Liquid crystal metasurface with crossed backplane optical reflector

Abstract

According to various embodiments, a tunable optical metasurface includes an array of elongate resonator tracks arranged parallel to each other. The liquid crystal is located within the light field between adjacent resonator tracks. The controller may selectively apply a voltage differential mode to the elongated resonator track to adjust its phase response. In accordance with various embodiments, a cross-backplane reflector is utilized that allows for either an intermediate array routing or an edge array routing of electrical connections between the controller and resonator tracks. The cross-backplane reflector includes a plurality of elongate optical reflectors extending parallel to each other and perpendicular to the resonator track array. An optically transmissive (e.g., transparent) dielectric may electrically separate the resonator track from the optical reflector. A via pattern formed therein facilitates an electrical connection between the optical reflector and the resonator track.

Description

Related Applications

[0001] This application claims priority to U.S. non-provisional patent application No. 17 / 685,621, entitled “Liquid Crystal Metasurfaces With Cross-Backplane Optical Reflectors,” filed on March 3, 2022, the entire contents of which are hereby incorporated by reference herein. Technical Field

[0002] The present disclosure relates to optical resonators and antennas. In particular, the present disclosure relates to tunable optical reflective metasurfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Figure 1A An example of a tunable liquid crystal metasurface (LCM) according to one embodiment is shown.

[0004] Figure 1B Shown is a close-up view of liquid crystal located between two parallel elongated resonator tracks of a tunable LCM according to one embodiment.

[0005] Figure 2A Shown is a top view of parallel resonator tracks arranged on a planar reflector surface according to one embodiment.

[0006] Figure 2B An optical wavefront incident on a resonator track arranged on a planar reflector surface is shown according to one embodiment.

[0007] Figure 3A Shown is a top view of parallel resonator tracks arranged on a crossed backplane reflector according to one embodiment.

[0008] Figure 3B An optical wavefront incident on a resonator track arranged parallel to a crossed backplane reflector is shown according to one embodiment.

[0009] Figure 3C shows a top view of parallel resonator tracks arranged on a crossed backplane reflector according to one embodiment, similar to Figure 3A Top view of the , but rotated 90 degrees.

[0010] Figure 3D Another side view of parallel reflector elements of a cross-backplate reflector is shown according to one embodiment.

[0011] Figure 4A A layout diagram of a cross-backplane reflector layer with an intermediate array via layout layer with vias between optical reflector strips is shown according to one embodiment.

[0012] Figure 4B According to one embodiment, Figure 4A Layout diagram of the resonator tracks in the resonator layer of the intermediate array layout.

[0013] Figure 4C A layout diagram of a portion of a mid-array LCM including a resonator layer, a via layout layer, and a cross-backplane reflector layer is shown according to one embodiment.

[0014] Figure 5A An alternative layout diagram of a portion of an LCM using edge wiring is shown according to one embodiment.

[0015] Figure 5B According to one embodiment, Figure 5A Layout diagram of the vias and resonator layers in the edge-routed portion of the LCM.

[0016] Figure 5C According to one embodiment, Figure 5A Layout diagram of the vias and reflector layers in the edge-routed portion of the LCM.

[0017] Fig. 6A A layout diagram of a portion of an LCM using an alternative edge wiring layout is shown according to one embodiment.

[0018] Figure 6B According to one embodiment, Fig. 6A Layout diagram of the vias and resonator layers in the edge-routed portion of the LCM.

[0019] Figure 6C According to one embodiment, Fig. 6A Layout diagram of the vias and reflector layers in the edge-routed portion of the LCM.

[0020] Fig. 7A A layout diagram of a portion of an LCM using an alternative single-sided edge wiring layout is shown according to one embodiment.

[0021] Figure 7B A layout diagram of a portion of an LCM with crossed backplane reflector layers is shown according to one embodiment.

[0022] Figure 7C A layout diagram of a portion of an LCM with a cross-backplane for single-sided edge wiring and solid reflectors in the active area is shown according to one embodiment.

[0023] Fig. 8A A perspective view of a vertical track of an LCM extending from a reflective surface is shown according to one embodiment.

[0024] Figure 8B An optically reflective copper surface covered with an insulating layer and metal tracks extending from the insulating layer with liquid crystals between the metal tracks is shown according to one embodiment.

[0025] Figure 8C Shown is a simulated resonant optomagnetic field between two adjacent tracks extending from an optically reflective copper surface, according to one embodiment.

[0026] Fig.9A Liquid crystal is shown between two metal tracks aligned in a first direction without any applied voltage to provide a first refractive index according to one embodiment.

[0027] Fig. 9B Liquid crystal is shown between two metal tracks aligned in a second direction with an applied voltage of 5 volts to provide a second refractive index according to one embodiment.

[0028] Fig. 9C A graph showing the phase response of an LCM unit cell with respect to applied voltage values ​​according to one embodiment.

[0029] Fig. 10A An example diagram of a tiled LCM is shown, where each tile includes multiple tracks, according to one embodiment.

[0030] Fig. 10B A phase response plot is shown relative to the position of tiles of multiple tracks of a diffraction order 4 LCM, according to one embodiment.

[0031] Fig. 10C Another phase response plot is shown relative to position on a tile of multiple tracks of a diffraction order 7 LCM, according to one embodiment.

[0032] Fig.11 An example diagram showing multiple tracks forming a single tile of a multi-tile LCM according to one embodiment. DETAILED DESCRIPTION

[0033] Tunable optical metasurfaces can be used for beamforming, including for three-dimensional beamforming, two-dimensional beam steering, and one-dimensional beam steering. In various embodiments, the tunable optical metasurface includes an array of elongated resonator tracks arranged parallel to each other on a first flat surface of an optically transmissive dielectric (e.g., optically transparent). Liquid crystal is located in the optical field region between each adjacent resonator track. For example, liquid crystal can fill the channel between the resonator tracks, and in some embodiments, a liquid crystal layer is formed above the track. The liquid crystal can be deposited between the resonator tracks and fixed by an optically transparent cover (e.g., glass). Other dielectric materials with electrically tunable refractive indices can also be located between the tracks, such as electro-optic polymers or chalcogenide glasses, etc. Therefore, although many of the embodiments described herein relate to liquid crystals, it will be understood that similar embodiments can be envisioned using alternative refractive index tunable dielectric materials.

[0034] The presently described systems and methods include various embodiments of a cross-backplane reflector layer below the resonator layer. The cross-backplane reflector layer includes a plurality of elongated optical reflectors that facilitate discrete electrical connections and via formation, as described herein. For example, the cross-backplane reflector can include a plurality of elongated optical reflectors extending parallel to each other and perpendicular to the array of resonator tracks. The cross-backplane reflector and the resonator tracks can be separated by a dielectric layer to provide electrical insulation therebetween. In other words, the cross-backplane reflector and the resonator tracks can be located on relatively flat surfaces of an optically transmissive dielectric layer.

[0035] As described herein, multiple through holes can be patterned in an optically transmissive dielectric at locations between adjacent optical reflectors in a cross backplane reflector. A controller can apply a voltage to each resonator track through an electrical connection therebetween. In some embodiments, the electrical connection can include a wire, trace, or other conductive element extending from the resonator track through a through hole in the optically transmissive dielectric and then extending from between adjacent elongated optical reflectors of the cross backplane reflector to a controller that is integrated on the same substrate below the reflector layer or externally connected to a metasurface substrate. In other embodiments, each resonator track can be connected to one or more elongated optical reflectors of a cross backplane reflector. The controller can apply a voltage differential mode to the resonator track by applying a corresponding voltage to the electrically connected elongated optical reflectors of the cross backplane reflector.

[0036] The presently described systems and methods include a cross-backplane reflector configuration in which vias for electrical connection to the resonator tracks are patterned in the middle of the active portion of the metasurface (a middle array wiring configuration). The presently described systems and methods include a cross-backplane reflector configuration in which vias for electrical connection to the resonator tracks are patterned on edge regions outside the active portion of the metasurface (an edge array wiring configuration).

[0037] As described herein, a controller can selectively apply a voltage differential pattern between adjacent resonator tracks to generate a corresponding reflection phase pattern for selective beam control. Depending on the electrical connection configuration utilized, the metasurface can include a plurality of through holes patterned in an optically transmissive dielectric that are located between adjacent optical reflectors in a cross-backplane reflector. The control lines connecting the controller to the resonator tracks can be routed as part of the cross-backplane reflector and through the plurality of through holes in the optically transmissive dielectric. In this way, the reflector layer serves as both an optical reflector beneath the resonator and as a voltage routing layer. This enables large optical apertures to be tiled with repeating groups of resonators. In such an embodiment, the controller can apply a non-zero bias voltage to the optical reflector in the cross-backplane reflector because the optical reflector itself is not used as part of the electrical connection between the controller and the resonator track.

[0038] As described herein, the resonator track can be embodied as a metal track or a doped dielectric or semiconductor track. Examples of suitable metal tracks include, but are not limited to, metal tracks comprising one or more of aluminum, gold, copper, silver, platinum, titanium, chromium, tantalum, tantalum nitride, titanium nitride, molybdenum, cobalt, and tungsten. Similarly, the optical reflector track of the cross-backplane reflector element can comprise one or more of aluminum, gold, copper, silver, platinum, titanium, chromium, tantalum, tantalum nitride, titanium nitride, molybdenum, cobalt, and tungsten or be composed of one or more of aluminum, gold, copper, silver, platinum, titanium, chromium, tantalum, tantalum nitride, titanium nitride, molybdenum, cobalt, and tungsten. In some embodiments, the optical reflector track includes a diffusion barrier comprising tantalum, tantalum nitride, and titanium nitride. The resonator tracks can be spaced from each other by less than half the wavelength within the operating bandwidth. Similarly, the spacing between the optical reflectors of the cross-backplane reflector can also be less than half the wavelength within the operating bandwidth. In other embodiments, the spacing between the optical reflectors of the cross-backplane reflector is greater than half the wavelength within the operating bandwidth. In embodiments where the crossed backplane has optical reflectors with dimensions comparable to the wavelength of light, the crossed backplane structure is symmetrical for p-polarized light (defined by the plane of incidence (see, e.g., Figure 2B )) behaves like a mirror. The electric field of light penetrating the resonator and impinging on the reflector is parallel to the walls of the reflector track, so the structure acts as a good reflector.

[0039] The tunable optical metasurface may utilize a cross-backplane reflector configuration referred to as a "middle array wiring" configuration, in which vias for electrical connection between the optical reflectors and resonator tracks of the cross-backplane reflector are patterned in diagonal or flag-shaped stripes within the active area of ​​the metasurface. In other embodiments, the tunable optical metasurface may utilize a cross-backplane reflector with vias in an "edge array wiring" configuration, in which the vias for electrical connection are patterned outside the active area of ​​the metasurface. In both arrangements, a set of different voltage signals are connected to many resonator tracks in a tiled manner, such that a single voltage is connected to a single resonator track in each tiled block. If the number of different voltage lines is large enough to cover the entire optical aperture, no tiled blocks are required.

[0040] In an edge array wiring configuration, the elongated resonator tracks are arranged parallel to each other and extend from a first edge of the active area to a second edge of the active area, and beyond the second edge of the active area into a first wiring area outside the active area. The cross backplane conductor may include a plurality of elongated conductors extending parallel to each other and perpendicular to the resonator tracks. The cross backplane conductor may be an optical reflector, similar to the optical reflector described in the intermediate array wiring configuration. In other embodiments, the cross backplane conductor is non-reflective within the wiring area. In the edge array wiring configuration, the optically reflective surface or layer below the resonator track can be formed as a single two-dimensional surface (e.g., a metal sheet or metal layer), a cross backplane reflector in an optical reflector, or a distributed Bragg reflector (DBR), which includes multiple layers of dielectrics with different refractive indices.

[0041] In some edge array wiring configurations, as shown and described in more detail below, each resonator track further extends beyond the first edge of the active area into a second wiring area outside the active area. The second cross-backplane conductor within the second wiring area may include a second plurality of elongated conductors extending parallel to each other and perpendicular to the resonator tracks.

[0042] The voltage difference applied between the two tracks that form the optical resonator determines the orientation angle of the liquid crystal, which changes the phase delay experienced by the incident light at the corresponding position on the surface. The set of voltages applied to the resonators within one tile of the resonator determines the properties of the diffracted beam from the tunable metasurface. When all resonators are turned off (the voltages are all zero or equal to each other), the metasurface acts as a mirror and the angle of the outgoing beam is equal to the incident beam. A periodic voltage pattern is applied so that the marked diffraction pattern is encoded on the entire surface, which is used to guide the incident beam to the desired angle. The period of the encoded propagated (blazed) diffraction pattern determines the angle of the outgoing (diffracted beam). Other modulation patterns that are non-periodic within the tile can be applied to guide light to multiple directions, or to perform other optical functions beyond lensing or plane wave beam guidance. If the number of control voltages is large enough so that tiling is not required, the metasurface can perform arbitrary optical functions.

[0043] Copper is an example of a metal that is suitable and cost-effective for fabricating resonator tracks and / or optical reflectors. Copper is suitable for use in the infrared bandwidth for light detection and ranging or LiDAR, such as 905 nm LiDAR systems and 1550 nm LiDAR systems, or for optical communications. Copper can also be used for various other operating wavelengths. Alternative metals (e.g., gold, silver, aluminum, etc.) and various dielectrics and metal-coated dielectrics are known to be highly reflective at various wavelengths and can be used in metasurfaces configured to operate at other wavelengths. Copper and aluminum are preferred metals for forming the tracks because they are commonly used as interconnects in integrated circuit manufacturing.

[0044] Various combinations of the above embodiments and features can be used as part of building a solid-state light detection and ranging (LiDAR) transmitter, receiver or transceiver system. According to various embodiments, the transceiver system may include a first tunable optical reflective metasurface for transmitting light and a second tunable optical reflective metasurface for receiving light reflected by a distant object (rebounded light). The distance to the distant object can be calculated by measuring the flight time of the transmitted light and the rebounded light. Each optical reflective metasurface includes an optical reflective surface (or reflective layered surface) having an array of sub-wavelength optical resonant antennas (e.g., a two-dimensional or one-dimensional array). The voltage bias pattern applied to the liquid crystal associated with the optical resonator track modifies its local reflection phase. The controller can selectively apply the voltage pattern to obtain a target beam steering angle.

[0045] LiDAR systems can utilize laser diode light sources for transmission, such as laser diodes that emit optical radiation at standard wavelengths of 905 nanometers or 1550 nanometers. Various other wavelengths can be used with the systems and methods described herein, including visible wavelengths, sub-infrared wavelengths, and infrared wavelengths. LiDAR systems can include receivers to reflect reflected optical radiation from a target steering angle or beam shape (e.g., corresponding to the steering angle of the transmission) to a receiving sensor (e.g., an avalanche photodiode array). The presently described systems and methods can be used in alternative applications that utilize beam steering in addition to LiDAR.

[0046] It should be understood that the metasurface technology described herein can be combined with or otherwise utilize previous advances in surface scattering antennas, such as those described in U.S. Patent Publication No. 2012 / 0194399, which is incorporated herein by reference in its entirety. Additional elements, applications, and features of surface scattering antennas featuring reference or feed waves are described in U.S. Patent Publication Nos. 2014 / 0266946, 2015 / 0318618, 2015 / 0318620, 2015 / 0380828, 2015 / 0162658, and 2015 / 0372389 (each of which is incorporated herein by reference in its entirety). Specific descriptions of optical resonant antenna configurations and feature dimensions are described in U.S. Patent Application Nos. 15 / 900,676, 15,900,683, and 15 / 924,744 (each of which is incorporated herein by reference in its entirety).

[0047] In the present disclosure, examples of transmit (or receive) embodiments are provided, with the understanding that mutual receive (or transmit) embodiments are also contemplated. Similarly, it should be understood that the system can operate only as a transmitter, only as a receiver, as a transmitter and a receiver at the same time, with a time-division multiplexed transmitter / receiver, with a frequency-division multiplexed transmitter / receiver, with a first metasurface acting as a transmitter and a second metasurface acting as a receiver, or other transmit / receive configurations or operating techniques.

[0048] The presently described embodiments support optical bandwidths and are therefore suitable for LiDAR and other optical-based sensing systems. Specifically, the systems and methods described herein operate in the sub-infrared, mid-infrared, high-infrared, and / or visible frequency ranges (generally referred to herein as "optical"). Given the feature sizes required for sub-wavelength optical resonant antennas and antenna spacing, the described metasurfaces can be fabricated using microlithography and / or nanolithography processes, such as those commonly used to fabricate complementary metal oxide semiconductor (CMOS) integrated circuits.

[0049] Some infrastructures that can be used with the embodiments disclosed herein are already available, such as general-purpose computers, computer programming tools and techniques, digital storage media, and communication links. Many systems, subsystems, modules, components, etc. described herein can be implemented as hardware, firmware, and / or software. Various systems, subsystems, modules, and components are described according to the functions they perform because there are such a wide variety of possible implementations. For example, it is understood that many existing programming languages, hardware devices, frequency bands, circuits, software platforms, network infrastructures, and / or data storage can be used alone or in combination to implement specific control functions.

[0050] It should also be understood that two or more of the elements, equipment, systems, subsystems, parts, modules, etc. described herein can be combined into a single element, equipment, system, subsystem, module or part. In addition, many elements, equipment, systems, subsystems, parts and modules can be duplicated or further divided into discrete elements, equipment, systems, subsystems, parts or modules to perform those subtasks described herein. Any embodiment described herein can be combined with any combination of other embodiments described herein. Various permutations and combinations of embodiments have been contemplated with their non-contradictory degree.

[0051] As used herein, a computing device, system, subsystem, module or controller may include a processor, such as a microprocessor, a microcontroller, a logic circuit, etc. The processor may include one or more special processing devices, such as an application specific integrated circuit (ASIC), a programmable array logic (PAL), a programmable logic array (PLA), a programmable logic device (PLD), a field programmable gate array (FPGA) or another customizable and / or programmable device. The computing device may also include a machine-readable storage device, such as a non-volatile memory, a static RAM, a dynamic RAM, a ROM, a CD-ROM, a disk, a tape, a magnetic, an optical, a flash memory or other machine-readable storage medium. Various aspects of certain embodiments may be implemented or enhanced using hardware, software, firmware or a combination thereof.

[0052] The parts of some disclosed embodiments are described and illustrated in the figures of this article to provide specific examples. Many parts thereof can be arranged and designed with a variety of different configurations. In addition, the features, structures and operations associated with an embodiment can be applied to the features, structures or operations described in conjunction with another embodiment or combined with them. In many examples, well-known structures, materials or operations are not shown or described in detail to avoid confusing the various aspects of the present disclosure. The right to add any described embodiment or feature to any one of the figures and / or as a new figure is expressly reserved.

[0053] The embodiments of the systems and methods provided in this disclosure are not intended to limit the scope of the disclosure, but are merely representative of possible embodiments. In addition, the steps of a method do not necessarily need to be performed in any particular order, or even sequentially, nor do the steps need to be performed only once. As previously mentioned, the descriptions and variations about the transmitter are equally applicable to the receiver, and vice versa.

[0054] Figure 1A An example of an adjustable liquid crystal (LCM) metasurface 100 according to one embodiment is shown. The adjustable liquid crystal metasurface (LCM) 100 can be used as part of, for example, a solid-state light transmitter system, a receiver system, or a transceiver system. As shown, the adjustable LCM 100 includes an optically reflective substrate 190 and a dielectric layer 195. A plurality of elongated tracks 191 are arranged on the optically reflective substrate 190 at subwavelength intervals and are electrically isolated by the dielectric layer 195. The elongated tracks 191 are referred to herein as "resonator tracks" because the gaps between them (filled with liquid crystals or other dielectrics that can be adjusted to adjust the refractive index) resonate within the optical operating bandwidth of the LCM metasurface. Liquid crystal or another refractive index adjustable dielectric material 193 is located between the elongated tracks 191. A controller (not shown) can apply a voltage differential bias pattern to the elongated tracks 191 to modify the reflection phase of the resonator. The combination of phase delays imparted by all resonators produces constructive interference in the desired beam steering direction.

[0055] According to one embodiment, Figure 1B A close-up view of a liquid crystal 193 is shown positioned between two parallel elongated resonator tracks 191 and 192. As shown, the elongated resonator tracks 191 and 192 extend from a reflective surface 190 and are electrically isolated from the reflective surface 190 by a dielectric layer 195.

[0056] Additional descriptions, variations, functions, and uses of optical metasurfaces are described in the following patents: U.S. Patent No. 10,451,800, issued on October 22, 2019, entitled "Plasmonic Surface-Scattering Elements and Metasurfaces for Optical Beam Steering"; U.S. Patent No. 10,665,953, issued on May 26, 2020, entitled "Tunable Liquid Crystal Metasurfaces"; and U.S. Patent No. 11,092,675, issued on August 17, 2021, entitled "Lidar Systems based on Tunable Optical Metasurfaces", each of which is hereby incorporated by reference in its entirety. Many of the metasurfaces described in the above U.S. patents include parallel tracks located above a two-dimensional or planar reflective surface or layer.

[0057] According to one embodiment, Figure 2A Shown is a top view of parallel resonator tracks 295 (shown as white tracks) arranged on a planar reflector surface 290 of an LCM 200. In the embodiment shown, the optically reflective backplane is a planar reflector surface 290, such as a copper or aluminum layer.

[0058] According to one embodiment, Figure 2B An optical wavefront 225 is shown incident on a resonator track 295 disposed on a planar reflector surface 290. As shown, a dielectric layer 280 electrically isolates the resonator track 295 from the planar reflector surface 290. A controller can apply a voltage bias pattern to the resonator track 295 to obtain a target reflection pattern of the incident optical wavefront 225. With the planar reflector surface 290, electrical connections from each track (or each subset of tracks) can be made from the edge of the LCM or through insulating holes formed in the planar reflector surface 290. Routing electrical connections through the planar reflector surface 290 can be difficult and / or result in unintended shorts between the electrical connections and the entire planar reflector surface 290.

[0059] According to one embodiment, Figure 3A A top view of an LCM 300 is shown, wherein parallel resonator tracks 395 are arranged on a cross backplane reflector 390 formed as a plurality of optical reflective tracks extending perpendicular to the direction of the parallel resonator tracks 395 .

[0060] According to one embodiment, Figure 3BAn optical wavefront 325 incident on a resonator track 395 and parallel to a cross backplane reflector 390 is shown. In the illustrated embodiment, the resonator track 395 is insulated from the underlying optical reflector by insulating layers 380, 381, and 382. Insulating layers 380, 381, and 382 can be a single insulating layer or multiple insulating layers (e.g., combined into one or two layers, rather than the three layers shown). The light radiation incident on the LCM perpendicular to the parallel elongated optical reflectors forming the cross backplane reflector 390 is reflected in the same manner as if the light reflective backplane were a solid layer. As described herein, the elongated optical reflectors or the spaces between the elongated optical reflectors can be used to route electrical connections between the controller and the resonator track 395.

[0061] As described herein, a plurality of through holes may be patterned in the optically transmissive dielectric insulating layers 380, 381, and 382 at locations between adjacent optical reflectors in the crossed backplane reflector 390 (e.g., for routing wires between the elongated optical reflectors of the crossed backplane reflector 390 and the resonator track 395). Alternatively, the through holes may be a pattern in the optically transmissive dielectric insulating layers 380, 381, and 382 at locations directly above the optical reflectors in the crossed backplane reflector 390 (e.g., for embodiments in which the elongated optical reflectors are used to electrically connect the controller to the resonator track 395).

[0062] As described herein, the controller can apply a voltage to each resonator track 395 through the electrical connections between the resonator tracks 395. In some embodiments, the electrical connections can include wires, traces, or other conductive elements that extend from the resonator tracks 395 through vias in the optically transmissive dielectric insulating layers 380, 381, and 382 and then to the controller (or a connected control layer or printed circuit board (PCB) layer) between adjacent elongated optical reflectors of the cross backplane reflector.

[0063] In other embodiments, each resonator track 395 can be connected to one or more elongated optical reflectors of the cross-backplane reflector 390 through vias in the optically transmissive dielectric insulating layers 380, 381, and 382. In such embodiments, the controller can apply a voltage differential pattern to the resonator track 395 by applying corresponding voltages to the electrically connected elongated optical reflectors of the cross-backplane reflector. As described herein, the controller can selectively apply the voltage differential pattern between adjacent resonator tracks 395 to produce corresponding reflected phase patterns for selective beam steering of the incident optical radiation 325.

[0064] Figure 3C A top view of parallel resonator tracks 395 of an LCM 300 is shown, arranged in parallel with Figure 3ASimilar cross-back reflector. Figure 3C LCM 300 and Figure 3A The same LCM 300 is shown in FIG. 1 but the view is rotated 90 degrees to facilitate Figure 3D Visualization.

[0065] Figure 3D Another side view of the parallel elongated optical reflectors of the cross backplane reflector 390 according to one embodiment is shown. As shown in the side view of the LCM 300, a single "end" resonator track 395 is visible, which is electrically isolated from the elongated optical reflectors of the cross backplane reflector 390 by insulating layers 380, 381 and 382. Examples of suitable resonator tracks 395 include dielectric tracks, doped silicon tracks, metal tracks, and combinations thereof. Examples of suitable metal tracks include, but are not limited to, metal tracks composed of one or more of aluminum, gold, copper, silver, platinum, titanium, and chromium. Similarly, the elongated optical reflectors of the cross backplane reflector 390 may include or be composed of one or more of aluminum, gold, copper, silver, platinum, titanium, and chromium. The resonator tracks 395 may be spaced apart from each other by less than half a wavelength within the operating bandwidth. Similarly, the spacing between the elongated optical reflectors of the cross backplane reflector 390 may also be spaced apart from each other by less than half a wavelength within the operating bandwidth.

[0066] Figure 4A A layout diagram of a cross-backplane reflector layer 400 is shown with an intermediate array via layout layer having vias 410 and 420 between optical reflectors 490 according to one embodiment. As shown, the vias 410 and 420 are arranged in parallel diagonal lines within the active reflective region of the cross-backplane reflector layer 400. Each via 410 and 420 can facilitate electrical connection of a resonator track to a corresponding elongated optical reflector 490. A controller can apply voltages V1, V2, V3, etc. (as shown) to a group of one or more elongated optical reflectors 490, wherein the voltages are passed through the vias 410 and 420 to the corresponding resonator tracks.

[0067] In the illustrated embodiment, the elongated optical reflector 490 serves two purposes. First, the elongated optical reflector 490 forms the cross-backplane reflector layer 400 of the LCM to reflect optical radiation incident thereon (perpendicular thereto for maximum reflection efficiency, but in some embodiments may be off-axis for slightly reduced reflection efficiency). Second, the optical reflector 490 supplies voltage from the controller to the resonator track through the vias 410 and 420.

[0068] According to one embodiment, Figure 4B Shows Figure 4ALayout diagram of resonator tracks 495 in a resonator layer 401 of an intermediate array layout. As shown, a plurality of through-holes 410 and 420 are aligned to connect each resonator track 495 to a different elongated optical resonator in an underlying layer. In the illustrated embodiment, each resonator track 495 is associated with two through-holes to provide redundancy in electrical connections to the underlying elongated optical resonator layer. The illustrated layout is referred to as an intermediate array layout of through-holes 410 and 420 in a flag-strip pattern within an optically active region of an LCM. The dimensions of the figure are exaggerated and shown with modified relative spacing to facilitate visualization. In an exemplary embodiment, the horizontal spacing (H) between the resonator tracks 495 on opposite sides of the through-hole flag stripes is 1 / 40. s ) is about 300 microns, and the vertical spacing (V s ) can be approximately 1,200 microns.

[0069] Figure 4C A layout diagram of a portion of the intermediate array LCM 402 is shown, including a resonator layer of resonator tracks 495, a via layout layer of vias 410 and 420, and a cross-backplane reflector layer of elongated optical reflectors 490, according to one embodiment.

[0070] Figure 5A An alternative layout diagram 502 of a portion of an LCM using edge wiring according to one embodiment is shown. The diagram 502 shown includes a crossed backplane reflector layer and resonator tracks of an elongated optical reflector. The dashed rectangle identifies the active area of ​​the LCM, and it is worth noting that vias are formed outside the LCM active area within the wiring area of ​​the LCM. The embodiment shown has dual connections through vias in the upper and lower wiring areas of the LCM on both sides of the active area of ​​the LCM.

[0071] Figure 5B According to one embodiment, Figure 5A Layout diagram 501 of vias and resonator layers in a portion of an edge-wired LCM. In an edge array wiring configuration, the optically reflective surface or layer below the resonator tracks can be formed as a single two-dimensional surface (e.g., a metal sheet or layer), a crossed backplane reflector of an optical reflector (as shown), or a distributed Bragg reflector (DBR) including multiple layers of dielectrics with different refractive indices.

[0072] Figure 5C According to one embodiment, Figure 5ALayout 500 of via and reflector layers for a portion of an edge wired LCM. An adjustable LCM utilizing a cross-backplane reflector with vias outside the active area is referred to as an "edge array wired". In an edge array wired configuration, elongated resonator tracks are arranged parallel to each other and extend from a first edge of the active area to a second edge of the active area and beyond the second edge of the active area into a first wired area outside the active area. The cross-backplane conductor (which may or may not be "reflective") may include a plurality of elongated conductors (which may but are not necessarily elongated optical reflectors) extending parallel to each other and perpendicular to the resonator tracks.

[0073] In some edge array wiring configurations, as shown and described in more detail below, each resonator track further extends beyond the first edge of the active area into a second wiring area outside the active area. The second cross-backplane conductor within the second wiring area may include a second plurality of elongated conductors extending parallel to each other and perpendicular to the resonator tracks.

[0074] According to one embodiment, Fig. 6A A layout diagram 602 of a portion of an LCM using an alternative edge routing layout is shown.

[0075] According to one embodiment, Figure 6B Shows Fig. 6A Layout 601 of vias and resonator layers in a portion of an edge-routed LCM.

[0076] According to one embodiment, Figure 6C Shows Fig. 6A Layout 600 of vias and reflector layers for a portion of an edge-routed LCM.

[0077] According to one embodiment, Fig. 7A A layout diagram 700 of a portion of an LCM using an alternative single-sided edge routing layout is shown. As shown, the resonator tracks 795 extend beyond the active area 791 into the routing area of ​​the LCM. The elongated optical reflectors 790 extend perpendicular to the resonator tracks 795 within the routing area of ​​the LCM to provide edge-applied voltages V1-V4 from a controller to each resonator track 795 using vias 720 and 725 formed through an insulating layer that separates the resonator tracks 795 from the elongated optical reflectors that cross the backplane optical reflector layer.

[0078] According to one embodiment, Figure 7B Shows Fig. 7A Layout diagram 701 of a portion of an LCM in FIG. 7 with a crossed backplane reflector layer having elongated optical reflectors within the active area 791 .

[0079] According to one embodiment, Figure 7C A layout diagram 702 of a portion of an LCM is shown with a cross-backplane and solid reflectors for single-sided edge wiring in the active area 792. Similarly, in an edge array wiring configuration, e.g. Figures 7A-7C In the configuration shown, the optically reflective surface or layer below the resonator tracks in the active region 792 can be formed as a single two-dimensional surface (e.g., a metal sheet or metal layer), such as Figure 7C As shown, a cross backplane reflector is formed as an optical reflector, such as Figure 7B As shown, or formed as a distributed Bragg reflector (DBR) (not shown) including multiple layers of dielectrics having different refractive indices.

[0080] Fig. 8A An example of an optically reflective metasurface 800 having a reflective surface 880 (e.g., a metal reflector or a dielectric reflector) is shown. The reflective surface 880 has an insulating layer (not shown) to provide electrical insulation from the resonator tracks 895. Each resonator track 895 is shown having an optional electrically insulating layer 896 ( Figure 8B ). In some embodiments, an electrically insulating layer 896 may also cover the top of each resonator track 895.

[0081] Figure 8B A specific embodiment of an adjustable optical resonant antenna is shown that includes two adjacent resonator tracks 891 and 892 extending from an optically reflective copper surface 890. The resonator tracks 891 and 892 extend vertically from the optically reflective surface 890 but are electrically insulated therefrom by an oxide layer or other dielectric material 880. An insulating layer 896 (e.g., silicon nitride or another electrically insulating layer) covers each of the copper resonator tracks 891 and 892. Liquid crystal 893 is deposited in the gap between the adjacent copper resonator tracks 891 and 892. A voltage controller 810 applies a voltage to the copper resonator tracks 891 and 892. The reflection phase associated with the liquid crystal 893 can be adjusted based on the voltage difference between the copper resonator tracks 891 and 892 generated by the voltage controller 810.

[0082] Figure 8C An optical field region is shown according to one embodiment with two resonant nodes 815 and 816 associated with adjacent copper resonator tracks 891 and 892 extending from an oxide layer 880 on an optically reflective surface 890. The electric field applied by the voltage controller 810 tunes the optical resonant antenna by modifying the refractive index of the liquid crystal 893 applied on, around and / or between the copper resonator tracks 891 and 892.

[0083] Fig.9AA liquid crystal 992 is shown between two metal tracks 991 and 992 according to one embodiment. As shown, in the absence of a voltage applied by the voltage controller 910, the liquid crystal is aligned along a first direction corresponding to a first refractive index.

[0084] According to one embodiment, Fig. 9B Liquid crystal 992 is shown between two metal tracks 991 and 992, which align in a second direction based on an applied voltage of 5 volts, thereby producing a second refractive index.

[0085] According to one embodiment, Fig. 9C Graph 950 showing the phase response of an LCM cell with respect to applied voltage values.

[0086] Fig. 10A An example diagram of a tiled LCM 1050 is shown, according to one embodiment, where each tile includes multiple tracks. The simplified diagram includes three reflector track subsets or "tiles" 1051, 1052, 1053, 1054, and 1055. Any number of tiles (tens, hundreds, thousands, etc.) can be used to form the LCM, and each tile can include any number of reflector tracks. During operation, the same voltage pattern V 1 To V x A resonator track is applied to each tile 1051-1055 to obtain a target reflection pattern.

[0087] According to one embodiment, Fig. 10B A phase response graph 1010 is shown as a function of position on a tile of multiple tracks of an LCM having diffraction order 4. As shown, the phase response at each position along the tile varies between 0 and 2π at a distance corresponding to the selected diffraction order.

[0088] According to one embodiment, Fig. 10C Another graph 1020 of phase response is shown as a function of position over a tile of multiple tracks of an LCM having diffraction order 7. The higher diffraction orders result in larger changes in phase over shorter distances than an LCM having diffraction order 4.

[0089] According to one embodiment, Fig.11 An example diagram of a plurality of resonator tracks 1195 forming a single tile 1150 of a multi-tile LCM is shown. As shown, the voltage V 1 、V 2 ,…V NA modulation pattern period P may be applied to the resonator tracks 1195 that is a function of the tile size divided by the diffraction order. The tile size W is a function of the center spacing or distance d between the resonator tracks (e.g., 300 nanometers) multiplied by the total number of tracks in each tile (e.g., 10, 100, 10,000, 100,000, or more).

[0090] The presently described systems and methods, including those relating to crossed backplane reflectors, edge routing of vias, and intermediate array routing of vias, can be used in conjunction with and better understood in the context of the embodiments described in the following U.S. patent applications, each of which is incorporated herein by reference in its entirety: U.S. patent application No. 16 / 357,288, entitled “Tunable Liquid Crystal Metasurfaces,” filed on March 18, 2019; U.S. patent application No. 15 / 924,744, entitled “Plasmonic Surface-Scattering Elements and Metasurfaces for Optical Beam Steering,” filed on March 19, 2018; and U.S. patent application No. 15 / 900,676, entitled “Optical Surface-Scattering Elements and Metasurfaces,” filed on February 20, 2018.

[0091] The present disclosure has been made with reference to various exemplary embodiments including the best mode. However, those skilled in the art will recognize that the exemplary embodiments may be changed and modified without departing from the scope of the present disclosure. Although the principles of the present disclosure have been shown in various embodiments, many modifications of structure, arrangement, ratio, elements, materials and components may be applicable to specific environments and / or operating requirements without departing from the principles and scope of the present disclosure. These and other changes or modifications are intended to be included within the scope of the present disclosure.

[0092] The present disclosure should be considered illustrative rather than restrictive, and all such modifications are intended to be included within its scope. Likewise, benefits, other advantages, and solutions to problems have been described above with respect to various embodiments. However, benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more apparent should not be construed as key, essential, or basic features or elements. Therefore, it should be determined that the present disclosure covers at least the following claims.

Claims

1. A tunable optical metasurface, comprising: an array of elongated resonator tracks arranged parallel to each other on a first planar surface of an optically transmissive dielectric; a tunable-index dielectric material located in the optical field region between adjacent resonator tracks; as well as Crossed backplane reflectors on opposing surfaces of the optically transmissive dielectric include a plurality of elongated optical reflectors extending parallel to each other and at an angle relative to the array of resonator tracks.

2. The metasurface of claim 1 , wherein the tunable dielectric material comprises a dielectric material having a tunable refractive index.

3. The metasurface of claim 2, wherein the plurality of elongated optical reflectors of the cross backplane reflector extend perpendicular to the array of resonator tracks.

4. The metasurface of claim 1 , wherein the tunable dielectric material comprises at least one of: a liquid crystal, an electro-optic polymer, and a chalcogenide glass.

5. The metasurface according to claim 1, further comprising: A plurality of vias are patterned in the optically transmissive dielectric, the vias being located to electrically connect each resonator track to at least one of the optical reflectors of the cross backplane reflector.

6. The metasurface according to claim 5, further comprising: A controller for selectively applying a voltage differential pattern between adjacent resonator tracks to generate a corresponding reflected phase pattern for selective beam steering.

7. A metasurface according to any one of claims 1-6, wherein each elongated resonator track comprises a metal track.

8. The metasurface of claim 7, wherein each metal track comprises at least one metal from the group consisting of aluminum, gold, copper, silver, platinum, titanium, chromium, molybdenum, cobalt, tungsten, tantalum, tantalum nitride, and titanium nitride.

9. The metasurface of any one of claims 1-6, wherein each resonator track is spaced apart from an adjacent resonator track by less than half a wavelength within an operating bandwidth.

10. The metasurface of any one of claims 1-6, wherein each optical reflector is spaced apart from an adjacent optical reflector by less than half a wavelength within an operating bandwidth.

11. The supersurface according to any one of claims 1 to 6, wherein: Each optical reflector in the cross-backplate reflector comprises at least one metal from the group consisting of aluminum, gold, copper, silver, platinum, chromium, titanium, molybdenum, cobalt, and tungsten.

12. The supersurface according to any one of claims 1 to 6, wherein: Each optical reflector in the cross-backplate reflector is at least partially coated with a coating material including at least one of tantalum, tantalum nitride, and titanium nitride.

13. A tunable optical metasurface, comprising: a cross-backplane reflector comprising a plurality of elongated optical reflectors extending parallel to each other; an array of elongated resonator tracks arranged parallel to each other and perpendicular to the optical reflector of the cross backplane reflector, wherein the array of resonator tracks is electrically isolated from the optical reflector of the cross backplane reflector; a tunable-index dielectric material located in the optical field region between adjacent resonator tracks; and A plurality of through holes are patterned within the array of resonator tracks for electrically connecting each resonator track to at least one of the optical reflectors.

14. The metasurface of claim 13, wherein the refractive index tunable dielectric material comprises at least one of: a liquid crystal, an electro-optic polymer, and a chalcogenide glass.

15. The metasurface of claim 14, wherein the array of resonator tracks is electrically insulated from the optical reflectors of the cross-backplane reflector by a dielectric insulation layer.

16. The metasurface of any one of claims 13-15, wherein the vias are patterned along diagonals within the array to provide mid-array wiring.

17. A tunable optical metasurface, comprising: an optical reflector within the active region for reflecting optical radiation within an operating bandwidth, an array of elongated resonator tracks arranged parallel to each other and extending from a first edge of the active area to a second edge of the active area and beyond the second edge of the active area into a first routing area outside the active area; a refractive index tunable dielectric material located in the optical field region between adjacent resonator tracks; as well as The first cross-backplane conductor in the first routing region includes a first plurality of elongated conductors extending parallel to each other and perpendicular to the resonator tracks.

18. The metasurface of claim 17, wherein the refractive index tunable dielectric material comprises at least one of: a liquid crystal, an electro-optic polymer, and a chalcogenide glass.

19. The metasurface of claim 17, wherein: The optical reflector within the active region includes a distributed Bragg reflector (DBR) including a plurality of dielectric layers having different refractive indices.

20. The metasurface of claim 19, wherein: The optical reflector within the active region includes a metallic reflector layer.

21. The metasurface of claim 20, wherein: The metal reflector layer includes at least one of copper and aluminum.

22. The metasurface according to claim 17 or 18, wherein: The optical reflector within the active region comprises a cross-backplane reflector having a plurality of elongated optical reflectors extending parallel to each other and perpendicular to the resonator tracks within the active region.

23. The metasurface of claim 22, further comprising a plurality of vias within the first routing region to connect each resonator track to at least one elongated conductor of the first cross-backplane conductor.

24. The metasurface of claim 17 or 18, wherein the first cross-backplane conductor comprises a cross-backplane reflector, wherein each of the elongated conductors comprises an elongated optical reflector.

25. The metasurface of claim 17 or 18, wherein each resonator track further extends beyond the first edge of the active area into a second routing area outside the active area.

26. The metasurface of claim 25, further comprising: A second cross-backplane conductor within the second routing region includes a second plurality of elongated conductors extending parallel to each other and perpendicular to the resonator tracks.

27. The metasurface of claim 26 , further comprising a second plurality of vias in the second routing region to connect each resonator track to at least one elongated conductor of the second cross-backplane conductor in the second routing region, such that each resonator track is connected to at least one elongated conductor in each of the first routing region and the second routing region.

28. The metasurface of claim 27, wherein the first crossed backplane conductor comprises a first crossed backplane reflector, and wherein the second crossed backplane conductor comprises a second crossed backplane reflector, such that each of the elongated conductors comprises an elongated optical reflector.

29. The metasurface of claim 28, wherein the optical reflector within the active region comprises a third cross-backplane reflector having a plurality of elongated optical reflectors extending parallel to each other and perpendicular to the resonator tracks within the active region.

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