Liquid crystal device and forming method thereof

Abstract

The embodiment of the invention relates to a liquid crystal device. The liquid crystal device may include a first electrode. The liquid crystal device may also include a second electrode. The liquid crystal device may further include a liquid crystal layer between the first electrode and the second electrode, the liquid crystal layer including liquid crystal molecules and an array of nanostructures adapted to enable the liquid crystal molecules to achieve a desired consistent arrangement and modulate light penetrating the liquid crystal device. The period of the nanostructure array or the aspect ratio of each nanostructure of the nanostructure array may be adapted to enable the liquid crystal molecules to achieve a desired consistent arrangement.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from Singapore application No. 10202300705Q filed on March 14, 2023, the contents of which are incorporated herein by reference in their entirety for all purposes. Technical Field

[0003] Embodiments of the present application relate to a liquid crystal device. Embodiments of the present application relate to a method of forming a liquid crystal device. Background Art

[0004] A liquid crystal on silicon (LCoS)-based spatial light modulator (SLM) is a multifunctional device consisting of a one- or two-dimensional array of pixels capable of arbitrarily reconstructing the wavefront of light. FIG. 1AA conventional liquid crystal on silicon (LCoS) based spatial light modulator (SLM) is shown. These devices use the birefringent properties of liquid crystals (LCs) to locally modulate the amplitude, phase, or polarization of light. These devices have applications in engineering, medicine, military, entertainment, communications, education, transportation, telecommunication, etc. For example, LCoS SLMs can be used in near-eye devices, augmented reality (AR) systems, virtual reality (VR) systems, three dimensional (3D) holographic displays, Light Detection And Ranging (LiDAR) systems, wavelength selective switches (WSS), photolithography systems, three dimensional (3D) printing systems, etc. Pixel miniaturization of these devices is challenging due to emerging inter-pixel crosstalk, which is an unintended, purposefully processed light modulation in the neighboring pixels of any given pixel. For phase modulating SLMs, the phase delay is achieved by electrically tuning the orientation of the liquid crystal molecules at the single pixel level, which thus changes the refractive index experienced by the light along the propagation path and in turn controls the phase shift (or retardation). The phase coverage is directly proportional to the thickness of the liquid crystal medium. For transmissive and reflective SLMs, the liquid crystal thickness should be at least λ / Δn and λ / 2Δn, respectively, to achieve a 2π phase modulation, where Δn is the birefringence of the liquid crystal (defined as the difference between the real part of the extraordinary refractive index and the real part of the ordinary refractive index of the liquid crystal) and λ is the operating wavelength. Under strong anchoring conditions, the response speed of the device is directly proportional to the square of the liquid crystal thickness; under weak anchoring conditions, the response speed of the device changes linearly with the liquid crystal thickness. The inter-pixel crosstalk sets the limit for the minimum pixel size of the device, and the inter-pixel crosstalk is in turn determined by the liquid crystal thickness. Therefore, the liquid crystal thickness is a key parameter for these devices, as it limits the pixel size and the response speed, and in turn limits the field of view (FOV) and the refresh rate of the device. FIG. 1BThe relationship between resolution and field of view (FOV), pixel pitch (PP), liquid crystal (LC) layer thickness, and frame rate is shown (top) and a comparison of the pixel pitch (PP) of devices produced by Holoeye and Jasper in 2000 and 2020 (bottom).

[0005] Super surface integration, i.e. two-dimensional (2D) arrangement of optical resonant elements, also known as nanoantennas, with liquid crystal cells (LC cells) constitutes a so-called super surface or nanoantenna spatial light modulator (NSLM). FIG. 1C A schematic of a nanoantenna spatial light modulator (NSLM) is shown. NSLMs have emerged as a promising platform for realizing pixel size miniaturization and have a variety of nano-photonics applications. Unlike conventional SLMs, abrupt optical phase shifts in NSLMs are induced by the resonant properties of nanoantennas. The reorientation of liquid crystal molecules locally changes the near-field environment of nanoantennas, which enables efficient spectral tuning of their resonance and associated phase modulation. Since only the near-field of nanoantennas (typically extending only a few hundred nanometers at optical frequencies) needs to be changed, their presence allows for a significant reduction in the thickness of the tunable medium (i.e. the liquid crystal layer). Crosstalk between neighboring electrodes is also reduced, enabling pixel miniaturization. This allows wavefront modulation devices to have a wider field of view and improved refresh rate. Typically, NSLM devices have miniaturized liquid crystal cells (each with a thickness of less than 1 pm).

[0006] However, for this thinner liquid crystal cell, problems arise if the common strategy of inducing a pre-alignment of the liquid crystal by using an alignment layer, such as a polyimide layer for rubbed alignment or a suitable photoactive material layer for photo-induced alignment, is employed. For ultra-thin liquid crystal cells, the dielectric screening effect can be more pronounced even with a thin alignment layer, and the effective phase shift can be reduced. Furthermore, the strong anchoring of the alignment layer to the ultra-thin liquid crystal cell slows down the electric field response of the liquid crystal and increases the range of voltage levels required for switching, which can again increase crosstalk, ultimately affecting the benefits gained from using a thinner liquid crystal cell. SUMMARY

[0007] Embodiments of the present application relate to a liquid crystal (LC) device. The liquid crystal (LC) device can include a first electrode. The liquid crystal (LC) device can also include a second electrode. The liquid crystal (LC) device can also include a liquid crystal layer between the first electrode and the second electrode, the liquid crystal layer including liquid crystal molecules and a nanostructure array, the nanostructure array adapted to achieve a desired uniform alignment of the liquid crystal molecules and to modulate light passing through the liquid crystal device. A period of the nanostructure array or an aspect ratio of each nanostructure of the nanostructure array can be adapted to achieve the desired uniform alignment of the liquid crystal molecules.

[0008] Embodiments of the present application relate to a method of forming a liquid crystal (LC) device. The method can include forming a first electrode. The method can also include forming a second electrode. The method can also include forming a liquid crystal layer between the first electrode and the second electrode, the liquid crystal layer including liquid crystal molecules and a nanostructure array, the nanostructure array adapted to achieve a desired uniform alignment of the liquid crystal molecules and to modulate light passing through the liquid crystal device. A period of the nanostructure array or an aspect ratio of each nanostructure of the nanostructure array can be adapted to achieve the desired uniform alignment of the liquid crystal molecules. BRIEF DESCRIPTION OF DRAWINGS

[0009] In the drawings, like reference numerals refer to same parts throughout different views. The drawings are not necessarily to scale, emphasis instead being placed on illustrating the principles of the different embodiments. In the following description, different embodiments of the application are described with reference to the drawings.

[0010] FIG. 1A A conventional liquid crystal on silicon (LCoS) based spatial light modulator (SLM) is shown.

[0011] FIG. 1B A relationship between resolution and field of view (FOV), pixel pitch (PP), liquid crystal (LC) layer thickness, and frame rate is shown (top figure); and a comparison of pixel pitch (PP) of devices produced by Holoeye and Jasper in 2000 and 2020 is shown (bottom figure).

[0012] FIG. 1C A schematic diagram of a nanoantenna spatial light modulator (NSLM) is shown. NSLMs have emerged as a promising platform for realizing pixel size miniaturization and have a wide range of applications in nanophotonics.

[0013] FIG. 2 A general illustration of a liquid crystal (LC) device according to different embodiments is shown.

[0014] FIG. 3 A general illustration of a method of forming a liquid crystal (LC) device according to different embodiments is shown.

[0015] FIG. 4AA cross-sectional side view schematic of a cell of a conventional transmissive nanoantenna spatial light modulator (NSLM) with disc-shaped nanoantennas is shown.

[0016] FIG. 4B Schematics showing the orientation of liquid crystal (LC) molecules used in liquid crystal devices according to different embodiments are shown.

[0017] FIG. 5 A cross-sectional side view schematic of a cell of an ultrathin liquid crystal (LC) device with disc-shaped nanoantennas and without a top electrode alignment layer is shown.

[0018] FIG. 6 A cross-sectional side view schematic of a cell of another ultrathin liquid crystal (LC) device with square-shaped nanoantennas 608 and without a top electrode alignment layer is shown.

[0019] FIG. 7 (a) shows an array of disc-shaped nanoantennas, and (b) shows a scanning electron microscopy (SEM) image of an array of square-shaped nanoantennas.

[0020] FIG. 8A A simulated plot showing the transmittance as a function of wavelength (in nanometers or nm) is shown, which shows FIG. 5 A measured plot showing the transmittance as a function of wavelength (in nanometers or nm) is shown, which shows the transmission spectrum of a liquid device (LC) with disc-shaped nanoantennas under normal incidence of light polarized along the X-axis (P-0, solid line), along the Y-axis (P-90, dashed line), and at a 45° angle to the X-axis (P-45, dashed line).

[0021] FIG. 8B A measured plot showing the transmittance as a function of wavelength (in nanometers or nm) is shown, which shows the transmission spectrum of a liquid crystal (LC) device with an alignment layer (W, dashed line) or without an alignment layer (WO, solid line) with a 1500 nm thick liquid crystal (LC) layer and an array of disc-shaped nanoantennas under incident light polarized along the X-axis, where the insets show microscopic images of the liquid crystal cell without an alignment layer (WO) and with an alignment layer (W) under a crossed polarizer (crossed polarizer) ) and an analyzer (analyzer) ).

[0022] FIG. 8CMeasured plot showing the transmittance as a function of wavelength (in nanometers or nm) of a liquid device (LC) with a 1500 nm thick liquid crystal (LC) layer and an array of disc-shaped nanoantennas with a top electrode alignment layer (W, dashed line) or without a top electrode alignment layer (WO, solid line) under normally incident light polarized at 135° to the X-axis, where the insets show microscopic images of the liquid crystal cell without an alignment layer (WO) and with an alignment layer (W) under crossed polarizers ( ) and an analyzer ( ).

[0023] FIG. 8D Measured plot showing the transmittance as a function of wavelength (in nanometers or nm) of a liquid device (LC) with a 750 nm thick liquid crystal (LC) layer and an array of disc-shaped nanoantennas with an alignment layer (W, dashed line) or without an alignment layer (WO, solid line) under normally incident light polarized along the X-axis, where the insets show microscopic images of the liquid crystal cell without an alignment layer (WO) and with an alignment layer (W) under crossed polarizers ( ) and an analyzer ( ).

[0024] FIG. 8E Measured plot showing the transmittance as a function of wavelength (in nanometers or nm) of a liquid device (LC) with a 750 nm thick liquid crystal (LC) layer and an array of disc-shaped nanoantennas with a top electrode alignment layer (W, dashed line) or without a top electrode alignment layer (WO, solid line) under normally incident light polarized at 45° to the X-axis, where the insets show microscopic images of the liquid crystal cell without an alignment layer (WO) and with an alignment layer (W) under crossed polarizers ( ) and an analyzer ( ).

[0025] FIG. 9A Simulated plot showing the transmittance as a function of wavelength (in nanometers or nm) of a liquid device (LC) with a square nanoantenna as shown in FIG. 6 , under normally incident light polarized along the X-axis, along the Y-axis, and at 45° to the X-axis.

[0026] FIG. 9B Plot showing the transmittance as a function of wavelength (in nanometers or nm) of a measured plot showing the transmittance as a function of wavelength (in nanometers or nm) of a liquid device (LC) with a 750 nm thick liquid crystal (LC) layer and an array of square nanoantennas with an alignment layer (rubbing direction along the X-axis) under normally incident light polarized along the X-axis for an applied 0 V rms and 4 V rmstransmission spectra under incident light of polarization P-0 and incident light of polarization P-135 for applied voltages of 0 V rms transmission spectra under incident light of polarization P-0 and incident light of polarization P-135 for applied voltages of 0 V microscopic images of liquid crystal cells with parallel orientation and 45° orientation under crossed polarizers microscopic images of liquid crystal cells with parallel orientation and 45° orientation under crossed polarizers

[0027] FIG. 9C transmission spectra under incident light of polarization P-0 and incident light of polarization P-135 for applied voltages of 0 V rms and 4 V rms transmission spectra under incident light of polarization P-0 and incident light of polarization P-135 for applied voltages of 0 V rms transmission spectra under incident light of polarization P-0 and incident light of polarization P-135 for applied voltages of 0 V microscopic images of liquid crystal cells with parallel orientation and 45° orientation under crossed polarizers microscopic images of liquid crystal cells with parallel orientation and 45° orientation under crossed polarizers

[0028] FIG. 10 (a, b) show schematic diagrams of liquid crystal (LC) uniform alignment induced by nanostructures or nanoantennas with a circular disk shape, and (c, d) show schematic diagrams of liquid crystal (LC) uniform alignment induced by nanostructures or nanoantennas with a square shape.

[0029] FIG. 11 show cross-sectional side view schematic diagrams of a cell box of an ultrathin liquid crystal (LC) device according to different embodiments.

[0030] FIG. 12 (a) shows a scanning electron microscope (SEM) image of a fabricated rectangular nanoantenna super surface according to different embodiments; and (b) shows a schematic diagram of a uniform alignment of liquid crystal molecules induced by rectangular nanostructures or nanoantennas according to different embodiments.

[0031] FIG. 13A show simulation plots of transmittance as a function of wavelength (in nanometers or nm) showing FIG. 11 transmission spectra of a liquid crystal device (LC) with rectangular nanoantennas according to different embodiments shown in FIG. 1 1 under normal incident light polarized along the X-axis (P-0, dashed line) and along the Y-axis (P-90, solid line).

[0032] FIG. 13BA graph showing the measured transmittance as a function of wavelength (in nanometers or nm) is shown. FIG. 11 Transmission spectra of a liquid crystal device (LC) with rectangular nanoantennas according to various embodiments are shown under normal incident light polarized along the X-axis (P-0, dashed line) and along the Y-axis (P-90, solid line).

[0033] FIG. 14 (a) shows the fabricated nano-square nanoantenna (L=W=270nm, H=200nm, P x =P y =360nm) scanning electron microscope (SEM) images; (b) to (d) show the square nanoantenna shown in (a) under the cross polarizer ( ) and the analyzer ( ) microscopic images of different array orientations; (e) shows scanning electron microscope (SEM) images of rectangular nanoantennas fabricated according to different embodiments (L = 260nm, W = 180nm, H = 200nm, P x =360nm, P y = 290 nm); (f) to (h) show the rectangular nanoantennas manufactured as shown in (e) according to different embodiments under the conditions of cross polarizers ( ) and the analyzer ( ) microscopic images of different array orientations under different embodiments; (i) shows scanning electron microscope (SEM) images of rectangular nanoantennas fabricated according to different embodiments (L = 350 nm, W = 180 nm, H = 200 nm, P x =430nm, P y = 270nm); (j) to (l) show the rectangular nanoantennas manufactured as shown in (i) according to different embodiments under the conditions of cross polarizers ( ) and the analyzer ( ) under different array orientations.

[0034] FIG. 15A Simulation graphs showing transmittance as a function of wavelength (in nanometers or nm) of a liquid crystal device (LC) with rectangular nanoantennas according to various embodiments under incident light polarized along the X-axis (P-0), along the homogeneous ( =90°, solid line) liquid crystal (LC) uniform arrangement and homeotropic ( =0°, dotted line) transmission spectrum of uniformly arranged liquid crystal (LC).

[0035] FIG. 15BMeasured graph showing transmittance as a function of wavelength (in nanometers or nm) for a liquid device (LC) with rectangular nanoantennas and no alignment layer according to various embodiments, for an applied voltage of 0 V rms , 3.5V rms and 5V rms , transmission spectrum under incident light polarized along the X-axis (P-0). FIG. 15C Measured graph showing transmittance as a function of wavelength (in nanometers or nm) for a liquid device (LC) with rectangular nanoantennas and an alignment layer, for an applied voltage of 0 V. rms , 3.5V rms and 5V rms , transmission spectrum under incident light polarized along the X-axis (P-0).

[0036] FIG. 16 The liquid crystal (LC) infiltrated rectangular nanoantenna is shown in Figure 2. ) and the analyzer ( ), where (a) to (c) show microscopic images of a 500 nm thick liquid crystal (LC) cell with a top electrode alignment layer at different applied voltages; (d) to (f) show microscopic images of a 500 nm thick liquid crystal (LC) cell with pure metasurface-induced uniform alignment and no top electrode alignment layer according to various embodiments at different applied voltages; and (h) to (j) show microscopic images of a 1000 nm thick liquid crystal (LC) cell with pure metasurface-induced uniform alignment and no top electrode alignment layer according to various embodiments at different applied voltages. One set of arrows represents the liquid crystal director oriented along the length or long axis of the rectangular nanoantenna, while the other set of arrows represents the direction of the uniform alignment induced by the top electrode alignment layer.

[0037] FIG. 17A Graphs showing waveform (in volts or V) / intensity as a function of time (in milliseconds or ms) illustrate the switching performance (voltage-dependent transmission intensity - black dashed line) of a 1000 nm thick liquid crystal cell without an alignment layer under an applied signal (grey line) according to different embodiments.

[0038] FIG. 17B A graph showing waveform (in volts or V) / intensity as a function of time (in milliseconds or ms) illustrates the switching performance (voltage-dependent transmission intensity - black dashed line) of a 750 nm thick liquid crystal cell without an alignment layer under an applied signal (grey line) according to different embodiments.

[0039] FIG. 17CA plot showing the waveforms (in volts or V) / intensity as a function of time (in milliseconds or ms) of the switching performance (voltage dependent transmission intensity - black dotted line) of a 750 nm thick liquid crystal cell with a top electrode alignment layer under an applied signal (grey line).

[0040] FIG. 18 A cross-sectional side view schematic of a cell of a liquid crystal (LC) device with rectangular nanoantennas according to different embodiments.

[0041] FIG. 19 A perspective view schematic of a cell of a liquid crystal (LC) device with rectangular nanoantennas and a pixelated second electrode according to different embodiments.

[0042] FIG. 20 A cross-sectional side view schematic of a cell of a transmissive liquid crystal (LC) device according to different embodiments with rectangular nanoantennas on or in contact with the first and second electrodes, respectively.

[0043] FIG. 21 A cross-sectional side view schematic of a cell of a reflective liquid crystal (LC) device according to different embodiments with rectangular nanoantennas on opposite sides of the liquid crystal layer.

[0044] FIG. 22 A cross-sectional side view schematic of a cell of a liquid crystal (LC) device according to different embodiments with two rectangular nanoantenna arrays aligned perpendicular to each other.

[0045] FIG. 23 A cross-sectional side view schematic of a cell of a transmissive liquid crystal (LC) device according to different embodiments with an array of nanopillars.

[0046] FIG. 24 A cross-sectional side view schematic of a cell of a reflective liquid crystal (LC) device according to different embodiments with an array of nanopillars.

[0047] FIG. 25A A cross-sectional side view schematic of a cell of a reflective liquid crystal (LC) device according to different embodiments with an array of nanopillars when the applied voltage is below the threshold voltage (V th ).

[0048] FIG. 25B A cross-sectional side view schematic of a cell of a reflective liquid crystal (LC) device according to different embodiments with an array of nanopillars when the applied voltage is above the threshold voltage (V th ).

[0049] FIG. 26A comparison table of liquid crystal (LC) devices according to different embodiments with previously reported devices is shown. DETAILED DESCRIPTION

[0050] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the application can be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the application. Other embodiments can be utilized and structural, logical, and electrical changes can be made without departing from the scope of the present application. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0051] Features described in the context of one embodiment can correspondingly be applied to the same or similar features in other embodiments. Features described in the context of one embodiment can correspondingly be applied to other embodiments, even if not explicitly described in those other embodiments. Furthermore, application and / or combination and / or substitution described in the context of one embodiment for one feature can correspondingly be applied to the same or similar features in other embodiments.

[0052] In the context of different embodiments, the articles "a", "an", and "the" as used with respect to a feature or element include a reference to one or more of the features or elements.

[0053] In the context of different embodiments, the term "about" or "approximately" applied to a numerical value means within 10% of the stated value.

[0054] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0055] "Include" means including, but not limited to, any specific listed item. Thus, the term "comprising" means that the listed elements are mandatory, but that other elements are optional and can or can not be present. "Include" and "comprising" do not exclude other elements not specifically listed.

[0056] "Consisting of" means including, and limited to, whatever follows the phrase "consisting of". Thus, the term "consisting of" indicates that the listed elements are mandatory, and that no other elements can be present. "Consisting of" excludes any element not specified in the "consisting of" clause.

[0057] Embodiments described in the context of one liquid crystal device are equally applicable to other liquid crystal devices, and embodiments described in the context of a method are equally applicable to liquid crystal devices, and vice versa.

[0058] Different embodiments can address one or more problems faced by conventional devices. Different embodiments can provide a different liquid crystal (LC) uniform alignment strategy than conventional devices. Different embodiments can not include a separate alignment layer. Rather, an array of metasurfaces or nanoantennas (also referred to as nanostructures) can provide a uniform alignment (i.e., a pre-alignment) for liquid crystal (LC) molecules. According to different embodiments, the nanostructures can have a dual purpose of maintaining optical resonance for light modulation and inducing a required uniform alignment for liquid crystal (LC) molecules. The liquid crystal molecule uniform alignment can be fully controlled by the periodicity and geometry of the nanoantennas without any additional alignment layer. Different embodiments can significantly shorten the response time and reduce the operating voltage requirement.

[0059] FIG. 2 A general schematic of a liquid crystal (LC) device according to different embodiments is shown. The device can be referred to as a metasurface liquid crystal device, a metasurface or nanoantenna spatial light modulator (NSLM), or simply a spatial light modulator (SLM). The liquid crystal (LC) device can include a first electrode 202. The liquid crystal (LC) device can also include a second electrode 204. The liquid crystal (LC) device can also include a liquid crystal layer 206 between or disposed between the first electrode 202 and the second electrode 204, the liquid crystal layer 206 including liquid crystal molecules and an array of nanostructures 208, the array of nanostructures 208 adapted to cause the liquid crystal molecules to achieve a required uniform alignment and to modulate light passing through the liquid crystal device. The periodicity of the array of nanostructures and / or the aspect ratio of each nanostructure of the array of nanostructures can be adapted to cause the liquid crystal molecules to achieve the required uniform alignment.

[0060] In other words, different embodiments can include two electrodes 202, 204 and a liquid crystal layer 206 between the two electrodes 202, 204. The liquid crystal layer 206 can have nanostructures or nanoantennas that have a dual function of modulating light and providing a uniform alignment (i.e., a pre-alignment) for liquid crystal molecules of the liquid crystal layer 206.

[0061] For the avoidance of doubt, FIG. 2 It is intended to illustrate some features of devices according to different embodiments and is not intended to limit the size, shape, orientation, arrangement, etc. of different embodiments. For example, while FIG. 2 A nanostructure 208 is shown having a rectangular cross-sectional shape, it is contemplated that the nanostructure 208 can have other suitable cross-sectional shapes, such as an elliptical shape or an ellipsoidal shape. Additionally, while FIG. 2 Two nanostructures are shown, different embodiments can include any suitable number of nanostructures.

[0062] The period of the nanostructure array and / or the aspect ratio of each nanostructure of the nanostructure array can be adapted to align / control the alignment of liquid crystal molecules such that the liquid crystal molecules are aligned / aligned in a desired direction / orientation. This can be achieved without the use of an alignment layer assistance in the liquid crystal device. The presence of an alignment layer in the device can increase the voltage required for resonance tuning and can reduce the efficiency of the light modulation. The presence of an alignment layer can also limit the thickness of the device, the switching speed of the device and the sensitivity of the device. This can be more pronounced for ultra-thin liquid crystal devices (e.g. devices with a liquid crystal layer thickness of sub-micron). These effects of the alignment layer in the liquid crystal device can be undesirable. Therefore, different embodiments can use a nanostructure array or nanoantenna to achieve the desired alignment of liquid crystal molecules without the use of an alignment layer and to modulate light passing through the liquid crystal device.

[0063] In different embodiments, the nanostructure array 208 can be arranged as a periodic lattice.

[0064] In different embodiments, the second electrode 204 can be pixelated or can be non-pixelated.

[0065] In different embodiments, the first electrode 202 can be continuous and the second electrode 204 can be pixelated. The nanostructure array 208 can be formed on the first electrode 202 or the second electrode 204. In other words, the nanostructure array 208 can be in contact with the first electrode 202 or the second electrode 204. In different embodiments, each pixel of the pixelated second electrode 204 can be arranged to be individually addressable by an integrated circuit. The nanoantennas or nanostructures 208 on the pixelated second electrode 204 can provide higher device efficiency compared to a non-pixelated electrode. In other different embodiments, the nanostructures 208 can be located on or in contact with the first continuous electrode 202.

[0066] In different embodiments, the first electrode 202 can be pixelated additionally or alternatively. The first electrode 202 can be arranged to be individually addressable by an integrated circuit.

[0067] In different embodiments, the liquid crystal layer 206 can further comprise another nanostructure array. The nanostructure array 208 and the other nanostructure array can be on opposite sides of the liquid crystal layer 206. In different embodiments, the nanostructure array 208 can be in contact with the second electrode 204 and the other nanostructure array can be in contact with the first electrode 202 or vice versa. In different embodiments, the longitudinal axis of the nanostructure array 208 can be rotated relative to the longitudinal axis of the other nanostructure array. The longitudinal axis of the nanostructure array 208 can be rotated relative to the longitudinal axis of the other nanostructure array by an angle greater than 0°.

[0068] In different embodiments, the longitudinal axis of the nanostructure array 208 can be substantially perpendicular to the longitudinal axis of the nanostructure array 208. For example, the longitudinal axis of the nanostructure array 208 can be selected from any one value in the range of 80° to 110°, e.g., 85° to 105°, from the longitudinal axis of the nanostructure array 208. In different embodiments, the longitudinal axis of the nanostructure array 208 can be perpendicular to the longitudinal axis of the nanostructure array 208.

[0069] In different embodiments, the first electrode 202 and the second electrode 204 can be optically transparent. In different embodiments, the first electrode 202 and the second electrode 204 can each allow a substantial amount of light (e.g., more than 80%, more than 90%, more than 95%, or more than 99%) having any one wavelength or wavelength range selected from the range of 400 nm to 1500 nm to pass through. The first electrode 202 and the second electrode 204 can include any suitable optically transparent material, such as indium tin oxide (ITO), gallium-doped ITO, fluorine-doped tin oxide (FTO), doped zinc oxide, aluminum-doped zinc oxide (AZO), carbon nanotubes, or graphene.

[0070] In different embodiments, the first electrode 202 can be optically transparent and the second electrode 204 can be optically reflective. In different embodiments, the first electrode 202 can allow a substantial amount of light (e.g., more than 80%, more than 90%, more than 95%, or more than 99%) having any one wavelength or wavelength range selected from the range of 400 nm to 700 nm to pass through. The second electrode 204 can reflect a substantial amount of light (e.g., more than 80%, more than 90%, more than 95%, or more than 99%) having any one wavelength or wavelength range selected from the range of 400 nm to 1500 nm. In different embodiments, the second electrode 204 can include an aluminum layer, a gold layer, a silver layer, or a copper layer. In other different embodiments, the second electrode 204 can include a dielectric mirror in combination with an optically transparent conductor. The first electrode 202, on the other hand, can include any suitable optically transparent material, such as indium tin oxide (ITO), gallium-doped ITO, fluorine-doped tin oxide (FTO), doped zinc oxide, aluminum-doped zinc oxide (AZO), carbon nanotubes, or graphene.

[0071] In various embodiments, the thickness of the liquid crystal layer 206 can be any value selected from the range of 200 nm to 800 nm. In various embodiments, the distance between the first electrode 202 and the second electrode 204 can be any value selected from the range of 200 nm to 800 nm. The minimum thickness of the liquid crystal layer 206 can be equal to the height of the nanostructure / nanoantenna, which can be any value selected from the range of 200 nm to 800 nm.

[0072] In various embodiments, the nanostructure array 208 and / or another nanostructure array can have at least two dimensions that are smaller than the operating optical wavelength of the liquid crystal device. In various embodiments, one, two, or all three dimensions of each nanostructure of the nanostructure array 208 or another nanostructure array can be any value that is less than 700 nm, less than 500 nm, less than 400 nm, or less than 100 nm.

[0073] In various embodiments, the nanostructure array 208 and / or another nanostructure array can include or be made of a dielectric material or a semiconductor material. In various embodiments, the nanostructure array 208 and / or another nanostructure array can be made of a dielectric material or a semiconductor material having a real part of the refractive index that is greater than or equal to 2 and an imaginary part of the refractive index that is less than or equal to 0.1. In various embodiments, the dielectric material can be or include titanium oxide (Ti02). In various embodiments, the nanostructure array 208 and / or another nanostructure array can include titanium oxide, silicon, germanium, gallium nitride, gallium phosphide, indium phosphide, gallium arsenide, silicon nitride, or copper oxide.

[0074] In various embodiments, the liquid crystal (LC) molecules can be any suitable molecules. For example, the liquid crystal molecules can be or include nematic liquid crystal molecules, dual frequency liquid crystal (DFLC) molecules, smectic liquid crystal molecules, or chiral liquid crystal molecules.

[0075] In various embodiments, the dimension of each nanostructure in the nanostructure array along the direction in which the liquid crystal (LC) molecules are expected to align can be larger than other dimensions of the nanostructure. In other words, the dimension of each nanostructure in the first nanostructure array can be adapted to have its largest dimension along the direction in which the liquid crystal molecules are expected to align. The dimension of the nanostructure along this direction in which the liquid crystal molecules are expected to align can be greater than the other dimensions of the nanostructure by more than 0%, more than 10%, more than 20%, more than 30%, more than 50%, more than 100%, more than 200%, more than 300%, or more than 500%. In various embodiments, for example, the aspect ratio (AR) of the nanostructure (e.g., the ratio of the dimension of the nanostructure along the direction in which the liquid crystal (LC) molecules are expected to align to the dimension perpendicular to this direction (the direction in which the liquid crystal (LC) molecules are expected to align)) can be greater than 1:1, greater than 1.1:1, greater than 1.2:1, greater than 1.3:1, greater than 1.5:1, greater than 2:1, greater than 3:1, greater than 4:1, or greater than 6:1.

[0076] In various embodiments, the periodic grating of the nanostructure array can include a longest grating vector along a direction in which the liquid crystal molecules are aligned. In other words, a grating vector of the periodic grating of the nanostructure array can be longer than other grating vectors of the periodic grating. The grating vector along the direction in which the liquid crystal molecules are aligned can be larger than each other grating vector by more than 0%, more than 10%, more than 20%, more than 30%, more than 50%, more than 100%, more than 200%, more than 300%, or more than 500%.

[0077] In various embodiments, the threshold voltage or potential difference applied between the first electrode 202 and the second electrode 204 for switching the liquid crystal device may be selected from 0.5V to rms to 0.8V rms Any value within the range. rms Represents the root mean square voltage. The applied voltage can be an alternating voltage or an alternating current (AC).

[0078] In various embodiments, the liquid crystal device may further include a passivation layer formed on the second electrode 204, the passivation layer being adapted to prevent direct contact between the liquid crystal molecules and the second electrode 204. The first electrode 202 may be in contact with the liquid crystal layer 206. The passivation layer may include an oxide having a refractive index less than 2 and may be light-transmissive. The oxide may be, for example, silicon oxide, germanium oxide, or aluminum oxide.

[0079] In other various embodiments, the first electrode 202 and the second electrode 204 can both be in contact with the liquid crystal layer 206. In other various embodiments, the first electrode 202 and the second electrode 204 can both be not in contact with the liquid crystal layer 206.

[0080] In various embodiments, the nanostructure array can include nanocolumns, each nanocolumn having a height greater than its width or its length. Each nanocolumn can include one or more materials. The nanocolumns can be adapted to align liquid crystal molecules in a direction along a longitudinal axis of the nanocolumns. The liquid crystal molecules can include a positive dielectric anisotropy. Switching of the liquid crystal device can be achieved by applying an in-plane electric field between the nanocolumns. The in-plane electric field can be an external electric field provided by a complementary metal oxide semiconductor (CMOS) device or circuit.

[0081] FIG. 3 A general schematic of a method of forming a liquid crystal (LC) device is shown, in accordance with various embodiments. The method can include forming a first electrode at step 302. The method can also include forming a second electrode at step 304. The method can also include forming a liquid crystal layer between the first electrode and the second electrode at step 306, the liquid crystal layer including liquid crystal molecules and a nanostructure array, the nanostructure array adapted to align the liquid crystal molecules in a desired alignment and to modulate light passing through the liquid crystal device. A period of the nanostructure array and / or an aspect ratio of each nanostructure of the nanostructure array can be adapted to align the liquid crystal molecules in the desired alignment.

[0082] In other words, the method of forming a liquid crystal device can include forming two electrodes and a liquid crystal layer between the two electrodes. The liquid crystal layer can include liquid crystal molecules and a nanostructure array that aims to align the liquid crystal molecules and to modulate light.

[0083] For the avoidance of doubt, FIG. 3 It is not intended to limit the order of the various steps. For example, step 302 can be performed before or after step 304. In various embodiments, the second electrode can be formed first, then the liquid crystal layer (with the nanostructure array) can be formed on the second electrode, and then the first electrode can be formed on the liquid crystal layer. In other various embodiments, the first electrode can be formed first, then the liquid crystal layer (with the nanostructure array) can be formed on the first electrode, and then the second electrode can be formed on the liquid crystal layer.

[0084] In different embodiments, the second electrode can be pixelated, while in other different embodiments, the second electrode can be continuous. In different embodiments, the first electrode can be pixelated, while in other different embodiments, the first electrode can be continuous.

[0085] In different embodiments, the liquid crystal layer can include another nanostructure array. The nanostructure array and the other nanostructure array can be on opposite sides of the liquid crystal layer. In different embodiments, the nanostructure array can be in contact with the second electrode, and the other nanostructure array can be in contact with the first electrode. In other different embodiments, the nanostructure array can be in contact with the first electrode, and the other nanostructure array can be in contact with the second electrode.

[0086] In different embodiments, the longitudinal axis of the nanostructure array can be rotated with respect to the longitudinal axis of the other nanostructure array. In different embodiments, the longitudinal axis of the nanostructure array is substantially perpendicular to the longitudinal axis of the other nanostructure array.

[0087] In different embodiments, the second electrode can be light transmissive. In other different embodiments, the second electrode can be light reflective.

[0088] In different embodiments, the first electrode can be light transmissive. In other different embodiments, the first electrode can be light reflective.

[0089] In different embodiments, the thickness of the liquid crystal layer can be selected from any value in the range of 200 nm to 800 nm.

[0090] In different embodiments, the nanostructure array can have at least two dimensions that are smaller than the operating light wavelength of the liquid crystal device.

[0091] In different embodiments, the dimension of each nanostructure of the nanostructure array that is aligned with the direction of the liquid crystal molecules can be larger than the other dimensions of the nanostructure. In different embodiments, the periodic grating of the nanostructure array includes the longest grating vector in the direction of the liquid crystal molecules.

[0092] In different embodiments, the method can further include forming a passivation layer on the second electrode, the passivation layer adapted to avoid direct contact of the liquid crystal molecules with the second electrode. The passivation layer can include an oxide having a refractive index less than 2, and can be light transmissive.

[0093] In different embodiments, the nanostructure array can include nano-pillars, each nano-pillar having a height that is larger than its width or its length.

[0094] Different embodiments can provide an ultrathin metasurface liquid crystal cell, where a metasurface (i.e., a metasurface composed of nanostructures or nanoantennas) sets the uniform alignment of the liquid crystal without the need for additional alignment layers. Moreover, the nanostructures or nanoantennas can modulate light, thereby controlling the liquid crystal orientation and light modulation. The set of nanostructures or nanoantennas can sustain optical resonance at the operating frequency (or frequencies) of the liquid crystal device. These nanostructures or nanoantennas can be arranged to constitute a so-called metasurface grating and can be embedded in a thin layer of nematic liquid crystal. In some embodiments, the liquid crystal can be a dual-frequency liquid crystal (DFLC). Electric-field-induced reorientation of the liquid crystal molecules locally changes the near-field environment of the nanoantennas, which enables efficient spectral tuning of their resonance and the associated amplitude and / or phase modulation. The presence of the nanoantennas or nanostructures can allow for a significant reduction in the thickness of the liquid crystal layer compared to conventional liquid crystal light modulators. Crosstalk between adjacent electrodes can also be reduced, thereby allowing for pixel miniaturization. Different embodiments can utilize the geometry and periodic arrangement of the nanostructures or nanoantennas to assist in eliminating the need for an alignment layer to set the pre-uniform alignment of the liquid crystal in the absence of an applied bias, which helps to reduce the operating voltage range of the device and increase its response speed compared to conventional devices.

[0095] FIG. 4AA schematic cross-sectional side view of a unit cell of a conventional transmissive nanoantenna spatial light modulator (NSLM) with a disk-shaped nanoantenna 408 is shown. Nanoantennas 408 are contained within a liquid crystal (LC) layer 406. The device is constructed by periodically repeating these unit cells along the X and Y directions. The device includes two substrates 410 and 412, each with transmissive electrodes 402 and 404, which are assembled to form the unit cell. Indium tin oxide (ITO) is used as the material for transmissive electrodes 402 and 404. Other transmissive conductive materials, such as aluminum-doped zinc oxide (AZO), can also be used instead of ITO. The bottom electrode 404 is pixelated, and the top electrode 402 is continuous. The top electrode is coated with an alignment layer 450, which is a polymer or monomer. The alignment layer 450 is treated to induce a preferential pre-alignment of the liquid crystal along the X axis. There are two common methods for controlling the orientation of the alignment layer, and thus the orientation of the liquid crystal director (the average orientation of the liquid crystal molecules). The first treatment method is performed by irradiating a photosensitive material (such as an azo dye) with a polarized light source (usually light in the ultraviolet (UV) range) and is called photoinduced alignment. The second method is to mechanically rub polyimide or polystyrene. The alignment direction is defined by the polarization of the UV light in the first method and by the rubbing direction in the second method. In addition, microstructure- or nanostructure-induced liquid crystal alignment has been reported, but in most cases, nanopatterning of at least one-sided alignment layers or the alignment layer 450 itself is used to achieve uniform liquid crystal alignment.

[0096] In contrast, various embodiments may not involve an alignment layer, and the metasurface itself may provide consistent liquid crystal alignment in addition to wavefront modulation. Unless otherwise noted, comparisons between various embodiments described herein and conventional methods using an alignment layer refer to comparisons between various embodiments and methods using an alignment layer formed by rubbing, as rubbing is known to provide greater reliability than photoinduced alignment.

[0097] In different embodiments, the nanostructures or nanoantennas can be made of a high refractive index dielectric material such as titanium oxide (Ti02) that can be formed on a bottom pixelated electrode. The geometry of the nanostructures or nanoantennas can be chosen such that both electric dipoles (ED) and magnetic dipoles (MD) are excited and the nanostructures or nanoantennas resonate in the visible wavelength range. When the electric resonance and the magnetic resonance overlap each other, the nanostructures or nanoantennas can cause a phase shift of 2π radians in transmission mode, or the nanostructures or nanoantennas can provide a similar shift in reflection mode using a single resonance. The supercell period (Λ) and ) can be about 400 nm or any other suitable dimension such that the cell has sub-diffractive properties. The precise gap between the top electrode and the bottom electrode can set the liquid crystal cell thickness and can be a critical parameter. To obtain sufficient precision, an ultraviolet light curing adhesive (e.g. Norland optical adhesive NOA81) can be used to set the gap between the electrodes. The dual-frequency liquid crystal (DFLC) molecules can be encapsulated in the liquid crystal cell by capillary filling action and thus the nanoantennas or nanostructures can be embedded in the liquid crystal layer.

[0098] FIG. 4B Schematic diagrams showing the orientation of liquid crystal (LC) molecules used in liquid crystal (LC) devices according to different embodiments. The polar and azimuthal angles are denoted by and , respectively. In the nematic phase, the long axes of the molecules tend to align parallel to each other along the so-called, non-polar director . The liquid crystal refractive indices parallel and perpendicular to the director are called the extraordinary refractive index and the ordinary refractive index , respectively. The difference, i.e. n e - n o , gives the birefringence (Δn). The birefringence of the DFLC used in the present example (DP002-016 of PhiChem-HCCH) is Δn = 0.268 (n e = 1.779, n o = 1.511 at λ = 589 nm, 20°C). The DFLC can be a liquid crystal mixture that exhibits positive dielectric anisotropy and negative dielectric anisotropy (negative Δε) at frequencies above the cross-over frequency (about 60 kHz for DP002-016) and negative dielectric anisotropy (negative Δε) at frequencies above the cross-over frequency (about 60 kHz for DP002-016) and azimuthal angle as shown in FIG. 4B For a conventional device as shown in FIG. 4A the polar angle can be changed from 90° to 0° by electrical tuning, and the azimuthal angle is usually controlled by the alignment layer. According to different embodiments, the azimuthal angle may alternatively be defined by the geometry of the nanostructures or nanoantennas and the period of the array. An incident electromagnetic wave with polarization along the X-axis can be denoted here as P-0, and an incident electromagnetic wave with polarization along the Y-axis can be denoted here as P-90.

[0099] FIG. 5 A cross-sectional side view schematic of a cell of an ultra-thin liquid crystal (LC) device with disc-shaped nanoantennas 508 and without a top electrode alignment layer is shown. The nanoantennas 508 can be dielectric nanoantennas and can be included in a liquid crystal layer 506 between a first electrode 502 (a top transparent electrode) and a second electrode 504 (a pixelated bottom transparent electrode). The first electrode 502 can be in contact with a first substrate 510, while the second electrode 504 can be in contact with a second substrate 512. The horizontal cross-section of each disc-shaped nanoantenna 508 is disc-shaped. The diameter (D) and height (H) of each nanoantenna are 270 nm and 200 nm, respectively, i.e., D = 270 nm, H = 200 nm. The period (P) of the array is 360 nm, i.e., P = 360 nm. The entire device is composed of a cell that is periodically repeated along the X- and Y-directions. FIG. 6A cross-sectional side view schematic of a cell of another ultra-thin liquid crystal (LC) device with square nanoantennas 608 and without a top electrode alignment layer is shown. The nanoantennas 608 can be dielectric nanoantennas and can be included in a liquid crystal layer 606 between a first electrode 602 (top transparent electrode) and a second electrode 604 (pixelated bottom transparent electrode). The first electrode 602 can be in contact with a first substrate 610 while the second electrode 604 can be in contact with a second substrate 612. The horizontal cross-section of each square nanoantenna 608 is a square. The length (L), width (W), and height (H) of each nanoantenna are 270 nm, 270 nm, and 200 nm, respectively, i.e., L = 270 nm, W = 270 nm, H = 200 nm. The period (P) of the array is 360 nm, i.e., P = 360 nm. In both setups, the uniform alignment of the liquid crystal is entirely set by the nanoantennas, i.e., there is no alignment layer. FIG. 7 (a) shows a scanning electron microscope (SEM) image of a circular disk nanoantenna array and (b) shows a scanning electron microscope (SEM) image of a square nanoantenna array.

[0100] FIG. 8A A simulated plot of transmittance as a function of wavelength (in nanometers or nm) is shown, which shows the transmission spectra of a liquid crystal device (LC) with circular disk nanoantennas under normally incident light polarized along the X-axis (P-0, solid line), along the Y-axis (P-90, dashed line), and at a 45° angle to the X-axis (P-45, dotted line) as shown in FIG. 5 The simulation was performed using COMSOL, and the refractive indices The X-axis is defined as = 90°, = 0°). For P-0, the electric resonance partially overlaps with the magnetic resonance, and the resonance dips at λ ~ 646 nm correspond to electric dipoles, and the resonance dip at λ ~ 657 nm corresponds to magnetic dipoles supported by the nanodisks. The dip at λ ~ 605 nm can be caused by cavity modes formed in the slab. For P-90, the resonance splits at λ ~ 610 nm correspond to electric dipoles, and λ ~ 640 nm corresponds to magnetic dipoles. For P-45, multiple resonances occur because both the parallel and perpendicular components of the electric and magnetic dipoles are excited. FIG. 8B A measured plot of transmittance as a function of wavelength (in nanometers or nm) is shown, which shows the transmission spectra of a liquid crystal (LC) device with an alignment layer (W, dashed line) or without an alignment layer (WO, solid line) with a 1500 nm thick liquid crystal (LC) layer and a circular disk nanoantenna array under incident light polarized along the X-axis, where the insets show the crossed polarizer (P) and analyzer (A) setup. ) and analyzer (A) setup. Microscope images of liquid crystal cells without (WO) and with (W) alignment layer under crossed polarizers (P-0) and analyzers (P-90). FIG. 8C Measured plots showing the transmittance as a function of wavelength (in nanometers or nm) of liquid crystal (LC) devices with a 1500 nm thick liquid crystal (LC) layer and a disc-shaped nanoantenna array with a top electrode alignment layer (W, dashed line) or without a top electrode alignment layer (WO, solid line) under incident light polarized at 135° to the X-axis, where the insets show the crossed polarizers (P-0) and analyzers (P-90) under which the measurements were taken. Microscope images of liquid crystal cells without (WO) and with (W) alignment layer under crossed polarizers (P-0) and analyzers (P-90). Microscope images of liquid crystal cells without (WO) and with (W) alignment layer under crossed polarizers (P-0) and analyzers (P-90). The rubbing direction is along the X-axis, and thus the liquid crystal orientation induced by the top electrode alignment layer is along the X-axis. The measured spectra are compared to the simulations shown in FIG. 8A The deviation of the resonance spectra of the liquid crystal cells without alignment indicates that the planar alignment of the liquid crystal is disrupted in the absence of an alignment layer for thicker liquid crystal cells. Thicker liquid crystal cells (>1 pm) require the support of an alignment layer to induce planar alignment of the liquid crystal throughout the thickness of the liquid crystal cell. The deviation of the uniformity of the alignment and the formation of defects disrupt the resonance spectra. For the parallel orientation and the 45° orientation of the metasurface array with respect to the X-axis, the insets provide images of the liquid crystal filled metasurface under crossed polarizers (P-0) and analyzers (P-90). Microscope images of liquid crystal cells without (WO) and with (W) alignment layer under crossed polarizers (P-0) and analyzers (P-90). Microscope images of liquid crystal cells without (WO) and with (W) alignment layer under crossed polarizers (P-0) and analyzers (P-90). The black arrows indicate the direction of the polarizers and analyzers during the image recording. The images show the misalignment of the liquid crystal molecules with the metasurface in the absence of an alignment layer. The resonance spectra measured with incident light polarized at 135° to the X-axis (P-135) match the simulations for P-0, and the resonance spectra measured with incident light polarized at P-0 match the simulations for P-45. This indicates that the metasurface can induce an angular alignment with respect to the X-axis even in the presence of an alignment layer, which indicates that the nanostructures have a strong anchoring. FIG. 8D to FIG. 8E Resonance spectra measured using a similar metasurface liquid crystal cell with a reduced thickness of 750 nm.

[0101] FIG. 8D Measured plots showing the transmittance as a function of wavelength (in nanometers or nm) of liquid crystal (LC) devices with a 750 nm thick liquid crystal (LC) layer and a disc-shaped nanoantenna array with an alignment layer (W, dashed line) or without an alignment layer (WO, solid line) under incident light polarized along the X-axis, where the insets show the crossed polarizers (P-0) and analyzers (P-90) under which the measurements were taken. Microscope images of liquid crystal cells without (WO) and with (W) alignment layer under crossed polarizers (P-0) and analyzers (P-90). Microscope images of liquid crystal cells without (WO) and with (W) alignment layer under crossed polarizers (P-0) and analyzers (P-90). FIG. 8EGraph showing measured transmittance as a function of wavelength (in nanometers or nm) for a liquid crystal (LC) device with a 750 nm thick LC layer and a disk-shaped nanoantenna array, with or without a top electrode alignment layer (W, dashed line) or a top electrode alignment layer (WO, solid line) for incident light polarized at 45° to the X-axis, with the inset showing the transmission spectra of the LC device under crossed polarizers ( ) and the analyzer ( ) with and without an alignment layer (WO). The resonance spectra measured from the P-45 LC cells with and without alignment show good correspondence with each other and are consistent with the FIG. 8A The simulation results for P-0 are consistent with those shown. The periodic arrangement of nanoantennas can induce uniform, uniform alignment of the liquid crystals within the thinner liquid crystal cell metasurface, but the induced alignment is angled. Due to the symmetrical structure of the nanoantennas, the induced alignment can be at 45° or 135° to the X-axis. The inset shows an image of the liquid crystal-filled metasurface under crossed polarizers and analyzers, demonstrating the uniform, uniform alignment of the liquid crystals within the metasurface array.

[0102] Metasurface-induced uniform liquid crystal alignment was verified using square nanoantenna arrays. FIG. 9A A simulated graph showing transmittance as a function of wavelength (in nanometers or nm) is shown. FIG. 6 Transmission spectra of a liquid crystal device (LC) with square nanoantennas shown under normal incident light along the X-axis, along the Y-axis, and at a 45° angle to the X-axis. = 90°, the observed valley at λ≈668nm for incident polarization P-0 corresponds to the electric and magnetic dipole resonances in the nanoantennas, with partially overlapping spectra. For the normal alignment of the liquid crystal, the molecules are aligned vertically ( = 0°), which corresponds to the case where a bias above the saturation value is applied between the top and bottom electrodes. In this case, the resonance redshifts to λ ≈ 682 nm, and a high-order mode is excited at 628 nm. The valley at 603 nm represents the cavity mode formed in the liquid crystal slab. Thus, by applying a field, a resonance shift from homogeneous to homeotropic realignment can be achieved.

[0103] FIG. 9BGraph showing the transmittance as a function of wavelength (in nanometers or nm), measured graph showing the transmittance as a function of wavelength (in nanometers or nm), measured graph showing a liquid crystal (LC) device with a 750 nm thick liquid crystal (LC) layer and a square nanometer antenna array with an alignment layer (rubbing direction along the X-axis), the transmittance spectra under incident light of polarization P-135 for applied voltages of 0 V rms and 4 V rms , and the transmittance spectra under incident light of polarization P-0 and incident light of polarization P-135 for applied voltages of 0 V rms , where the insets show microscopic images of the liquid crystal cell with parallel and 45° orientation under crossed polarizer ( ) and analyzer ( ). Black arrows indicate the direction of the polarizer and analyzer during image recording. FIG. 9C Graph showing the transmittance as a function of wavelength (in nanometers or nm), measured graph showing the transmittance as a function of wavelength (in nanometers or nm), measured graph showing a liquid crystal (LC) device without an alignment layer with a 750 nm thick liquid crystal (LC) layer and a square nanometer antenna, the transmittance spectra under incident light of polarization P-45 for applied voltages of 0 V rms and 4 V rms , and the transmittance spectra under incident light of polarization P-0 and incident light of polarization P-135 for applied voltages of 0 V rms , where the insets show microscopic images of the liquid crystal cell with parallel and 45° orientation under crossed polarizer ( ) and analyzer ( ). Black arrows indicate the direction of the polarizer and analyzer during image recording. FIG. 9B Measured transmittance spectra of the fabricated metasurface liquid crystal device with an alignment layer (with rubbing direction along the X-axis) in the top electrode, while FIG. 9C Measured transmittance spectra of the metasurface liquid crystal device with uniform metasurface-induced alignment for different applied voltages and incident polarization conditions. Comparing FIG. 9B to FIG. 9C with FIG. 9A , for ultrathin liquid crystal cells (thickness below 1 pm), metasurfaces can induce uniform liquid crystal molecular alignment without the need for any alignment layer. However, for these nanostuctures or nanometer antennas with an aspect ratio (AR) of about 1 : 1, including disc-shaped and square nanostuctures or nanometer antennas, the metasurface can induce an angular uniform alignment with azimuthal angles of 45° or 135° as shown by the transmission measurements.

[0104] FIG. 10(a, b) are schematic diagrams showing the consistent arrangement of liquid crystal (LC) induced by nanostructures or nanoantennas having a disk shape, and (c, d) are schematic diagrams showing the consistent arrangement of liquid crystal (LC) induced by nanostructures or nanoantennas having a square shape. FIG. 10 As shown, the nanostructure or nanoantenna with AR ≈ 1:1 may include a nanostructure or nanoantenna with an azimuth angle of 45° or 135°. In these nanostructures or nanoantennas, the anchoring energy along the X direction is the same as the anchoring energy along the U direction, and the free energy minimization is achieved. ≠0° liquid crystals are arranged uniformly. The incident light polarization can be adjusted based on the initial light orientation angle of the liquid crystal, that is, adjusted along the extraordinary refractive index to achieve FIG. 5 to FIG. 6 The maximum phase modulation of the device described. Furthermore, for devices with nanostructures or nanoantennas with an AR of ~1:1, even with ultrathin liquid crystal cells and strong alignment from the top electrode alignment layer, angular alignment may not be completely eliminated. Instead, a complex alignment of the liquid crystal molecules may be induced.

[0105] In summary, the ultrathin metasurface LC cells can induce uniform LC alignment along the surface, thus eliminating the need for standard LC alignment layers. However, for nanoantennas with AR ~ 1:1 (and square grids), only angular LC alignment is feasible. This can be a problem or undesirable for some applications. The above problems can be overcome by using other antenna configurations that can include =0° or =90° induces the liquid crystal to align uniformly while maintaining the optical resonance required for light modulation.

[0106] Different embodiments can induce the liquid crystal (LC) molecules to be aligned in parallel along a desired or specified direction. In different embodiments, each nanostructure or nanoantenna can have a larger aspect ratio along the direction of the desired aligned arrangement. In other words, the size of the nanostructure or nanoantenna along the desired liquid crystal aligned direction should be larger than the size along any other direction. The aspect ratio can be 2:1, 3:1, etc. The nanostructure or nanoantenna can be a rectangular block, a cylinder with an elliptical cross-section, or an ellipsoidal nanoparticle, etc. In addition to the azimuth angles of 45° and / or 135°, the nanostructure or nanoantenna can also be shaped like a rectangular block, a cylinder with an elliptical cross-section, or an ellipsoidal nanoparticle. In addition to the uniform arrangement of the liquid crystal molecules along the desired direction or the specified direction, different embodiments can induce the liquid crystal molecules to be uniformly arranged along the desired direction or the specified direction. FIG. 11A cross-sectional side view schematic of a cell of an ultra-thin liquid crystal (LC) device is shown, according to different embodiments. The nano-antennas 1108 can be dielectric nano-antennas and can be included in a liquid crystal layer 1106 between a first electrode 1102 (top transparent electrode) and a second electrode 1104 (pixelated bottom transparent electrode). The first electrode 1102 can be in contact with a first substrate 1110, while the second electrode 1104 can be in contact with a second substrate 1112. The nano-antennas 1108 can be rectangular blocks, i.e., cuboids. The horizontal cross-section of each nano-antenna 1108 can be rectangular and can be referred to as a rectangular nanostructure or nano-antenna.

[0107] An additional or alternative means of inducing uniform alignment of liquid crystals in a certain direction is to use a periodic grating with a longer grating vector in the desired uniform alignment direction. For example, this can be achieved using a rectangular grating instead of a square grating. In FIG. 11 In the device shown, the period of the array along the X-axis can be greater than the period along the Y-axis. FIG. 12 (a) shows a scanning electron microscope (SEM) image of a fabricated rectangular nano-antenna super surface, according to different embodiments; and (b) shows a schematic of the uniform alignment of liquid crystal molecules induced by the rectangular nanostructures or nano-antennas, according to different embodiments. FIG. 12 (a) the length (L), width (W), and height (H) of each nano-antenna shown are 370 nm, 200 nm, and 200 nm, respectively, i.e., L = 370 nm, W = 200 nm, H = 200 nm. The period of the array along the X-axis (P x ) is 430 nm, while the period of the array along the Y-axis (P y ) is 280 nm, i.e., P x = 430 nm, P y = 280 nm. FIG. 12 (a) the scale bar shown is 450 nm.

[0108] FIG. 13A A simulated plot of transmittance as a function of wavelength (in nanometers or nm) is shown, which shows FIG. 11 The transmittance spectra of a liquid crystal device (LC) with rectangular nano-antennas, according to different embodiments, under normally incident light polarized along the X-axis (P-0, dashed line) and the Y-axis (P-90, solid line) is shown. The liquid crystal molecules can be induced to align uniformly along the X-direction, i.e., along the length or major axis of the rectangular nano-antennas (L = 370 nm, W = 200 nm, H = 200 nm, P x= 430nm). For incident waves polarized along the X-axis (P-0), magnetic and electric dipoles coexist at λ = 768nm, while the nanoantenna exhibits higher-order modes with both electric and magnetic resonances at λ = 544nm. These resonances can be tuned by applying an electric field to the liquid crystal device, as shown below. When polarized along the Y-axis (P-90), blue shifts of the main mode at longer wavelengths are observed. FIG. 13B A measured graph showing transmittance as a function of wavelength (in nanometers or nm) is shown. FIG. 11 Transmission spectra of a liquid crystal device (LC) with rectangular nanoantennas according to various embodiments are shown under normal incident light polarized along the X axis (P-0, dashed line) and along the Y axis (P-90, solid line). FIG. 13A The simulation results shown are consistent with FIG. 13B Compared with the measured results shown in the figure, it can be seen that FIG. 11 The device shown can provide uniform alignment of liquid crystal along the desired direction, i.e., azimuthal angle The uniform arrangement of the liquid crystal can be determined by the AR of the nanoantenna (i.e., the longest dimension of the nanoantenna) and / or the periodic grid.

[0109] FIG. 14 (a) shows the fabricated nano-square nanoantenna (L=W=270nm, H=200nm, P x =P y =360nm) scanning electron microscope (SEM) images; (b) to (d) show the square nanoantennas fabricated as shown in (a) under the cross polarizers ( ) and the analyzer ( ) microscopic images of different array orientations; (e) shows scanning electron microscope (SEM) images of rectangular nanoantennas fabricated according to different embodiments (L = 260nm, W = 180nm, H = 200nm, P x =360nm, P y = 290 nm); (f) to (h) show the rectangular nanoantennas manufactured as shown in (e) according to different embodiments under the conditions of cross polarizers ( ) and the analyzer ( ) microscopic images of different array orientations under different embodiments; (i) shows scanning electron microscope (SEM) images of rectangular nanoantennas fabricated according to different embodiments (L = 350 nm, W = 180 nm, H = 200 nm, P x =430nm, P y = 270nm); (j) to (l) show the rectangular nanoantennas manufactured according to different embodiments, as shown in (i), in the cross polarizer ( ) and the analyzer ( Microscopic images of different array orientations. FIG. 14 Depicts the correlation of liquid crystal uniform alignment based on the aspect ratio of the nanoantennas for liquid crystal devices without alignment layers. All nanoantennas were fabricated on a single substrate, where the nanoantennas comprised of Ti02. The liquid crystal devices had a thickness of 500 nm, where there were no alignment layers. The images show that nanoantennas with an AR of 1 : 1 can induce an angular uniform alignment, and rectangular nanoantennas with AR > 1 : 1 can allow for the control of the liquid crystal uniform alignment in the desired direction. Different embodiments can provide a means for precise control of the liquid crystal uniform alignment without the need for any additional alignment layers, while still retaining the required optical response of the liquid crystal device. FIG. 14 The scale bars shown in (a), (e), (i) represent 270 nm.

[0110] Different embodiments can improve the device performance parameters, namely the response speed and the driving voltage. Since there is no need for additional alignment layers that are known to strongly affect the properties of neighboring liquid crystal molecules, the voltage level required for optical modulation can be reduced (e.g., by half), and the response speed can be increased (e.g., by a factor of 3 compared to devices with alignment layers). The shortened response time can contribute to an increased refresh rate of the device. FIG. 15A to FIG. 15C Depicts the electrical tuning of the resonance of rectangular nanoantennas. FIG. 15A Depicts a simulated plot of transmittance as a function of wavelength (in nanometers or nm) showing the transmittance spectra of a liquid crystal device (LC) with rectangular nanoantennas according to different embodiments for an incident light polarized along the X-axis (P-0) for the uniform alignment of the liquid crystal (LC) along the plane = 90°, solid line) and the normal = 0°, dashed line) uniform alignment of the liquid crystal (LC). FIG. 15B Depicts a measured plot of transmittance as a function of wavelength (in nanometers or nm) showing the transmittance spectra of a liquid crystal (LC) device with rectangular nanoantennas and without alignment layers according to different embodiments for an incident light polarized along the X-axis (P-0) for applied voltages of 0 V rms , 3.5 V rms , and 5 V rms . FIG. 15C Depicts a measured plot of transmittance as a function of wavelength (in nanometers or nm) showing the transmittance spectra of a liquid crystal (LC) device with rectangular nanoantennas and with alignment layers according to different embodiments for an incident light polarized along the X-axis (P-0) for applied voltages of 0 V rms , 3.5 V rms , and 5 V rms . The measurements of the liquid crystal cell with pure super- surface induced uniform alignment FIG. 15B are compared to the measurements of the liquid crystal cell with a top electrode alignment layer FIG. 15CComparing in terms of resonance shift with respect to the applied voltage, a liquid crystal cell with a pure metasurface induced uniform alignment can require a lower voltage for wavefront modulation than a liquid crystal cell with a top electrode alignment layer.

[0111] FIG. 16 (a) to (c) show microscopic images of liquid crystal filled rectangular nanoantennas under crossed polarizers (P) and analyzer (A) at different applied voltages for a 500 nm thick liquid crystal (LC) cell with a top electrode alignment layer; (d) to (f) show microscopic images of liquid crystal filled rectangular nanoantennas under crossed polarizers (P) and analyzer (A) at different applied voltages for a 500 nm thick liquid crystal (LC) cell with a pure metasurface induced uniform alignment without a top electrode alignment layer according to different embodiments; and (h) to (j) show microscopic images of liquid crystal filled rectangular nanoantennas under crossed polarizers (P) and analyzer (A) at different applied voltages for a 1000 nm thick liquid crystal (LC) cell with a pure metasurface induced uniform alignment without a top electrode alignment layer according to different embodiments. The set of arrows indicates the liquid crystal director orientation along the length or long axis of the rectangular nanoantenna, while the other set of arrows indicates the uniform alignment direction induced by the top electrode alignment layer. The set of arrows indicates the liquid crystal director orientation along the length or long axis of the rectangular nanoantenna, while the other set of arrows indicates the uniform alignment direction induced by the top electrode alignment layer. FIG. 16 The polarizer and analyzer directions are also shown. As shown in FIG. 16 , the threshold voltage required for liquid crystal switching in a liquid crystal cell with a pure metasurface induced uniform alignment can be in the range of 0.6 V rms to 0.8 V rms , while the threshold voltage required for liquid crystal switching in a liquid crystal cell with an alignment layer requires a minimum voltage of 1.4 V rms .

[0112] Another driving parameter, the response time, can also be related to the anchoring strength and the liquid crystal cell thickness. The total response time can be defined as the sum of the rise time and the fall time.

[0113] FIG. 17A to FIG. 17C Response time measurements for a miniaturized metasurface liquid crystal cell with rectangular nanoantennas according to different embodiments are shown. FIG. 17A A plot showing the wave form (in volts or V) / intensity as a function of time (in milliseconds or ms) showing the switching performance (voltage dependent transmission intensity - black dashed line) of a 1000 nm thick liquid crystal cell without an alignment layer under an applied signal (gray line) according to different embodiments. FIG. 17B ​​​​​Graph showing the wave form (in volts or V) / intensity as a function of time (in milliseconds or ms) illustrating the switching performance (voltage dependent transmission intensity - black dotted line) of a 750 nm thick liquid crystal cell without alignment layers under an applied signal (grey line) according to different embodiments. FIG. 17C Graph showing the wave form (in volts or V) / intensity as a function of time (in milliseconds or ms) illustrating the switching performance (voltage dependent transmission intensity - black dotted line) of a 750 nm thick liquid crystal cell with a top electrode alignment layer under an applied signal (grey line). In these measurements a dual frequency driving method was employed, where both "on" and "off are driven by voltage. For an applied voltage of 10 V pp , the dual frequency pulses are switched between and .

[0114] It can be seen that for a liquid crystal cell with pure super surface induced uniform alignment the total response time is shortened to below 1 ms. While the "off time of both liquid crystal cells is almost identical and changes according to the liquid crystal cell thickness, as shown in FIG. 17C , the "on time of the super surface induced uniform alignment is shortened by more than a factor of 3 compared to the case where an alignment layer is present due to the increased anchoring energy caused by the alignment layer. In FIG. 17A to FIG. 17C , the "on" and "off times can not be equal even though both are voltage driven. This can be caused by the difference in dielectric anisotropy at 20 kHz (Δε = 4.7) and 200 kHz (Δε = -2.7). By optimizing the combination of voltage and frequency of the applied signal both "on" and "off times can be equalized to a few hundred microseconds.

[0115] Different embodiments can be modified to achieve better performance or different functionality. In this regard, it can be beneficial to include additional elements or element characteristics. For example, different embodiments can include a conductive mirror (e.g., a combination of a dielectric mirror and a light transparent electrical conductor) in place of a transmissive bottom electrode to assist in accumulating more phase as light passes through the device multiple times. In other different embodiments, the transmissive bottom electrode can be replaced by a metallic electrode which can act as a mirror.

[0116] FIG. 18A cross-sectional side view schematic of a cell of a liquid crystal (LC) device with a rectangular nanoantenna 1808 is shown, in accordance with different embodiments. The nanoantenna 1808 can be a dielectric nanoantenna and can be included in a liquid crystal layer 1806 between a first electrode 1802 (a top transparent electrode) and a second electrode 1804 (a pixelated bottom reflective electrode). The first electrode 1802 can be in contact with a first substrate 1810. The first electrode 1802 can be made of indium tin oxide (ITO), while the second electrode 1804 can be made of aluminum (Al) or any other suitable metal, such as gold (Au), silver (Ag), copper (Cu), etc. Alternatively, the second electrode 1804 can be a combination of a dielectric mirror (e.g., a Bragg reflector) and a transparent conductive material. The first electrode 1802 can be transparent and conductive. The second electrode 1804 can serve as both an electrode and a mirror. The second electrode 1804 can be highly reflective and at the same time conductive and pixelated. The liquid crystal device can also include a passivation layer 1814 formed on or in contact with the second electrode 1804 to avoid direct contact of the liquid crystal molecules with the second electrode 1804. The passivation layer 1814 can include a material (e.g., an oxide material) with a low refractive index (n < 2) and transparent to light to avoid light loss in the metal of the second electrode 1804.

[0117] Embodiments with a pixelated bottom electrode can include pixels individually addressed by integrated circuits in a complementary metal oxide semiconductor (CMOS) backplane. FIG. 19 A perspective view schematic of a cell of a liquid crystal (LC) device with a rectangular nanoantenna 1908 and a pixelated second electrode 1904 is shown, in accordance with different embodiments. The nanoantenna 1908 can be a dielectric nanoantenna and can be included in a liquid crystal layer 1906 between a first electrode 1902 and a second electrode 1904. The first electrode 1902 can be a transparent electrode, while the second electrode 1904 can include two-dimensional (2D) pixels. The second electrode 1904 can be in electrical contact with a CMOS backplane 1916.

[0118] FIG. 20A cross-sectional side view schematic of a cell of a transmissive liquid crystal (LC) device is shown, according to different embodiments, with rectangular nanoantennas 2008a, 2008b on or in contact with first and second electrodes 2002, 2004, respectively. The rectangular nanoantennas 2008a, 2008b can be included in a liquid crystal layer 2006 between the first electrode 2002 (top transmissive electrode) and the second electrode 2004 (pixelated bottom transmissive electrode). The rectangular nanoantennas 2008a, 2008b can be on opposite sides of the liquid crystal layer 2006. The rectangular nanoantenna 2008a can be in contact with the first electrode 2002, while the rectangular nanoantenna 2008b can be in contact with the second electrode 2004. The first electrode 2002 can be in contact with a first substrate 2010, while the second electrode 2004 can be in contact with a second substrate 2012. FIG. 21 A cross-sectional side view schematic of a cell of a reflective liquid crystal (LC) device is shown, according to different embodiments, with rectangular nanoantennas 2108a, 2108b on opposite sides of a liquid crystal layer 2106. The nanoantennas 2108a, 2108b can be dielectric nanoantennas and can be included in a liquid crystal layer 2106 between a first electrode 2102 (top transmissive electrode) and a second electrode 2104 (pixelated bottom metal electrode). The first electrode 2102 can be in contact with a first substrate 2110, and the second electrode 2104 can be in contact with a second substrate 2112. The liquid crystal device can also include a passivation layer 2114 formed on or in contact with the second electrode 2104 to avoid direct contact of the liquid crystal molecules with the second electrode 2104. The rectangular nanoantenna 2108b can be in contact with the passivation layer 2114.

[0119] FIG. 20 to FIG. 21 A device with two arrays of nanoantennas or nanostructures is shown. The two arrays of nanoantennas or nanostructures can be on opposite sides of a liquid crystal layer. The presence of the nanoantennas or nanostructures can provide a well-defined uniform alignment of the liquid crystal, even for thicker liquid crystal cells, and can also assist in achieving a larger light modulation at the same time. For example, the independent phase accumulation of the top and bottom nanoantenna arrays can add up at a certain wavelength, providing a larger phase modulation. Changing the structure or orientation of the nanoantennas can also help achieve other functionalities or other uniform alignment of the liquid crystal.

[0120] FIG. 22A cross-sectional side view schematic of a cell of a liquid crystal (LC) device according to different embodiments is shown, in which two arrays of rectangular nanorods 2208a, 2208b are aligned perpendicular to each other. The length of the rectangular nanorods 2208a can be perpendicular to the length of the rectangular nanorods 2208b. The array of nanorods 2208a can be aligned along the Y-axis, while the array of nanorods 2208b can be aligned along the X-axis. The two arrays of rectangular nanorods 2208a, 2208b can be included on opposite sides of a liquid crystal layer containing liquid crystal molecules 2206. The orientation of the two arrays of rectangular nanorods 2208a, 2208b can enable a twisted nematic alignment of the liquid crystal molecules (along the Z-axis). The liquid crystal layer can be between a first electrode 2202 (top transparent electrode) and a second electrode 2204 (pixelated bottom transparent electrode). The first electrode 2202 can be in contact with a first substrate 2210, while the second electrode 2204 can be in contact with a second substrate 2212. The resonant properties of the nanorods can simultaneously enhance the polarization conversion or chirality of light.

[0121] FIG. 23 A cross-sectional side view schematic of a cell of a light-transmissive liquid crystal (LC) device according to different embodiments is shown, having an array of nanorods 2308. The height of the nanorods 2308 can be greater than the other dimensions of the nanorods. The nanorods 2308 can be dielectric nanorods and can be included in a liquid crystal layer 2306 between a first electrode 2302 (top transparent electrode) and a second electrode 2304 (pixelated bottom transparent electrode). The first electrode 2302 can be in contact with a first substrate 2310, while the second electrode 2304 can be in contact with a second substrate 2312.

[0122] FIG. 24 A cross-sectional side view schematic of a cell of a light-reflective liquid crystal (LC) device according to different embodiments is shown, having an array of nanorods 2408. The nanorods 2408 can be dielectric nanorods and can be included in a liquid crystal layer 2406 between a first electrode 2402 (top transparent electrode) and a second electrode 2404 (pixelated bottom metal electrode). The first electrode 2402 can be in contact with a first substrate 2410, while the second electrode 2404 can be in contact with a second substrate 4312. The liquid crystal device can further include a passivation layer 2414 formed on or in contact with the second electrode 2404 to avoid direct contact of the liquid crystal molecules with the second electrode 2404.

[0123] For FIG. 23 to FIG. 24The height of the nanopillars 2308 and 2408 shown is the longest dimension. In various embodiments, the nanopillars 2308 and 2408 can be made of the same material. In other various embodiments, the nanopillars 2308 and 2408 can be made of a stack of different materials.

[0124] In the gaps between the nanopillars, the liquid crystals can be aligned vertically. Electrical tuning can be achieved by using negative dielectric anisotropy liquid crystals or by high-frequency driving of DFLC. FIG. 26 It is shown that a switching operation is performed using positive dielectric anisotropic liquid crystals by applying an in-plane electric field between nanopillars. FIG. 25A shows that when the applied voltage is lower than the threshold voltage (V th ), schematic cross-sectional side views of a unit cell of a reflective liquid crystal (LC) device having a nanorod array 2508 according to various embodiments. FIG. 25B shows that when the applied voltage is higher than the threshold voltage (V th ), a schematic cross-sectional side view of a cell of a reflective liquid crystal (LC) device having a nanopillar array 2508 according to various embodiments. Nanopillar array 2508 may be included in liquid crystal layer 2506 and may be in contact with pixelated electrode 2504. Pixelated electrode 2504 may be in contact with bottom substrate 2512, while top substrate 2510 may be in contact with liquid crystal layer 2506.

[0125] Various embodiments may involve the use of subwavelength resonant nanoantennas to construct ultrathin liquid crystal cells with uniform liquid crystal alignment (without any alignment layer), and also devices for achieving efficient light and / or wavefront modulation. Electrical tuning of the liquid crystal refractive index can provide dynamic light modulation by spectral tuning of the nanoantenna resonance. The liquid crystal alignment can be effectively set (e.g., diagonal, parallel, twisted, or vertical) based on the aspect ratio and configuration of the nanoantennas. By selecting appropriate materials and driving mechanisms, efficient dynamic light modulation can be achieved. In various embodiments, the geometry of the nanoantennas sets the liquid crystal alignment, resulting in lower switching voltages and faster switching speeds compared to liquid crystal cells with alignment layers.

[0126] FIG. 26 A table showing comparisons of liquid crystal (LC) devices according to different embodiments with previously reported devices is shown.

[0127] Different embodiments can involve liquid crystal devices in which a metasurface (nanostructure) can provide light modulation / wavefront modulation and uniform liquid crystal alignment. The nanostructure can aim to maintain optical resonance for light modulation. The liquid crystal molecule alignment can be fully controlled by the periodicity and geometry of the nanoantenna without any additional alignment layers. Compared to conventional liquid crystal alignment (using alignment layers), the metasurface-induced alignment can provide pixel size miniaturization, microsecond switching, and low voltage driving for LCOS-NSLM devices. Different embodiments without alignment layers can simplify device fabrication and aid in improving device lifetime by eliminating photo-induced and thermal-induced alignment layer degradation, thereby improving the quality of the liquid crystal cell. Compared to conventional / commercially available devices, different embodiments can achieve smaller, miniaturized pixel size (PP < 1 pm), lower voltage driving (V < 5 V), and / or microsecond switching. Different embodiments can be potential candidates for next-generation spatial light modulators with a wide range of applications, including augmented reality (AR), solid-state light detection and ranging (LiDAR), holographic display, and optical communication.

Claims

1. A liquid crystal device comprising: a first electrode; a second electrode; as well as a liquid crystal layer between the first electrode and the second electrode, the liquid crystal layer comprising liquid crystal molecules and a nanostructure array, the nanostructure array being adapted to achieve a desired uniform arrangement of the liquid crystal molecules and modulate light passing through the liquid crystal device; The period of the nanostructure array or the aspect ratio of each nanostructure in the nanostructure array is adapted to enable the liquid crystal molecules to achieve a desired uniform arrangement. 2 . The liquid crystal device according to claim 1 , wherein the first electrode is continuous and the second electrode is pixelated, and the nanostructure array is formed on the first electrode or the second electrode.

3. A liquid crystal device according to claim 2, wherein each pixel of the pixelated second electrode is arranged to be individually addressed by an integrated circuit. 4 . The liquid crystal device according to claim 1 , wherein the liquid crystal layer further comprises another nanostructure array, wherein the nanostructure array and the another nanostructure array are on opposite sides of the liquid crystal layer. 5 . The liquid crystal device of claim 4 , wherein the longitudinal axis of the nanostructure array is rotated relative to the longitudinal axis of the another nanostructure array. 6 . The liquid crystal device of claim 5 , wherein a longitudinal axis of the nanostructure array is substantially perpendicular to a longitudinal axis of the another nanostructure array.

7. The liquid crystal device according to claim 1, wherein the first electrode and the second electrode are light-transmissive.

8. The liquid crystal device according to claim 1, wherein the first electrode is light-transmissive and the second electrode is light-reflective. 9 . The liquid crystal device according to claim 8 , wherein the second electrode comprises an aluminum layer, a gold layer, a silver layer, or a copper layer.

10. The liquid crystal device according to claim 8, wherein the second electrode comprises a dielectric mirror combined with a light-transmitting optical conductor. The liquid crystal device according to claim 1 , wherein the first electrode comprises indium titanium oxide. 12 . The liquid crystal device according to claim 1 , wherein a thickness of the liquid crystal layer is any one value selected from a range of 200 nm to 800 nm.

13. The liquid crystal device of claim 1, wherein the array of nanostructures has at least two dimensions that are smaller than a wavelength of operating light of the liquid crystal device. 14 . The liquid crystal device according to claim 1 , wherein the nanostructure array is made of a dielectric material having a real part of a refractive index greater than or equal to 2 and an imaginary part of a refractive index less than or equal to 0.

1. 15 . The liquid crystal device according to claim 1 , wherein a dimension of each nanostructure of the nanostructure array along a direction in which the liquid crystal molecules are aligned is larger than other dimensions of the nanostructure.

16. The liquid crystal device of claim 1, wherein the periodic grating of the nanostructure array includes a longest grating vector along a direction in which the liquid crystal molecules will align uniformly. 17 . The liquid crystal device according to claim 1 , further comprising a passivation layer formed on the second electrode, the passivation layer being adapted to prevent the liquid crystal molecules from directly contacting the second electrode.

18. The liquid crystal device of claim 1, wherein the array of nanostructures comprises nanopillars, each of the nanopillars having a height greater than its width or its length.

19. The liquid crystal device according to claim 18, wherein the nanorods are adapted to align the liquid crystal molecules along a longitudinal axis of the nanorods.

20. A method of forming a liquid crystal device, the method comprising: forming a first electrode; forming a second electrode; as well as A liquid crystal layer is formed between the first electrode and the second electrode, the liquid crystal layer comprising liquid crystal molecules and a nanostructure array, wherein the nanostructure array is adapted to achieve a desired uniform arrangement of the liquid crystal molecules and modulate light passing through the liquid crystal device. The period of the nanostructure array or the aspect ratio of each nanostructure in the nanostructure array is adapted to enable the liquid crystal molecules to achieve a desired uniform arrangement.

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