Electro-optical modulator and preparation method thereof

Abstract

The invention discloses an electro-optical modulator and a preparation method thereof. The electro-optical modulator comprises a substrate layer; the resin layer is arranged on one side of the substrate layer; the film lithium niobate layer is arranged on the side, away from the substrate layer, of the resin layer, and ridge waveguides are arranged on the surface of the part, close to the resin layer, of the film lithium niobate layer; and the metal electrode layer is arranged on the partial surface, far away from the resin layer, of the thin film lithium niobate layer. The thin-film lithium niobate electro-optical modulator with the metal electrode layer and the ridge waveguide in different planes is adopted, low half-wave voltage and low light absorption loss can be achieved, meanwhile, the speed and impedance matching of microwaves and light waves are achieved, and therefore microwave loss is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of electro-optic modulators, and in particular to an electro-optic modulator and a method for preparing the same. Background Art

[0002] Electro-optic modulators are key components for optical interconnects, RF photonic links, optical phased arrays, and optical information processing in data centers and high-performance computers, and play an important role in high-capacity fiber-optic communications and microwave photonic links. Among them, electro-optic modulators can convert electrical signals into optical signals to achieve low-loss processing and transmission. With the continuous increase in the baud rate of digital communications and the carrier frequency of analog links, the market needs electro-optic modulators with a 3dB bandwidth greater than 100GHz, an operating voltage close to the CMOS compatible voltage, and a linear response.

[0003] Currently, among various materials such as silicon on insulator, indium phosphate, polymer, silicon germanium and thin-film lithium niobate, thin-film lithium niobate is the preferred material for the next generation of high-speed modulation because of its high electro-optic coefficient, wide transmission window, low optical loss at telecommunication wavelength, large linear Pockels effect and good temperature stability.

[0004] However, the current electro-optic modulators based on thin-film lithium niobate generally adopt a structure of traveling wave electrodes and ridge waveguides on the same plane, that is, the traveling wave electrodes are located on both sides of the ridge waveguide. Although this structure can achieve a larger overlap factor between the electric field and the optical field, this structure will also lead to greater light absorption losses in the thin-film lithium niobate electro-optic modulator. Summary of the invention

[0005] The present application aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the purpose of the present application is to provide an electro-optic modulator and a method for manufacturing the same.

[0006] In a first aspect, the present application provides an electro-optic modulator.

[0007] In some embodiments, the electro-optic modulator comprises:

[0008] substrate layer;

[0009] a resin layer, the resin layer being arranged on one side of the substrate layer;

[0010] A thin-film lithium niobate layer, wherein the thin-film lithium niobate layer is arranged on a side of the resin layer away from the substrate layer, and a ridge waveguide is arranged on a portion of the surface of the thin-film lithium niobate layer close to the resin layer;

[0011] A metal electrode layer is provided on a surface of the thin-film lithium niobate layer that is away from the resin layer.

[0012] In some embodiments, the thickness of the resin layer is in the range of [3 μm, 500 μm];

[0013] And / or, the refractive index range of the resin layer is [1.4, 1.6].

[0014] In some embodiments, the ridge waveguide includes an input spot converter, a beam splitter, two optical waveguides, a beam combiner, and an output spot converter connected to each other;

[0015] Wherein, the beam splitter and the beam combiner respectively include multi-mode interference coupler structures.

[0016] In some embodiments, the interference region length of the multimode interference coupler structure ranges from [50 μm, 100 μm].

[0017] In some embodiments, the input spot converter and the output spot converter respectively include a double-layer lithium niobate tapered waveguide structure, and the resin layer covers the double-layer lithium niobate tapered waveguide structure;

[0018] The length range of the double-layer lithium niobate tapered waveguide structure is [0.3 μm, 1 μm].

[0019] In some embodiments, the metal electrode layer includes a traveling wave signal electrode and two traveling wave ground electrodes, and the two traveling wave ground electrodes are arranged in parallel on opposite sides of the traveling wave signal electrode;

[0020] The orthographic projections of the two optical waveguides on the substrate layer are located between the orthographic projections of the traveling wave signal electrode and the traveling wave ground electrode on the substrate layer.

[0021] In some embodiments, the width of the traveling wave signal electrode ranges from [3 μm, 30 μm];

[0022] And / or, the spacing between the traveling wave signal electrode and the traveling wave ground electrode is in the range of [4 μm, 10 μm];

[0023] And / or, the width of a single optical waveguide is in the range of [1 μm, 3 μm].

[0024] In some embodiments, the thin film lithium niobate layer has a thickness in the range of [200 nm, 1000 nm];

[0025] and / or, the etching depth of the ridge waveguide is in the range of [100 nm, 700 nm];

[0026] And / or, the thickness of the metal electrode layer is in the range of [0.2 μm, 2 μm].

[0027] In some embodiments, the substrate layer includes at least one of a quartz substrate layer or a silicon substrate layer.

[0028] The electro-optic modulator provided in the present application adopts a structure of skew traveling wave electrodes and ridge waveguides (hereinafter collectively referred to as skew structures), that is, the traveling wave electrodes and ridge waveguides are respectively located on both sides of the thin film lithium niobate layer, and are not on the same plane. Specifically, the traveling wave electrode is located on the side of the thin film lithium niobate layer away from the resin layer, and the ridge waveguide is located on the side of the thin film lithium niobate layer close to the resin layer, and the ridge waveguide is completely located in the resin layer.

[0029] Compared with the electro-optic modulator provided by the related art with a coplanar structure (the traveling wave electrode and the ridge waveguide structure in the electro-optic modulator are located in the same plane), the electro-optic modulator provided by the present application can not only reduce the absorption loss of the metal electrode layer to the transmitted light, allow a smaller electrode spacing, but also facilitate metal leads and radio frequency testing, and does not affect the transmission of light, does not introduce additional light loss, and has stronger compatibility. In addition, the electro-optic modulator with a heterogeneous structure provided by the present application is more flexible in the design of the electrode (traveling wave signal electrode, traveling wave ground electrode) structure in the metal electrode layer, which helps to realize a large-bandwidth electro-optic modulator.

[0030] In a second aspect, the present application provides a method for preparing an electro-optic modulator.

[0031] In some embodiments, the method comprises:

[0032] A ridge waveguide is formed by etching on a lithium niobate substrate;

[0033] The plane where the ridge waveguide of the lithium niobate substrate is located is bonded upside down on the substrate layer through a resin layer, and the side of the lithium niobate substrate away from the resin layer is thinned to form a thin-film lithium niobate layer;

[0034] A modulation metal electrode layer is deposited on a side of the thin film lithium niobate layer away from the resin layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0036] Figure 1A A schematic diagram of the structure of an electro-optic modulator provided in an embodiment of the present application;

[0037] Figure 1B A cross-sectional schematic diagram of an electro-optic modulator provided in an embodiment of the present application;

[0038] Figure 2A A schematic diagram of a partial structure of a thin-film lithium niobate layer of an electro-optic modulator provided in an embodiment of the present application;

[0039] Figure 2B A schematic diagram of the structure of a ridge waveguide of an electro-optic modulator provided in an embodiment of the present application;

[0040] Figure 2C A schematic diagram of the structure of a thin-film lithium niobate layer of an electro-optic modulator provided in an embodiment of the present application;

[0041] Figure 3A A modulation electric field diagram of an electro-optic modulator provided in an embodiment of the present application;

[0042] Figure 3B A schematic diagram of superposition of a modulated electric field and a propagated light field of an electro-optic modulator provided in an embodiment of the present application;

[0043] Figure 3C A schematic diagram of the superposition of the modulated electric field and the propagation light field of an electro-optic modulator provided for related technologies;

[0044] Figure 4A A schematic diagram of a curve showing the variation of light absorption loss of an electro-optic modulator with electrode spacing provided by the embodiments of the present application and related technologies respectively;

[0045] Figure 4B A schematic diagram of a curve showing a change in the half-wave voltage-length product of an electro-optic modulator provided by the embodiments of the present application and related technologies as a function of the electrode spacing;

[0046] Figure 5 A schematic diagram of a curve showing a characteristic impedance of an electro-optic modulator varying with frequency provided in an embodiment of the present application;

[0047] Figure 6 A schematic diagram of a curve showing the variation of microwave refractive index with frequency for an electro-optic modulator provided in an embodiment of the present application.

[0048] Among them, 1. substrate layer, 2. resin layer, 3. thin film lithium niobate layer, 4. metal electrode layer, 5. lithium niobate plate layer, 6. input spot mode converter, 7-beam splitter, 8-traveling wave signal electrode, 9-traveling wave ground electrode, 10-beam combiner, 11-output spot mode converter, 12-two-way optical waveguide. DETAILED DESCRIPTION

[0049] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0050] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred elements must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present application.

[0051] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0052] In this application, unless otherwise clearly specified and limited, the terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0053] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0054] Currently, electro-optic modulators are key components for optical interconnects, radio frequency photonic links, optical phase arrays, and optical information processing in data centers and high-performance computers, and play an important role in high-capacity fiber-optic communications and microwave photonic links. In these systems, electro-optic modulators are used to convert electrical signals into optical signals and achieve low-loss processing and transmission.

[0055] As the baud rate of digital communications and the carrier frequency of analog links continue to increase, the market begins to require electro-optic modulators with 3dB bandwidth greater than 100GHz, operating voltages close to CMOS compatible voltages, and linear response.

[0056] According to research, among various materials such as silicon on insulator, indium phosphate, polymer, silicon germanium and thin-film lithium niobate, thin-film lithium niobate can be used as the preferred material for high-speed modulation because of its high electro-optic coefficient, wide transmission window, low optical loss at telecommunication wavelength, large linear Pockels effect and good temperature stability.

[0057] However, the refractive index contrast of conventional lithium niobate waveguides based on titanium diffusion or proton exchange is less than 0.1, and they face problems such as large optical mode size, high bending loss, low power efficiency, and difficulty in integration. Photonic platforms based on silicon, polymers, and III-V compound semiconductors cannot simultaneously ensure large modulation bandwidth, low driving voltage, low insertion loss, and temperature stability.

[0058] With the development of technology, thin-film lithium niobate fabricated by crystal ion slicing and wafer bonding has been demonstrated to have great potential for realizing compact integrated devices.

[0059] Compared with traditional electro-optic modulators based on lithium niobate, the ridge waveguide in the electro-optic modulator based on thin-film lithium niobate has a high refractive index contrast, which can greatly improve the modulation efficiency of the electro-optic modulator. At present, the Mach-Zehnder modulator based on thin-film lithium niobate can already achieve the requirements of small size, large modulation bandwidth, and low half-wave voltage, but in order to meet the requirements of high-speed communication and large-capacity data transmission, the modulation performance of the electro-optic modulator still needs to be further improved.

[0060] However, electro-optic modulators based on thin-film lithium niobate generally use silicon as the substrate layer and are combined with other photonic platforms with relatively mature processing technology. However, the relative dielectric constant of silicon material is large, which will cause greater RF attenuation in the electro-optic modulator and make it difficult to achieve low half-wave voltage and large modulation bandwidth at the same time.

[0061] In electro-optic modulators, quartz has a lower dielectric constant than silicon. Quartz can also provide a low RF index for traveling wave electrodes and allow for larger electrode spacing and more uniform current distribution, thereby significantly reducing RF losses.

[0062] In the related art, the electro-optic modulator based on thin-film lithium niobate adopts the arrangement of traveling wave electrodes and ridge waveguides on the same plane, and the traveling wave electrodes are located on both sides of the ridge waveguide. Although this structure can make the electric field and the optical field have a larger overlap factor, it will also cause the electro-optic modulator to have a larger light absorption loss.

[0063] To solve at least one of the above problems, the present application provides an electro-optic modulator and a method for manufacturing the same.

[0064] In a first aspect, an embodiment of the present application provides an electro-optic modulator. Figure 1A A schematic diagram of the structure of an electro-optic modulator provided in an embodiment of the present application is shown in FIG. Figure 1B A cross-sectional schematic diagram of an electro-optic modulator provided in an embodiment of the present application is shown in FIG. Figure 1A and Figure 1B As shown, the electro-optic modulator comprises a substrate layer 1, a resin layer 2, a thin-film lithium niobate layer 3, and a metal electrode layer 4. The resin layer 2 is arranged on one side of the substrate layer 1, the thin-film lithium niobate layer 3 is arranged on the side of the resin layer 2 away from the substrate layer 1, and a ridge waveguide is arranged on a portion of the surface of the thin-film lithium niobate layer 3 close to the resin layer 2.

[0065] Furthermore, the metal electrode layer 4 is disposed on a portion of the surface of the thin-film lithium niobate layer 3 that is away from the resin layer 2 .

[0066] It should be noted that in the attached Figures 1A to 1B In 2A to 2C, X represents the length direction of the electro-optic modulator, Y represents the width direction of the electro-optic modulator, and Z represents the thickness direction of the electro-optic modulator.

[0067] The beneficial effects that can be achieved by the electro-optical modulator provided by the present application are described in detail below:

[0068] In the electro-optic modulator provided in the present application, the thin-film lithium niobate layer 3 with the ridge waveguide is bonded to the substrate layer 1 through the resin layer 2 with a low dielectric constant, so that the ridge waveguide is completely covered in the resin layer 2 with a low dielectric constant. Among them, the resin layer 2 can protect and bind the light field, and in the process of mode field diffusion, it is ensured that the light does not escape into the air, thereby achieving low-loss coupling.

[0069] In the electro-optic modulator provided by the present application, a ridge waveguide is prepared on a resin layer 2 with a low dielectric constant and a quartz substrate layer (or a silicon substrate layer) in combination with bonding and thinning processes, which can reduce microwave loss in the electro-optic modulator, and achieve speed matching between microwave signals and optical signals in the electro-optic modulator, as well as impedance matching between microwave signals and ridge waveguides, thereby significantly improving the bandwidth performance of the electro-optic modulator. In addition, the electro-optic modulator provided by the present application can simplify the preparation process while ensuring the high performance of the electro-optic modulator, which is helpful for realizing mass production of the electro-optic modulator.

[0070] Since the electro-optic modulator provided in the present application adopts the structure of skew traveling wave electrodes (traveling wave signal electrode 8 and traveling wave ground electrode 9) and ridge waveguide (hereinafter collectively referred to as skew structure), that is, the traveling wave electrode and ridge waveguide are respectively located on both sides of the thin film lithium niobate layer 3, and are not on the same plane. Specifically, Figure 1B As shown, the traveling wave electrode is located on the side of the thin film lithium niobate layer 3 away from the resin layer 2 , the ridge waveguide is located on the side of the thin film lithium niobate layer 3 close to the resin layer 2 , and the ridge waveguide is completely located in the resin layer 2 .

[0071] Compared with the electro-optic modulator in the related art in which the waveguide is exposed to the air, the electro-optic modulator provided in the present application can not only reduce the losses such as light refraction and light scattering of the ridge waveguide, improve the light transmission efficiency, and enable the ridge waveguide to transmit signals over a longer distance, but also effectively reduce the interference of the external environment, thereby enhancing the stability and reliability of the electro-optic modulator.

[0072] The refractive index range of the resin layer 2 in the present application is [1.4, 1.6]. The use of a resin layer 2 within this refractive index range can not only enhance the concentration of the ridge waveguide light mode and reduce coupling loss, but also improve the compatibility of the electro-optical modulator, making the design of the electro-optical modulator more flexible, thereby facilitating the integration of other optoelectronic devices.

[0073] In addition, the electro-optic modulator provided by the present application adopts a heteroplanar structure. Compared with the electro-optic modulator adopting a coplanar structure in the related art, the electro-optic modulator provided by the present application can not only reduce the absorption loss of the metal electrode layer 4 to the transmitted light, allow a smaller electrode spacing, but also facilitate metal leads and radio frequency testing, and does not affect the transmission of light, does not introduce additional light loss, and has stronger compatibility. The electro-optic modulator adopting a heteroplanar structure provided by the present application is more flexible in the design of the electrode structure in the metal electrode layer 4, which helps to realize a large-bandwidth electro-optic modulator.

[0074] In the above embodiments, the substrate layer 1 includes at least one of a quartz substrate layer or a silicon substrate layer.

[0075] Preferably, the substrate layer 1 is a quartz substrate layer with a low dielectric constant.

[0076] The present application uses a quartz substrate layer with a lower relative dielectric constant as the substrate layer 1 of the electro-optic modulator, thereby ensuring the speed matching of microwaves and light waves in the electro-optic modulator, while taking into account transmission line impedance matching and modulating low driving voltage.

[0077] In the embodiment of the present application, the thickness range of the resin layer 2 is [3μm, 500μm]. For example, in one example, the thickness of the resin layer 2 can be 3μm, 30μm, 90μm, 250μm, 300μm, 450μm, or 500μm.

[0078] By limiting the thickness of the resin layer 2 within the above range, the present application can make the resin layer 2 effectively bond the substrate layer 1 with the thin film lithium niobate layer 3 with the ridge waveguide, and further ensure that the ridge waveguide can be completely covered in the resin layer, so that the resin layer 2 plays a role in protecting and confining the light field.

[0079] In the embodiment of the present application, the refractive index of the resin layer 2 is in the range of [1.4, 1.6]. For example, in one example, the refractive index of the resin layer 2 can be 1.4, 1.44, 1.48, 1.52, 1.56, 1.6. By limiting the refractive index of the resin layer 2 to the above range, the resin layer 2 can have the function of protecting and binding the light field.

[0080] In the embodiments of the present application, the specific type of material of the above-mentioned resin layer 2 is not particularly limited, and those skilled in the art can select it according to actual needs. As some specific embodiments, the material of the above-mentioned resin layer 2 includes at least one of epoxy acrylate, polyurethane acrylic resin, polyester acrylic resin, amino acrylic resin, acryloxy resin, methacryloxy resin, vinyl resin and allyl resin.

[0081] Figure 2A A schematic diagram of a partial structure of a thin-film lithium niobate layer of an electro-optic modulator provided in an embodiment of the present application, Figure 2B A schematic diagram of the structure of a ridge waveguide of an electro-optic modulator provided in an embodiment of the present application, Figure 2C A schematic diagram of the structure of a thin-film lithium niobate layer of an electro-optic modulator provided in an embodiment of the present application is shown in FIG. FIG. 2A to FIG. 2C As shown, in an embodiment of the present application, the ridge waveguide includes an input spot converter 6, a beam splitter 7, two optical waveguides 12, a combiner 10 and an output spot converter 11, which are connected in sequence. Among them, the input spot converter 6 is terminated with the input optical fiber for spot matching of the input light. The 1×2 beam splitter 7 divides the input light into two equal-power light paths through a multimode interference coupler structure, and transmits them to the Mach-Zehnder modulation structure part. The 2×1 combiner 10 combines the two modulated lights. The output spot converter 11 is connected to the output optical fiber for spot matching of the output light and output. The optical fiber is directly terminated at the spot converters at the input and output ends of the electro-optic modulator.

[0082] Furthermore, the beam splitter and the beam combiner are respectively multi-mode interference coupler structures.

[0083] In the embodiment of the present application, the interference region length of the multimode interference coupler structure ranges from [50 μm, 100 μm]. For example, in one example, the interference region length of the multimode interference coupler structure can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 90 μm, 100 μm.

[0084] In the embodiment of the present application, the input spot converter 6 and the output spot converter 11 are both double-layer lithium niobate tapered waveguide structures, and the resin layer 2 covers the double-layer lithium niobate tapered waveguide structure.

[0085] The present application can realize low-loss conversion of the large mode field of the optical fiber to the small mode field of the ridge waveguide of the thin film lithium niobate layer 3 by setting the input spot mode converter 6 and the output spot mode converter 11 as a double-layer tapered waveguide structure.

[0086] Furthermore, the length range of the double-layer lithium niobate tapered waveguide structure is [0.3 μm, 1 μm].

[0087] For example, in one example, the length of the double-layer lithium niobate tapered waveguide structure can be 0.3 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm.

[0088] In some embodiments, refer to the attached Figure 1B The metal electrode layer 4 includes a traveling wave signal electrode 8 and two traveling wave grounding electrodes 9 . The two traveling wave grounding electrodes 9 are arranged in parallel on opposite sides of the traveling wave signal electrode 8 .

[0089] Furthermore, the orthographic projections of the two optical waveguides 12 on the substrate layer 1 are located between the orthographic projections of the traveling wave signal electrode 8 and the traveling wave ground electrode 9 on the substrate layer 1 .

[0090] In the embodiment of the present application, the width of the traveling wave signal electrode 8 ranges from 3 μm to 30 μm. For example, in one example, the width of the traveling wave signal electrode 8 may be 3 μm, 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm.

[0091] Further, the spacing between the traveling wave signal electrode 8 and the traveling wave ground electrode 9 ranges from [4 μm, 10 μm]. For example, in one example, the spacing between the traveling wave signal electrode 8 and the traveling wave ground electrode 9 can be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0092] In the embodiment of the present application, the width of a single optical waveguide (optical waveguide 12a or optical waveguide 12b) ranges from [1 μm, 3 μm]. For example, in one example, the width of a single optical waveguide (optical waveguide 12a or optical waveguide 12b) may be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm.

[0093] In the embodiment of the present application, the thickness of the thin film lithium niobate layer 3 is in the range of [200nm, 1000nm]. For example, in one example, the thickness of the thin film lithium niobate layer 3 can be 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm.

[0094] In the embodiment of the present application, the etching depth of the ridge waveguide ranges from [100 nm to 700 nm]. For example, in one example, the etching depth of the ridge waveguide may be 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, or 700 nm.

[0095] In the embodiment of the present application, the thickness of the metal electrode layer 4 is in the range of [0.2 μm, 2 μm]. For example, in one example, the thickness of the metal electrode layer 4 can be 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, or 2 μm.

[0096] In the embodiment of the present application, the specific process of the electro-optical modulator performing electro-optical modulation is as follows:

[0097] The input spot converter 6 is connected to the input optical fiber end (not shown), and the input light is transmitted into the input spot converter 6 from the input optical fiber.

[0098] The input mode spot converter 6 couples the input light to the beam splitter 7 with low loss, and through the multimode interference coupler structure, divides a beam of light into two beams of equal power and enters the two optical waveguides 12. A modulation signal is applied to the metal electrode layer 4 on the thin film lithium niobate layer 3 to modulate the light in the two optical waveguides 12.

[0099] Furthermore, the traveling wave signal electrode 8 is connected to an external signal terminal (not shown), and the two traveling wave grounding electrodes 9 are respectively connected to external grounding terminals (not shown). The two modulated light beams are combined into one modulated light beam through a beam combiner 10 and enter the output mode spot converter 11.

[0100] The present application realizes mode field matching through a double-layer tapered waveguide structure, and couples the output light into the output optical fiber with low loss.

[0101] In a second aspect, an embodiment of the present application provides a method for preparing an electro-optic modulator. The method comprises the following steps:

[0102] S100. Etching to form a ridge waveguide on a lithium niobate substrate.

[0103] Furthermore, a ridge waveguide is formed by etching on the lithium niobate substrate, including: etching an input spot converter 6, a beam splitter 7, a modulated two-path optical waveguide 12, a beam combiner 10 and an output spot converter 11 on the lithium niobate substrate.

[0104] S200, the plane where the ridge waveguide of the lithium niobate substrate is located is bonded to the substrate layer by a resin layer, and the lithium niobate substrate is thinned on the side away from the resin layer to form a thin film lithium niobate layer.

[0105] In this step, the plane where the ridge waveguide of the lithium niobate substrate is located is bonded to the substrate layer 1 by means of the resin layer 2, and then the lithium niobate substrate is thinned on the side of the lithium niobate substrate away from the resin layer 2 to form a final thin film lithium niobate layer 3.

[0106] S300, depositing a modulated metal electrode layer on a side of the thin film lithium niobate layer away from the resin layer.

[0107] Furthermore, a modulated metal electrode layer 4 is deposited on the side of the thin film lithium niobate layer 3 away from the resin layer 2, including: a modulated traveling wave signal electrode 8 and two traveling wave grounding electrodes 9 are deposited on the side of the thin film lithium niobate layer 3 away from the resin layer 2, wherein the two traveling wave grounding electrodes 9 are arranged in parallel on opposite sides of the traveling wave signal electrode 8, and the orthographic projections of the two optical waveguides 12 on the substrate layer 1 are located between the orthographic projections of the traveling wave signal electrode 8 and the traveling wave grounding electrode 9 on the substrate layer 1.

[0108] Based on the above embodiments, the present application also provides some specific embodiments, as described below:

[0109] Example 1

[0110] This embodiment provides an electro-optic modulator, and the preparation method thereof is as follows:

[0111] 1) First, a ridge waveguide structure is prepared on a lithium niobate substrate, including: etching an input spot converter, a beam splitter, modulating two-path optical waveguides, a beam combiner and an output spot converter.

[0112] 2) The surface of the lithium niobate layer with the ridge waveguide structure is bonded to a quartz substrate by an epoxy acrylate resin layer, and the lithium niobate substrate away from the resin layer is thinned to a film thickness, and the epoxy acrylate forms an epoxy acrylate resin layer.

[0113] 3) A metal electrode layer is deposited on the side of the thin-film lithium niobate layer away from the resin layer, including a traveling wave signal electrode and two traveling wave grounding electrodes, wherein the two traveling wave grounding electrodes are arranged in parallel on opposite sides of the traveling wave signal electrode; and the orthographic projections of the two optical waveguides on the substrate layer are located between the orthographic projections of the traveling wave signal electrode and the traveling wave grounding electrode on the substrate layer.

[0114] Among them, the thickness of the epoxy acrylate resin layer 2 is 10μm; the thickness of the thin film lithium niobate layer 3 is 700nm, wherein the depth of the ridge waveguide etched in the thin film lithium niobate layer 3 is 370nm. The width of the two optical waveguides 12 is 2μm. Under the isolation of the resin layer 2 with a refractive index of 1.5, the electrode spacing between the traveling wave signal electrode 8 and the traveling wave grounding electrode 9 is 6μm, and the thickness of the metal electrode layer 4 is 0.5μm. The present application adopts a traveling wave signal electrode 8 with a width of 20μm and a traveling wave grounding electrode 9 with a width of 120μm to reduce microwave loss. Furthermore, the waveguide lengths of the input spot converter and the output spot converter structures are 0.5μm, respectively.

[0115] Example 2

[0116] This embodiment provides an electro-optic modulator, and its preparation method is basically the same as that of Embodiment 1, except that:

[0117] The thickness of the epoxy acrylate resin layer 2 is 5 μm; the thickness of the thin-film lithium niobate layer 3 after thinning is 600 nm, wherein the depth of the etched ridge waveguide is 300 nm.

[0118] Example 3

[0119] This embodiment provides an electro-optic modulator, and its preparation method is basically the same as that of Embodiment 1, except that:

[0120] The widths of the two optical waveguides are 1.5 μm respectively. Under the isolation of the resin layer 2 with a refractive index of 1.5, the electrode spacing between the traveling wave signal electrode 8 and the traveling wave grounding electrode 9 is reduced to 5 μm. The thickness of the metal electrode layer 4 is 0.8 μm. A traveling wave signal electrode 8 with a width of 10 μm and a traveling wave grounding electrode 9 with a width of 120 μm are used to reduce microwave loss. The input spot converter structure waveguide length and the output spot converter structure waveguide length are 0.8 μm.

[0121] Figure 3A A modulation electric field diagram of an electro-optic modulator provided in Example 1 of the present application, Figure 3B A schematic diagram of superposition of a modulated electric field and a propagation light field of an electro-optic modulator provided in Example 1 of the present application, Figure 3C A schematic diagram of the superposition of the modulated electric field and the propagation light field of an electro-optic modulator provided for related technologies, Figure 4A Schematic diagram of the curves showing the light absorption loss of the electro-optic modulator provided by Embodiment 1 of the present application and the related art respectively as a function of the electrode spacing, Figure 4B The schematic diagram of the curve of the half-wave voltage-length product of the electro-optic modulator provided by the embodiment of the present application and the related art respectively with the variation of the electrode spacing is as follows: FIG. 3A to FIG. 3C as well as Figure 4A and Figure 4BAs shown, the modulation electric field and propagation light field of an electro-optical modulator provided by the related art have a larger overlap factor, but also generate a larger light absorption loss.

[0122] Compared with the electro-optic modulator provided by the related art, the electro-optic modulator provided by the present application has a different planar structure that can reduce the absorption loss of the metal electrode layer to the transmitted light, allowing for a smaller electrode spacing; it is convenient for metal leads and radio frequency testing without affecting the transmission of light and introducing additional light loss. In addition, it has stronger compatibility, is more flexible in the design of the electrode structure, and is more conducive to the realization of a large-bandwidth electro-optic modulator.

[0123] Figure 5 A schematic diagram of a curve showing the variation of characteristic impedance of an electro-optic modulator with frequency provided in Example 1 of the present application, Figure 6 A schematic diagram of a curve showing the variation of microwave refractive index with frequency of an electro-optic modulator provided in Example 1 of the present application, such as Figure 5 and Figure 6 As shown, an electro-optic modulator provided in Example 1 of the present application has a characteristic impedance close to 50Ω in the high-frequency range, which meets the requirement of matching the characteristic impedance of the transmission line with the impedance of the external driving circuit and the load. At the same time, in the high-frequency range, the microwave refractive index is close to the refractive index of the light wave group, which meets the speed matching requirement and has the conditions for realizing high-speed modulation.

[0124] The modulated electric field diagram, characteristic impedance diagram and microwave refractive index diagram of Examples 2 and 3 provided in this application are similar to those of Example 1 and are not repeated here. It can be seen from the modulated electric field diagram, characteristic impedance comparison diagram and microwave refractive index and light wave group refractive index comparison diagram of Examples 2-3 that the lithium niobate thin film modulator of Examples 2-3 has a characteristic impedance close to 50Ω in the high frequency range, which meets the requirement of matching the characteristic impedance of the transmission line with the impedance of the external driving circuit and the load. At the same time, in the high frequency range, the microwave refractive index is close to the light wave group refractive index, which meets the speed matching requirement and has the conditions for realizing high-speed modulation.

[0125] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0126] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An electro-optic modulator, characterized in that: include: substrate layer; a resin layer, the resin layer being arranged on one side of the substrate layer; A thin-film lithium niobate layer, wherein the thin-film lithium niobate layer is arranged on a side of the resin layer away from the substrate layer, and a ridge waveguide is arranged on a portion of the surface of the thin-film lithium niobate layer close to the resin layer; A metal electrode layer is provided on a surface of the thin-film lithium niobate layer that is away from the resin layer.

2. The electro-optic modulator according to claim 1, characterized in that: The thickness of the resin layer is in the range of [3 μm, 500 μm]; And / or, the refractive index range of the resin layer is [1.4, 1.6].

3. The electro-optic modulator according to claim 1, characterized in that: The ridge waveguide includes an input spot mode converter, a beam splitter, two optical waveguides, a beam combiner and an output spot mode converter connected to each other; Wherein, the beam splitter and the beam combiner respectively include multi-mode interference coupler structures.

4. The electro-optic modulator according to claim 3, characterized in that: The interference region length range of the multimode interference coupler structure is [50 μm, 100 μm].

5. The electro-optic modulator according to claim 3, characterized in that: The input spot converter and the output spot converter respectively include a double-layer lithium niobate tapered waveguide structure, and the resin layer covers the double-layer lithium niobate tapered waveguide structure; The length range of the double-layer lithium niobate tapered waveguide structure is [0.3 μm, 1 μm].

6. The electro-optic modulator according to claim 3, characterized in that: The metal electrode layer includes a traveling wave signal electrode and two traveling wave grounding electrodes, and the two traveling wave grounding electrodes are arranged in parallel on opposite sides of the traveling wave signal electrode; The orthographic projections of the two optical waveguides on the substrate layer are located between the orthographic projections of the traveling wave signal electrode and the traveling wave ground electrode on the substrate layer.

7. The electro-optic modulator according to claim 6, characterized in that The width range of the traveling wave signal electrode is [3 μm, 30 μm]; And / or, the spacing between the traveling wave signal electrode and the traveling wave ground electrode is in the range of [4 μm, 10 μm]; And / or, the width of a single optical waveguide is in the range of [1 μm, 3 μm].

8. The electro-optic modulator according to any one of claims 1 to 7, characterized in that: The thickness of the thin film lithium niobate layer is in the range of [200nm, 1000nm]; and / or, the etching depth of the ridge waveguide is in the range of [100 nm, 700 nm]; And / or, the thickness of the metal electrode layer is in the range of [0.2 μm, 2 μm].

9. The electro-optic modulator according to any one of claims 1 to 7, characterized in that: The substrate layer includes at least one of a quartz substrate layer or a silicon substrate layer.

10. A method for preparing an electro-optic modulator, characterized in that: include: A ridge waveguide is formed by etching on a lithium niobate substrate; The plane where the ridge waveguide of the lithium niobate substrate is located is bonded upside down on the substrate layer through a resin layer, and the side of the lithium niobate substrate away from the resin layer is thinned to form a thin-film lithium niobate layer; A modulation metal electrode layer is deposited on a side of the thin film lithium niobate layer away from the resin layer.

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