Lithium niobate electro-optical modulator and preparation method and application thereof

Abstract

The invention relates to a lithium niobate electro-optical modulator and a preparation method and application thereof. The lithium niobate electro-optical modulator sequentially comprises a ground electrode, a substrate layer, a buried oxide layer, a lithium niobate waveguide and a high-dielectric-constant cladding from bottom to top. Optical isolation grooves which are symmetrically distributed are formed in two sides of the lithium niobate waveguide; the high-dielectric-constant wrapping layer comprises a first wrapping layer and a second wrapping layer from inside to outside, and the dielectric constant of the first wrapping layer is smaller than that of the second wrapping layer; the number of the high-dielectric-constant claddings is greater than or equal to 2; the lithium niobate electro-optical modulator further comprises a signal electrode, and the signal electrode is embedded in the high-dielectric-constant cladding and located above the optical isolation groove. Due to the synergistic effect of the optical isolation groove and the high-dielectric-constant cladding, the lithium niobate electro-optical modulator not only has high modulation efficiency, but also has high bandwidth. In addition, the lithium niobate electro-optical modulator disclosed by the invention has excellent power tolerance.

Description

Technical Field

[0001] The present application relates to the field of integrated optical technology, and in particular to a lithium niobate electro-optical modulator and a preparation method and application thereof. Background Art

[0002] Electro-optic modulators (EO modulators) are crucial components in high-speed photonic communications. Serving as a bridge between optical fiber transmission and data centers, they transmit information by modulating the phase and amplitude of optical signals. The performance of the EO modulator itself determines the system's data transmission capacity. Lithium niobate (LiNbO3, LN) has become a popular material for EO modulators due to its excellent electro-optic coefficient and broad spectral transparency. The LNbO3 waveguide in EO modulators offers strong light confinement, enabling a reduction in device size while lowering the modulation voltage.

[0003] Driven by emerging technologies such as 5G communications, artificial intelligence, and quantum computing, optical communication networks are undergoing a leapfrog upgrade from 400G to 800G / 1.6T ultra-high-speed optical modules. This development trend places more stringent requirements on electro-optical modulators in terms of bandwidth and modulation efficiency.

[0004] Patent publication number CN115268122A provides a composite cladding electro-optical modulator with high modulation efficiency, which improves the modulation efficiency of the electro-optical modulator by adopting a composite cladding, but does not focus on bandwidth.

[0005] Therefore, there is an urgent need to develop lithium niobate electro-optical modulators with high modulation efficiency and high bandwidth to meet the current market demand. Summary of the Invention

[0006] The primary purpose of the present invention is to overcome the problems of low modulation efficiency and low bandwidth of the above-mentioned existing lithium niobate electro-optical modulator and to provide a lithium niobate electro-optical modulator.

[0007] A further object of the present invention is to provide a method for preparing a lithium niobate electro-optical modulator.

[0008] Another object of the present invention is to provide an application of the lithium niobate electro-optical modulator in the preparation of high-speed optical communication devices or integrated photonic chips.

[0009] The above-mentioned purpose of the present invention is achieved through the following technical solutions: A lithium niobate electro-optic modulator comprises, from bottom to top, a ground electrode, a substrate layer, a buried oxide layer, a lithium niobate waveguide and a high dielectric constant cladding; Symmetrically distributed optical isolation grooves are provided on both sides of the lithium niobate waveguide; The high dielectric constant cladding includes a first cladding and a second cladding from the inside to the outside, wherein the dielectric constant of the first cladding is smaller than the dielectric constant of the second cladding; The number of layers of the high dielectric constant cladding is ≥2; The lithium niobate electro-optical modulator further includes a signal electrode, which is embedded in the high dielectric constant cladding and located above the optical isolation groove.

[0010] The inventors of the present invention have found that the synergistic effect of the optical isolation groove and the high dielectric constant cladding provided in the present invention enables the lithium niobate electro-optical modulator of the present invention to have not only high modulation efficiency but also high bandwidth.

[0011] The principle is as follows: a high-permittivity cladding with a gradient dielectric constant (the dielectric constant of the first cladding is less than that of the second cladding) can reduce the phase mismatch between the microwave signal and the light wave, while the optical isolation slot can confine the light field to the waveguide core. Combined with the embedded signal electrode, this shortens the distance between the signal electrode and the bottom electrode, guiding the microwave electric field to be more concentrated in the optical waveguide region. The two work together to significantly improve the bandwidth of the lithium niobate electro-optical modulator. At the same time, the design of the high-permittivity cladding with a gradient dielectric constant not only regulates the distribution of the light field but also optimizes the electric field distribution. The optical isolation slot reduces the electric field distortion at the edge of the signal electrode and avoids the parasitic capacitance effect in the non-modulation region, thereby synergistically improving the modulation efficiency of the lithium niobate electro-optical modulator (reducing the half-wave voltage).

[0012] In addition, the inventors also found that the lithium niobate electro-optical modulator of the present invention has excellent power tolerance. The principle is: the optical isolation groove limits the outward diffusion of the light field, and the high dielectric cladding enhances the electric field utilization efficiency and suppresses microwave loss. The combined effect of the two can improve the power tolerance of the lithium niobate electro-optical modulator of the present invention.

[0013] Preferably, the optical isolation groove contains a medium.

[0014] More preferably, the refractive index of the medium is lower than that of lithium niobate, the refractive index of the material of the first cladding is smaller than that of the lithium niobate waveguide, and the refractive index of the material of the second cladding is smaller than that of the material of the first cladding.

[0015] Optical isolation slots are introduced on both sides of the lithium niobate waveguide. The refractive index of the medium contained in the optical isolation slots is lower than that of the lithium niobate waveguide itself. This variation in lateral refractive index effectively limits the lateral diffusion of the light field and reduces crosstalk between adjacent waveguides. Furthermore, by providing a vertical gradient of refractive index between the first and second cladding materials, vertical leakage of the light field is effectively suppressed, achieving perfect matching of the light field mode with the waveguide structure. This synergistic effect enables the lithium niobate electro-optical modulator of the present invention to suppress light field crosstalk and thus reduce losses.

[0016] Preferably, the medium is at least one of silicon dioxide, air or magnesium fluoride.

[0017] Preferably, nanomaterials are embedded in the medium. Embedding nanomaterials in the medium can enhance the electric field at the edge of the optical isolation groove through localized surface plasmon resonance, thereby reducing the driving voltage of the device.

[0018] More preferably, the nanomaterials are embedded in the medium in the form of an array.

[0019] More preferably, the nanomaterial is at least one of titanium dioxide or aluminum oxide.

[0020] More preferably, the morphology of the nanomaterial is at least one of nanoparticles or nanowires.

[0021] Further preferably, the average diameter of the nanoparticles is 10-150 nm.

[0022] Further preferably, the average diameter of the cross section of the nanowire is 10-50 nm, and the aspect ratio is ≥5:1.

[0023] Further preferably, when the morphology of the nanomaterial in the optical isolation groove is nanoparticles, the volume ratio of the nanomaterial to the medium is (1-6): (4-9); when the morphology of the nanomaterial in the optical isolation groove is nanowires, the nanomaterial is embedded in the surface of the medium in a two-dimensional distribution, and the density of the nanomaterial is 10 6 ~10 9 wires / cm 2 .

[0024] Preferably, the cross-section of the optical isolation groove is rectangular.

[0025] Preferably, the optical isolation groove has a depth of 0.5-5 μm and a width of 0.5-20 μm.

[0026] Preferably, the ratio of the maximum width of the cross section of the lithium niobate waveguide to the width of the optical isolation groove is 1:(1-5).

[0027] Preferably, the number of layers of the high dielectric constant cladding is 2 to 4.

[0028] Preferably, the dielectric constant of the first cladding layer is ≥7.5.

[0029] More preferably, the dielectric constant of the first cladding layer is 7.5-80.

[0030] Preferably, the difference in dielectric constant between the first cladding layer and the second cladding layer is ≥5.

[0031] Preferably, the refractive index of the material of the first cladding layer and the material of the second cladding layer are independently ≤2.2.

[0032] Preferably, the difference in refractive index between the material of the first cladding layer and the material of the second cladding layer is ≥0.1.

[0033] Preferably, the thickness of the first cladding layer is 10-80 nm.

[0034] Preferably, the thickness of the second cladding layer is 10-80 nm.

[0035] Preferably, the materials of the first cladding layer and the second cladding layer are independently at least one of aluminum nitride, hafnium oxide, aluminum oxide, titanium oxide, lanthanum fluoride or silicon nitride.

[0036] Preferably, the lithium niobate electro-optic modulator further includes a titanium oxide layer located above the high dielectric constant cladding layer, and the titanium oxide layer only covers the non-light field area.

[0037] Setting a titanium oxide layer can further optimize the distribution of optical and electric fields, thereby improving the performance of the lithium niobate electro-optical modulator.

[0038] More preferably, the thickness of the titanium oxide layer is 10-50 nm.

[0039] Preferably, the thickness of the high dielectric constant cladding is 50-150 nm.

[0040] Preferably, the distance between the center of the lithium niobate waveguide and the center of the adjacent signal electrode in the horizontal direction is 1-10 μm.

[0041] Preferably, the cross section of the signal electrode is trapezoidal or T-shaped.

[0042] Preferably, the signal electrode includes a side extension structure, and the width of the side extension structure increases outward along the lithium niobate waveguide with an increase of 20-50 nm / μm.

[0043] Preferably, the signal electrode comprises an adhesion layer and a conductive layer from bottom to top.

[0044] More preferably, the material of the adhesion layer is at least one of chromium or titanium.

[0045] More preferably, the material of the conductive layer is at least one of gold, copper, aluminum, indium tin oxide or graphene.

[0046] More preferably, the thickness of the conductive layer is 200-1000 nm, the thickness of the adhesion layer is 10-50 nm, and the width of the adhesion layer is 1-5 μm.

[0047] Preferably, the material of the substrate layer is at least one of Si, Al2O3, quartz or lithium niobate.

[0048] Preferably, the thickness of the substrate layer is 250-600 μm.

[0049] Preferably, the material of the buried oxide layer is at least one of SiO2, BCB or Si3N4.

[0050] Preferably, the buried oxide layer has a thickness of 1-5 μm.

[0051] Preferably, the lithium niobate waveguide has a height of 50-1000 nm and a width of 0.2-5 μm.

[0052] Preferably, the lithium niobate waveguide is a ridge waveguide or a strip waveguide.

[0053] More preferably, the cross-section of the strip waveguide is rectangular.

[0054] Preferably, the ground electrode comprises a conductive layer and an adhesion layer from bottom to top.

[0055] More preferably, the material of the adhesion layer is at least one of chromium or titanium.

[0056] More preferably, the material of the conductive layer is at least one of gold, copper, aluminum, indium tin oxide or graphene.

[0057] More preferably, the thickness of the conductive layer is 200-1000 nm, and the thickness of the adhesion layer is 10-50 nm.

[0058] A method for preparing a lithium niobate electro-optical modulator comprises the following steps: S1. Etching the lithium niobate thin film layer of a wafer having a buried oxide layer and a lithium niobate thin film layer on a substrate to form a lithium niobate waveguide and an optical isolation groove; S2. In the optical isolation groove filled with a medium; S3 forming a high dielectric constant cladding layer above the lithium niobate waveguide; S4. Prepare a signal electrode and a ground electrode to obtain the lithium niobate electro-optical modulator.

[0059] Preferably, the thickness of the lithium niobate thin film layer is 100-900 nm.

[0060] Preferably, the specific process of step S2 is: coating a photoresist on the lithium niobate thin film layer, exposing the photoresist to form a lithium niobate waveguide pattern and an optical isolation groove pattern, and etching the lithium niobate waveguide pattern and the optical isolation groove pattern to form a lithium niobate waveguide and an optical isolation groove.

[0061] Preferably, the etching process is at least one of dry etching, wet etching or femtosecond laser etching.

[0062] More preferably, the etching power is 100-400 W, and the bias voltage is 50-400 V.

[0063] Preferably, the specific process of step S2 is: growing a medium in the optical isolation groove by atomic layer deposition.

[0064] More preferably, the growth temperature is 100-300°C.

[0065] Preferably, after filling the medium, the method further comprises the step of embedding the nanomaterial into the medium.

[0066] More preferably, the embedding method is magnetron sputtering or sol-gel method.

[0067] Further preferably, the conditions of the magnetron sputtering method include: sputtering power of 100-400 W, gas pressure of 1-5 mTorr, and atmosphere of inert gas.

[0068] Preferably, the specific process of step S3 is: preparing the first cladding layer and the second cladding layer on the lithium niobate waveguide by selective atomic layer deposition or plasma enhanced atomic layer deposition.

[0069] The present invention also protects the use of the lithium niobate electro-optical modulator in the preparation of high-speed optical communication devices or integrated photonic chips.

[0070] Compared with the prior art, the present invention has the following beneficial effects: The synergistic effect of the optical isolation groove and the high dielectric constant cladding provided in the present invention enables the lithium niobate electro-optical modulator of the present invention to have not only high modulation efficiency but also high bandwidth.

[0071] In addition, the lithium niobate electro-optical modulator of the present invention has excellent power tolerance. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 Schematic diagram of the structure of the lithium niobate electro-optic modulator of Example 1.

[0073] Figure 2 This is the SEM image of the lithium niobate electro-optical modulator of Example 1.

[0074] Figure 3 Diagram of the instrument for testing insertion loss.

[0075] Figure 4 Figure 2 shows the instrument and equipment for testing bandwidth.

[0076] In the figure, 1 is the ground electrode, 2 is the substrate layer, 3 is the buried oxide layer, 4 is the lithium niobate waveguide, 5 is the optical isolation groove, 6 is the dielectric, 7 is the nanomaterial, 81 is the first cladding, 82 is the second cladding, 9 is the titanium oxide layer, and 10 is the signal electrode. DETAILED DESCRIPTION

[0077] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0078] Example 1 This embodiment provides a lithium niobate electro-optical modulator, such as Figure 1 As shown, from bottom to top, it includes a ground electrode 1, a substrate layer 2, a buried oxide layer 3, a lithium niobate waveguide 4, and a high-dielectric constant cladding 8. Optical isolation slots 5 are symmetrically arranged on both sides of each lithium niobate waveguide. The optical isolation slots 5 contain a dielectric 6, and the dielectric 6 is embedded with a nanomaterial 7. The high-dielectric constant cladding 8 includes a first cladding 81 and a second cladding 82 covering from the inside out. The number of high-dielectric constant claddings 8 is two, and the non-optical field region of each high-dielectric constant cladding 8 is covered with a titanium oxide layer 9. The lithium niobate electro-optical modulator also includes a signal electrode 10 embedded in the high-dielectric constant cladding 8 and located above the optical isolation slots 5.

[0079] Among them, the thickness of the substrate layer 2 is 450 μm, the thickness of the buried oxide layer 3 is 2.7 μm, the thickness of the single-layer first cladding layer 81 is 40 nm, the thickness of the single-layer second cladding layer 82 is 40 nm, and the thickness of the single-layer titanium oxide layer is 50 nm; the cross-section of the lithium niobate waveguide 4 is rectangular, the width a of the rectangle is 1 μm, and the height b is 500 nm; the cross-section of the optical isolation groove 5 is rectangular, the width c of the rectangle is 2 μm, and the depth d is 0.5 μm; the horizontal distance e between the center of the lithium niobate waveguide 4 and the center of the adjacent signal electrode 10 is 3 μm.

[0080] The material of substrate layer 2 is silicon, the material of buried oxide layer 3 is silicon dioxide, and medium 6 is silicon dioxide with a refractive index of 1.44; the material of first cladding layer 81 is aluminum nitride with a refractive index of 2.1 and a dielectric constant of 9; the material of second cladding layer 82 is hafnium oxide with a refractive index of 2.0 and a dielectric constant of 22; the refractive index of titanium oxide in titanium oxide layer 9 is 2.5 and a dielectric constant of 80; the refractive index of lithium niobate in lithium niobate waveguide 4 is 2.2; nanomaterial 7 is titanium dioxide nanoparticles, the volume ratio of nanomaterial 7 to medium 6 is 4:6, and the average diameter of titanium dioxide nanoparticles is 80 nm.

[0081] The signal electrode has a trapezoidal cross-section. From bottom to top, the signal electrode consists of an adhesion layer made of chromium and a conductive layer made of gold. The adhesion layer is 50 nm thick and 1 μm wide, and the conductive layer is 800 nm thick. The ground electrode consists of a conductive layer and an adhesion layer made of chromium and gold. The adhesion layer is 50 nm thick and the conductive layer is 800 nm thick.

[0082] The method for preparing the lithium niobate electro-optical modulator of this embodiment includes the following steps: (1) An X-cut LNOI wafer with a 600 nm thick lithium niobate film layer and a 2.7 μm buried oxide layer was cleaned using RCA standards to remove surface contaminants and organic matter. An electron beam photoresist was then spin-coated on the surface of the lithium niobate film layer, and a waveguide pattern and optical isolation groove pattern were formed using electron beam exposure.

[0083] (2) The waveguide pattern and the optical isolation groove pattern obtained in step (1) are etched by wet etching to form a lithium niobate waveguide and an optical isolation groove; wherein the etching power is 300 W and the bias voltage is 100 V.

[0084] (3) Silicon dioxide was grown in the optical isolation groove by atomic layer deposition (the precursors of the growth material were SiH2Cl2 and H2O, and the growth temperature was 200°C). After the growth was completed, titanium dioxide nanoparticles (average diameter of 80 nm) were embedded into the silicon dioxide by magnetron sputtering (the conditions of the magnetron sputtering method included: sputtering power of 200 W, Ar gas pressure of 4 mTorr).

[0085] (4) A first cladding layer is formed on the lithium niobate waveguide by selective atomic layer deposition. Next, a second cladding layer is formed on the first cladding layer by plasma-enhanced atomic layer deposition to form a high-dielectric constant cladding layer. Next, a titanium oxide layer is formed on top of the high-dielectric constant cladding layer by plasma-enhanced atomic layer deposition. Then, another high-dielectric constant cladding layer and another titanium oxide layer are formed, so that the number of high-dielectric constant cladding layers and the number of titanium oxide layers are also two.

[0086] (5) Prepare the signal electrode and ground electrode. The surfaces of the signal electrode and ground electrode are flattened. The polishing liquid is silica colloidal, the removal amount is 500 nm, and the surface roughness is less than 1 nm.

[0087] Example 2 This embodiment provides a lithium niobate electro-optic modulator. Unlike Example 1, the first cladding layer 81 is made of aluminum oxide, and the second cladding layer 82 is made of lanthanum fluoride. Aluminum oxide has a refractive index of 1.76 and a dielectric constant of 9.8, while lanthanum fluoride has a refractive index of 1.6 and a dielectric constant of 10.

[0088] The method for preparing the lithium niobate electro-optical modulator of this embodiment is different from that of Example 1 in that: The materials used in preparing the first cladding layer and the second cladding layer in step (3) are adjusted accordingly.

[0089] Example 3 This embodiment provides a lithium niobate electro-optic modulator. Unlike Embodiment 1, the first cladding layer 81 is made of silicon nitride, and the second cladding layer 82 is made of aluminum oxide. Silicon nitride has a refractive index of 2.0 and a dielectric constant of 7.5, while aluminum oxide has a refractive index of 1.76 and a dielectric constant of 9.8.

[0090] The method for preparing the lithium niobate electro-optical modulator of this embodiment is different from that of Example 1 in that: The materials used in preparing the first cladding layer and the second cladding layer in step (3) are adjusted accordingly.

[0091] Comparative Example 1 This comparative example provides a comparative lithium niobate electro-optical modulator, which differs from Example 1 in that: the optical isolation groove 5 is not provided, the high dielectric constant cladding 8 is replaced by a silicon dioxide cladding, and the thickness of the single-layer silicon dioxide cladding is equal to the thickness of the high dielectric constant cladding in Example 1.

[0092] The preparation method of the comparative lithium niobate electro-optical modulator of this comparative example is different from that of Example 1 in that: Step (1) is changed to: spin-coating a layer of electron beam photoresist on the surface of the lithium niobate thin film layer, and forming a waveguide pattern by electron beam exposure; Step (2) is changed to: etching the waveguide pattern obtained in step (1) by wet etching to form a lithium niobate waveguide; Do not proceed to step (3); Step (4) is changed to: prepare a silicon dioxide cladding on the lithium niobate waveguide by selected atomic layer deposition, then prepare a titanium oxide layer on top of the silicon dioxide cladding by plasma enhanced atomic layer deposition; then, prepare another silicon dioxide cladding layer and another titanium oxide layer, so that the number of silicon dioxide cladding layers is 2 and the number of titanium oxide layers is also 2.

[0093] Comparative Example 2 This comparative example provides a comparative lithium niobate electro-optic modulator, which differs from Example 1 in that the material of the first cladding layer 81 is hafnium oxide (ie, the high dielectric constant cladding layer is a hafnium oxide cladding layer).

[0094] The preparation method of the comparative lithium niobate electro-optical modulator of this comparative example is different from that of Example 1 in that: Step (4) is to prepare a first cladding layer (hafnium oxide cladding layer) on the lithium niobate waveguide by selective atomic layer deposition. Then, a second cladding layer (hafnium oxide cladding layer) is prepared on the first cladding layer by plasma enhanced atomic layer deposition to form a high dielectric constant cladding layer. Then, a titanium oxide layer is prepared on top of the high dielectric constant cladding layer by plasma enhanced atomic layer deposition. Then, another high dielectric constant cladding layer and another titanium oxide layer are prepared, so that the number of high dielectric constant cladding layers is 2 and the number of titanium oxide layers is also 2.

[0095] Comparative Example 3 This comparative example provides a comparative lithium niobate electro-optical modulator, which is different from Example 1 in that the optical isolation groove 5 is not provided.

[0096] The preparation method of the comparative lithium niobate electro-optical modulator of this comparative example is different from that of Example 1 in that: Step (1) is changed to: spin-coating a layer of electron beam photoresist on the surface of the lithium niobate thin film layer, and forming a waveguide by electron beam exposure; Step (2) is changed to: wet etching the lithium niobate waveguide pattern obtained in step (1) to form a lithium niobate waveguide; Do not proceed to step (3).

[0097] Comparative Example 4 This comparative example provides a comparative lithium niobate electro-optic modulator, which differs from Example 1 in that the high dielectric constant cladding 8 is replaced by a silicon dioxide cladding, and the thickness of the single-layer silicon dioxide cladding is equal to the thickness of the high dielectric constant cladding in Example 1.

[0098] The preparation method of the comparative lithium niobate electro-optical modulator of this comparative example is different from that of Example 1 in that: Step (4) is changed to: prepare a silicon dioxide cladding on the lithium niobate waveguide by selected atomic layer deposition, then prepare a titanium oxide layer on top of the silicon dioxide cladding by plasma enhanced atomic layer deposition; then, prepare another silicon dioxide cladding layer and another titanium oxide layer, so that the number of silicon dioxide cladding layers is 2 and the number of titanium oxide layers is also 2.

[0099] Comparative Example 5 This comparative example provides a comparative lithium niobate electro-optic modulator, which differs from Example 1 in that the material of the first cladding layer 81 is hafnium oxide, and the material of the second cladding layer 82 is aluminum nitride.

[0100] The preparation method of the comparative lithium niobate electro-optical modulator of this comparative example is different from that of Example 1 in that: The materials used in preparing the first cladding layer and the second cladding layer in step (3) are adjusted accordingly.

[0101] Performance Testing 1. Insertion loss, half-wave voltage and bandwidth testing The insertion loss, half-wave voltage and bandwidth of the lithium niobate electro-optic modulator of the embodiment and the comparative lithium niobate electro-optic modulators of the comparative examples were tested. The results are shown in Table 1.

[0102] Among them, using Figure 3 The benchtop optical power meter shown in the figure tests the insertion loss. The insertion loss calculation formula is as follows: Where, P out is the output power of the lithium niobate electro-optic modulator, P in is the input power of the lithium niobate electro-optic modulator. The test steps of half-wave voltage are as follows: (1) Apply 0 to V π (2) Fit the optical power-voltage curve to determine the voltage value that makes the light intensity change complete one cycle. The present invention uses half-wave voltage as the core evaluation index of modulation efficiency. The physical meaning of half-wave voltage is: the driving voltage required to change the phase of the light wave by π radians (corresponding to the complete switching of the light intensity). Generally, the smaller the half-wave voltage, the higher the modulation efficiency (the greater the phase change produced by unit voltage). Figure 4 The probe station test bandwidth shown in the figure is as follows: (1) connect the modulator to the optoelectronic test port of the VNA; (2) scan the frequency range (10 MHz~40 GHz) and record S 21 Parameters; (3) Read the 3 dB bandwidth value through the vector network analyzer.

[0103] 2. Power tolerance The maximum power that the lithium niobate electro-optic modulators of the embodiment and the comparative lithium niobate electro-optic modulators of each comparative example can withstand is tested, and the results are shown in Table 1. The test steps are as follows: (1) gradually increase the input optical power, and record the output power and temperature rise; (2) when the optical transmission suddenly attenuates and the infrared thermal image shows that the thermoelectric temperature is greater than 150°C, it is determined that a critical failure point has occurred. The output power corresponding to the critical failure point is the power tolerance.

[0104] Table 1 Test results of various performances

[0105] As shown in Table 1, the lithium niobate electro-optic modulators of Examples 1-3 have an insertion loss below 1.8 dB, a half-wave voltage below 1.5 V, a 3 dB bandwidth above 80 GHz, and a tolerable power above 3800 mW. This demonstrates that the lithium niobate electro-optic modulators of the present invention not only have high modulation efficiency but also high bandwidth, low loss, and excellent power tolerance.

[0106] The comparative lithium niobate electro-optical modulator of Comparative Example 1 does not have an optical isolation groove and replaces the high dielectric constant cladding with a low dielectric constant silicon dioxide cladding. Its 3 dB bandwidth and tolerable power are low, and its insertion loss and half-wave voltage are high (low modulation efficiency).

[0107] Comparative Example 3 provides a high dielectric constant cladding, and Comparative Example 4 provides an optical isolation groove. The performance of the lithium niobate electro-optical modulators of Comparative Example 3 and Comparative Example 4 is improved compared with that of Comparative Example 1. Example 1 provides a high dielectric constant cladding and an optical isolation groove. Not only are the performances significantly improved compared with Comparative Example 1, but the degree of improvement is greater than the sum of the degrees of improvement of Comparative Example 3 and Comparative Example 4 relative to Comparative Example 1. This demonstrates that the high dielectric constant cladding and the optical isolation groove can synergistically improve the performances.

[0108] The high dielectric constant cladding of the lithium niobate electro-optic modulator of Comparative Example 2 is not a cladding with a dielectric constant gradient, and its 3 dB bandwidth and tolerable power are low, as well as its insertion loss and half-wave voltage are high (low modulation efficiency).

[0109] In the comparative example 5, the dielectric constant of the cladding in the high dielectric constant cladding of the lithium niobate electro-optic modulator decreases layer by layer from the inside to the outside, and its 3 dB bandwidth and tolerable power are low, and the insertion loss and half-wave voltage are high (low modulation efficiency).

[0110] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A lithium niobate electro-optic modulator, characterized in that: From bottom to top, it includes a ground electrode (1), a substrate layer (2), a buried oxide layer (3), a lithium niobate waveguide (4) and a high dielectric constant cladding (8); Symmetrically distributed optical isolation grooves (5) are provided on both sides of the lithium niobate waveguide (4); The high dielectric constant cladding (8) includes a first cladding (81) and a second cladding (82) from the inside to the outside, and the dielectric constant of the first cladding (81) is smaller than the dielectric constant of the second cladding (82); The number of layers of the high dielectric constant cladding (8) is ≥2; The lithium niobate electro-optical modulator further comprises a signal electrode (10), wherein the signal electrode (10) is embedded in the high dielectric constant cladding (8) and is located above the optical isolation groove (5).

2. The lithium niobate electro-optic modulator according to claim 1, wherein: The optical isolation groove (5) contains a medium (6).

3. The lithium niobate electro-optic modulator according to claim 2, wherein: The refractive index of the medium (6) is lower than the refractive index of lithium niobate, the refractive index of the material of the first cladding (81) is lower than the refractive index of the lithium niobate waveguide (4), and the refractive index of the material of the second cladding (82) is lower than the refractive index of the material of the first cladding (81).

4. The lithium niobate electro-optic modulator according to claim 1, wherein: The difference between the dielectric constants of the first cladding (81) and the second cladding (82) is ≥5.

5. The lithium niobate electro-optic modulator according to claim 1, wherein: The ratio of the maximum width of the cross section of the lithium niobate waveguide (4) to the width of the optical isolation groove (5) is 1:(1-5).

6. The lithium niobate electro-optic modulator according to claim 1, wherein: The materials of the first cladding (81) and the second cladding (82) are independently at least one of aluminum nitride, hafnium oxide, aluminum oxide, titanium oxide, lanthanum fluoride or silicon nitride.

7. The lithium niobate electro-optic modulator according to claim 1, wherein: The refractive index of the material of the first cladding layer (81) and the material of the second cladding layer (82) are independently ≤2.

2.

8. The lithium niobate electro-optic modulator according to claim 1, wherein: The thickness of the high dielectric constant cladding (8) is 50-150 nm.

9. The method for preparing the lithium niobate electro-optical modulator according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Etching the lithium niobate thin film layer of a wafer having a buried oxide layer and a lithium niobate thin film layer on a substrate to form a lithium niobate waveguide and an optical isolation groove; S2. In the optical isolation groove filled with a medium; S3 forming a high dielectric constant cladding layer above the lithium niobate waveguide; S4. Prepare a signal electrode and a ground electrode to obtain the lithium niobate electro-optical modulator.

10. Use of the lithium niobate electro-optical modulator according to any one of claims 1 to 8 in the preparation of high-speed optical communication devices or integrated photonic chips.

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