Liquid crystal device

Abstract

A liquid crystal device comprising a single or multiple pixel elements is provided. Each pixel element comprises: a first substrate; a second substrate parallel to the first substrate; a liquid crystal layer disposed between the first and second substrates; a first plurality of electrodes formed between the first substrate and the liquid crystal layer; and a second plurality of electrodes formed between the second substrate and the liquid crystal layer. The first and second plurality of electrodes are configured to generate electric fields in three orthogonal directions, wherein the electric fields in two of the three orthogonal directions are in-plane electric fields, and the electric field in another of the three orthogonal directions is out-of-plane electric fields.

Description

Technical Field

[0001] The present disclosure relates to a liquid crystal device, and more particularly to implementing liquid crystals to provide a device with a continuously adjustable phase shift or delay (ie, a phase shifter) for terahertz (THz) (1 THz = 10 12 Various applications in high-frequency (Hz) electromagnetic waves or submillimeter electromagnetic waves. Background Art

[0002] Terahertz technology shows great potential in fields including time-domain spectroscopy, terahertz imaging, and medical applications. Furthermore, terahertz communications and phased array radar are becoming feasible. All of these applications require terahertz quasi-optical devices (e.g., polarizers, filters, phase shifters, and modulators for signal processing).

[0003] Liquid crystal (LC) devices are widely used in terahertz frequencies. To operate at terahertz frequencies, LC devices use a thick cell gap to meet the required retardation. However, a thick cell gap results in an extremely slow response. Summary of the Invention

[0004] The present disclosure provides a liquid crystal device, and more specifically, a liquid crystal phase shifter for terahertz electromagnetic waves with liquid crystal switching (LC switching). The LC switching brings about hexa-directional switching between the initial, intrinsic in-plane, and out-of-plane redirection of the liquid crystal, providing a wider phase shift range while maintaining a fast response time.

[0005] According to exemplary embodiments, a liquid crystal device may include, but is not limited to, a single or multiple pixel elements, as each pixel element may include: a first substrate; a second substrate facing the first substrate and parallel to the first substrate; a liquid crystal layer disposed between the first substrate and the second substrate; a first plurality of electrodes formed between the first substrate and the liquid crystal layer, wherein the first plurality of electrodes are grid-type electrodes and / or finger-type electrodes; a second plurality of electrodes formed between the second substrate and the liquid crystal layer, wherein the second plurality of electrodes are grid-type electrodes and / or finger-type electrodes, wherein the same grid-type electrodes and / or finger-type electrodes of the first plurality of electrodes and the second plurality of electrodes are formed and face each other with a cell gap, wherein the first plurality of electrodes and the second plurality of electrodes are composed to generate electric fields in three orthogonal directions, and the electric fields in two of the three orthogonal directions are in-plane electric fields and are substantially parallel to the first substrate, the second substrate, and the liquid crystal layer, while the electric field in another of the three orthogonal directions is out-of-plane electric field and is substantially perpendicular to the first substrate and the second substrate.

[0006] In order to make the above features and advantages of the present disclosure more easily understood, several embodiments accompanied by the accompanying drawings are described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and together with the description serve to explain the principles of the disclosure.

[0008] Figure 1 is a schematic cross-sectional view of a liquid crystal pixel element.

[0009] Figure 2A is a schematic three-dimensional diagram of a liquid crystal pixel element.

[0010] Figure 2B yes Figure 2A Schematic top view of a liquid crystal pixel element.

[0011] Figure 2C yes Figure 2A Schematic top view of a liquid crystal pixel element.

[0012] Figure 2D yes Figure 2A Schematic cross-sectional view of a liquid crystal pixel element.

[0013] Figure 3A is a schematic three-dimensional diagram of a liquid crystal pixel element.

[0014] Figure 3B yes Figure 3A Schematic top view of a liquid crystal pixel element.

[0015] Figure 3C yes Figure 3A Schematic cross-sectional view of a liquid crystal pixel element.

[0016] Figure 4A is a schematic three-dimensional diagram of a liquid crystal pixel element.

[0017] Figure 4B yes Figure 4A Schematic top view of a liquid crystal pixel element.

[0018] Figure 4C yes Figure 4A Schematic cross-sectional view of a liquid crystal pixel element.

[0019] Figure 5A is a schematic three-dimensional diagram of a liquid crystal pixel element.

[0020] Figure 5B yes Figure 5A Schematic top view of a liquid crystal pixel element.

[0021] Figure 5C yes Figure 5A Schematic cross-sectional view of a liquid crystal pixel element.

[0022] Figure 6 yes Figure 3A 、 Figure 4A and Figure 5A Schematic top view and cross-sectional view of a liquid crystal pixel element.

[0023] Figure 7A is a schematic top view of a portion of a liquid crystal pixel element.

[0024] Figure 7B yes Figure 7A Schematic cross-sectional view of the portion of the liquid crystal pixel element.

[0025] Figure 8A is a schematic top view of a portion of a liquid crystal pixel element.

[0026] Figure 8B yes Figure 8A Schematic cross-sectional view of the portion of the liquid crystal pixel element.

[0027] Figure 9A is a schematic top view of a portion of a liquid crystal pixel element.

[0028] Figure 9B yes Figure 9A Schematic cross-sectional view of the portion of the liquid crystal pixel element.

[0029] Figure 10A is a schematic top view of a portion of a liquid crystal pixel element.

[0030] Figure 10B yes Figure 10A Schematic cross-sectional view of the portion of the liquid crystal pixel element.

[0031] Figure 11A is a schematic top view of a portion of a liquid crystal pixel element.

[0032] Figure 11B yes Figure 11A Schematic cross-sectional view of the portion of the liquid crystal pixel element.

[0033] Figure 12 is a schematic top view of a portion of a liquid crystal device.

[0034] Figure 13 is a schematic top view of a portion of a liquid crystal device.

[0035] Figure 14 Schematic top view and cross-sectional view of a portion of a liquid crystal device.

[0036] Figure 15 is a cross-sectional view of a portion of a liquid crystal device.

[0037] Figure 16 Schematic top view and cross-sectional view of a portion of a liquid crystal device.

[0038] Figure 17 Schematic top view and cross-sectional view of a portion of a liquid crystal device.

[0039] Figure 18 Schematic top view and cross-sectional view of a portion of a liquid crystal device.

[0040] Figure 19 is a block diagram of a photonic device for terahertz electromagnetic waves. DETAILED DESCRIPTION

[0041] In the following detailed description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the disclosed embodiments. However, it will be apparent that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown to simplify the drawings.

[0042] In the following embodiments, words used to indicate directions, such as "upper," "lower," "front," "backward," "left," and "right," refer only to directions in the accompanying drawings. Therefore, directional terms are used to illustrate, not to limit, the present disclosure. In the accompanying drawings, each figure illustrates the general characteristics of the methods, structures, and / or materials used in a particular exemplary embodiment. The accompanying drawings should not be construed as defining or limiting the intended scope and properties of a particular exemplary embodiment. For example, the relative thicknesses and positions of layers, regions, or structures may be reduced or exaggerated for clarity.

[0043] Figure 1 is a schematic cross-sectional view of a liquid crystal pixel element 100 according to an embodiment of the present invention.

[0044] exist Figure 1 In the embodiment, the liquid crystal pixel element 100 includes a first substrate 110a and a second substrate 110b. The second substrate 110b faces the first substrate 110a and is parallel to the first substrate 110a. The first substrate 110a and the second substrate 110b have similar structures and properties. The first substrate 110a and the second substrate 110b are both substrates with uniform thickness in the Z direction. The first substrate 110a and the second substrate 110b are made of a material that is transparent to terahertz frequencies. In some embodiments, the terahertz frequency ranges from 0.1 THz to 10 THz, but is not limited thereto. In some embodiments, the material of the first substrate 110a and the second substrate 110b is glass or plastic, but is not limited thereto.

[0045] The liquid crystal pixel element 100 further includes a liquid crystal layer 120 having liquid crystal molecules 122. The liquid crystal layer 120 is disposed between the first substrate 110a and the second substrate 110b in the vertical Z direction. The liquid crystal layer 120 has a uniform thickness in the Z direction. In some embodiments, the thickness of the liquid crystal layer 120 is between 50 micrometers (μm) and 150 μm, preferably 100 μm or less, but is not limited thereto.

[0046] The liquid crystal pixel element 100 further includes a plurality of electrodes 130a formed between the first substrate 110a and the liquid crystal layer 120, and a plurality of electrodes 130b formed between the second substrate 110b and the liquid crystal layer 120. The electrodes 130a and 130b are separated by a cell gap in the Z direction, wherein the liquid crystal layer 120 is disposed in the cell gap. Insulating layers 140a and 140b are respectively formed on the electrodes 130a and 130b to insulate the electrodes 130a and 130b from the other layers of the liquid crystal pixel element 100. In some embodiments, the material of the electrodes 130a and 130b is metal or any other conductive material, such as copper, aluminum, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, and graphene, but is not limited thereto. In some embodiments, the thickness of the electrodes 130a and 130b is between 100 nm and 500 nm, and preferably 200 nm, but is not limited thereto. The width of the electrodes 130a and 130b is between 5 μm and 15 μm, preferably 10 μm, but not limited thereto. In some embodiments, the thickness of the insulating layers 140a and 140b may be between 200 nm and 1000 nm, preferably 500 nm, but not limited thereto.

[0047] The electrodes 130a and 130b include grating-type electrodes and / or finger-type electrodes. When a voltage difference is applied to the electrodes 130a and 130b by a power supply controlled by a driving module (not shown), the electrodes 130a and 130b together generate an electric field in three orthogonal directions (e.g., along the X direction, the Y direction, and / or the Z direction). The electric fields generated by the electrodes 130a and 130b in two of the three orthogonal directions (e.g., along the X direction and the Y direction) are referred to as in-plane electric fields and are substantially parallel to the first substrate 110a, the second substrate 110b, and the liquid crystal layer 120. The other electric field in the three orthogonal directions (e.g., along the Z direction) is referred to as an out-of-plane electric field and is substantially perpendicular to the first substrate 110a and the second substrate 110b.

[0048] By applying electric fields in the three orthogonal directions, two of which are in-plane electric fields perpendicular to each other and one is an out-of-plane electric field, the liquid crystal molecules 122 in the liquid crystal layer 120 can perform six-way switching between in-plane and out-of-plane alignments.

[0049] The liquid crystal pixel element 100 further includes alignment layers 150a and 150b, respectively disposed on the electrodes 130a and 130b, and contacting opposite sides of the liquid crystal layer 120. The alignment layers 150a and 150b are configured to align the liquid crystal molecules 122 to an initial alignment when no electric field is applied to the liquid crystal layer 120 by controlling the pretilt angle and polar angle of the liquid crystal molecules 122. The pretilt angle is the angle between the long axis of the liquid crystal molecule 122 and the surface (XY plane) of the alignment layer, while the azimuth angle is the angle between the long axis of the liquid crystal molecule 122 projected onto the XY plane and a fixed axis (e.g., along the X direction) in the XY plane perpendicular to the Z direction. In some embodiments, the material of the alignment layers 150a and 150b is a polymer (e.g., polyimide), but is not limited thereto.

[0050] The liquid crystal pixel element 100 further includes polarizers 160a and 160b disposed on the first substrate 110a and the second substrate 110b, respectively. The first polarizer 160a and the second polarizer 160b are configured to polarize light entering or exiting the liquid crystal layer 120. In some embodiments, the polarizer 160a may be formed between the first substrate 110a and the insulating layer 140a, and the polarizer 160b may be formed between the second substrate 110b and the insulating layer 140b. In some embodiments, the finger-type or strip-type electrodes 130a and 130b together function as a wire-grid polarizer.

[0051] In some embodiments, the polarization directions of polarizers 160a and 160b are perpendicular or parallel to each other. When a voltage is applied across the liquid crystal layer 120, the liquid crystal molecules 122 are twisted, causing the polarization of light passing through the liquid crystal layer 120 to rotate. Terahertz light oscillating in one direction may pass through the liquid crystal layer 120 more easily than light oscillating in another direction. The refractive index (how much slower the light propagates in the material) may be different for light oscillating parallel or perpendicular to the liquid crystal molecules. This is called "optical anisotropy," which is defined as the extraordinary refractive index n. e With ordinary refractive index n o The difference between (Δn=n e -n o ), and is called "birefringence".

[0052] Figure 2A is a schematic three-dimensional diagram of a liquid crystal pixel element. Figure 2B yes Figure 2A Schematic top view of a liquid crystal pixel element. Figure 2C yes Figure 2A Schematic top view of a liquid crystal pixel element. Figure 2D yes Figure 2A Schematic cross-sectional view of a liquid crystal pixel element.

[0053] Please refer to Figures 2A to 2D For the sake of clarity, some elements of the liquid crystal pixel element 100 are omitted.

[0054] like Figure 2A As shown in FIG, a first plurality of electrodes 130a and a second plurality of electrodes 130b are presented. The first plurality of electrodes 130a includes a pair of electrodes 132a, a pair of electrodes 134a, and an electrode 136a, all of which are formed at the same level on the first substrate 110a. The second plurality of electrodes 130b includes a pair of electrodes 132b, a pair of electrodes 134b, and an electrode 136b, all of which are formed at the same level on the second substrate 110b. The first plurality of electrodes 130a and the second plurality of electrodes 130b are formed in the same arrangement and face each other. Electrodes 132a, 132b, 134a, and 134b are finger-type electrodes. Electrodes 136a and 136b are grid-type electrodes.

[0055] Reference Figure 2A and Figure 2B The pair of electrodes 132a are formed on the first substrate 110a. The electrodes 132a, which are finger-type electrodes, are parallel to each other. Each of the electrodes 132a has a bar shape, wherein the long axis of each of the electrodes 132a is perpendicular to the X direction. In some embodiments, the electrodes 132a may have other shapes, but are not limited thereto. When a voltage difference is applied between the electrodes 132a, the pair of electrodes 132a generates an in-plane electric field substantially parallel to the first substrate 110a and the liquid crystal layer 120. Depending on the direction of the voltage applied to the electrodes 132a, the direction of the in-plane electric field generated by the electrodes 132a can be along the positive X direction or the negative X direction. The electric field generated along the X direction reorients the liquid crystal molecules 122 in the liquid crystal layer 120 along the X direction. The pair of electrodes 132b formed on the second substrate 110b have properties similar to those of the pair of electrodes 132a and will not be repeated here.

[0056] Reference Figure 2A and Figure 2BThe pair of electrodes 134a are formed on the first substrate 110a. The electrodes 134a, which are finger-type electrodes, are parallel to each other. Each of the electrodes 134a has a strip shape, wherein the long axis of each of the electrodes 134a is perpendicular to the Y direction. In some embodiments, the electrodes 134a may have other shapes, but are not limited thereto. When a voltage difference is applied between the electrodes 134a, the pair of electrodes 134a generates an in-plane electric field substantially parallel to the first substrate 110a and the liquid crystal layer 120. Depending on the direction of the voltage applied to the electrodes 134a, the direction of the in-plane electric field generated by the electrodes 134a can be along the positive Y direction or the negative Y direction. The electric field generated along the Y direction redirects the liquid crystal molecules 122 in the liquid crystal layer 120 along the Y direction. The pair of electrodes 134b formed on the second substrate 110b have properties similar to those of the pair of electrodes 134a and will not be repeated here.

[0057] Reference Figure 2A and Figure 2B , the electrode 136a is formed on the first substrate 110a, and the electrode 136b is formed on the second substrate 110b. Figure 2A and Figure 2B As shown in FIG, electrodes 136a and 136b are grid-type electrodes. In some embodiments, electrodes 136a and 136b may have other shapes, but are not limited thereto. The grid-type electrodes 136a and 136b are both oriented along the Y direction. When a voltage difference is applied between electrodes 136a and 136b, electrodes 136a and 136b together generate an out-of-plane electric field that is substantially perpendicular to the first substrate 110a, the second substrate 110b, and the liquid crystal layer 120. Depending on the direction of the voltage applied to electrodes 136a and 136b, the direction of the out-of-plane electric field can be along the positive Z direction or the negative Z direction. In some embodiments, the electric field generated along the Z direction causes the liquid crystal molecules 122 in the liquid crystal layer 120 to reorient along the Z direction.

[0058] Reference Figure 2B and Figure 2D , when no voltage is applied to the electrodes 132a, 132b, 134a, 134b, 136a and / or 136b, no electric field is generated in the liquid crystal layer 120. Therefore, the liquid crystal molecules 122 assume their initial alignment. In some embodiments, the initial alignment of the liquid crystal molecules 122 is in-plane, wherein the long axis of the liquid crystal molecules 122 is parallel to the first substrate 110a and the second substrate 110b. In some embodiments, the initial alignment of the liquid crystal molecules 122 is almost perpendicular to the extension direction of the grid-type electrode 136a. In other words, the angle between the long axis of the liquid crystal molecules 122 and the extension direction of the electrode 136a is almost perpendicular. Figure 2B, the extension direction of the electrode 136a is along the Y direction. In some embodiments, the angle between the long axis of the liquid crystal molecules 122 and the extension direction of the electrode 136a is between 85 degrees and 95 degrees, which is almost the direction of the X direction, as shown in FIG. Figure 2D As shown in , but the initial orientation angle is not limited thereto.

[0059] Reference Figure 2B The electrodes 132a and 134a are configured to generate an in-plane electric field. Figure 2B As shown in FIG, the distance between the two electrodes 132a is defined as d1, and the distance between the two electrodes 134a is defined as d2. In some embodiments, the ratio d1 / d2 of the distance d1 between the two electrodes 132a and the distance d2 between the two electrodes 134a is substantially equal to 1. In some embodiments, the ratio d1 / d2 is between 0.9 and 1.1. Because the distance d1 between the two electrodes 132a and the distance d2 between the two electrodes 134a are substantially the same, when a similar voltage difference is applied to the electrodes 132a and 134a, the electric field generated by the electrode 132a and the electric field generated by the electrode 134a can be substantially the same, and thus the two in-plane electric fields in the liquid crystal layer 120 can have more similar electric field strengths.

[0060] Reference Figure 2B , the initial alignment of the liquid crystal molecules 122 is along the X direction. In some embodiments, the distance d2 between the electrodes 134a that generate an in-plane electric field perpendicular to the initial alignment of the liquid crystal molecules 122 is shorter than the distance d1 between the electrodes 132a that generate an in-plane electric field perpendicular to the initial alignment of the liquid crystal molecules 122, such that d2 / d1<1 or d1 / d2>1. The electrodes 132a generate an in-plane electric field along the X direction (the X direction is parallel to the initial alignment of the liquid crystal molecules 122). The electrodes 134a generate an in-plane electric field along the Y direction (the Y direction is perpendicular to the initial alignment of the liquid crystal molecules 122). When the distance d2 between the electrodes 134a is shorter than the distance d1 between the electrodes 132a, the electric field intensity generated by the electrodes 134a is stronger than the electric field intensity generated by the electrodes 132a, which makes it easier to align the liquid crystal molecules 122 along the direction of the electric field generated by the electrodes 134a (which is perpendicular to the initial alignment of the liquid crystal molecules 122).

[0061] Reference Figure 2CIn some embodiments, the extension direction of the electrode 136a is along the Y direction. The initial alignment of the liquid crystal molecules 122 is in-plane, wherein the long axis of the liquid crystal molecules 122 is parallel to the first substrate 110a and the second substrate 110b. In some embodiments, the initial alignment of the liquid crystal molecules 122 is approximately 45 degrees relative to the extension direction of the electrode 136a. In other words, the angle between the long axis of the liquid crystal molecules 122 and the extension direction of the electrode 136a is approximately 45 degrees. In some embodiments, the angle between the long axis of the liquid crystal molecules 122 and the extension direction of the electrode 136a is between 40 degrees and 50 degrees, but is not limited thereto.

[0062] Figure 3A is a schematic three-dimensional diagram of a liquid crystal pixel element. Figure 3B yes Figure 3A Schematic top view of a liquid crystal pixel element. Figure 3C yes Figure 3A Schematic cross-sectional view of a liquid crystal pixel element.

[0063] Please refer to Figure 3A 、 Figure 3B and Figure 3C In this embodiment, the power source 138 is connected to the pair of electrodes 132a located on the first substrate 110a and the pair of electrodes 132b located on the second substrate 110b. When a voltage difference is applied between the electrodes 132a, the pair of electrodes 132a generates an in-plane electric field substantially parallel to the first substrate 110a and the liquid crystal layer 120. The electric field generated by the electrodes 132a can be along the positive X direction or the negative X direction, which causes the liquid crystal molecules 122 in the liquid crystal layer 120 to reorient along the same direction. Similarly, when a voltage difference is applied between the electrodes 132b, the pair of electrodes 132b generates an in-plane electric field substantially parallel to the second substrate 110b and the liquid crystal layer 120. The electric field generated by the electrodes 132b is along the positive X direction or the negative X direction, which also causes the liquid crystal molecules 122 in the liquid crystal layer 120 to align along the same direction.

[0064] Therefore, by applying a voltage difference between the pair of electrodes 132a and the pair of electrodes 132b, the liquid crystal molecules 122 in the liquid crystal layer 120 are reoriented along the generated electric field, which is along the positive X direction or the negative X direction. Generally speaking, the average orientation direction of the liquid crystal molecules 122 is along the X direction.

[0065] Figure 4A is a schematic three-dimensional diagram of a liquid crystal pixel element. Figure 4B yes Figure 4A Schematic top view of a liquid crystal pixel element. Figure 4C yes Figure 4A Schematic cross-sectional view of a liquid crystal pixel element.

[0066] Please refer to Figure 4A 、 Figure 4B and Figure 4C . In this embodiment, the power supply 138 is connected to the pair of electrodes 134a located on the first substrate 110a and the pair of electrodes 134b located on the second substrate 110b. When a voltage difference is applied between the electrodes 134a, the pair of electrodes 134a generates an in-plane electric field substantially parallel to the first substrate 110a and the liquid crystal layer 120. The electric field generated by the pair of electrodes 134a is perpendicular to the electric field generated by the electrode 132a. The electric field generated by the electrode 134a can be along the positive Y direction or the negative Y direction, which causes the liquid crystal molecules 122 in the liquid crystal layer 120 to reorient along the same direction. Similarly, when a voltage difference is applied between the electrodes 134b, the pair of electrodes 134b generates an in-plane electric field substantially parallel to the second substrate 110b and the liquid crystal layer 120. The electric field generated by the electrode 134b is along the positive Y direction or the negative Y direction, which also causes the liquid crystal molecules 122 in the liquid crystal layer 120 to align along the same direction.

[0067] Therefore, by applying a voltage difference between the pair of electrodes 134a and the pair of electrodes 134b, the liquid crystal molecules 122 in the liquid crystal layer 120 are reoriented along the generated electric field, which is along the positive Y direction or the negative Y direction. Generally speaking, the average orientation direction of the liquid crystal molecules 122 is along the positive Y direction or the negative Y direction.

[0068] Figure 5A is a schematic three-dimensional diagram of a liquid crystal pixel element. Figure 5B yes Figure 5A Schematic top view of a liquid crystal pixel element. Figure 5C yes Figure 5A Schematic cross-sectional view of a liquid crystal pixel element.

[0069] Please refer to Figure 5A 、 Figure 5B and Figure 5C In this embodiment, a power source 138 is connected to an electrode 136a located on the first substrate 110a and an electrode 136b located on the second substrate 110b. When a voltage difference is applied between the electrodes 136a and 136b, the electrodes 136a and 136b generate an out-of-plane electric field that is substantially perpendicular to the first substrate 110a, the second substrate 110b, and the liquid crystal layer 120. The electric field generated by the electrodes 136a and 136b is perpendicular to the electric field generated by the pair of electrodes 132a and perpendicular to the electric field generated by the pair of electrodes 134a. The electric field generated by the electrodes 136a and 136b can be along the positive Z direction or the negative Z direction, which reorients the liquid crystal molecules 122 in the liquid crystal layer 120 along the same direction.

[0070] Therefore, by applying a voltage difference between electrodes 136a and 136b, the liquid crystal molecules 122 in the liquid crystal layer 120 are reoriented along the generated electric field, which is along the positive Z direction or the negative Z direction. Generally speaking, the average orientation direction of the liquid crystal molecules 122 is along the positive Z direction or the negative Z direction.

[0071] Therefore, by applying a voltage difference to the electrodes 132a, 132b, 134a, 134b, 136a and / or 136b located on the first substrate 110a and the second substrate 110b, an electric field along three orthogonal directions (positive X direction or negative X direction, positive Y direction or negative Y direction, and positive Z direction or negative Z direction) can be generated to reorient the liquid crystal molecules 122 in the liquid crystal layer along a desired direction. Figure 6 As shown in , the orientation of the liquid crystal molecules 122 between the X, Y, and Z directions can also be switched by applying appropriate voltage differences to the corresponding electrodes. By utilizing the different orientations of the liquid crystal molecules, the phase of the incoming terahertz wave incident on the liquid crystal pixel element can be delayed to a desired phase.

[0072] In the foregoing discussion, liquid crystal molecules 122 having positive dielectric anisotropy (Δε>0) are used. However, when liquid crystal molecules 122 having negative dielectric anisotropy (Δε<0) are used, when an electric field is applied to the liquid crystal layer, the orientation of the liquid crystal molecules differs by 90 degrees from the orientation of the liquid crystal molecules having positive dielectric anisotropy (Δε>0).

[0073] like Figures 2A to 5C As shown in , the thickness of the liquid crystal layer 120 is between 50 μm and 150 μm, and is preferably 100 μm or less than 100 μm, but not limited thereto. In some embodiments, when the thickness of the liquid crystal layer 120 is less than 100 μm, the liquid crystal pixel element 100 becomes more efficient. A smaller thickness of the liquid crystal layer 120 is preferred in terms of a low-loss phase shifter. In addition, for the purpose of a low-loss phase shifter, the material of the substrates 110a and 110b of the liquid crystal pixel element 100 may be a low-loss material, such as fused quartz, silicon dioxide, lithium niobate and other materials, which are not limited thereto. By using a low-loss substrate material in the liquid crystal pixel element, the total thickness of the liquid crystal pixel element 100 can be further reduced. In some embodiments, the disclosed liquid crystal device can be combined with a birefringent substrate (such as quartz, silicon dioxide, lithium niobate, which are not limited thereto) that can be rotated in an azimuth angle. The birefringent substrate compensates for the phase shift, which makes it possible to reduce the thickness of the liquid crystal layer in the disclosed liquid crystal device while maintaining the maximum phase shift as a phase shifter.

[0074] In other inventions, the change in the alignment direction of the liquid crystal molecules is limited to a value of approximately 90 degrees or less, which is usually achieved in the in-plane direction or between the in-plane direction and the out-of-plane direction. Figures 3A to 5CAs shown in FIG, depending on the electric field applied to the liquid crystal layer, the liquid crystal pixel element 100 can produce three 90-degree changes in the orientation direction of the liquid crystal molecules 122 in space, and the three 90-degree changes are realized in the XY plane, the XZ plane, and the XZ plane. Thus, three pairs of bidirectional 90-degree switches are realized. Therefore, by combining a pair of polarizers 160a and 160b, the phase change range accompanying the orientation of the liquid crystal molecules 122 becomes more nonlinear compared to conventional technologies. In addition, each switch in each 90-degree orientation direction is bidirectionally controlled by the electric field, which means that all responses to the orientation changes are adjustable and faster than those in conventional technologies.

[0075] The electrodes on the substrate can have various arrangements to suit various requirements. 7A to 11B In these figures, various arrangements of electrodes are presented. In these figures, since the arrangements of electrodes 132a, 134a and 136a on the first substrate 110a and the second substrate 110b are the same, only the arrangement of electrodes 132a, 134a and 136a on the first substrate 110a is presented and discussed below.

[0076] Figure 7A is a schematic top view of a portion of a liquid crystal pixel element. Figure 7B yes Figure 7A Schematic cross-sectional view of a portion of a liquid crystal pixel element. For clarity, only the elements formed on the first substrate 110a are presented. The electrodes formed on the second substrate 110b are arranged similarly. Figure 7A From the top view, the arrangement of electrodes 132a, 134a and 136a is similar to Figure 2B However, as Figure 7B As shown in , only electrode 132a is formed on substrate 110a. Electrode 132a is covered by insulating layer 140a. Electrodes 134a and 136a are formed on insulating layer 140a. Electrodes 134a and 136a are covered by insulating layer 142a. In other words, electrodes 134a and 136a are formed on the same plane, but are formed on a plane different from the plane on which electrode 132a is formed. By arranging the electrodes in different planes, since there is more space available in one plane, wiring to the electrodes can be easier and the shape of the electrodes can be more flexible. In some embodiments, the thickness of insulating layers 140a and 142a is 200nm to 1000nm, preferably 500nm, but not limited thereto. In some embodiments, the thickness of electrodes 132a, 134a and 136a is 100nm to 500nm, preferably 200nm, but not limited thereto. The width of the electrodes 130 a and 130 b is between 5 μm and 15 μm, and preferably 10 μm, but is not limited thereto.

[0077] Figure 8Ais a schematic top view of a portion of a liquid crystal pixel element. Figure 8B yes Figure 8A Schematic cross-sectional view of a portion of a liquid crystal pixel element. Figure 8A From the top view, the arrangement of electrodes 132a, 134a and 136a is similar to Figure 7A However, as Figure 8B As shown in FIG, only electrode 136a is formed on substrate 110a. Electrode 136a is covered by insulating layer 140a. Electrode 132a is formed on insulating layer 140a. Electrode 132a is covered by insulating layer 142a. Electrode 134a is formed on insulating layer 142a. Electrode 136a is also covered by insulating layer 144a. In other words, electrodes 132a, 134a, and 136a are each formed on a different plane. In some embodiments, electrodes 132a, 134a, and 136a may be formed on different planes. Figure 8B . By arranging the electrodes in different planes, wiring to the electrodes can be easier and the shape of the electrodes can be more flexible because there is more space available in one plane. In some embodiments, the thickness of the insulating layers 140a and 142a is 200nm to 1000nm, preferably 500nm, but not limited thereto. In some embodiments, the thickness of the electrodes 132a, 134a and 136a is 100nm to 500nm, preferably 200nm, but not limited thereto. The width of the electrodes 130a and 130b is between 5μm and 15μm, and preferably 10μm, but not limited thereto.

[0078] Figure 9A is a schematic top view of a portion of a liquid crystal pixel element. Figure 9B yes Figure 9A Schematic cross-sectional view of the portion of the liquid crystal pixel element. Figure 9A and Figure 9B The arrangement of electrodes 132a and 134a in is similar to that of Figure 8A The arrangement of electrodes 132a and 134a in. Figure 9A and Figure 9B The difference is that the electrode 136a extends above the top surface of the first substrate 110a located below the electrodes 132a and 134a. With a similar arrangement of the electrode 136b formed on the second substrate 110b (not shown), the electrodes 136a and 136b can form a more uniform electric field along the Z direction, and thus the out-of-plane electric field generated in the liquid crystal layer 120 can be more uniform.

[0079] Figure 10A is a schematic top view of a portion of a liquid crystal pixel element. Figure 10B yes Figure 10A Schematic cross-sectional view of the portion of the liquid crystal pixel element. Figure 10A and Figure 10B The arrangement of electrodes 132a and 134a in is similar to that of Figure 9A and Figure 9B The arrangement of electrodes 132a and 134a in. Figure 10A and Figure 10B The difference is that electrode 136a is now a plurality of finger-type electrodes extending along the Y direction, rather than a grid-type electrode. In some embodiments, each of the finger-type electrodes has the same width in the X direction. In some embodiments, the gaps between the finger-type electrodes are the same. Using a similar arrangement of electrode 136b formed on second substrate 110b (not shown), electrodes 136a and 136b can form a periodically varying electric field along the Z direction.

[0080] Figure 11A is a schematic top view of a portion of a liquid crystal pixel element. Figure 11B yes Figure 11A Schematic cross-sectional view of the portion of the liquid crystal pixel element. Figure 11A and Figure 11B The arrangement of the middle electrodes 132a and 134a is similar to Figure 10A and Figure 10B Arrangement of the middle electrodes 132a and 134a. Figure 11A and Figure 11B The difference in FIG. 1 is that the finger-shaped electrode 136a is now displaced in the X direction so that from a top view, the electrode 132a and the electrode 136a now overlap, rather than Figure 10A and Figure 10B shown do not overlap with each other.

[0081] With various arrangements of electrodes, various electric fields can be generated in the liquid crystal layer 120 according to the desired purpose.

[0082] Figure 12 1 is a schematic top view of a portion of a liquid crystal device 200a. For clarity, only the electrodes located on the first substrate 110a are shown. The electrodes formed on the second substrate 110b are similarly arranged. The liquid crystal device 200a is formed by an array of liquid crystal pixel elements 100. In the liquid crystal device 200a, the electrode 132a is shared with adjacent liquid crystal pixel elements in the X direction, and the electrode 134a is shared with adjacent liquid crystal pixel elements in the Y direction. The electrode 136a of the liquid crystal pixel element 100 is not shared by adjacent liquid crystal pixel elements.

[0083] like Figure 12As shown in FIG, the array of liquid crystal pixel elements 100 in the liquid crystal device 200a can expand the area of ​​beam shaping by utilizing phase shifting. Even if a single liquid crystal pixel element may be too small for a terahertz beam, forming a liquid crystal device using an array of liquid crystal pixel elements of the present disclosure can expand the area receiving the terahertz beam.

[0084] Figure 13 1 is a schematic top view of a portion of another liquid crystal device 200b. For clarity, only the electrodes formed on the first substrate 110a are shown. The electrodes formed on the second substrate 110b are arranged similarly. The arrangement of electrodes 132a and 134a is similar to that of Figure 12 The difference is that Figure 12 The electrode 136a in the liquid crystal pixel element now merges with the electrode 136a in the adjacent liquid crystal pixel element along the Y direction to form a new electrode 137a. Figure 13 As shown in , electrode 137a is now shared by several liquid crystal pixel elements along the Y direction. The number of liquid crystal pixel elements that share electrode 137a depends on the desired purpose, but is not limited thereto. In some embodiments, electrode 137a can extend along the X direction.

[0085] Figure 14 1 and 2 are schematic top and cross-sectional views of a portion of a liquid crystal device 200c. For clarity, only the electrodes formed on the first substrate 110a are shown. The electrodes formed on the second substrate 110b are arranged similarly. Figure 14 The liquid crystal device 200c shown in FIG is similar to Figure 12 The difference is that in Figure 14In the embodiment of the present invention, the liquid crystal device 200c further includes driving modules 162a, 164a, and 166a connected to the electrodes 132a, 134a, and 136a, respectively. The driving modules 162a, 164a, and 166a control the electrodes 132a, 134a, and 136a to generate electric fields in the three orthogonal directions. In the cross-sectional view taken along line AA', the electrode 136a is formed on the substrate 110a and covered by the insulating layer 140a. The electrode 132a is formed on the insulating layer 140a and covered by the insulating layer 142a. The driving module 164a is formed on the insulating layer 142a. In the cross-sectional view taken along line BB', the driving module 166a is formed on the substrate 110a and connected to the electrode 136a. The driving module 162a is formed on the insulating layer 140a. The electrode 134a is formed on the insulating layer 142a. In some embodiments, the thickness of insulating layers 140a and 142a is 200 nm to 1000 nm, preferably 500 nm, but not limited thereto. In some embodiments, the thickness of electrodes 132a, 134a, and 136a is 100 nm to 500 nm, preferably 200 nm, but not limited thereto. The width of electrodes 130a and 130b is between 5 μm and 15 μm, preferably 10 μm, but not limited thereto.

[0086] use Figure 14 In the arrangement shown in FIG, driving modules 162a, 164a, and 166a can supply voltage differences to electrodes 132a, 134a, and 136a, respectively, which can generate an electric field in the liquid crystal layer along a desired direction.

[0087] In order to operate the array of liquid crystal pixel elements in the liquid crystal device 200c, the same electric potential is provided to each liquid crystal element via electrodes (e.g., electrodes 132a, 134a, and 136a) so that uniform liquid crystal orientation is achieved throughout the pixel array. The driving modules 162a, 164a, and 166a that provide such uniform electrical signals are much simpler than the driving modules in liquid crystal displays. One electrode is overlapped with another electrode via an insulating layer to act as a capacitor, which can be added to the capacitor formed by the liquid crystal layer in the liquid crystal pixel element. When each element is operated via a thin film transistor (not shown), the added capacitor from the layered electrode has an advantage in maintaining the voltage characteristics in the liquid crystal pixel element. When the voltage characteristics are maintained well, various types of liquid crystals with different properties (e.g., large dielectric anisotropy, low resistivity, and low absorption loss) can be used in the liquid crystal layer.

[0088] Figure 15 is a cross-sectional view of a portion of a liquid crystal device 200d. The liquid crystal device 200d includes a first substrate 110a having Figure 14The structure shown in the cross section of liquid crystal device 200c along line AA' in FIG. Liquid crystal device 200d has a second substrate 110b facing the first substrate 110a, and the second substrate 110b has the same structure as the first substrate 110a. The first substrate 110a and the second substrate 110b are separated by a cell gap. The cell gap is the distance between the top surface of insulating layer 144a and the top surface of insulating layer 144b. In some embodiments, the thickness t of the cell gap is 50 μm to 150 μm, and preferably 100 μm or less, but is not limited thereto.

[0089] Figure 16 Schematic top view and cross-sectional view of a portion of the liquid crystal device 200e. Figure 16 The liquid crystal device 200e shown in FIG is similar to Figure 14 The difference is that in Figure 16 In the embodiment, the horizontal finger-shaped electrode 132a and the vertical finger-shaped electrode 134a are connected to form an electrode 132a'. Figure 16 As shown in FIG. 1 . The electrode 132a' is connected to the driving module 164a. As shown in the cross-sectional view along lines AA' and BB', the electrode 132a' and the driving module 164a are formed on the insulating layer 140a and covered by the insulating layer 142a. Figure 14 Compared with the liquid crystal device 200c shown in FIG, the number of insulating layers is reduced from three to two, which simplifies the overall structure of the liquid crystal device 200e.

[0090] However, because the vertical finger-shaped electrodes 134a and the horizontal finger-shaped electrodes 132a are connected to form electrode 132a', the electric field generated by electrode 132a' is not completely along the X or Y directions. Consequently, the orientation range of the liquid crystal molecules in liquid crystal device 200 becomes narrower, and liquid crystal device 200e does not have the precise six-way switching as liquid crystal device 200c. In some embodiments, the x and y dimensions of each pixel element are approximately the same.

[0091] Figure 17 1 and 2 are schematic top and cross-sectional views of a portion of the liquid crystal device 200f. For clarity, only the electrodes formed on the first substrate 110a are shown. The electrodes formed on the second substrate 110b are arranged similarly. Figure 17 The liquid crystal device 200f shown in FIG is similar to Figure 14 The difference is that in Figure 17 In the embodiment, electrode 136a is replaced by Figure 13The driving module 166a is now connected to the electrode 137a, which extends through several liquid crystal pixel elements along the Y direction. With this arrangement, the driving module 166a can control the electric field in the Z direction for several liquid crystal pixel elements at the same time.

[0092] Figure 18 Schematic top view and cross-sectional view of a portion of the liquid crystal device 200g. Figure 18 The liquid crystal device 200g shown in FIG is similar to Figure 17 The difference is that in Figure 18 In the embodiment, the horizontal finger-shaped electrode 132a and the vertical finger-shaped electrode 134a are connected to form an electrode 134a'. Figure 18 As shown in FIG. 1 . The electrode 134a' is connected to the driving module 162a. As shown in the cross-sectional view along lines AA' and BB', the electrode 134a' and the driving module 162a are formed on the insulating layer 140a and covered by the insulating layer 142a. Figure 17 Compared with the liquid crystal device 200f shown in FIG, the number of insulating layers is reduced from three to two, which simplifies the overall structure of the liquid crystal device 200f.

[0093] Figure 19 Figure 1 is a block diagram of a photonic device for terahertz electromagnetic waves. Figure 19 As shown in , a photonic device 10 for terahertz electromagnetic waves is presented. In some embodiments, the photonic device 10 is a polarizer, a filter, a phase shifter or a modulator, or is a broadband wireless communication system, a security monitoring system, a medical imaging system or a material characterization system, but is not limited thereto. The photonic device 10 includes a liquid crystal device 200, and the liquid crystal device 200 includes a plurality of liquid crystal pixel elements 100. In some embodiments, the liquid crystal device 200 includes the liquid crystal devices 200a, 200b, 200c, 200d and / or 200e described in this application, but is not limited thereto. By utilizing the three orthogonal directions of the electric field in the liquid crystal pixel element 100, the liquid crystal molecules in the liquid crystal pixel element 100 can be rotated to any direction according to the applied electric field, which is suitable for applications in terahertz electromagnetic wave applications.

[0094] The disclosed structure is capable of continuously switching the orientation of the liquid crystal molecules between the initial, intrinsic in-plane and out-of-plane states, thereby providing a wider phase shift range while maintaining a fast response. In addition, using the three orthogonal electric fields generated by the three pairs of electrodes, mutual switching between the three orientation states of the liquid crystal molecules becomes possible. In other words, the disclosed structure effectively allows for six-way switching between the initial, intrinsic in-plane and out-of-plane states. In principle, the use of the three liquid crystal orientation states increases the variation in phase shift. In addition, switching between the three liquid crystal orientation states by applying an electric field maintains a faster response time. By optimizing some device and material parameters (including greater retardation using liquid crystals with greater birefringence), the phase shift range provided by the new liquid crystal switching mode for terahertz devices (such as phase shifters) can potentially be further improved.

[0095] The liquid crystal devices disclosed herein may have a wide range of applications, such as integration into terahertz antenna arrays or integration into terahertz photonic crystals.

[0096] It is intended that various modifications and variations to the disclosed embodiments will be apparent to those skilled in the art.It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.

Claims

1. A liquid crystal device, characterized in that: include: A single or multiple pixel elements, each pixel element comprising: first substrate, a second substrate facing the first substrate and parallel to the first substrate, a liquid crystal layer disposed between the first substrate and the second substrate, a first plurality of electrodes formed between the first substrate and the liquid crystal layer, wherein the first plurality of electrodes are grid-type electrodes and / or finger-type electrodes; a second plurality of electrodes formed between the second substrate and the liquid crystal layer, wherein the second plurality of electrodes are grid-type electrodes and / or finger-type electrodes, wherein the same grid-type electrodes and / or finger-type electrodes of the first plurality of electrodes and the second plurality of electrodes are formed to face each other with a cell gap; wherein the first plurality of electrodes and the second plurality of electrodes are configured to generate electric fields in three orthogonal directions, and the electric fields in two of the three orthogonal directions are in-plane electric fields and are substantially parallel to the first substrate, the second substrate, and the liquid crystal layer, and the electric field in another of the three orthogonal directions is an out-of-plane electric field and is substantially perpendicular to the first substrate and the second substrate, The first plurality of electrodes and the second plurality of electrodes each include a pair of electrodes for generating an in-plane electric field in one of the two directions, and a pair of electrodes for generating an in-plane electric field in the other of the two directions.

2. The liquid crystal device according to claim 1, wherein An initial alignment of liquid crystal molecules in the liquid crystal layer is substantially perpendicular to an extending direction of one of the grid-type electrodes and / or the finger-type electrodes of the first and second electrodes.

3. The liquid crystal device according to claim 2, wherein The initial alignment of the liquid crystal molecules in the liquid crystal layer is 40 degrees to 50 degrees relative to the extending direction of one of the grid-type electrodes and / or the finger-type electrodes of the first and second electrodes.

4. The liquid crystal device according to claim 1, wherein An initial alignment of liquid crystal molecules in the liquid crystal layer is 85 degrees to 95 degrees relative to an extension direction of one of the grid-type electrodes and / or the finger-type electrodes of the first and second electrodes.

5. The liquid crystal device according to claim 1, wherein The liquid crystal device further includes: a first alignment layer disposed between the first plurality of electrodes and the liquid crystal layer; and a second alignment layer disposed between the second plurality of electrodes and the liquid crystal layer; The first alignment layer and the second alignment layer are configured to align the liquid crystal molecules in the liquid crystal layer to an initial alignment.

6. The liquid crystal device according to claim 1, wherein A ratio of a distance between a first pair of electrodes of the first plurality of electrodes generating a first in-plane electric field to a distance between a second pair of electrodes of the first plurality of electrodes generating a second in-plane electric field is substantially equal to 1.

7. The liquid crystal device according to claim 6, wherein The ratio of the distance between the first pair of electrodes of the first plurality of electrodes generating the first in-plane electric field to the distance between the second pair of electrodes of the first plurality of electrodes generating the second in-plane electric field is between 0.9 and 1.

1.

8. The liquid crystal device according to claim 1, wherein The distance between the first pair of electrodes of the first plurality of electrodes that generate a first in-plane electric field along a direction perpendicular to the initial alignment of the liquid crystal of the liquid crystal layer is shorter than the distance between the second pair of electrodes of the first plurality of electrodes that generate a second in-plane electric field along a direction parallel to the initial alignment of the liquid crystal of the liquid crystal layer.

9. The liquid crystal device according to claim 1, wherein The electrodes of the first plurality of electrodes generating a first in-plane electric field, the electrodes of the first plurality of electrodes generating a second in-plane electric field perpendicular to the first in-plane electric field, and the electrodes of the first plurality of electrodes generating an out-of-plane electric field are formed on the same level parallel to the first substrate.

10. The liquid crystal device according to claim 1, wherein Electrodes of the first plurality of electrodes generating a first in-plane electric field, electrodes of the first plurality of electrodes generating a second in-plane electric field perpendicular to the first in-plane electric field, and electrodes of the first plurality of electrodes generating an out-of-plane electric field are at different levels parallel to the first substrate.

11. The liquid crystal device according to claim 1, wherein Also includes: a first polarizer disposed on one side of the liquid crystal layer; and a second polarizer, disposed on the other side of the liquid crystal layer, The first polarizer and the second polarizer are configured to polarize light entering or leaving the liquid crystal layer.

12. The liquid crystal device according to claim 1, wherein Also includes: A plurality of driving modules are connected to the first plurality of electrodes and the second plurality of electrodes to control the first plurality of electrodes and the second plurality of electrodes to generate the electric field in the three orthogonal directions.

13. A system for terahertz electromagnetic waves, characterized in that: include: The liquid crystal device according to claim 1.

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