at least 95%, preferably ≥98%, more preferably ≥99%, and most preferably ≥99.5% of one of these metals. Most preferably, the scattering structure comprises at least 95%, preferably ≥98%, more preferably ≥99%, and most preferably ≥99.5% gold. Gold has been found to be advantageous because it has extremely strong oxidation resistance, provides very good electrical conductivity, and techniques for producing nanoscale structures (such as electron beam lithography (EBL)) are known.

[0014] Advantageously, the scattering structure is deployed as an optical antenna. Preferably, when electromagnetic radiation strikes a single scattering structure, it causes oscillations in the charge present in the scattering structure. This is known as surface plasmon resonance. The interaction between the striking electromagnetic radiation and the surface plasmon resonance results in a phase discontinuity. Therefore, electromagnetic radiation transmitted through or reflected from the optical assembly undergoes a phase jump.

[0015] In a preferred embodiment, the scattering structure is deployed as an optical antenna, preferably in the form of a rod. It should be understood that the "rod" object has a cylindrical or cubic geometry that provides an extension along its longitudinal direction that is at least 1.2 times longer, preferably ≥1.5 times, and more preferably ≥2 times longer than any extension along the width direction perpendicular to the longitudinal direction. These rods have been found to be particularly suitable antennas. Preferably, the rod is oriented in the plane of the metasurface, more preferably in a spatially varying orientation. The antenna is most effective at such orientations.

[0016] Preferably, the geometry and size of the first and / or second scattering structures in the array are substantially the same. "Substantially the same" should be understood as the difference in geometry and size between the first and / or second scattering structures in the array being ≤5%, preferably ≤3%, more preferably ≤1%. Most preferably, the geometry and size of the first and / or second scattering structures in the array are identical. This can be achieved using techniques such as electron beam lithography, which allows for shape manipulation at the atomic level. The geometry and size of the first and second scattering structures can differ. However, it is preferred that all first scattering structures provide substantially the same geometry and size, and all second scattering structures provide substantially the same geometry and size. Most preferably, the geometry and size of all (first and second) scattering structures in the array are substantially the same.

[0017] In a preferred embodiment, the first and / or second scattering structures provide a cylindrical or cubic geometry (“bar”), preferably a straight cylinder or rectangular cube geometry. The longitudinal extension of each scattering structure is preferably in the range of 100-400 nm, more preferably 150-300 nm, more preferably 175-225 nm, and most preferably about 200 nm. In the width direction perpendicular to the longitudinal direction, an extension in the range of 10-200 nm, preferably 20-150 nm, more preferably 30-100 nm, and most preferably 50-80 nm has been found advantageous. In the case of a (straight) cylinder, the width direction is the diameter of the cylinder. For irregular cylinders or cubes, the extensions along two mutually perpendicular width directions can be independently selected from these preferred ranges. For a square cube, the two width directions can be the same.

[0018] Preferably, the size of the scattering structure is smaller than the wavelength of the incident electromagnetic radiation to be manipulated by the optical components. Small-sized scattering structures provide higher resolution for optical components.

[0019] Furthermore, the spacing between the scattering structures affects the resolution. To provide high resolution, the spacing between the scattering structures is preferably smaller than the wavelength of the incident electromagnetic radiation to be manipulated by the optical components. Half of it.

[0020] Preferably, the optical properties of the metasurface can transition from a first optical property to a second optical property in less than 500 ms, preferably ≤250 ms, more preferably ≤100 ms, more preferably ≤50 ms, and most preferably ≤35 ms. It has been found that rapid transitions between two different optical properties are advantageous for many applications.

[0021] Preferably, the volume above the metasurface is filled with a defined (inert) medium to avoid undesirable chemical reactions. Generally, there is no limitation on the volume disposed between the first substrate and the top layer. However, especially when the top layer is used as an electrode, it has been found that optimal performance can be achieved if the top layer is not too close to the metasurface. Preferably, the height of the volume between the first substrate and the top layer is at least 3 times the height of the scattering structure, preferably ≥5 times, more preferably ≥10 times, more preferably ≥20 times, and most preferably ≥50 times. Preferably, the height of the volume between the first substrate and the top layer is less than 500 times the height of the scattering structure, preferably ≤200 times, more preferably ≤100 times, more preferably ≤75 times, and most preferably ≤50 times. A medium, preferably a liquid medium, is disposed in this volume. Preferably, the medium is a conductive medium, and most preferably an ionic solution. Such a medium not only protects the metasurface but also provides conductivity when the top layer is used as an electrode.

[0022] In a preferred embodiment, the first substance comprises a dielectric material, preferably a dielectric polymer. More preferably, the polymer is an acrylate polymer, most preferably polymethyl methacrylate (PMMA). Polymethyl methacrylate is preferred because its refractive index (n1+ik1) in the visible light wavelength range is n1=1.5, k1≈0. Preferably, the refractive index of the first substance does not change significantly with the control signal. This means that after the control signal is applied, the change in the refractive index of the first substance does not exceed 10%, preferably ≤5%, more preferably ≤2%. Preferably, the refractive index of the first substance does not change significantly in the temperature range of 0-40°C. This means that in this temperature range, the change in the refractive index of the first substance does not exceed 10%, preferably ≤5%, more preferably ≤2%.

[0023] Preferably, the first material at least partially surrounds the first scattering structure, and more preferably, it contacts the first scattering structure on all sides that do not contact the first substrate. Therefore, preferably, the first scattering structure is surrounded by the first substrate on one side and by the first material on all other sides.

[0024] Preferably, the real part n and / or imaginary part κ of the variable refractive index (n2+ik2) of the second material can be transformed to the corresponding value of the first material via a control signal. As described below, it is advantageous if the variable refractive index of the second material can be adjusted to the same value as the refractive index of the first material (e.g., n1 = 1.6 for PMMA). When the refractive index of the second material is adjusted to almost no absorption (k2≈0), anomalous transmission becomes very weak. When n2 reaches the value of n1 (=1.5), the light intensity approaches zero because the refractive index is equivalent to that of a metasurface uniformly covered only by PMMA.

[0025] In a preferred embodiment, the geometry of the first and / or second scattering structure is a cylinder or parallelepiped. These structures have been found to be easy to manufacture and provide sufficient optical performance. However, geometries offering fewer degrees of freedom, such as straight cylinders or rectangular cubes, are preferred. Preferably, the longitudinal extension of the first and / or second scattering structure is preferably in the range of 100-400 nm, more preferably 150-300 nm, more preferably 175-225 nm, and most preferably about 200 nm. This longitudinal extension provides suitable optical effects for a wide range of wavelengths including visible light. Preferably, the width of the first and / or second scattering structure (which should be understood as the extension along a direction perpendicular to the longitudinal direction) is in the range of 10-200 nm, preferably 20-150 nm, more preferably 30-100 nm, and most preferably 50-80 nm. This width also provides good optical properties and is easy to process with common techniques. Most preferably, the two width extensions of the cube or irregular cylinder can be selected independently from these preferred ranges. It should be understood that this wording should cover minor deviations from the ideal geometry described above (such as chamfered edges or corners).

[0026] As described above, the first and second scattering structures are arranged in an array to provide a repeating pattern of unit cells. In a preferred embodiment, each unit cell includes a row of first scattering structures and a row of second scattering structures. Preferably, adjacent unit cells are arranged relative to each other such that the first and second scattering structures form alternating rows in the array. Therefore, preferably, the first and second scattering structures are arranged in alternating rows in the array. This arrangement provides a uniform distribution of different scattering structures. Furthermore, the first and second scattering structures can be easily covered by different first and second substances.

[0027] Preferably, each unit cell can be addressed independently by a control signal. This means that each unit cell can be transitioned from a first state providing a first optical property to a second state providing a different optical property by a control signal, regardless of the states of adjacent units. Preferably, the states of adjacent units have no effect on the convertibility of the unit to be transitioned, and adjacent units do not change their states when the state of the unit to be transitioned changes.

[0028] In a preferred embodiment, the first substrate comprises a support. This is advantageous because such a support can support different scattering structures. It has been found advantageous for the support to comprise silicon dioxide, preferably quartz. The chemical properties (especially electrochemical properties) of silicon dioxide (particularly quartz) can be readily adapted to specific needs. In a particularly preferred embodiment, the support is composed of quartz coated with a conductive coating. As stated above regarding the materials of the scattering structure, "composed of" should be understood to allow for impurities to reach a certain level. The coating is preferably metallic. Many metals can be readily applied as thin layers to the quartz surface by desorption from the gas phase. Coatings comprising indium tin oxide or preferably composed of indium tin oxide have been found to be particularly suitable.

[0029] Another aspect of the invention is an optical device comprising the optical components described above. Due to the modulation of the phase profile of incident electromagnetic radiation, the application of an electric field can cause modulation of the optical function of such an optical device, which is transmitted through or reflected by the optical components. Such an optical device can be very thin compared to those comprising conventional optical components (such as conventional (glass) lenses). Furthermore, the modulation of the phase profile can be easily triggered by a control signal.

[0030] Preferably, the optical device is a holographic device, a lens, or a beam control device. For these applications, optical components as described above have been found to be particularly suitable due to the variability of their optical properties and their small size.

[0031] Scattering structures are also known as building blocks of metaatoms or metasurfaces. Advantageously, electromagnetic radiation has wavelengths from 10 nm to 1000 nm. Preferably, the electromagnetic radiation is in the infrared spectrum from about 700 nm to about 1000 nm. Preferably, the electromagnetic radiation is in the visible spectrum from about 380 nm to 740 nm.

[0032] According to a preferred embodiment, the phase profile induced on the incident electromagnetic radiation includes a geometric phase component. Preferably, the geometric phase component is introduced due to the (local) phase delay of the incident electromagnetic radiation. Advantageously, the (local) phase delay depends on the orientation of the scattering structure. Such a phase delay can be based on the Pancharatnam-Berry (PB) phase principle. The spatial control of the polarization state of light inevitably introduces a nontrivial spatial variation phase distribution, called the PB phase. If two parts of a uniformly polarized wave are changed to a common polarization state along two different paths on the Poincaré sphere (polarization state space), a relative phase appears between the two polarization states, which is equal to half the solid angle enclosed by the paths.

[0033] The PB phase represents the evolution of the polarization conversion history, and thus clockwise and counterclockwise evolution will flip the sign of such a geometric phase. Therefore, when a beam of circularly polarized (CP) light strikes a preferred scattering structure (deployed as an optical antenna with a preferred linearly polarized resonance, such as a dipole), the scattered beam is partially converted to an opposite helicity with a phase shift determined solely by the antenna's geometric orientation. Near the normal incident angle, the CP beam is primarily scattered into a beam with the same polarization but no phase change, and a beam with opposite circular polarization but a phase change equivalent to twice the angle formed between the dipole and the reference axis. Preferably, the normal incident axis is arbitrary. The sign of the phase shift depends on the helicity state of the incident beam (right-hand or left-hand helicity). On the other hand, the amplitude of the scattered field is preferably independent of the orientation of the scattering structure, but rather depends on its frequency response. Advantageously, the phase delay depends entirely on the orientation of the scattering structure.

[0034] Metasurfaces that shape the wavefront via geometric phase (e.g., Pancharatnam-Berry (PB) phase) can preferably be achieved by controlling the in-plane orientation of the optical antenna. This approach not only allows for highly precise control of the phase profile but also reduces fabrication complexity. Importantly, the PB phase is independent of specific antenna design or wavelength, enabling broadband performance.

[0035] Pixel-level addressability is achieved through a favorable selective combination of the geometric phase component and the propagation phase component on a single subwavelength pixel. This concept is general and applicable to any active material that exhibits a change in refractive index under electrical, optical, thermal, or other external stimuli.

[0036] Preferably, the geometric phase is independent of the dynamic (propagation) phase accumulated along the light propagation path of the electromagnetic radiation. Advantageously, geometric phase modulation can be achieved by using anisotropic subwavelength metal / dielectric scattering structures with identical geometric parameters but spatially varied orientations. Preferably, the scattering structure is resonantly excited by electromagnetic radiation. This has the advantage of obtaining a large scattering cross section. Based on the PB phase principle, the phase delay of each nanorod is equal to... in, It is the orientation angle of the scattering structure. Therefore, by arranging scattering structures with different orientations on the metasurface, arbitrary phase profiles can be obtained.

[0037] A preferred application of optical components is the design of holograms. This can be achieved, for example, by using a Fourier hologram designed to obtain the desired beam profile in the far field. Preferably, the desired phase mask is the inverse Fourier transform of the desired image. Designing such a phase mask may require iterative numerical methods. For optical devices with simpler functionality (e.g., lens beam reflectors), the pattern of the phase mask can be analytically derived. Furthermore, the calculated phase map, found numerically or analytically, is advantageously quantized. Once the quantized phase map is found, pixels (i.e., scattering structures) are deposited using orientation / dielectric pillars according to the desired local phase shift.

[0038] The optical device may include one or more optical components, each comprising a single feature or a combination of features described above. The same advantages can be applied to optical devices for optical components as described above, and vice versa.

[0039] Preferably, the optical device is a holographic device, a lens, or a beam control device.

[0040] With appropriate phase profile design, fully interchangeable functions, such as transitions between different holographic patterns within a hologram, or multifunctional transitions between beam control, focusing, holography, optical vortexes, etc., can be successfully achieved within milliseconds and exhibit excellent reversibility under electrical control at visible frequencies.

[0041] This optical device and its components possess immense potential to achieve a wide range of optical functions while maintaining a high degree of independence for each function within a single nanophotonic device. This will enable novel optical communication systems using ultrathin devices with high spatial resolution, potentially crucial for modern cryptography and security applications. Such highly integrated nanophotonic metasurfaces will allow for the manipulation of light propagation to unprecedented levels, paving the way for compact, multi-tasking optical devices.

[0042] Another problem is addressed by a method for producing optical components that include metasurfaces and provide optical properties controllable by control signals. This method includes the following steps:

[0043] -Provide a first substrate,

[0044] - Provides top-level information

[0045] - Optionally, an array of scattering structures is produced on the surface of a first substrate by electron beam lithography, and

[0046] - By applying a first material having a first refractive index to at least a portion of the surface of a first part of the scattering structure and a second material having a second refractive index to at least a portion of the surface of a second part of the scattering structure, a repeating pattern comprising unit cells of at least two different scattering structures is created in the array, wherein the second material is different from the first material and provides a variable refractive index according to a control signal.

[0047] This method provides a simple way to manufacture optical components with excellent optical properties. Furthermore, the optical properties can be transformed between at least two different states. The metasurface is preferably planar. Attached Figure Description

[0048] Other advantages, objects and features of the present invention will be described with reference to the accompanying drawings and the following description.

[0049] In the attached diagram:

[0050] Figure 1A and Figure 1B Examples of optical components according to the present invention are shown from different angles;

[0051] Figure 1C This is a schematic diagram of the holographic image in open (left) and closed (right) positions, including the letters "MPI";

[0052] Figure 2A The chemical structures of polyaniline (PANI) in its emerald green imine state (ES) and colorless emerald green imine state (LS) are shown, as well as the electrochemical reactions that lead to the transition between these two states.

[0053] Figure 2B Examples of optical components according to the present invention are shown from different angles;

[0054] Figure 2C The correction for the normalized intensity relative to Δθ is shown;

[0055] Figure 2D The correction for anomalous transmission as a function of complex refractive indices n2 and k2 is shown;

[0056] Figure 3A The correction for light intensity as a function of applied voltage is shown;

[0057] Figure 3BThe switching times of the optical components are shown ("off → on" (left) and "on → off" (right));

[0058] Figure 3C The optical components showed almost no degradation over at least 100 switching cycles;

[0059] Figure 4A A schematic diagram of an experimental setup is shown;

[0060] Figure 4B The cyclic voltammograms of PANI electrochemically deposited on the metasurface sample are shown.

[0061] Figure 4C SEM images of the metasurface of the optical component are shown;

[0062] Figure 4D The image shows an AFM image of the metasurface of the optical component (left) and an overlay of two selected height profiles (right);

[0063] Figure 4E The normalized intensity of anomalous transmission during in-situ recorded PANI growth is shown. Detailed Implementation

[0064] Figure 1A and Figure 1B Examples of the optical component 1 according to the present invention are shown from different angles. For example... Figure 1A As shown, a planar metasurface 2 is disposed between the upper surface 3a of the first substrate 3 and the top layer 4. Although the metasurface is directly disposed on the upper surface 3a of the first substrate 3, the top layer 4 (in...) Figure 1B (Not shown in the image) are spaced apart along the height direction h. The first substrate 3 and the top layer 4 are both conductive and serve as the bottom electrode 3 and the top electrode 4, respectively.

[0065] The metasurface 2 includes multiple scattering structures 5, 5a, and 5b. The scattering structures 5a and 5b are arranged in rows 8a and 8b. The first scattering structures 5a in some rows 8a are covered by a first material 6a having a first refractive index, while the scattering structures 5b in other rows 8b are covered by a second material 6b, which is different from the first material and provides a variable refractive index according to a control signal. In this example, the control signal is a potential (V) applied between the top electrode 3 and the bottom electrode 4. In the example shown, the first scattering structures 5a and the second scattering structures 5b are arranged in alternating rows 8a and 8b. The first material 6a covering the first scattering structures 5a is a dielectric material. The second material 6b covering the second scattering structures 5b is an electrochromic polymer.

[0066] In this example, all scattering structures 5, 5a, and 5b have the same geometry, which is a rectangular cube. Because these structures are preferably made of gold, the term "gold nanorods" is also used instead of "scattering structure." It should be understood that the preferred embodiments disclosed only for "gold nanorods" 5, 5a, and 5b can also be applied to "scattering structures" that do not include gold and / or have different geometries. However, gold nanorods are preferred because they can be fabricated on an ITO-coated quartz substrate by electron beam lithography (EBL). The gold nanorods 5, 5a, and 5b have a size of 200 nm × 80 nm × 50 nm. Odd-numbered rows (or columns) 8a are coated with PMMA (h1 = 100 nm) via a double-layer EBL process. Even-numbered rows (or columns) 8b of gold nanorods 5, 5a, and 5b have been coated with PANI by electrochemical polymerization of a metasurface sample in an aqueous electrolyte containing (2 M) HNO3 and (0.1 M) aniline.

[0067] The longitudinal direction of each cube 5 extends in the plane of the upper surface 3a of the first substrate 3. However, these directions in this plane differ among some scattering structures 5, 5a, 5b. The different in-plane orientations of the scattering structures 5, 5a, 5b, which serve as optical antennas, allow for the shaping of the light wavefront by geometric phase (e.g., Pancharatnam-Berry (PB) phase). The scattering structures have subwavelength dimensions, and the spacing between rows 8a, 8b of adjacent scattering structures 5, 5a, 5b and / or scattering structures 5, 5a, 5b with different covers also has a subwavelength dimension.

[0068] Figure 1B Cross-sections of the metasurface 2 and the bottom electrode 3 are shown. The top electrode 4 is not shown. All nanorods 5, 5a, and 5b have the same height; however, the forms in which the first material 6a and the second material 6b are covered differ. While the first material 6a covers a row of gold nanorods 5a, thus forming a continuous band, the second material 6b covers only individual nanorods 5b, thus forming islands of the second material 6b. The bands of the first material 6a have an approximately rectangular cross-section. The cross-section of the second material 6a resembles a dome surrounding each nanorod 5a.

[0069] The optical properties of this metasurface 2 can be controlled by applying a potential (V) between electrodes 3 and 4. In response to this potential (V), the second material 6b polyaniline (PANI) in this embodiment can transition from its emerald green imine state (ES) to its colorless emerald green imine state (LS), and vice versa. The electrochemical reactions between these two states and their interconversion are as follows... Figure 2A As shown.

[0070] In response to this transformation, the optical properties of metasurface 2 change, and... Figure 1CIn the illustrative embodiment, the holographic image including the letters "MPI" can be turned on (left) or off (right).

[0071] Figure 2B Again, it shows from Figure 1A and Figure 1B Optical component 1. However, top electrode 4 is not shown. Figure 2B In the left image, a single cell 7 of array 9 is highlighted. The cross-section of such a cell 7 is shown in... Figure 2B It is shown on the right side.

[0072] The complex refractive indices n2 and k2 of the second substance 6b (PANI in this embodiment) differ under different applied voltages. For example... Figure 2D As shown, since the anomalous transmission of light through PANI depends on the complex refractive indices n2 and k2, the anomalous transmission can be corrected by applying a voltage (V). When the first substance 6a is PMMA and the first substance 6a and the second substance 6b are applied in alternating rows 8a, 8b to the scattering structures 5a, 5b, 1, 9, the light intensity increases continuously until the applied voltage (V) reaches approximately 0.6V (“on”) (all mentioned electrochemical potentials are measured relative to an Ag / AgCl reference electrode). This can be explained by gradually changing the refractive index of PANI through electrochemical modulation, while the refractive index of PMMA remains constant. Figure 3A As shown, the minimum light intensity can be observed at an applied voltage (V) of approximately -0.2V (“off”).

[0073] The switching times τ for the rising ("off → on") and falling ("on → off") processes are approximately 48 ms and 35 ms, respectively. Figure 3B As shown. Figure 3C The transition between the "on" (0.6V) and "off" (0.2V) states is shown, with no significant degradation observed over at least 100 cycles. Figures 3A to 3C As shown, the tested optical component 1 offers excellent performance in its switching characteristics, including fast switching speed, high light intensity contrast and excellent reversibility.

[0074] The response of metasurface 2 can be monitored and optimized in situ by controlling the thickness of the conductive polymer during its electrochemical growth. The operation of metasurface 2 is electrochemically driven and exhibits excellent performance with a high intensity contrast ratio of up to 1000:1, a fast switching rate in the millisecond range, and remarkable reversibility without significant degradation for more than 100 cycles.

[0075] Figure 4CSEM images of the metasurface 2 of optical component 1 are shown. The bars 5, 5a, and 5b shown are arranged in alternating rows 8a and 8b. The bars in the first row 81 and the third row 83 (from top to bottom) are covered with PMMA, and the bars in the second row 82 and the fourth row 84 are covered with PANI. The scale bar in the lower left corner indicates a length of 200 nm. Figure 3C It can be concluded that rows 81 to 82 of the gold bars 5, 5a, and 5b are covered by PMMA 6a. 2n+1 It is evenly covered. In contrast, PANI 6b is only present in bars 82 to 84 of the second row 82 and the fourth row 84. 2n The immediate surroundings. Therefore, PANI 6b does not follow even-numbered rows 82 to 8. 2n Forming a continuous belt.

[0076] Figure 4D An AFM image of the metasurface 2 of the optical component (left) 1 is shown. On the right, the superposition of two selected height profiles is shown. In the AFM image on the left, the rows along which the height profiles were measured are shown as rows L1 and L2. Since the heights of nanorods 5, 5a, and 5b are known to be 50 nm, the thickness t of the PANI coating 6a on the gold nanorod 5a is... PANI It can be determined to be approximately 50nm. The height profile confirms the odd-numbered rows 81 to 8. 2n+1 And even-numbered rows 82 to 8 2n The different coatings of gold rods 5, 5a, and 5b. The height profile of the row indicated by gray L1, passing through the spacing between adjacent nanorods 5, 5a, and 5b in each row of 8, is shown along the even-numbered rows 82. 2n The width is very small and the height is very small, while along the odd-numbered rows 81 to 8 2n+1 The width-to-height profile is approximately 100 nm. Therefore, for the two measurement rows L1 and L2, along the odd-numbered rows 81 to 8... 2n+1 The height profiles of the widths are similar, regardless of whether rows L1 and L2 pass through nanorod 5a. In contrast, the height profiles of the two measured rows L1 and L2 differ when passing through even-numbered rows 82 to 83. 2n The timing is significantly different, depending on whether the corresponding rows L1 and L2 pass through the nanorod 5b.

[0077] Figure 4B Cyclic voltammograms of PANI5b electrochemically deposited on metasurface sample 1 are shown. A potential range from -0.2 V to 0.8 V and a scan rate of 25 mV / s were used.

[0078] Figure 4AA schematic diagram of an experimental setup is shown. The metasurface 2 on the ITO (working electrode 3), along with the Pt line (counter electrode 4) and the Ag / AgCl reference electrode, is immersed in an electrolyte within a glass bath. Right-handed circularly polarized light (RCP) is incident normally onto the sample, and the intensity of anomalous transmission is recorded.

[0079] Figure 4E The normalized intensity of anomalous transmission during the in-situ recorded growth of PANI 6b is shown. The electrochemical process ceases when the intensity reaches a minimum (period 36, circle). The intensity contrast is defined as the ratio of the maximum intensity to the minimum intensity, reaching as high as 860:1.

[0080] This invention has great potential to realize a variety of optical functions, such as optical switches for communication systems and dynamic holography for data storage.

[0081] If all features disclosed in the application are novel, individually or in combination, relative to the prior art, they are considered essential features of the invention.

Claims

1. An optical component (1) comprising a planar metasurface (2) disposed on a surface of a first substrate (3) and a top layer (4) disposed above the metasurface (2) along a height direction Z, wherein the metasurface (2) comprises an array (9) of scattering structures (5, 5a, 5b) comprising metal, wherein the array (9) is a repeating pattern of unit cells (7), wherein the unit cells (7) comprise at least two different scattering structures (5, 5a, 5b). Its features The optical properties of the metasurface (2) can be controlled by a control signal, wherein a first scattering structure (5a) at least partially contacts a layer of a first substance (6a) comprising a dielectric material and having a first refractive index, and a second scattering structure (5b) at least partially contacts a layer of a second substance (6b) comprising a polymer, the second substance (6b) being different from the first substance (6a) and providing a variable refractive index according to the control signal, wherein the real part n and / or imaginary part κ of the variable refractive index of the second substance (6b) can be transformed into corresponding values ​​of the first substance by the control signal.

2. The optical component (1) according to claim 1, Its features The second substance (6b) includes a conductive polymer and / or an electrochromic polymer that can switch between an oxidized state and a reduced state.

3. The optical component (1) according to claim 2, Its features The conductive polymer and / or electrochromic polymer can electrochemically switch between oxidized and reduced states.

4. The optical component (1) according to claim 2, Its features The second substance (6b) comprises polymers of conjugated double bonds and / or conjugated p-orbitals.

5. The optical component (1) according to claim 2, Its features The second substance (6b) comprises multiple aromatic rings.

6. The optical component (1) according to claim 2, Its features The second substance (6b) includes selectively substituted or unsubstituted polyaniline.

7. The optical component (1) according to any one of claims 1 to 6, Its features The metals in the scattering structures (5, 5a, 5b) are selected from the group consisting of ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, rhenium, copper and gold.

8. The optical component (1) according to claim 7, Its features The scattering structure (5, 5a, 5b) is composed of one or more elements selected from the group consisting of ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, rhenium, copper and gold.

9. The optical component (1) according to claim 7, Its features The scattering structure (5, 5a, 5b) comprises at least 95% of a component selected from the group consisting of ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, rhenium, copper, and gold.

10. The optical component (1) according to claim 7, Its features The scattering structures (5, 5a, 5b) comprise ≥98% of one element selected from the group consisting of ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, rhenium, copper, and gold.

11. The optical component (1) according to claim 7, Its features The scattering structures (5, 5a, 5b) comprise ≥99% of one element selected from the group consisting of ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, rhenium, copper, and gold.

12. The optical component (1) according to claim 7, Its features The scattering structures (5, 5a, 5b) comprise ≥99.5% of one element selected from the group consisting of ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, rhenium, copper, and gold.

13. The optical component (1) according to claim 7, Its features The scattering structures (5, 5a, 5b) include gold.

14. The optical component (1) according to any one of claims 1 to 6, Its features The scattering structures (5, 5a, 5b) are deployed as optical antennas in the form of rods.

15. The optical component (1) according to claim 14, Its features The rod is oriented in the plane of the metasurface (2).

16. The optical component (1) according to claim 14, Its features The rod is oriented in a spatially varying orientation.

17. The optical component (1) according to any one of claims 1 to 6, Its features The geometry and size of the first scattering structure (5a) and / or the second scattering structure (5b) in the array differ by ≤5%, wherein the size of the scattering structure (5, 5a, 5b) is smaller than the wavelength of the incident electromagnetic radiation to be manipulated by the optical component. And / or the spacing between the scattering structures (5, 5a, 5b) is smaller than the wavelength of the incident electromagnetic radiation to be manipulated by the optical component (1). Half of it.

18. The optical component (1) according to claim 17, Its features The geometry and size of the first scattering structure (5a) and / or the second scattering structure (5b) in the array differ by ≤3%.

19. The optical component (1) according to claim 17, Its features The geometry and size of the first scattering structure (5a) and / or the second scattering structure (5b) in the array differ by ≤1%.

20. The optical component (1) according to claim 17, Its features The first scattering structure (5a) and / or the second scattering structure (5b) in the array have the same geometry and size.

21. The optical component (1) according to any one of claims 1 to 6, Its features The optical properties of the metasurface (2) can change from the first optical property to the second optical property in less than 500 ms.

22. The optical component (1) according to claim 21, Its features The optical properties of the metasurface (2) can change from the first optical property to the second optical property within ≤250ms.

23. The optical component (1) according to claim 21, Its features The optical properties of the metasurface (2) can change from the first optical property to the second optical property within ≤100ms.

24. The optical component (1) according to claim 21, Its features The optical properties of the metasurface (2) can change from the first optical property to the second optical property within ≤50ms.

25. The optical component (1) according to claim 21, Its features The optical properties of the metasurface (2) can change from the first optical property to the second optical property within ≤35ms.

26. The optical component (1) according to any one of claims 1 to 6, Its features The height of the volume between the first substrate (3) and the top layer (4) is at least three times the height of the scattering structure (5, 5a, 5b), wherein the dielectric is disposed in the volume.

27. The optical component (1) according to claim 26, Its features The height of the volume between the first substrate (3) and the top layer (4) is ≥5 times the height of the scattering structure (5, 5a, 5b).

28. The optical component (1) according to claim 26, Its features The height of the volume between the first substrate (3) and the top layer (4) is ≥10 times the height of the scattering structure (5, 5a, 5b).

29. The optical component (1) according to claim 26, Its features The height of the volume between the first substrate (3) and the top layer (4) is ≥20 times the height of the scattering structure (5, 5a, 5b).

30. The optical component (1) according to claim 26, Its features The height of the volume between the first substrate (3) and the top layer (4) is ≥50 times the height of the scattering structure (5, 5a, 5b).

31. The optical component (1) according to claim 26, Its features The medium is a liquid medium.

32. The optical component (1) according to claim 26, Its features The medium is a conductive medium.

33. The optical component (1) according to claim 26, Its features The medium is an ionic solution.

34. The optical component (1) according to any one of claims 1 to 6, Its features The first substance (6a) comprises a dielectric polymer.

35. The optical component (1) according to claim 34, Its features The first substance (6a) includes an acrylate polymer.

36. The optical component (1) according to claim 34, Its features The first substance (6a) includes polymethyl methacrylate.

37. The optical component (1) according to claim 34, Its features The first substance (6a) at least partially surrounds the first scattering structure (5, 5a).

38. The optical component (1) according to claim 34, Its features The first material (6a) contacts the first scattering structure (5, 5a) on all sides that do not contact the first substrate (3).

39. The optical component (1) according to any one of claims 1 to 6, Its features The first scattering structure (5a) and / or the second scattering structure (5b) provides a cylindrical or parallelepiped geometry, wherein the longitudinal extension is in the range of 100-400 nm and the width extension perpendicular to the longitudinal direction is in the range of 10-200 nm, wherein the longitudinal extension and width extension of the cube or irregular cylinder are independently selected from these ranges.

40. The optical component (1) according to claim 39, Its features The first scattering structure (5a) and / or the second scattering structure (5b) provide a straight cylindrical or rectangular cube geometry.

41. The optical component (1) according to claim 39, Its features The longitudinal extension is in the range of 150-300 nm.

42. The optical component (1) according to claim 39, Its features The longitudinal extension is in the range of 175-225 nm.

43. The optical component (1) according to claim 39, Its features The longitudinal extension is 200 nm.

44. The optical component (1) according to claim 39, Its features The width extends in the range of 20-150 nm.

45. The optical component (1) according to claim 39, Its features The width extends in the range of 30-100nm.

46. ​​The optical component (1) according to claim 39, Its features The width extends in the range of 50-80nm.

47. The optical component (1) according to any one of claims 1 to 6, Its features Each unit cell (7) includes a row (8a) of a first scattering structure (5a) and a row (8b) of a second scattering structure (5b), wherein adjacent unit cells (7) are arranged relative to each other such that the first scattering structure (5a) and the second scattering structure (5b) form alternating rows in the array (9).

48. The optical component (1) according to any one of claims 1 to 6, Its features The first substrate (3) includes a carrier, which includes silicon dioxide.

49. The optical component (1) according to claim 48, Its features The carrier includes quartz.

50. The optical component (1) according to claim 48, Its features The carrier is composed of quartz and coated with a conductive coating.

51. The optical component (1) according to claim 50, Its features The conductive coating is a metal coating.

52. The optical component (1) according to claim 50, Its features The conductive coating is an indium tin oxide coating.

53. The optical component (1) according to any one of claims 1 to 6, Its features Each unit (7) can be addressed independently by the control signal (11).

54. An optical device comprising an optical component (1) according to any one of claims 1 to 53, wherein the application of an electric field causes modulation of the optical function of the optical device due to the modulation phase profile of incident electromagnetic radiation, the incident electromagnetic radiation being transmitted through the optical component (1) or reflected by the optical component (1).

55. The optical device (100) according to claim 54, Its features The optical device is a holographic device, a lens, or a beam control device.

56. A method for producing a metasurface (2) comprising a plane and an optical component (1) providing optical properties controllable by a control signal, comprising the following steps: Provide a first substrate (3), Provide top-level (4), Optionally, an array (9) comprising metallic scattering structures (5, 5a, 5b) is produced on the surface of the first substrate (3) by electron beam lithography. By applying a first substance (6a) comprising a dielectric material and having a first refractive index to at least a portion of the surface of the first part of the scattering structure (5, 5a, 5b) and a second substance (6b) comprising a polymer and having a second refractive index to at least a portion of the surface of the second part of the scattering structure (5, 5a, 5b), a repeating pattern of unit cells (7) comprising at least two different scattering structures (5, 5a, 5b) is created in the array, wherein the second substance (6b) is different from the first substance (6a) and provides a variable refractive index according to the control signal, wherein the real part n and / or imaginary part κ of the variable refractive index of the second substance (6b) can be transformed into corresponding values ​​of the first substance by the control signal.

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