Electro-optical modulator based on slit type silicon-lithium niobate film

Abstract

The invention provides an electro-optical modulator based on a slit type silicon-lithium niobate thin film. The electro-optical modulator comprises a substrate, a lithium niobate film layer, a waveguide structure layer, a first metal electrode layer, a second metal electrode layer, a wrapping layer and a high dielectric constant layer. According to the invention, the high-refractive-index material is used for clamping the slit-type waveguide of the low-refractive-index material, so that the constraint effect on a light field is enhanced; through the design of the two functional covering layers, the silicon dioxide covering layer located on the waveguide structure layer is firstly designed, leakage of an optical mode field is reduced, radiation loss is reduced, and through optimization of structure parameters such as the too narrow distance between the first metal electrode layer and the second metal electrode layer and proper widening of the distance, the optical mode field can be effectively improved. The absorption loss of the metal electrode to the waveguide is reduced again; and secondly, through the design of the high dielectric constant layer at the top, the electric field intensity of the waveguide center is greatly enhanced, the problem that the modulation efficiency and the loss need to be balanced is solved, and the purpose of considering both low loss and high efficiency is finally achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photonic devices, and particularly relates to a slit type silicon-lithium niobate film based electro-optical modulator. BACKGROUND

[0002] A common slab waveguide is composed of a substrate layer, a high refractive index thin film layer and an external cladding layer, wherein the high refractive index thin film layer is between the cladding layer and the substrate layer. In a dielectric waveguide, if the energy of light waves is completely limited and attenuated in the horizontal direction, the propagation direction can be regarded as being perpendicular to the constraint plane. Such electromagnetic wave modes capable of being stably transmitted in the waveguide structure are referred to as guided waves. When the light waves are completely constrained by the total reflection effect at the thin film-cladding interface and the thin film-substrate interface, the light energy will be limited in the thin film dielectric layer, forming a guided wave transmission mode along the thin film plane direction.

[0003] In combination with the total reflection condition and the refractive index distribution law, the light field energy is usually concentrated in the high refractive index dielectric layer. In recent years, new waveguide structures such as ridge waveguides (light field compression through geometric deformation) and slit waveguides (excitation of strong evanescent field by high refractive index boundary) have emerged to break through the limitation of the traditional slab waveguide on the light field distribution, so as to realize the effective localized transmission of light waves in the high refractive index region.

[0004] The current electro-optical modulator is still pursuing the indicators of low loss and high modulation efficiency, but it is difficult to balance the two. SUMMARY

[0005] In order to solve the defects in the prior art, the application provides an electro-optical modulator based on a slit type silicon-lithium niobate film.

[0006] The application adopts the following technical scheme:

[0007] The application provides an electro-optical modulator based on a slit type silicon-lithium niobate film, comprising:

[0008] a substrate;

[0009] a lithium niobate film layer located on the surface of the substrate, and waveguide structure layers respectively arranged on both sides of the surface of the lithium niobate film layer; each waveguide structure layer comprises two silicon waveguide layers, and a groove is arranged on the surface of the lithium niobate film layer corresponding to the silicon waveguide layer, and each silicon waveguide layer is located in the groove;

[0010] a first metal electrode layer located on the surface of the lithium niobate film layer and between the two waveguide structure layers;

[0011] second metal electrode layers respectively arranged on the surface of the lithium niobate film layer and outside the two waveguide structure layers;

[0012] The cladding layer is arranged on the surface of the lithium niobate thin film layer and between the first metal electrode layer and the second metal electrode layer.

[0013] The high dielectric constant layer is arranged on the first metal electrode layer, the second metal electrode layer and the cladding layer and covers the first metal electrode layer, the second metal electrode layer and the cladding layer.

[0014] Preferably, the cladding layer is a silicon dioxide cladding layer, and the thickness of the silicon dioxide cladding layer is 1-3 microns.

[0015] Preferably, the interval between the first metal electrode layer and the second metal electrode layer is 4-9 microns.

[0016] Preferably, the material of the high dielectric constant layer is silicon nitride, and the thickness of the high dielectric constant layer is 50-300 nm.

[0017] Preferably, the width of the slit is 50-200 nm.

[0018] Preferably, the width of the silicon waveguide layer is 150-800 nm, and the thickness of the silicon waveguide layer is 150-400 nm.

[0019] Preferably, the thickness of the lithium niobate thin film layer is 600-700 nm.

[0020] Preferably, the material of the first metal electrode layer and the second metal electrode layer is gold.

[0021] Preferably, the thickness of the first metal electrode layer and the second metal electrode layer is 1-2 microns.

[0022] Preferably, the substrate is a silicon dioxide substrate, and the thickness of the silicon dioxide substrate is 3-4 microns.

[0023] The slit-type silicon-lithium niobate thin film-based electro-optical modulator has the following effects compared with the prior art.

[0024] 1. The slit-type silicon-lithium niobate thin film-based electro-optical modulator strengthens the binding effect on the light field by the slit-type waveguide of the high refractive index material clamping the low refractive index material; through the design of the two-part functional cladding layer, firstly, the silicon dioxide cladding layer arranged on the waveguide structure layer is designed to reduce the leakage of the light mode field and reduce the radiation loss, and through the optimization of the structural parameters such as the interval between the first metal electrode layer and the second metal electrode layer, the interval is appropriately widened, and the absorption loss of the metal electrode to the waveguide is reduced again; secondly, through the design of the high dielectric constant layer at the top, the electric field strength in the center of the waveguide is greatly enhanced, the problem of balancing between the modulation efficiency and the loss is solved, and the purpose of low loss and high efficiency is finally realized.

[0025] 2. The slit-type silicon-lithium niobate thin film-based electro-optical modulator of the present application, when the width of the silicon waveguide layer is 195 nm, the thickness is 150 nm, the slit width is 120 nm, the spacing between the first metal electrode layer and the second metal electrode layer is 4.5 μm, the thickness of the silicon dioxide cladding layer is 0.8 μm, and the thickness of the high dielectric constant layer is 200 nm, the transmission loss is reduced to 0.24 dB / cm, and a half-wave voltage length product of 1.782 V·cm is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0027] Figure 1 A three-dimensional structure schematic diagram of the slit-type silicon-lithium niobate thin film-based electro-optical modulator of the present application;

[0028] Figure 2 A front view of the slit-type silicon-lithium niobate thin film-based electro-optical modulator of the present application;

[0029] Figure 3 A simulation result of the electro-optical modulator in COMSOL in Example 6;

[0030] Figure 4 Influence of different silicon dioxide cladding layer thicknesses on the transmission loss (dB / cm) of the electro-optical modulator in Example 1;

[0031] Figure 5 Influence of different silicon dioxide cladding layer thicknesses on the half-wave voltage length product (V·cm) of the electro-optical modulator in Example 1;

[0032] Figure 6 Influence of different electrode spacings on the transmission loss (dB / cm) of the electro-optical modulator in Example 2;

[0033] Figure 7 Influence of different electrode spacings on the half-wave voltage length product (V·cm) of the electro-optical modulator in Example 2;

[0034] Figure 8 Influence of different high dielectric constant layer thicknesses on the transmission loss (dB / cm) of the electro-optical modulator in Example 3;

[0035] Figure 9 Influence of different high dielectric constant layer thicknesses on the half-wave voltage length product (V·cm) of the electro-optical modulator in Example 3;

[0036] Figure 10 Effect of different slot widths on the transmission loss (dB / cm) of electro-optic modulators in Example 4;

[0037] Figure 11 Effect of different slot widths on the half-wave voltage-length product (V-cm) of electro-optic modulators in Example 4;

[0038] Figure 12 Effect of different silicon waveguide layer widths on the transmission loss (dB / cm) of electro-optic modulators in Example 5;

[0039] Figure 13 Effect of different silicon waveguide layer widths on the half-wave voltage-length product (V-cm) of electro-optic modulators in Example 5;

[0040] Figure 14 Effect of different silicon waveguide layer thicknesses on the transmission loss (dB / cm) of electro-optic modulators in Example 6;

[0041] Figure 15 Effect of different silicon waveguide layer thicknesses on the half-wave voltage-length product (V-cm) of electro-optic modulators in Example 6. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present application, a more complete understanding thereof can be had by reference to the following description when taken in conjunction with the accompanying drawings, in which:

[0043] The sequence of the following examples is not intended to limit the preferred order of the examples. In addition, in the description of the application, the term "comprising" is intended to mean "including but not limited to." Various embodiments of the application can be presented in a range format; it is to be understood that the description in range format is merely for convenience and brevity and in no way limits the scope of the application to a range format. In addition, every numerical range given throughout this specification will include all combinations and subcombinations of the numerical values stated and ranges formed by the permutations of those values. Any numerical range

[0044] The present application provides an electro-optic modulator based on a slot-type silicon-lithium niobate thin film, as shown inFigures 1-2 As shown, comprising:

[0045] a substrate 1;

[0046] a lithium niobate (LiNbO3) film layer 2 located on the surface of the substrate 1, and waveguide structure layers are respectively arranged on both sides of the surface of the lithium niobate film layer 2; each waveguide structure layer comprises two silicon waveguide layers 3, and a recess is arranged on the surface of the lithium niobate film layer 2 corresponding to the silicon waveguide layer 3, and each silicon waveguide layer 3 is located in the recess;

[0047] a first metal electrode layer 4 located on the surface of the lithium niobate film layer 2 and between the two waveguide structure layers;

[0048] second metal electrode layers 5 are respectively arranged on the surface of the lithium niobate film layer 2 and outside the two waveguide structure layers;

[0049] a cladding layer 6 is arranged on the surface of the lithium niobate film layer 2 and between the first metal electrode layer 4 and the second metal electrode layer 5;

[0050] a high dielectric constant layer 7 is arranged on the first metal electrode layer 4, the second metal electrode layer 5 and the cladding layer 6, and covers the first metal electrode layer 4, the second metal electrode layer 5 and the cladding layer 6.

[0051] The slit type silicon-lithium niobate thin film based electro-optical modulator of the present application comprises a substrate 1, a lithium niobate (LiNbO3) thin film layer 2, a waveguide structure layer, a first metal electrode layer 4, a second metal electrode layer 5, a cladding layer 6, and a high dielectric constant layer 7; wherein the waveguide structure layer is arranged on both sides of the surface of the lithium niobate thin film layer 2, each waveguide structure layer comprises two silicon waveguide layers 3, the material of the silicon waveguide layer 3 is silicon, recesses are arranged on the surface of the lithium niobate thin film layer 2 corresponding to the silicon waveguide layers, each silicon waveguide layer 3 is located in the recess, that is, four recesses are arranged on the surface of the lithium niobate thin film layer 2, the recesses are matched with the silicon waveguide layers 3, the silicon waveguide layers 3 are located in the recesses, and the four silicon waveguide layers 3 form two slit type waveguides; the first metal electrode layer 4 is located between the two waveguide structure layers, the two second metal electrode layers 5 are located outside the two waveguide structure layers, the first metal electrode layer 4 is located between the two second metal electrode layers 5, the first metal electrode layer 4 is a metal signal electrode for applying voltage, the second metal electrode layer 5 is a metal ground electrode for generating an electric field, thereby changing the characteristics of the waveguide material, the optical transmission characteristics are changed, and finally the electro-optical modulation is realized; the cladding layer 6 is located between the first metal electrode layer 4 and the second metal electrode layer 5, and the high dielectric constant layer 7 is located on and covers the first metal electrode layer 4, the second metal electrode layer 5, and the cladding layer 6; the present application adopts lithium niobate thin film and silicon material to design waveguide, uses the slit type silicon waveguide layer with enhanced light beam binding ability to improve the electro-optical overlap degree of the modulator, reduces the half-wave voltage length product of the device, and realizes high-efficiency modulation of the optical signal; meanwhile, the functional cover layer designed above the silicon waveguide layer comprises the cladding layer for limiting the optical field and the high dielectric constant layer for enhancing the electric field in the center of the waveguide, which maximally reduces the transmission loss and also increases the electro-optical overlap integral and improves the modulation efficiency.

[0052] In some embodiments, the waveguide structure layer is a slit type waveguide structure layer, each waveguide structure layer comprises two silicon waveguide layers 3, the cross section of each silicon waveguide layer 3 is rectangular, the two silicon waveguide layers 3 form a slit type silicon waveguide layer, and the material between the two silicon waveguide layers 3 is still lithium niobate.

[0053] In some embodiments, the cladding layer 6 is a silicon dioxide cladding layer, the thickness of the silicon dioxide cladding layer is 1-3 μm, preferably, the thickness of the silicon dioxide cladding layer is 0.5-1 μm; the cross section of the silicon dioxide cladding layer is polygonal and covers the waveguide structure layer; specifically, the cross section below the silicon dioxide cladding layer is rectangular and the cross section above the silicon dioxide cladding layer is trapezoidal.

[0054] In some embodiments, the material of the first metal electrode layer 4 and the second metal electrode layer 5 is gold, the spacing between the first metal electrode layer 4 and the second metal electrode layer 5 is 4-9 μm, the thickness of the first metal electrode layer 4 and the second metal electrode layer 5 is 1-2 μm, preferably, the spacing between the first metal electrode layer 4 and the second metal electrode layer 5 is 4-7 μm; the first metal electrode layer 4 and the second metal electrode layer 5 are both cuboid structures.

[0055] In some embodiments, the material of the high dielectric constant layer 7 is silicon nitride (Si3N4), the cross section of the high dielectric constant layer 7 is a polygonal structure, and the high dielectric constant layer 7 is disposed on the top layer; when the material with high dielectric constant is used as the material of the top layer, the electric field intensity in the center of the waveguide is enhanced; the thickness of the high dielectric constant layer 7 is 50-300 nm, preferably, the thickness of the high dielectric constant layer 7 is 180-220 nm.

[0056] In some embodiments, the spacing between the two silicon waveguide layers 3 in each waveguide structure layer is 50-200 nm, and the spacing between the two silicon waveguide layers 3 is the slit width; the slit width is 50-200 nm, preferably, the slit width is 75-135 nm.

[0057] In some embodiments, the width of the silicon waveguide layer 3 is 150-800 nm, and the thickness of the silicon waveguide layer 3 is 150-400 nm, preferably, the width of the silicon waveguide layer 3 is 195-200 nm, and the thickness of the silicon waveguide layer 3 is 150-165 nm.

[0058] In some embodiments, the thickness of the lithium niobate thin film layer 2 is 600-700 nm.

[0059] In some embodiments, the substrate 1 is a silicon dioxide substrate, the thickness of the silicon dioxide substrate is 3-4 μm, and the substrate 1 is a cuboid.

[0060] In some embodiments, the thickness of the lithium niobate thin film layer 2 is 600-700 nm, specifically, the lithium niobate thin film layer 2 is an x-cut lithium niobate thin film, the electro-optic coefficient γ 33 of the x-cut lithium niobate thin film is 30.8 pm / V, the relative dielectric constant ε 33 of the x-cut lithium niobate thin film is 27.9, the ε 11 of the x-cut lithium niobate thin film is 44.3, the ordinary light refractive index is 2.2111, and the extraordinary light refractive index is 2.1376; specifically, because lithium niobate is a crystal, the optical properties of different directions (x / y / z) are different, the x-cut refers to the crystal cutting direction, which determines the refractive index of the ordinary light (o light, electric field perpendicular to the optical axis) and the extraordinary light (e light, electric field parallel to the optical axis) when the light propagates in the crystal, and affects the polarization state control of the light; the electro-optic coefficient γ 33 = 30.8 pm / V: this is an index of the strength of the electro-optic effect, and γ 33The larger the ε value, the more pronounced the change in refractive index under the same electric field; lithium niobate is an anisotropic crystalline material, meaning that its physical properties differ in different directions. 33 ε 11 This describes the relative permittivity of lithium niobate along different crystal axes. The first subscript represents the crystal axis direction; in Cartesian coordinates, 3 typically corresponds to the z-axis and 1 to the x-axis. ε 33 ε represents the ability of a material to store electric field energy in the z-axis direction when an electric field is applied. 11 This indicates the material's ability to store electric field energy in the x-axis direction when an electric field is applied. This invention uses x-cut lithium niobate, fully utilizing the maximum value γ of the electro-optic coefficient of lithium niobate. 33 Since the components are defined, the horizontal direction is set as the z-axis, the vertical direction as the x-axis, and the light propagates along the y-axis.

[0061] In some embodiments, both the substrate and the cladding are made of silicon dioxide, which better confines the light field while reducing radiation loss. The slit-type silicon waveguide used in this embodiment extends in the same direction as the lithium niobate film. By adjusting the thickness and width of the silicon material and the slit width, the light field is confined and concentrated at the center of the waveguide, thus reducing the effective mode area.

[0062] In this embodiment of the invention, a high dielectric constant layer with a polygonal cross-section is placed on the top layer. When a high dielectric constant material is used as the top layer material, the electric field strength at the center of the waveguide is enhanced.

[0063] In this embodiment of the invention, both the substrate and the cladding are made of silicon dioxide, with a refractive index of 1.444 and a relative permittivity of 4.2; the silicon waveguide layer 3 is made of silicon, with a refractive index of 3.48 and a relative permittivity of 12.11; the high permittivity layer is made of silicon nitride, with a refractive index of 1.97 and a relative permittivity of 11.1.

[0064] This invention enhances the confinement of the optical field by using a slit-type waveguide (i.e., two silicon waveguide layers sandwiching lithium niobate) sandwiched between high-refractive-index silicon material and low-refractive-index lithium niobate material. Through the design of two functional cladding layers, firstly, a silicon dioxide cladding layer is designed on the waveguide structure layer to reduce leakage of the optical mode field and decrease radiation loss. Furthermore, by optimizing structural parameters such as the excessively narrow spacing between the first metal electrode layer 4 and the second metal electrode layer 5, the spacing is appropriately widened, further reducing the absorption loss of the metal electrodes on the waveguide. Secondly, the design of a high-dielectric-constant layer at the top significantly enhances the electric field strength at the center of the waveguide, addressing the need to balance modulation efficiency and loss, ultimately achieving a balance between low loss and high efficiency.

[0065] The following further describes the electro-optic modulator based on a slit-type silicon-lithium niobate thin film of the present invention. This section further illustrates the content of the invention with reference to specific embodiments, but should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0066] In the following embodiments, COMSOL Multiphysics software is used to simulate the electro-optic modulator; specifically, in COMSOL Multiphysics software, simulation calculations are performed based on the specific design and... Figure 2 A two-dimensional planar model was established for the structure shown. During modeling, the crystal orientation was set to x-cut lithium niobate, and the correspondence between the software coordinate system and the crystal orientation was carefully observed: the X-direction in the software corresponds to the z-axis direction of the crystal, and the Y-direction corresponds to the x-axis direction. To accurately simulate the actual effects of the device materials, the silicon dioxide, silicon, silicon nitride, and gold materials used in the model were directly taken from the software's built-in material library. For lithium niobate, custom settings were required based on its anisotropic optical and electrical properties. Specifically, at a wavelength of 1550 nm, the refractive index ne (i.e., the unusual light refractive index mentioned above) along the z-direction (lateral) is 2.1376, and the relative permittivity is 27.9; while the refractive index no (i.e., the ordinary light refractive index mentioned above) in the x and y directions (lateral and propagation directions) is 2.2111, and the relative permittivity is 44.3 in both cases. When setting up the software, both the refractive index and relative permittivity of lithium niobate were selected as "anisotropic (diagonal)". Based on the correspondence between the crystal direction and the modeling direction, the diagonal elements of the refractive index matrix were set to (2.1376, 2.2111, 2.2111) and the diagonal elements of the relative permittivity matrix were set to (27.9, 44.3, 44.3) to correctly reflect its anisotropic characteristics.

[0067] After completing the cross-sectional modeling and material parameter import of the electro-optic modulator, the physical field needs to be set.

[0068] In order to evaluate the electro-optic mechanism and performance of the modulator structure, it is necessary to accurately obtain the spatial electric field distribution of the lithium niobate waveguide region under the action of the applied external electric field. For this purpose, the COMSOL Multiphysics multi-physical field simulation software is used to perform high-precision numerical simulation of the electric field distribution of the modulator structure under static conditions based on the finite element method. The core principle of introducing the electrostatic field calculation module in the simulation software is to numerically solve the Maxwell equations in the form of static electricity based on the finite element method. The specific process includes: first, discretize the calculation region into fine triangular grid elements, and then apply voltage conditions on the electrode boundaries. The control equation is the electrostatic potential equation: where ε represents the dielectric constant of the material, V is the electric potential, and ρ is the free charge density, represents the Nabla operator (vector differential operator, which appears twice in this equation, representing the gradient and divergence ). In terms of boundary condition setting, the left electrode (i.e. the surface of the first metal electrode layer 4 in Figure 2 is set as the terminal (Terminal) and a voltage of 1V is applied; the surface of the right electrode (the second metal electrode layer 5 in Figure 2 is set as the ground (Ground), i.e. the electric potential is 0V. The remaining boundaries are set according to the actual physical conditions. In the calculation of electrostatic force, the Maxwell stress tensor method is used for integral solution. The tensor expression used is: where T is the Maxwell stress tensor, E is the electric field intensity, D is the electric displacement vector, I is the unit tensor, represents the dyadic product, the dyadic product of two vectors (such as E and D) produces a second-order tensor; the electrostatic force acting on a surface can be calculated by area integration of the stress tensor on the outer normal direction n of the surface, i.e. F = ∮_S(n·T)dS This method strictly satisfies the charge conservation and mechanical equilibrium conditions in the electrostatic system, and is suitable for accurately calculating the mechanical force of a medium or conductor in a static electric field. In order to calculate the static electric force acting on an object, an arbitrary shaped closed surface S can be used to completely enclose the object; n·T: is the projection of the stress tensor in the surface normal direction, which is a vector representing the force acting on a unit area (traction vector); ∮_S...dS: integrate all traction vectors on the closed surface to obtain the total static electric force vector F acting on the enclosed object.

[0069] Next, the electromagnetic modes in the optical waveguide are numerically solved. In the simulation software, the "electromagnetic wave, frequency domain" research module is added, and the Maxwell equations in the frequency domain are discretely solved by the finite element method. The control equation is: where, represents the curl operator, meaning: vector differential operator, the role is to calculate the curl of the vector field, E is the electric field vector, ω is the angular frequency, ε and μ are the dielectric constant and magnetic permeability, respectively. The scattering boundary condition (SBC) is a boundary condition for truncating the calculation domain, which is primarily used to allow waves to be transmitted out of the calculation domain with minimal reflection, thereby simulating the free propagation of waves in an infinite space and avoiding the interference of non-physical reflections on the mode results. It is usually applied to the boundary where the wave propagation direction is known. When solving, by setting the search interval near the expected effective refractive index, a series of eigenmodes supported by the waveguide structure can be calculated. After completing the simulation, the complex effective refractive index n eff = n eff′ + in eff″ of each propagation mode can be obtained. The real part n eff′ determines the phase velocity of the mode, and the imaginary part n eff″ represents the transmission loss of the mode, which is directly related to the mode attenuation constant.

[0070] It should be noted that, in order to accurately simulate the influence of the electrostatic field on the waveguide mode characteristics, the refractive index change of lithium niobate crystal caused by the electric field must be considered. This change is mainly caused by the linear electro-optic effect (Pockels effect). Next, based on the refractive index ellipsoid equation, the Pockels effect in lithium niobate crystal will be theoretically analyzed under the x, y, z coordinate system. Therefore, in the previous simulation settings, the material properties of lithium niobate need to be modified to reflect the anisotropic change of refractive index caused by the external electric field. When an electric field Ez is applied along the z-axis direction of the crystal, it will cause changes in the refractive indices of the x, y, and z three principal axes, and the specific change amount is given by the following formula:

[0071]

[0072] where, 13 (the electro-optic coefficient is 8.6pm / V) and r 33 (that is, the electro-optic coefficient γ 33 mentioned above is 30.8pm / V) are the electro-optic coefficient tensor elements of lithium niobate crystal, n x , n y , n z are the principal refractive indices of the three directions without an electric field. In the simulation, the modified refractive indices n x + Δn x , n y + Δny ,n z +Δn z Substitute the values ​​into the model for calculation to accurately reflect the modulation effect of the electrostatic field on the optical wave pattern.

[0073] After completing the above settings, mesh generation and study steps will be configured. The mesh generation strategy is as follows: To improve computational accuracy, a finer mesh generation is used for the lithium niobate thin film waveguide layer, with the maximum and minimum element sizes set to λ / (n). eff ×8) and λ / (n eff ×9), where λ is the operating wavelength (1550nm), n eff This is the complex effective refractive index. This setting effectively controls computational load while maintaining accuracy. For other non-critical regions (such as the cladding and substrate), a relatively coarse mesh is used to improve computational efficiency.

[0074] In terms of research setup, two research steps are added sequentially: "Steady State" and "Mode Analysis." The steady-state study uses a physics-controlled solver setup to calculate the electrostatic field distribution. The mode analysis study is used to solve for the optical field modes in the waveguide, with the following parameter settings: the mode analysis frequency is set to c / λ, where c is the speed of light in vacuum and λ is the operating wavelength (1550 nm); the number of modes to be solved can be appropriately increased to ensure complete capture of all dominant modes, including the TE mode; the search benchmark is set to the unusual refractive index value of lithium niobate crystal, 2.1376, and a certain search offset range can be set around it to cover possible effective refractive index distributions. After completing all settings, the simulation calculation can be executed.

[0075] After the above steps, the result is as follows: Figure 3 Simulation results for the electro-optic modulator in Example 6 (with a silicon waveguide layer thickness of 150 nm). The horizontal and vertical axes represent the position of the modulator in the xz plane, and its scale is limited to the micrometer level, hence the unit is micrometers (μm). The figure shows "Effective mode refractive index = 2.09121", indicating that the effective refractive index of the solved optical mode is n. eff= 2.09121. The effective refractive index determines the phase velocity and propagation constant of the optical wave, and is a key parameter for designing modulators, phase matching, etc. The value is between the refractive index of lithium niobate (about 2.2) and the cladding (such as silica, about 1.44) or air (1.0), which is consistent with the effective refractive index law of the optical waveguide mode. Since the lithium niobate crystal is x-cut, the value is close to the refractive index of ordinary light (no≈2.211) or extraordinary light (ne≈2.137), indicating that the mode is mainly limited within the lithium niobate thin film. "Surface: Electric field mode (V / m)" indicates that the color mapping represents the electric field amplitude (unit: V / m), and the arrow represents the direction and size of the electric field vector. The electric field distribution shows that the energy is mainly concentrated in the central region (within about ±2μm), and has symmetry, indicating that it is a fundamental mode. The main reason for the fundamental mode is the dual consideration of physical limitation and performance optimization. Because the fundamental mode Gaussian field of the single-mode fiber is most matched with the waveguide fundamental mode field, the coupling efficiency is highest (loss can be <1dB); secondly, single mode propagation ensures that the optical pulse does not spread, supporting high-speed and high-fidelity signal transmission; and the optical field is concentrated in the center of the waveguide, which is best overlapped with the external modulation electric field, and the modulation response is uniform and predictable. Generally, the arrow direction (electric field vector) is mainly transverse (may be along the x or y direction), if it is parallel to the waveguide plane, it is a TE mode; if there is a significant longitudinal component, it is a TM mode. It needs to be further confirmed in combination with the polarization direction. The electric field strength gradually decays from the center to the edge (the color changes from warm to cold), indicating that the optical field is well confined in the waveguide core. The electric field strength at the edge is reduced to 10-20V / m, which is in contrast to the center (about 100V / m), confirming the guided mode characteristics of the waveguide. The simulation distribution results of the electrostatic field are shown in Figure 3 It can be observed that the electric field line direction is mainly from the left positive electrode to the right ground electrode. The waveguide structure is located in the central region between the two electrodes, and therefore is completely within the distribution range of the electrostatic field. Through finite element numerical solution, the accurate spatial electric field distribution in the entire simulation domain is obtained, and the electric field strength value |E| and the vector direction E(x,y) at each discrete grid node inside the waveguide region can be extracted accordingly.

[0076] The effective refractive index n eff , the electric field Ez(x,z) along the z-axis direction, the electric field strength ez(x,z) of the TE mode, etc. obtained in combination with the simulation results, the concepts of transmission loss and half-wave voltage length product are introduced to evaluate the performance of the electro-optic modulator.

[0077] The transmission loss combines the field form of the light propagating in the waveguide and the relationship principle of the complex effective refractive index n eff and the complex propagation constant β, and the imaginary part Im(n eff)(a dimensionless number, the imaginary part of the complex effective refractive index mentioned above) is converted to an engineering practical transmission loss value a. The formula is as follows:

[0078]

[0079] where Im(neff) refers to the imaginary part of the effective mode index obtained in the above experiment; 40π is derived from 4π (the conversion coefficient from field attenuation to power attenuation) multiplied by 10 (the conversion from bel to decibel); log(10) is ln(10), which is derived from the conversion of the logarithm base in the decibel definition (from natural logarithm ln to common logarithm log10). Whether the final unit is dB / m or dB / cm depends on the unit used for the wavelength λ in the model. In this experiment, the final unit of transmission loss is dB / cm.

[0080] VπL is an intrinsic parameter determined only by the physical structure of the modulator (material, electrode configuration, the degree of overlap between the optical field and the electric field). The smaller the value, the higher the energy utilization efficiency of the modulator structure. The half-wave voltage length product (VπL) refers to the product of the driving voltage (Vπ) and the interaction length (L) of the modulator required to achieve a π radian (180°) optical phase change. Its unit is usually V·cm or V·m. It is a core indicator to measure the efficiency of electro-optic modulators. Generally, the lower the voltage, the better the compatibility with the driving circuit, and the better the compatibility with the driving circuit. Generally, the modulator should be as short as possible. Shorter device size is beneficial to chip integration and allows higher operating speed (because the photon and electron transmission time is shorter).

[0081] In order to calculate the half-wave voltage length product of the modulator, a physical quantity, i.e. electro-optic overlap factor Γ, is also needed. The electro-optic overlap factor Γ quantitatively describes how much proportion of the applied modulation electric field energy is effectively utilized by the optical mode to produce the required phase or intensity modulation. It is a dimensionless parameter, with a value range of 0 to 1. For example, Γ = 1: ideal case, 100% utilization, the modulation electric field completely and uniformly covers the entire optical mode; Γ = 0: worst case, 0% utilization, the modulation electric field and the optical mode are completely separated in space and do not interact with each other; 0 < Γ < 1: actual case, only a part of the electric field energy interacts with the optical field. In fact, when the electrostatic field acts on the lithium niobate waveguide, the electric field at each point in lithium niobate is different in size, so an integral operation needs to be performed on the structure to obtain the theoretical value of Vπ or VπL in actual calculation. The formula is as follows:

[0082]

[0083] where E z(x,z) is the electric field along the z-axis direction, ez(x,z) is the electric field intensity of the TE mode, the numerator of the molecule is integrated respectively for the lithium niobate thin film area and the entire modulation area cross section, G is the gap between the electrodes, V0 is the applied modulation voltage, which is set to 1V.

[0084] After obtaining the electro-optical overlap factor Γ, it is substituted into the definition formula of the half-wave voltage length product:

[0085]

[0086] Where, λ is the optical wavelength in vacuum (Wavelength), here refers to the wavelength of the modulated light wave, taking 1550nm; G is the electrode gap (the distance between the first metal electrode layer 4 and the second metal electrode layer 5); n eff is the complex effective refractive index; n e is the extraordinary light refractive index of the lithium niobate crystal, which is 2.1376; r 33 is the electro-optic coefficient 33 component of the lithium niobate crystal (the electro-optic coefficient r 33 is 30.8pm / V); The formula is divided by 2 because the electro-optic modulator design usually adopts push-pull structure, so it is divided by 2 in actual calculation.

[0087] The above is the process of the entire simulation experiment. The following examples will optimize the structure parameters by optimizing the thickness of the silicon dioxide cladding layer, the electrode gap, the thickness and width of Si, the slit width, and the thickness of the high dielectric constant layer, and the optimization is based on the above steps.

[0088] Example 1

[0089] The embodiment provides a slit type silicon-lithium niobate thin film based electro-optic modulator, which comprises:

[0090] a substrate;

[0091] a lithium niobate (LiNbO3) thin film layer located on the surface of the substrate, and a waveguide structure layer is arranged on each side of the surface of the lithium niobate thin film layer; each waveguide structure layer comprises two silicon waveguide layers, and a groove is arranged at the position corresponding to the silicon waveguide layer on the surface of the lithium niobate thin film layer, and each silicon waveguide layer is located in the groove;

[0092] a first metal electrode layer located on the surface of the lithium niobate thin film layer and between the two waveguide structure layers;

[0093] second metal electrode layers are arranged on the surface of the lithium niobate thin film layer and outside the two waveguide structure layers;

[0094] a cladding layer is arranged on the surface of the lithium niobate thin film layer and between the first metal electrode layer and the second metal electrode layer;

[0095] a high dielectric constant layer, which is located on the first metal electrode layer, the second metal electrode layer and the cladding layer, and covers the first metal electrode layer, the second metal electrode layer and the cladding layer;

[0096] The substrate is a silicon dioxide substrate, and the thickness is 3 μm.

[0097] The thickness of the lithium niobate (LiNbO3) film layer is 600 nm.

[0098] The silicon waveguide layer has a width of 200 nm and a thickness of 150 nm, and the slit has a width of 100 nm.

[0099] The materials of the first metal electrode layer and the second metal electrode layer are gold, the spacing between the first metal electrode layer and the second metal electrode layer is 5 μm, and the thickness of the first metal electrode layer and the second metal electrode layer is 1 μm.

[0100] The cladding layer is a silicon dioxide cladding layer, and the cross section of the silicon dioxide cladding layer is a combination of a rectangular and a trapezoidal shape. The thickness of the silicon dioxide cladding layer is 0.5-1 μm (since the thickness of the silicon dioxide cladding layer should not be too thick, the thickness range of 0.5-1 μm is parameterized in this embodiment).

[0101] The material of the high dielectric constant layer is silicon nitride, and the thickness is 100 nm.

[0102] Specifically, Table 1 below shows the influence of the thickness of the silicon dioxide cladding layer on the transmission loss (dB / cm) and the half-wave voltage length product (V·cm).

[0103] Table 1 Influence of the thickness of the silicon dioxide cladding layer on the transmission loss and the half-wave voltage length product

[0104] Silica cladding thickness (pm) Transmission loss (dB / cm) Half-wave voltage-length product (V-cm) 0.5 1.77 2.034 0.6 0.97 2.033 0.7 0.54 2.033 0.8 0.3 2.033 0.9 0.18 2.032 1 0.11 2.032

[0105] The influence of the thickness of the silicon dioxide cladding layer on the transmission loss (dB / cm) of the electro-optical modulator in Example 1 is shown in Figure 4 .

[0106] The influence of the thickness of the silicon dioxide cladding layer on the half-wave voltage length product (V·cm) of the electro-optical modulator in Example 1 is shown in Figure 5 .

[0107] As can be seen from Figures 4-5 , as the thickness of the silicon dioxide cladding layer increases, the transmission loss of the electro-optical modulator gradually decreases, while the half-wave voltage length product changes little. Considering that a too thin silicon dioxide cladding layer cannot effectively reduce the loss, and a too thick silicon dioxide cladding layer may affect the role of the high dielectric constant layer, the appropriate thickness of the silicon dioxide cladding layer is 0.7-0.9 μm.

[0108] Example 2

[0109] The embodiment provides a slit-type silicon-lithium niobate thin film-based electro-optical modulator, which comprises the following components:

[0110] a substrate;

[0111] a lithium niobate (LiNbO3) thin film layer located on the surface of the substrate, and waveguide structure layers located on both sides of the surface of the lithium niobate thin film layer; each waveguide structure layer comprises two silicon waveguide layers, and a groove is arranged at the position corresponding to the silicon waveguide layer on the surface of the lithium niobate thin film layer, and each silicon waveguide layer is located in the groove;

[0112] a first metal electrode layer located on the surface of the lithium niobate thin film layer and between the two waveguide structure layers;

[0113] second metal electrode layers located on the surface of the lithium niobate thin film layer and outside the two waveguide structure layers;

[0114] a cladding layer located between the first metal electrode layer and the second metal electrode layer on the surface of the lithium niobate thin film layer;

[0115] a high dielectric constant layer located on the first metal electrode layer, the second metal electrode layer and the cladding layer and covering the first metal electrode layer, the second metal electrode layer and the cladding layer;

[0116] The substrate is a silicon dioxide substrate, and the thickness is 3 μm.

[0117] The thickness of the lithium niobate (LiNbO3) thin film layer is 650 nm.

[0118] The width of the silicon waveguide layer is 200 nm, the thickness is 150 nm, and the slit width is 100 nm.

[0119] The materials of the first metal electrode layer and the second metal electrode layer are gold, the spacing between the first metal electrode layer and the second metal electrode layer is 4-7 μm (in the embodiment, the spacing range of 4-7 μm is parameterized and scanned), and the thickness of the first metal electrode layer and the second metal electrode layer is 1 μm.

[0120] The cladding layer is a silicon dioxide cladding layer, the cross section of the silicon dioxide cladding layer is a combination of a rectangle and a trapezoid, the thickness of the silicon dioxide cladding layer is 0.8 μm, and the material of the high dielectric constant layer is silicon nitride and the thickness is 100 nm.

[0121] Specifically, Table 2 shows the influence of the electrode spacing on the transmission loss (dB / cm) and the half-wave voltage length product (V·cm).

[0122] Table 2 shows the influence of the electrode spacing on the transmission loss and the half-wave voltage length product

[0123] Electrode pitch (pm) Transmission loss (dB / cm) Half-wave voltage-length product (V-cm) 4 0.42 1.647 4.5 0.33 1.840 5 0.3 2.033 5.5 0.3 2.225 6 0.3 2.417 6.5 0.3 2.608 7 0.3 2.797

[0124] The influence of different electrode spacings on the transmission loss (dB / cm) of the electro-optical modulator in Example 2 is shown in Figure 6

[0125] The influence of different electrode spacings on the half-wave voltage-length product (V cm) of the electro-optical modulator in Example 2 is shown in Figure 7

[0126] As can be seen from Figures 6-7 , as the spacing between the first metal electrode layer and the second metal electrode layer increases, the transmission loss of the electro-optical modulator gradually decreases, and the half-wave voltage-length product also increases; in comprehensive consideration, a suitable electrode spacing needs to be selected to achieve a balance between low transmission loss and high electric field strength, low half-wave voltage-length product. Therefore, the finally selected electrode spacing range is 4-5 μm.

[0127] Example 3

[0128] The present embodiment provides a slit-type silicon-lithium niobate thin film-based electro-optical modulator, comprising:

[0129] a substrate;

[0130] a lithium niobate (LiNbO3) thin film layer located on the surface of the substrate, and a waveguide structure layer is arranged on each side of the surface of the lithium niobate thin film layer; each waveguide structure layer comprises two silicon waveguide layers, and a groove is arranged on the surface of the lithium niobate thin film layer corresponding to the silicon waveguide layer, and each silicon waveguide layer is located in the groove;

[0131] a first metal electrode layer located on the surface of the lithium niobate thin film layer and between the two waveguide structure layers;

[0132] a second metal electrode layer arranged on the surface of the lithium niobate thin film layer and outside the two waveguide structure layers;

[0133] a cladding layer arranged on the surface of the lithium niobate thin film layer and between the first metal electrode layer and the second metal electrode layer;

[0134] a high dielectric constant layer located on the first metal electrode layer, the second metal electrode layer and the cladding layer, and covering the first metal electrode layer, the second metal electrode layer and the cladding layer;

[0135] The substrate is a silicon dioxide substrate with a thickness of 3 μm.

[0136] The lithium niobate (LiNbO3) thin film layer has a thickness of 620 nm.

[0137] The silicon waveguide layer has a width of 200 nm and a thickness of 150 nm, and the slit has a width of 100 nm.

[0138] ​​Both the first and second metal electrode layers are made of gold, and the spacing between the first and second metal electrode layers is 4.5 μm; the thickness of the first and second metal electrode layers is 1 μm.

[0139] The cladding is a silica cladding with a cross-section combining rectangular and trapezoidal shapes, and the silica cladding thickness is 0.8 μm;

[0140] The high dielectric constant layer is made of silicon nitride with a thickness of 50–300 nm. In this embodiment, a parametric scan will be performed on the thickness range of 50–300 nm.

[0141] Specifically, Table 3 below shows the effect of the thickness of the high dielectric constant layer on transmission loss (dB / cm) and half-wave voltage-length product (V·cm).

[0142] Table 3 - Effect of high dielectric constant layer thickness on transmission loss and half-wave voltage length product

[0143] High-k layer thickness (nm) Transmission loss (dB / cm) Half-wave voltage-length product (V-cm) 50 0.45 1.842 100 0.33 1.84 150 0.24 1.839 200 0.18 1.838 250 0.13 1.839 300 0.1 1.839

[0144] The effect of different high dielectric constant layer thicknesses on the transmission loss (dB / cm) of the electro-optic modulator in Example 3 is as follows: Figure 8 As shown;

[0145] The effect of different high-dielectric-constant layer thicknesses on the half-wave voltage-length product (V·cm) of the electro-optic modulator in Example 3 is as follows: Figure 9 As shown;

[0146] from Figures 8-9 As can be seen, as the thickness of the high dielectric constant layer increases, the transmission loss of the electro-optic modulator gradually decreases, and the half-wave voltage-length product also decreases accordingly; however, after exceeding a certain thickness range, it will continue to increase; the suitable thickness of the high dielectric constant layer is 180-220 nm.

[0147] Example 4

[0148] This embodiment provides an electro-optic modulator based on a slit-type silicon-lithium niobate thin film, comprising:

[0149] Substrate;

[0150] A lithium niobate (LiNbO3) thin film layer is located on the surface of a substrate, and waveguide structure layers are respectively provided on both sides of the surface of the lithium niobate thin film layer; each waveguide structure layer includes two silicon waveguide layers, and a groove is provided on the surface of the lithium niobate thin film layer corresponding to the silicon waveguide layer, with each silicon waveguide layer located in the groove.

[0151] The first metal electrode layer is located on the surface of the lithium niobate thin film layer and between the two waveguide structure layers.

[0152] A second metal electrode layer is provided on the surface of the lithium niobate thin film layer and outside the two waveguide structure layers respectively;

[0153] A cladding layer is provided on the surface of the lithium niobate thin film layer and between the first metal electrode layer and the second metal electrode layer;

[0154] A high dielectric constant layer is located on the first metal electrode layer, the second metal electrode layer and the cladding layer, and covers the first metal electrode layer, the second metal electrode layer and the cladding layer;

[0155] The substrate is a silicon dioxide substrate with a thickness of 3 μm;

[0156] The thickness of the lithium niobate (LiNbO3) thin film is 630 nm;

[0157] The silicon waveguide layer has a width of 200nm and a thickness of 150nm, and the slit width is 75-135nm. In this embodiment, the slit width range of 75-135nm will be parametrically scanned.

[0158] Both the first and second metal electrode layers are made of gold, and the spacing between the first and second metal electrode layers is 4.5 μm; the thickness of the first and second metal electrode layers is 1 μm.

[0159] The cladding is a silica cladding with a cross-section combining rectangular and trapezoidal shapes, and the silica cladding thickness is 0.8 μm;

[0160] The high dielectric constant layer is made of silicon nitride and has a thickness of 200 nm.

[0161] Specifically, Table 4 below shows the effect of slit width on transmission loss (dB / cm) and half-wave voltage length product (V·cm).

[0162] Table 4 - Effects of partial slit width on transmission loss and half-wave voltage length product

[0163] Slit width (nm) Transmission loss (dB / cm) Half-wave voltage-length product (V-cm) 75 0.14 1.898 80 0.15 1.885 85 0.16 1.871 90 0.17 1.86 95 0.17 1.849 100 0.18 1.838 105 0.18 1.83 110 0.19 1.819 115 0.2 1.811 120 0.21 1.803 125 0.22 1.796 130 0.23 1.788 135 0.24 1.783

[0164] The effect of different slit widths on the transmission loss (dB / cm) of the electro-optic modulator in Example 4 is as follows: Figure 10 As shown;

[0165] The effect of different slit widths on the half-wave voltage-length product (V·cm) of the electro-optic modulator in Example 4 is as follows: Figure 11 As shown;

[0166] from Figures 10-11 As can be seen, as the slit width increases, the transmission loss of the electro-optic modulator gradually increases, while the half-wave voltage-length product decreases accordingly; the suitable slit width is 120-130 nm.

[0167] Embodiment 5

[0168] The embodiment provides a slit type silicon-lithium niobate thin film based electro-optical modulator, comprising:

[0169] a substrate;

[0170] a lithium niobate (LiNbO3) thin film layer located on a surface of the substrate, and waveguide structure layers located on both sides of a surface of the lithium niobate thin film layer; each waveguide structure layer comprises two silicon waveguide layers, and a groove is arranged at a position corresponding to the silicon waveguide layer on the surface of the lithium niobate thin film layer, and each silicon waveguide layer is located in the groove;

[0171] a first metal electrode layer located on the surface of the lithium niobate thin film layer and between the two waveguide structure layers;

[0172] second metal electrode layers located on the surface of the lithium niobate thin film layer and outside the two waveguide structure layers;

[0173] a cladding layer located on the surface of the lithium niobate thin film layer and between the first metal electrode layer and the second metal electrode layer;

[0174] a high dielectric constant layer located on the first metal electrode layer, the second metal electrode layer and the cladding layer and covering the first metal electrode layer, the second metal electrode layer and the cladding layer;

[0175] The substrate is a silicon dioxide substrate, and the thickness is 3 μm.

[0176] The thickness of the lithium niobate (LiNbO3) thin film layer is 610 nm.

[0177] The width of the silicon waveguide layer is 195-215 nm, and the thickness is 150 nm. In the embodiment, the width of the silicon waveguide layer is parameterized and scanned in the range of 195-215 nm, and the slit width is 120 nm.

[0178] The materials of the first metal electrode layer and the second metal electrode layer are gold, the spacing between the first metal electrode layer and the second metal electrode layer is 4.5 μm, and the thickness of the first metal electrode layer and the second metal electrode layer is 1 μm.

[0179] The cladding layer is a silicon dioxide cladding layer, and the cross section of the silicon dioxide cladding layer is a combination of a rectangular and a trapezoidal silicon dioxide cladding layer. The thickness of the silicon dioxide cladding layer is 0.8 μm.

[0180] The material of the high dielectric constant layer is silicon nitride, and the thickness is 200 nm.

[0181] Specifically, Table 5 shows the influence of the width of the silicon waveguide layer on the transmission loss (dB / cm) and the half-wave voltage length product (V·cm).

[0182] Table 5 - Effect of width of silicon waveguide layer on transmission loss, half-wave voltage-length product

[0183] Si width (i.e., silicon waveguide layer width) (nm) Transmission loss (dB / cm) Half-wave voltage-length product (V-cm) 195 0.24 1.782 200 0.21 1.803 205 0.19 1.823 210 0.18 1.845 215 0.16 1.867

[0184] Effect of width of different silicon waveguide layers on transmission loss (dB / cm) of electro-optic modulator in Example 5 is shown in Figure 12

[0185] Effect of width of different silicon waveguide layers on half-wave voltage-length product (V cm) of electro-optic modulator in Example 5 is shown in Figure 13

[0186] As can be seen from Figures 12-13 , with the increase of width of silicon waveguide layer, the transmission loss of electro-optic modulator gradually decreases, while the half-wave voltage-length product increases; the suitable width of silicon waveguide layer is 195-200 nm.

[0187] Example 6

[0188] The embodiment provides an electro-optic modulator based on a slit type silicon-lithium niobate thin film, comprising:

[0189] a substrate;

[0190] a lithium niobate (LiNbO3) thin film layer located on the surface of the substrate, and waveguide structure layers are respectively arranged on both sides of the surface of the lithium niobate thin film layer; each waveguide structure layer comprises two silicon waveguide layers, and a groove is arranged on the surface of the lithium niobate thin film layer corresponding to the silicon waveguide layer, and each silicon waveguide layer is located in the groove;

[0191] a first metal electrode layer located on the surface of the lithium niobate thin film layer and between the two waveguide structure layers;

[0192] second metal electrode layers are respectively arranged on the surface of the lithium niobate thin film layer and outside the two waveguide structure layers;

[0193] a cladding layer arranged on the surface of the lithium niobate thin film layer and between the first metal electrode layer and the second metal electrode layer;

[0194] a high dielectric constant layer located on and covering the first metal electrode layer, the second metal electrode layer and the cladding layer;

[0195] The substrate is a silicon dioxide substrate, and the thickness is 3 μm.

[0196] The thickness of the lithium niobate (LiNbO3) thin film layer is 640 nm.

[0197] ​​The width of the silicon waveguide layer is 195nm, and the thickness is 150-165nm, and in this embodiment, the thickness of the silicon waveguide layer is parameterized scanning in the range of 150-165nm, and the slit width is 120nm.

[0198] The material of the first metal electrode layer and the second metal electrode layer is gold, and the spacing between the first metal electrode layer and the second metal electrode layer is 4.5μm; the thickness of the first metal electrode layer and the second metal electrode layer is 1μm.

[0199] The cladding layer is a silica cladding layer, and the cross section of the silica cladding layer is a combination of a rectangular and a trapezoidal silica cladding layer, and the thickness of the silica cladding layer is 0.8μm.

[0200] The material of the high dielectric constant layer is silicon nitride, and the thickness is 200nm.

[0201] Specifically, Table 6 below shows the effect of the thickness of the silicon waveguide layer on the transmission loss (dB / cm) and the half-wave voltage length product (V·cm).

[0202] Table 6-Effect of the thickness of the silicon waveguide layer on the transmission loss and the half-wave voltage length product

[0203] Si thickness (i.e., silicon waveguide layer thickness) (nm) Transmission loss (dB / cm) Half-wave voltage-length product (V-cm) 150 0.24 1.782 155 0.2 1.799 160 0.17 1.815 165 0.16 1.831

[0204] The effect of the thickness of the silicon waveguide layer on the transmission loss (dB / cm) of the electro-optical modulator in Example 6 is shown in Figure 14 ;

[0205] The effect of the thickness of the silicon waveguide layer on the half-wave voltage length product (V·cm) of the electro-optical modulator in Example 6 is shown in Figure 15 ;

[0206] As can be seen from Figures 14-15 , as the thickness of the silicon waveguide layer increases, the transmission loss of the electro-optical modulator gradually decreases, and the half-wave voltage length product increases accordingly; the appropriate thickness of the silicon waveguide layer is 150-155nm.

[0207] The technical advantages of the present application compared with the same type of conventional electro-optical modulator are:

[0208] Smaller effective mode area: due to the use of the slit waveguide, the light is better confined in the slit, and the energy is also concentrated in the center of the waveguide, reducing the lateral diffusion of the optical mode field.

[0209] Lower transmission loss: based on the natural limitation of the optical mode field and the characteristics of reducing loss of the slit waveguide, in the selection of the upper layer medium, a silica low refractive index cladding layer is additionally designed, which further limits the optical field and reduces the longitudinal diffusion of the optical mode field.

[0210] Stronger electric field intensity: compared with the traditional upper cover layer only low refractive index cladding layer electro-optic modulator, the embodiment of the application utilizes high dielectric constant material, so that the electric field intensity in the center of the waveguide is greatly enhanced, the electric field-optical field overlap factor is greatly increased, and finally a lower half-wave voltage length product (the half-wave voltage length product is directly inversely proportional to the modulation efficiency, the smaller the modulation efficiency, the higher the modulation efficiency) is obtained.

[0211] Higher modulation efficiency: through simulation software test, finally when the width of the silicon waveguide layer is 195nm, the thickness is 150nm, the slit width is 120nm, the spacing between the first metal electrode layer and the second metal electrode layer is 4.5μm, the thickness of the silicon dioxide cladding layer is 0.8μm, and the thickness of the high dielectric constant layer is 200nm, the transmission loss is reduced to 0.24dB / cm, and the half-wave voltage length product of 1.782V·cm is obtained.

[0212] It can be understood that the technical features of the above-described embodiments can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0213] The above is only the preferred embodiment of the present application, only the technical principle of the present application is specifically described, and these descriptions are only for explaining the principle of the present application, and cannot be explained as the limitation of the protection scope of the present application in any way. Based on the explanation here, any modification, equivalent replacement and improvement made within the spirit and principle of the present application, and other specific embodiments of the present application which can be thought by those skilled in the art without creative labor, should be included in the protection scope of the present application.

Claims

1. A slit-type silicon-lithium niobate thin film based electro-optic modulator, characterized by, The application relates to a lithium niobate film waveguide structure, which comprises the following parts: a substrate; a lithium niobate film layer on the surface of the substrate, wherein two waveguide structure layers are arranged on the surface of the lithium niobate film layer respectively; each waveguide structure layer comprises two silicon waveguide layers, and a groove is arranged on the surface of the lithium niobate film layer corresponding to the silicon waveguide layer, and each silicon waveguide layer is arranged in the groove; a first metal electrode layer is arranged on the surface of the lithium niobate film layer and between the two waveguide structure layers; a second metal electrode layer is arranged on the surface of the lithium niobate film layer and outside the two waveguide structure layers; a cladding layer is arranged on the surface of the lithium niobate film layer and between the first metal electrode layer and the second metal electrode layer; a high dielectric constant layer is arranged on the first metal electrode layer, the second metal electrode layer and the cladding layer and covers the first metal electrode layer, the second metal electrode layer and the cladding layer. The cladding layer is a silicon dioxide cladding layer, and the thickness of the silicon dioxide cladding layer is 1-3 mu m. The interval between the first metal electrode layer and the second metal electrode layer is 4-9 mu m. The material of the high dielectric constant layer is silicon nitride, and the thickness of the high dielectric constant layer is 50-300 nm. The slit width is 50-200 nm. The width of the silicon waveguide layer is 150-800 nm, and the thickness of the silicon waveguide layer is 150-400 nm. The thickness of the lithium niobate film layer is 600-700 nm.

2. The slit-type silicon-lithium niobate thin film based electro-optic modulator as claimed in claim 1, wherein, The material of the first metal electrode layer and the second metal electrode layer is gold.

3. The slit-type silicon-lithium niobate thin film based electro-optic modulator as claimed in claim 1, wherein, The thickness of the first metal electrode layer and the second metal electrode layer is 1-2 mu m.

4. The slit-type silicon-lithium niobate thin film based electro-optic modulator as claimed in claim 1, wherein, The substrate is a silicon dioxide substrate, and the thickness of the silicon dioxide substrate is 3-4 mu m.

5. The slit-type silicon-lithium niobate thin film based electro-optic modulator as claimed in claim 1, wherein, ​ 6. The slit-type silicon-lithium niobate thin film based electro-optic modulator as claimed in claim 1, wherein, ​ 7. The slit-type silicon-lithium niobate thin film based electro- optical modulator as claimed in claim 1, wherein, ​ 8. The slit-type silicon-lithium niobate thin film based electro- optical modulator as claimed in claim 1, wherein, ​ 9. The slit-type silicon-lithium niobate thin film based electro- optical modulator as claimed in claim 1, wherein, ​ 10. The slit-type silicon-lithium niobate thin film based electro- optical modulator as claimed in claim 1, wherein, ​

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