Thin-film lithium niobate spatial light modulator based on high-quality factor guided-mode resonance

Abstract

The invention discloses a thin-film lithium niobate spatial light modulator based on high-quality factor guided-mode resonance. A two-dimensional asymmetric guided-mode resonance structure is distributed on the thin-film lithium niobate spatial light modulator, and the quality factor of guided-mode resonance is greatly improved through two-dimensional expansion and symmetric breaking, so that the quality factor is higher than 10000. In combination with the asymmetric structure, the spatial light modulator can realize a modulation depth higher than 90% under a driving voltage of 80V. The two-dimensional asymmetric guided-mode resonance structure not only improves the modulation depth of the spatial light modulator, but also reduces the driving voltage of the device, and can be used for free space optical communication, optical display, optical switch arrays and other application scenes.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical modulators and relates to a thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance, and more specifically to a thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance, a two-dimensional asymmetric array structure, and an optical device. Background Art

[0002] Spatial light modulator technology has been widely used in many fields, including free-space optical communications, holographic projection, optical microscopy, holographic optical tweezers, and wavefront shaping. A spatial light modulator is a device that modulates light in free space by changing the amplitude, phase, polarization state, and other properties of the incident light. In terms of working principle, traditional spatial light modulators mainly include micro-electro-mechanical system (MEMS) spatial light modulators and liquid crystal (LC) spatial light modulators. Both MEMS and LC spatial light modulators achieve modulation through mechanical deflection of mechanical structures or liquid crystal molecules under the action of an external electric field. Therefore, the response time is relatively long, and the modulation rate is only a few hundred kHz.

[0003] In addition to the two types of spatial light modulators mentioned above, spatial light modulators based on the electro-optic effect (EO effect) have also been developed in recent years. EO spatial light modulators use electro-optical materials as their functional materials, and their surfaces are typically fabricated with micro-nanostructured optical resonators. By applying an external electric field, they can change the refractive index of the medium, thereby modulating light. Compared to traditional MEMS and LC spatial light modulators, all-solid-state EO spatial light modulators can achieve high-speed modulation, with theoretical modulation rates reaching the GHz range.

[0004] Lithium niobate material has excellent linear electro-optic effect and large electro-optic coefficient. In recent years, thin-film lithium niobate has the advantages of miniaturization and easy integration, making it the preferred material for electro-optic modulation devices. However, the current spatial light modulators based on thin-film lithium niobate have problems such as low modulation depth. Increasing the modulation depth of spatial light modulators generally requires the use of high-quality factor resonant cavities including guided mode resonance structures. However, the quality factor of existing resonant cavities based on thin-film lithium niobate is still low, making it impossible to achieve high modulation depth. The spatial light modulator described in the document "High quality factor resonant metasurface with etchless lithium niobate" (Optics and Laser Technology, 2023, 161, 11: 109163) adopts a guided mode resonance structure composed of a one-dimensional polymer grating, thin-film lithium niobate and silicon dioxide. Its quality factor is only 1810, which cannot achieve a high modulation depth. The paper "Electricallytunable plasmonic meta-grating on thin film lithium niobate" (Optics Express, 2025, 33, 6: 13198-13204) proposes a quasi-continuum bound state (qBIC) structure composed of a gold grating and thin-film lithium niobate. However, this scheme has a Q value of only 1012, making it impossible to achieve a high modulation depth. The experimentally measured modulation depth is only 23%. The paper "Electro-optic metasurface-based free-space modulators" (Nanoscale, 2022, 14, 31: 11407-11414) uses a Fabry-Perot resonant cavity to form a spatial light modulator. The cavity consists of a gold film and gold nanostripes sandwiched between thin-film lithium niobate. The gold nanostripes also serve as electrodes. This scheme achieves a modulation depth of 20%. The paper “Tunable Transmissive Metasurface Based on Thin-Film Lithium Niobate” (ACSPhotonics, 2025, 12, 2: 1174-1183) proposes a thin-film lithium niobate spatial light modulator with transparent conductive oxide as electrodes. The quality factor is 440, and the measured modulation depth is only 4.6%.

[0005] The operating principle of an electro-optic spatial light modulator (SLM) is as follows: an optical resonant cavity is fabricated on an electro-optic material. Under the action of the resonant cavity, a short region of minimum transmittance appears near a certain wavelength. This region is called the resonant peak, and the wavelength of minimum transmittance is the resonant wavelength. The resonant wavelength is determined by the refractive index of the cavity material and the cavity's structural dimensions, while the width of this region (i.e., the full width at half maximum) is determined by the quality factor. A narrower width facilitates the modulator's high modulation depth. Modulation is achieved by the electro-optic material, such as thin-film lithium niobate. The refractive index of the electro-optic material changes under the influence of a driving voltage. Since the resonant cavity material contains electro-optic material, the refractive index change caused by changes in the driving voltage will shift the resonant wavelength of the cavity. Therefore, when the incident light wavelength is fixed, the resonant wavelength can be adjusted to match or shift away from the incident light wavelength by adjusting the driving voltage. When the resonant wavelength matches the incident light wavelength, the modulator's transmittance is minimum, and when the resonant wavelength shifts away from the incident light wavelength, the transmittance increases. Therefore, by varying the modulator's driving voltage, its transmittance can be adjusted, achieving modulation. Under a specific driving voltage, the larger the quality factor of the resonant cavity and the smaller the half-maximum full width, the easier it is to cause the resonant wavelength to shift, and correspondingly, the easier it is to achieve a high modulation depth.

[0006] In existing thin-film lithium niobate spatial light modulators, the resonant cavity mostly uses a one-dimensional grating structure with a quality factor below 2000. This low quality factor results in a large full-width at half maximum (FWHM) of the resonant cavity and weak selectivity for specific wavelengths, which makes it impossible to achieve a large modulation depth under limited voltage.

[0007] Generally speaking, spatial light modulators can turn incident light on and off, and combined with control electrical signals, they can convert electrical signals into optical signals. They are the core components of free-space optical communication systems. Thin-film lithium niobate spatial light modulators, thanks to the excellent electro-optical effect of lithium niobate, can achieve sub-nanosecond modulation times, making them the key to high-speed, high-throughput free-space optical communications. However, existing thin-film lithium niobate spatial light modulators suffer from low modulation depth. Although various high-quality resonant cavities can be used to increase their modulation depth, the modulation depth of existing thin-film lithium niobate spatial light modulators is still limited and difficult to meet the needs of practical applications. Summary of the Invention

[0008] The purpose of the present invention is to solve the problem in the prior art that the existing thin-film lithium niobate spatial light modulator has a low modulation depth and is difficult to meet the needs of practical applications, and to provide a thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance, a two-dimensional asymmetric array structure and an optical device.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A two-dimensional asymmetric array structure based on guided mode resonance effect includes array-distributed subunits, each of which has a hollow structure inside. The hollow structure has an asymmetric geometric profile, which is asymmetric relative to both the x-axis and the y-axis. The x-axis and the y-axis are respectively parallel to the outer profile of the subunit.

[0011] A further improvement of the present invention is:

[0012] The outline of the hollow structure is composed of irregular polygons.

[0013] The hollow structure includes a first side and a second side that are vertically connected.

[0014] There are m×n subunits, where m represents the number of subunits distributed along the x-axis array, and m is greater than or equal to 2200; and n represents the number of subunits distributed along the y-axis array, and n is greater than or equal to 75.

[0015] A thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance comprises a substrate layer, a buried layer and a thin-film lithium niobate layer connected in sequence from bottom to top;

[0016] A structural layer and an electrode layer are provided on the upper end of the thin film lithium niobate layer, and the electrode layers are located on both sides of the structural layer;

[0017] The structural layer includes the two-dimensional asymmetric array structure described in any one of the present inventions.

[0018] The distance between the structural layer and the electrode layer is greater than or equal to 1.5 μm.

[0019] The distance between the two electrode layers on both sides of the structural layer is 70 μm to 200 μm.

[0020] The electrode layer has a thickness of 100 nm to 500 nm and a width of 200 μm to 500 μm.

[0021] The length of the electrode layer is greater than that of the structural layer.

[0022] An optical device comprises the thin-film lithium niobate spatial light modulator described in the present invention.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention discloses a two-dimensional asymmetric array structure based on the guided mode resonance effect. Specifically, the two-dimensional asymmetric guided mode resonance structure is disclosed. A hollow structure is provided within the subunits, and the geometric profile is asymmetric with respect to both the x-axis and the y-axis. Through two-dimensional expansion and symmetry breaking, the quality factor of the guided mode resonance is greatly improved, reaching a quality factor exceeding 10,000. Furthermore, by varying the array period of the subunits, modulation of different incident light wavelengths can be achieved, thereby improving the quality factor of the thin-film lithium niobate guided mode resonance structure. When applied to a thin-film lithium niobate spatial light modulator, the modulation depth of the thin-film lithium niobate spatial light modulator can be increased, and the modulation voltage can be reduced. The structure is applicable to high-speed free-space optical communications, optical displays, and other fields.

[0025] The present invention discloses a thin-film lithium niobate spatial light modulator based on high-quality guided mode resonance. A two-dimensional asymmetric guided mode resonance structure is distributed on the thin-film lithium niobate spatial light modulator. Through two-dimensional expansion and symmetry breaking, the quality factor of the guided mode resonance is greatly improved, and its quality factor is higher than 10,000. Combined with this asymmetric structure, the spatial light modulator can achieve a modulation depth higher than 90% at a driving voltage of 80V, thereby improving the modulation depth of the spatial light modulator and reducing the driving voltage of the device. It can realize functions such as free-space optical communication, optical display, and optical switch array.

[0026] Furthermore, in this embodiment, the length of the electrode layer is greater than that of the structural layer, which can avoid edge effects and make the electric field acting on the lithium niobate thin film a quasi-uniform electric field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly describes the drawings required for use in the embodiments. It should be understood that the following drawings illustrate only certain embodiments of the present invention and should not be construed as limiting the scope of the present invention. Those skilled in the art can, without inventive effort, derive other relevant drawings from these drawings.

[0028] Figure 1 Schematic diagram of a thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance proposed by the present invention;

[0029] Figure 2 Schematic diagram of a unit structure of a two-dimensional asymmetric guided mode resonance structure proposed in the present invention. The figure takes the inverted "L"-shaped structure in the embodiment as an example, but any shape asymmetric along the x-axis or y-axis may also be used (where a represents a top view of the unit structure of the two-dimensional asymmetric guided mode resonance structure; b represents a three-dimensional stereogram of the unit structure of the two-dimensional asymmetric guided mode resonance structure);

[0030] Figure 3 It is the arrangement of m×n unit structures to form the guided mode resonant cavity;

[0031] Figure 4 It is a structural diagram of the yz plane;

[0032] Figure 5 is the transmission spectrum of the embodiment at different driving voltages;

[0033] Figure 6 Schematic diagram of signal transmission in Example 3, wherein (a is a schematic diagram showing that the spatial light modulator can convert an electrical signal that varies according to a sinusoidal law into an infrared light signal; b is a schematic diagram showing the free-space infrared light communication function of the spatial light modulator);

[0034] Figure 7 Schematic diagram of signal transmission in Example 4.

[0035] Wherein: 1-substrate layer; 2-buried layer; 3-thin-film lithium niobate layer; 4-structural layer; 5-electrode layer; 501-positive electrode; 502-negative electrode. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in a variety of different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0039] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "inner," etc. appear to indicate an orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings, or are the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and simplify the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," etc. are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0040] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0041] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0042] The present invention is described in further detail below with reference to the accompanying drawings:

[0043] See also Figure 1 The present invention discloses a thin-film lithium niobate spatial light modulator based on high-quality guided-mode resonance (GMR). This design significantly improves the GMR's quality factor, achieving a quality factor exceeding 10,000, through two-dimensional expansion and symmetry breaking. The thin-film lithium niobate spatial light modulator (SLM) utilizing this structural design can achieve a modulation depth exceeding 90% at a drive voltage of 80V. This solution significantly improves the modulation depth of the SLM and is of great significance for the practical application of SLMs.

[0044] The embodiment of the present invention provides a thin film lithium niobate spatial light modulator based on high quality factor guided mode resonance, such as Figure 1 As shown, it includes a guided mode resonant optical cavity and a driving electrode.

[0045] Among them, the guided mode resonant optical cavity is composed of a structural layer, a thin film lithium niobate and a buried layer, and is the core component of the present invention.

[0046] The embodiment of the present invention specifically includes the following structure:

[0047] Example 1

[0048] An embodiment of the present invention discloses a two-dimensional asymmetric array structure based on the guided mode resonance effect, including array-distributed subunits, each of which has a hollow structure inside. The hollow structure has an asymmetric geometric profile, which is asymmetric relative to both the x-axis and the y-axis, and the x-axis and the y-axis are respectively parallel to the outer profile of the subunit.

[0049] For further information, see Figure 2, which is a schematic diagram of the unit structure of the top layer of the guided mode resonance cavity. The two-dimensional asymmetric array structure is an inverted "L"-shaped hollow silica structure, including a first side and a second side vertically connected, and the unit structure period is p.

[0050] Furthermore, in addition to the inverted "L" shape, it can also be any shape that is asymmetric along the x-axis or y-axis.

[0051] Furthermore, the subunit structure is a square, and the guided mode resonant cavity is composed of m×n unit structures arranged periodically, where m is not less than 2200 and n is not less than 75. Figure 3 As shown, the periods of the unit structure along the x-direction and the y-direction are both p, and the length and width of the guided mode resonance cavity are m×p and n×p, respectively.

[0052] In this embodiment, thin-film lithium niobate acts as a slab waveguide in a guided-mode resonant optical cavity. This waveguide formation requires that both the top structure material and the buried layer material have a lower refractive index than the thin-film lithium niobate. When incident light is incident perpendicularly above the guided-mode resonant cavity, upon resonance, the light is confined within the thin-film lithium niobate layer and does not radiate outward.

[0053] Example 2

[0054] The present invention also discloses a thin film lithium niobate spatial light modulator based on high quality factor guided mode resonance, such as Figure 1 As shown, it includes a guided mode resonant optical cavity and a driving electrode. The guided mode resonant optical cavity is used to resonate the incident light source outside the chip. When the wavelength of the light source is the resonant wavelength of the guided mode resonant cavity, resonance occurs, and the light will be confined to propagate within the planar waveguide without radiating outward, and the transmittance is minimized. The driving electrode is used to generate an electric field, causing the refractive index of the thin film lithium niobate to change under the action of the electro-optical effect, thereby changing the resonant wavelength of the resonant cavity and changing the transmittance of the off-chip light source to achieve a modulation effect. Specifically, it includes the following structures:

[0055] A thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance comprises, from top to bottom, an electrode layer 5, a structural layer 4, a thin-film lithium niobate layer 3, a buried layer 2, and a substrate layer 1.

[0056] like Figure 4 As shown, the electrode layer 5 and the structural layer 4 are located in the same layer. Specifically, the material of the electrode layer 5 can be conductive materials such as gold, aluminum, transparent conductive oxide, etc., but is not limited thereto.

[0057] Furthermore, its thickness is between 100nm and 500nm, its width is between 200μm and 500μm, and the spacing between the two electrodes is between 70μm and 200μm. The smaller the spacing, the smaller the required driving voltage. However, too small a spacing will limit the size of the guided mode resonance cavity and affect the modulation effect.

[0058] Two driving electrodes, a positive electrode 501 and a negative electrode 502, are located on either side of the guided mode resonant cavity, parallel to the x-axis. Applying a voltage across the two electrodes creates a potential difference between them, generating an electric field along the y-axis. This, in turn, causes the refractive index of the lithium niobate thin film to change, achieving a modulation effect.

[0059] Furthermore, the distance between the electrode and the structural layer 4 is not less than 1.5 μm, which can effectively reduce the plasma absorption loss of the metal.

[0060] Furthermore, the material of the structural layer 4 can be silicon oxide, silicon nitride, a high molecular polymer, etc., but is not limited thereto; the thickness of the structural layer 4 is 60nm to 100nm, and it is attached to the thin film lithium niobate layer 3 by a thin film deposition process or a bonding process, and then formed into a periodic pattern by an inductively coupled plasma etching process;

[0061] Furthermore, the tangent direction of the thin film lithium niobate layer 3 is X-tangent, and the optical axis is along the y direction in the figure, and the thickness of the thin film lithium niobate is 300 nm;

[0062] Furthermore, the refractive index of the structural layer 4 and the refractive index of the buried layer 2 should be smaller than the refractive index of the thin film lithium niobate layer 3 to meet the conditions for forming a guided mode resonant cavity;

[0063] Furthermore, the material of the substrate layer 1 includes one or more of silicon, silicon oxide, and lithium niobate, and has a thickness of 450 μm to 550 μm, which plays a supporting role.

[0064] The working principle of the present invention is:

[0065] When an external light source is incident vertically from above on the spatial light modulator, it will diffract after passing through the asymmetric two-dimensional array, producing a certain diffraction pattern. Only light of a specific mode can propagate in the slab waveguide. If the diffraction pattern generated by the incident light of a certain wavelength matches the guided mode of the slab waveguide, a guided mode resonance phenomenon will occur. The wavelength of the incident light is the resonant wavelength of the guided mode resonant cavity. At the resonant wavelength, the transmittance of the incident light through the spatial light modulator reaches its minimum value (the reflectivity reaches its maximum value). The formula for calculating the resonant wavelength is:

[0066] λ=n eff ×p (1)

[0067] Where λ is the resonant wavelength, n eff is the effective refractive index of the slab waveguide. The resonant wavelength λ can be controlled by changing the structural period p.

[0068] When a voltage is applied between the driving electrodes to generate an electric field, the refractive index of lithium niobate changes by:

[0069]

[0070] Among them, n e is the extraordinary refractive index of lithium niobate, γ 33 is the electro-optic coefficient of lithium niobate, and E is the driving electric field.

[0071] The change of refractive index will cause the change of resonant wavelength. Assume that the resonant wavelengths when the driving voltage is -U and U are λ1 and λ2 respectively, as shown in Figure 5 As shown. When light with a wavelength of λ1 is incident vertically, a voltage -U is applied to the spatial light modulator, resulting in minimum transmittance and a low output optical power. Adjusting the voltage to U increases the output optical power. By varying the input voltage, the output optical power can be switched between high and low, achieving amplitude modulation of the light. If the incident light is in the C-band, optical communication can be achieved by varying the driving voltage. Arranging multiple spatial light modulators in an array allows for simultaneous multi-channel data transmission. If the incident light source is visible light, two-dimensional optical display can be achieved by individually switching individual pixels in the spatial light modulator array.

[0072] The embodiment of the present invention improves the quality factor Q of the guided mode resonant optical cavity by using an asymmetric two-dimensional periodic array on the thin film lithium niobate layer. For a periodic one-dimensional grating and a two-dimensional asymmetric structure, if there is a structural parameter perturbation δ, then Q∝δ -2 Expanding the one-dimensional grating into a two-dimensional structure can make the perturbation δ smaller, and the asymmetric pattern structure in the unit cell can further reduce δ. The present invention uses this mechanism to significantly improve the Q value. In the spectrum of the spatial light modulator, FWHM is the full width at half maximum, such as Figure 5 As shown, the relationship between FWHM and Q is:

[0073]

[0074] It can be seen that the increase of Q will lead to the decrease of FWHM. Figure 5 Under the same applied modulation voltage, the resonant wavelength shift Δλ remains constant. Assuming the incident light wavelength is the resonant wavelength when the voltage is -U, it can be seen that the smaller the FWHM, the greater the change in transmittance ΔT, that is, the higher the modulation depth. Therefore, the thin-film lithium niobate spatial light modulator based on high-quality guided mode resonance proposed in this invention can achieve a high modulation depth, solving the low modulation depth problem of existing thin-film lithium niobate spatial light modulators while also maintaining the high modulation speed advantage of EO spatial light modulators, meeting the requirements of high-speed free-space optical communications.

[0075] Secondly, by composing the thin-film lithium niobate spatial light modulator of the present invention into an optical switch array, multi-channel data transmission and two-dimensional optical display functions can be realized.

[0076] It can be seen that the present invention applies a guided mode resonant cavity based on thin-film lithium niobate to a spatial light modulator. Through reasonable structural design, the quality factor of the resonant cavity is increased, thereby significantly improving the modulation depth of the thin-film lithium niobate spatial light modulator. At the same time, the driving voltage of the device is also reduced, and functions such as free-space optical communication, optical display, and optical switch array can be realized. It has the advantages of convenient design, flexible resonant wavelength control, high modulation speed, low power consumption, and a wide range of applications, and has outstanding and significant technical effects.

[0077] Specifically, the guided mode resonant optical resonant cavity of this embodiment adopts the following structural composition scheme:

[0078] The thickness of the structural layer 4 is 80nm, and the material is silicon dioxide, and its refractive index near the wavelength of 1550nm is 1.444; the thickness of the thin film lithium niobate layer 3 is 300nm, and the tangent direction is X-cut. The refractive index of ordinary light near the wavelength of 1550nm is 2.2111, and the refractive index of extraordinary light is 2.1376; the thickness of the buried layer 2 is 4.7μm, and the material is also silicon dioxide. The unit structure is as follows Figure 2 As shown in Figure 1, the period p of the guided mode resonant cavity is 880nm, and the inner structure is an inverted "L" shape composed of air medium, with a long side a of 400nm and a short side l of 200nm. The entire guided mode resonant cavity consists of an m×n array, as shown in Figure 1. Figure 3 As shown, m is 2300, n is 76, the total length of the guided mode resonance cavity is 2024 μm, and the width is 66.88 μm.

[0079] In this embodiment, an inverted "L"-shaped pattern with a smaller structural size is used, which can generate a small disturbance and satisfy the asymmetry of the pattern along both the x-axis and the y-axis, thereby achieving an ultra-high quality factor. Figure 5 The curve corresponding to 0V in the middle represents the transmission spectrum of this embodiment. Its resonant wavelength is 1546.12nm, its quality factor (Q) is 15460, and its full width at half maximum (FWHM) is only 0.1nm. In the absence of a driving voltage, the transmittance is 0 for an incident light wavelength of 1546.12nm, and exceeds 80% for incident light wavelengths less than 1546.04nm or greater than 1546.74nm. This resonant cavity exhibits extremely strong wavelength selectivity, enabling it to meet the requirements of high modulation depths when used in spatial light modulators.

[0080] The driving electrode of this embodiment adopts the following structure: the driving electrode has a thickness of 150nm and is composed of a bottom layer of 10nm thick chromium and a top layer of 140nm thick gold, with chromium serving as an adhesion layer; the driving electrode layer is located above the thin-film lithium niobate layer and is on the same layer as the structural layer 4; the length of the electrode is 2400μm and the width is 450μm. The electrode length is approximately 400μm longer than the total length of the guided mode resonant cavity, which can avoid edge effects and make the electric field acting on the thin-film lithium niobate a quasi-uniform electric field; the spacing between the two electrodes is 70μm, which ensures that the electric field generated when the same driving voltage is applied is the maximum, while ensuring that the spacing between the electrode and the guided mode resonant cavity is not less than 1.5μm. e is 2.1376, γ 33 is 31.19pm / V. When a driving voltage of ±80V is applied, the electric field generated by the driving voltage is 1.143kV / mm. According to formula (2), the refractive index change of lithium niobate is 0.00017. Figure 5 As shown in the figure, when the driving voltages are -80V, 0V, and 80V, respectively, the resonant wavelengths are 1546.01nm, 1546.12nm, and 1546.22nm. When the wavelength of the incident light is 1546.01nm, increasing the driving voltage from -80V to 80V can change the transmittance from 0 to 91%, and the modulation depth is as high as 99.93%, which can realize the conversion of the optical signal from "0" to "1" and achieve the modulation purpose.

[0081] Example 3

[0082] For the thin-film lithium niobate spatial light modulator constructed with the structural parameters in the above specific embodiment, free-space optical communication can be achieved through a single spatial light modulator. When the incident light wavelength is 1546.01nm, the driving voltages of -80V and 80V correspond to the low and high values ​​of the output optical power, respectively. Figure 6 As shown in a, the spatial light modulator can convert the electrical signal that changes according to the sinusoidal law into an infrared light signal. Figure 6 Figure b demonstrates the free-space infrared optical communication function of the spatial light modulator. When the driving voltage changes from U1 to U8 in sequence, the output infrared light signal changes to "01101010"; this process completes the transmission of an 8-bit binary number and realizes the optical communication function.

[0083] Example 4

[0084] For the thin-film lithium niobate spatial light modulator composed of the structural parameters in the above specific embodiment, if a plurality of spatial light modulators are formed into an array, multi-channel data transmission can be achieved, and the transmission rate is greatly improved. Figure 7The figure shows an 8-channel spatial light modulator array. By individually controlling the voltage of each channel, it can simultaneously transmit eight binary numbers, meaning a two-digit hexadecimal number can be transmitted in a single cycle. For the binary number 01101010 shown, its hexadecimal representation is 6A. Using the method of Example 1 would require eight cycles to complete, while Example 2 only requires one cycle, significantly improving the transmission rate. Similarly, by using more spatial light modulator arrays and modifying the structural parameters to achieve a resonant wavelength of visible light, two-dimensional display capabilities can be achieved.

[0085] In summary, the thin-film lithium niobate spatial light modulator proposed in this invention achieves both low drive voltage and high modulation depth. It can also be arrayed for multi-channel data transmission in free space, further improving transmission rates. Comparative solutions cannot achieve these combined properties simultaneously.

[0086] The high-quality-factor guided-mode-resonance (GMR) thin-film lithium niobate spatial light modulator (SLM) disclosed in this embodiment utilizes the principle of GMR to design a high-quality resonant cavity, enabling modulation of varying incident light wavelengths. Furthermore, leveraging the excellent electro-optical properties of thin-film lithium niobate, an amplitude SLM is designed, achieving high-speed amplitude modulation. This solution significantly increases the modulation depth of the SLM and reduces the modulation voltage, enabling applications in high-speed free-space optical communications, optical displays, and other fields.

[0087] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A two-dimensional asymmetric array structure based on guided mode resonance effect, characterized in that: The invention comprises subunits distributed in an array, wherein a hollow structure is provided inside the subunits, and the hollow structure has an asymmetric geometric outline, which is asymmetric relative to both the x-axis and the y-axis, and the x-axis and the y-axis are respectively parallel to the outer outline of the subunits.

2. A two-dimensional asymmetric array structure based on guided mode resonance effect according to claim 1, characterized in that: The outline of the hollow structure is composed of irregular polygons.

3. The two-dimensional asymmetric array structure based on guided mode resonance effect according to claim 1, characterized in that: The hollow structure includes a first side and a second side that are vertically connected.

4. The two-dimensional asymmetric array structure based on guided mode resonance effect according to claim 1, characterized in that: There are m×n subunits, where m represents the number of subunits distributed along the x-axis array, and m is greater than or equal to 2200; and n represents the number of subunits distributed along the y-axis array, and n is greater than or equal to 75.

5. A thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance, characterized in that: It comprises a substrate layer (1), a buried layer (2) and a thin-film lithium niobate layer (3) which are sequentially connected from bottom to top; A structural layer (4) and an electrode layer (5) are provided on the upper end of the thin-film lithium niobate layer (3), and the electrode layer (5) is located on both sides of the structural layer (4); The structural layer (4) comprises the two-dimensional asymmetric array structure according to any one of claims 1 to 4.

6. The thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance according to claim 5, characterized in that: The distance between the structural layer (4) and the electrode layer (5) is greater than or equal to 1.5 μm.

7. The thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance according to claim 5, characterized in that: The distance between the two electrode layers (5) on both sides of the structural layer (4) is 70 μm to 200 μm.

8. The thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance according to claim 6, characterized in that: The electrode layer (5) has a thickness of 100 nm to 500 nm and a width of 200 μm to 500 μm.

9. The thin-film lithium niobate spatial light modulator based on high-quality factor guided mode resonance according to claim 5, characterized in that: The length of the electrode layer (5) is greater than the length of the structural layer (4).

10. An optical device, characterized in that: The device comprises the thin film lithium niobate spatial light modulator as claimed in claim 5.

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