Direct-current bias embedded thin-film lithium niobate electro-optical modulator and preparation method thereof

Abstract

The invention discloses a direct-current bias embedded thin-film lithium niobate electro-optical modulator and a preparation method of the direct-current bias embedded thin-film lithium niobate electro-optical modulator. A lithium niobate optical waveguide for transmitting optical signals is formed on the upper surface of the substrate layer; a cladding layer on the base layer; the T-structure electrode on the top surface of the cladding is used for modulating an optical signal through a radio frequency modulation signal; the traveling wave electrode structure on the top surface of the cladding is used for loading a radio frequency modulation signal to the capacitance load type T structure electrode; the direct current bias metal plate on the top surface of the cladding is used for loading a direct current bias signal to the traveling wave electrode structure; the traveling wave electrode structure comprises two pairs of grounding electrodes arranged in a stacked mode and a pair of signal electrodes arranged in a stacked mode. And the direct current bias metal plate is electrically connected with the signal lower layer electrode or one of the grounding lower layer electrodes. According to the thin film lithium niobate electro-optical modulator, low driving voltage, low microwave loss and large electro-optical bandwidth are achieved under a silicon-based substrate, an embedded structure for direct current bias point regulation and control is achieved, and low-power and high-speed direct current bias point regulation is achieved.

Description

Technical Field

[0001] The present invention relates to the fields of optical communication, optical sensing and optical integration, and particularly relates to a thin-film lithium niobate electro-optic modulator with embedded DC bias and a preparation method thereof. Background Art

[0003] Currently, silicon-based optoelectronic integration technology with silicon as the substrate has developed rapidly due to its advantages such as low cost, excellent passive performance, and CMOS process compatibility. However, in the field of modulators, since silicon material has almost no electro-optic effect, only the free carrier dispersion effect can be used to achieve the electro-optic modulation function, and the modulation rate cannot reach a very high speed (ns level). In addition to the limitation of the modulation rate, the bandwidth of a pure-silicon electro-optic modulator can only reach about 40 GHz, far from meeting the current requirements of 100G, 400G, and even the future 1.6T modulation rates. Therefore, electro-optic modulators based on thin-film lithium niobate with large bandwidth, low power consumption, low insertion loss, and high speed have received extensive attention in recent years. For an electro-optic modulator, the DC bias point is one of the important parameters for the normal operation of the modulator. The current mainstream method is to use a thermo-optic phase shifter on a section of silicon waveguide to achieve the regulation of the DC bias. However, using such a structure will instead increase the coupling loss, power consumption, and device length, and the modulation speed is slow, which is contrary to the goals of low power consumption, low loss, and more compactness. Therefore, how to achieve the embedded adjustment of the DC bias point is also very important.

[0004] With the continuous in-depth research on thin-film lithium niobate modulators, the attention in related fields has also continued to rise. In 2018, a research team at Harvard University reported the first CMOS-driven thin-film lithium niobate electro-optic modulator in the Nature journal. This modulator achieved a driving voltage of 1.4 V and an electro-optic bandwidth of up to 45 GHz, showing the characteristics of large bandwidth and low power consumption. One year later, our research group proposed the first silicon-based heterogeneous integrated thin-film lithium niobate electro-optic modulator in Nature Photonics and successfully achieved a driving voltage of 5.1 V and an electro-optic bandwidth of up to 70 GHz, demonstrating the feasibility of heterogeneous integration of thin-film lithium niobate electro-optic modulators on a silicon-based platform. In 2024, our research group published a silicon-based thin-film lithium niobate modulator with a backside hollowing, which achieved high-speed and stable electro-optic modulation by using a capacitive load T-shaped electrode and a substrate hollowing method. In order to further reduce the volume of the electro-optic modulator, reduce the loss and power consumption, and be able to quickly adjust the DC bias point, we propose a new type of silicon-based thin-film lithium niobate electro-optic modulator with embedded DC bias on this basis to further promote the performance improvement of this modulator. Summary of the Invention

[0005] To solve the problems in the background technology that the DC bias point modulation structure increases the device length and loss, has slow adjustment, and high power consumption, the present invention proposes a thin-film lithium niobate electro-optic modulator with embedded DC bias and its manufacturing method. The electro-optic modulator of the present invention has the characteristics of low-voltage drive and high bandwidth, and at the same time realizes low-power and high-speed embedded adjustment of DC bias.

[0006] The technical solution adopted by the present invention is as follows:

[0007] I. A thin-film lithium niobate electro-optic modulator with embedded DC bias

[0008] The thin-film lithium niobate electro-optic modulator includes:

[0009] A base layer, on the upper surface of which a lithium niobate optical waveguide for transmitting optical signals is formed, and the lithium niobate optical waveguide includes a Mach-Zehnder structure;

[0010] A cladding layer, covering the base layer;

[0011] A capacitive load type T-structure electrode, arranged on the top surface of the cladding layer, for modulating optical signals through a radio frequency modulation signal;

[0012] A traveling wave electrode structure, arranged on the top surface of the cladding layer, for loading a radio frequency modulation signal onto the capacitive load type T-structure electrode;

[0013] A DC bias metal plate, arranged on the top surface of the cladding layer, electrically connected to the traveling wave electrode structure, for loading a DC bias signal onto the traveling wave electrode structure.

[0014] Specifically, the traveling wave electrode structure includes two pairs of upper and lower grounded upper electrodes and grounded lower electrodes, and a pair of upper and lower signal upper electrodes and signal lower electrodes. Optionally, the DC bias metal plate is electrically connected to the signal lower electrode or one of the grounded lower electrodes.

[0015] Further, the lithium niobate modulator further includes an insulating layer for realizing embedded adjustment of DC bias.

[0016] The embedded adjustment of DC bias includes the following two implementation methods:

[0017] ① When the signal lower electrode and the signal upper electrode are separated by an insulating layer and the grounded lower electrode is connected to the grounded upper electrode, the DC bias metal plate is electrically connected to the signal lower electrode.

[0018] ② When the grounded lower electrode and the grounded upper electrode are separated by an insulating layer and the signal lower electrode is connected to the signal upper electrode, the DC bias metal plate is electrically connected to one of the grounded lower electrodes, and the two grounded lower electrodes are electrically connected.

[0019] Preferably, the insulating layer covers the capacitive load type T-structure electrode.

[0020] Preferably, the signal electrode is arranged above the inner sides of the two optical waveguide arms of the Mach-Zehnder structure, and the two grounded electrodes are respectively arranged above the outer sides of the two optical waveguide arms.

[0021] Specifically, a plurality of capacitive load type T-structure electrodes are arranged above each optical waveguide arm of the Mach-Zehnder structure, and the capacitive load type T-structure electrodes are arranged at equal intervals along the length direction of the lower optical waveguide arm; the capacitive load type T-structure electrode is mainly composed of a grounded T-shaped electrode and a signal T-shaped electrode, and the grounded T-shaped electrode and the signal T-shaped electrode are symmetrically arranged with respect to the lower optical waveguide arm, the grounded T-shaped electrode is connected to the grounded lower layer electrode outside the optical waveguide arm, and the signal T-shaped electrode is connected to the signal lower layer electrode.

[0022] Preferably, the base layer includes a substrate, a buried oxide layer, and a lithium niobate layer arranged from bottom to top. The top surface of the lithium niobate layer is etched to form a lithium niobate optical waveguide. The substrate is provided with two hollowing structures, and the two hollowing structures are respectively arranged below the two optical waveguide arms of the Mach-Zehnder structure. The hollowing structures are used to reduce the effective refractive index of the microwave signal.

[0023] Preferably, the lithium niobate optical waveguide is mainly composed of an input grating coupler, a 1*2 beam splitter, a Mach-Zehnder structure, a 2*1 beam splitter, and an output coupling grating connected in sequence.

[0024] II. A preparation method applied to the above thin film lithium niobate electro-optic modulator

[0025] The preparation method includes the following steps:

[0026] S1) Form a lithium niobate optical waveguide on the upper surface of the lithium niobate on insulator wafer by etching;

[0027] S2) Deposit a cladding layer above the lithium niobate layer containing the lithium niobate optical waveguide;

[0028] S3) Adopt a sputtering or evaporation method to form a grounded T-shaped electrode, a signal T-shaped electrode, a DC bias metal plate, a grounded lower layer electrode, and a signal lower layer electrode on the cladding layer to form a lower electrode layer;

[0029] S4) Deposit an insulating layer on the lower electrode layer;

[0030] S5) Use photolithography or electron beam exposure to prepare a micro-nano pattern on the insulating layer, and use etching to etch away the insulating layer at the grounded lower layer electrode or the signal lower layer electrode;

[0031] S6) Form the upper ground electrode and the upper signal electrode by sputtering or evaporation.

[0032] S7) Sequentially process the partial substrate structure under the buried oxide layer by photolithography or electron beam lithography and etching methods to obtain a hollowed-out structure, completing the preparation of the thin-film lithium niobate electro-optic modulator.

[0033] III. An electro-optic modulation system using the above thin-film lithium niobate electro-optic modulator

[0034] A light source, connected to the input grating coupler of the electro-optic modulator, for inputting the light to be modulated into the electro-optic modulator.

[0035] A DC source, with its output terminal electrically connected to the DC bias metal plate of the electro-optic modulator, for inputting a DC bias signal into the electro-optic modulator.

[0036] An AC source, with its output terminal electrically connected to the input terminal of the upper signal electrode of the electro-optic modulator, for inputting a radio frequency modulation signal into the electro-optic modulator.

[0037] Compared with the prior art, the present invention has the following remarkable advantages and beneficial effects:

[0038] 1. In the present invention, the integratability and application scope of the electro-optic modulator are improved. The modulator with silicon as the substrate material can be effectively integrated with the CMOS-compatible silicon-based optoelectronic platform, expanding the application scenarios of the electro-optic modulator. At the same time, when this electro-optic modulator structure is applied to the silicon-based heterogeneous integration platform, the feasibility of applying this electro-optic modulator to other fields such as optical communication is also improved.

[0039] 2. The present invention has the characteristics of low-voltage drive and high bandwidth. This thin-film lithium niobate electro-optic modulator achieves an electro-optic bandwidth of up to more than 120 GHz at a low drive voltage of 2V on a silicon-based substrate.

[0040] 3. The present invention realizes low-power DC bias regulation. While applying a microwave signal for modulation in the traveling-wave signal electrode formed by the upper ground electrode and the upper signal electrode of this DC bias-embedded thin-film lithium niobate electro-optic modulator, the regulation of the DC bias point is achieved by applying a DC bias voltage on the DC metal plate. Among them, the lower ground electrode and the upper ground electrode or the lower signal electrode and the upper signal electrode are insulated from each other, so the applied DC bias voltage will not generate current, that is, no power consumption is generated, realizing low-power DC bias regulation.

[0041] 4. The present invention realizes high-speed DC bias adjustment. This DC bias adjustment method is achieved by applying a DC bias voltage between the DC bias electrode and the traveling wave ground electrode to control the DC bias point, that is, the voltage is applied to the opposite capacitive load type T-structure electrodes, and the electro-optic effect of the lithium niobate material is directly utilized for adjustment. Due to the large electro-optic coefficient of the lithium niobate material, high-speed DC bias adjustment can be realized. Description of the Drawings

[0042] Figure 1 is a top view of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0043] Figure 2 is a flowchart of the preparation method of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0044] Figure 3 is a cross-sectional view of the structure obtained in step 1 in the preparation method of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0045] Figure 4 is a cross-sectional view of the structure obtained in step 2 in the preparation method of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0046] Figure 5 is a cross-sectional view of the structure obtained in step 3 in the preparation method of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0047] Figure 6 is a cross-sectional view of the structure obtained in step 4 in the preparation method of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0048] Figure 7 is a cross-sectional view of the structure obtained in step 5 in the preparation method of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0049] Figure 8 is a cross-sectional view of the structure obtained in step 6 in the preparation method of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0050] Figure 9 is a cross-sectional view of the structure obtained in step 7 in the preparation method of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0051] Figure 10 is a cross-sectional view of the structure obtained in step 8 in the preparation method of the electro-optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0052] Figure 11 It is a partial view of the capacitive load type T - structure electrode of the electro - optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention.

[0053] Figure 12 It is a schematic circuit diagram of the electro - optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention, loading radio frequency signals and DC signals;

[0054] Figure 13 It is a voltage relationship curve applied on the modulator of the electro - optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0055] Figure 14 It is a voltage - frequency response curve on the modulator of the electro - optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0056] Figure 15 It is a microwave loss curve on the modulator of the electro - optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention;

[0057] Figure 16 It is an electro - optic response curve on the modulator of the electro - optic modulator with the connection of the upper and lower ground electrodes and the insulation structure of the upper and lower signal electrodes in the present invention.

[0058] Figure 17 It is a top view of the electro - optic modulator with the insulation of the upper and lower ground electrodes and the connection of the upper and lower signal electrodes in the present invention;

[0059] Figure 18 It is a flowchart of the preparation method of the electro - optic modulator with the insulation of the upper and lower ground electrodes and the connection of the upper and lower signal electrodes in the present invention;

[0060] Figure 19 It is a cross - sectional view of the structure obtained in step 1 in the preparation method of the electro - optic modulator with the insulation of the upper and lower ground electrodes and the connection of the upper and lower signal electrodes in the present invention;

[0061] Figure 20 It is a cross - sectional view of the structure obtained in step 2 in the preparation method of the electro - optic modulator with the insulation of the upper and lower ground electrodes and the connection of the upper and lower signal electrodes in the present invention;

[0062] Figure 21 It is a cross - sectional view of the structure obtained in step 3 in the preparation method of the electro - optic modulator with the insulation of the upper and lower ground electrodes and the connection of the upper and lower signal electrodes in the present invention;

[0063] Figure 22It is a cross-sectional view of the structure obtained in step 4 of the preparation method of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention;

[0064] Figure 23 It is a cross-sectional view of the structure obtained in step 5 of the preparation method of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention;

[0065] Figure 24 It is a cross-sectional view of the structure obtained in step 6 of the preparation method of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention;

[0066] Figure 25 It is a cross-sectional view of the structure obtained in step 7 of the preparation method of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention;

[0067] Figure 26 It is a cross-sectional view of the structure obtained in step 8 of the preparation method of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention;

[0068] Figure 27 It is a partial view of the capacitive load type T-structure electrode of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention;

[0069] Figure 28 It is a schematic circuit diagram of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention for loading radio frequency signals and direct current signals;

[0070] Figure 29 It is a voltage relationship curve applied to the modulator of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention;

[0071] Figure 30 It is a voltage frequency response curve of the modulator of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention;

[0072] Figure 31 It is a microwave loss curve of the modulator of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention;

[0073] Figure 32 It is an electro-optic response curve of the modulator of the electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure according to the present invention.

[0074] In the figure, 1 is the substrate; 2 is the buried oxide layer; 3 is the lithium niobate layer; 4 is the lithium niobate optical waveguide; 5 is the cladding layer; 6 is the DC bias metal plate; 7 is the grounded lower electrode; 8 is the grounded T-shaped electrode; 9 is the signal T-shaped electrode; 10 is the signal lower electrode; 11 is the insulating layer; 12 is the grounded upper electrode; 13 is the signal upper electrode; 14 is the hollowed-out structure; 15 is the grating coupler; 16 is the 1×2 beam splitter; 17 is the Mach-Zehnder structure; 18 is the 2×1 beam splitter; 19 is the output coupling grating. Detailed implementation manners

[0075] The following further elaborates in detail on the specific implementation manners of the present invention, such as the shapes, structures of the various components involved, the mutual connection relationships between the various parts, the functions and working principles of the various parts, the manufacturing process, and the operation and usage methods, etc., so as to have a more complete, accurate, and in-depth understanding of the concept and technical solution of the present invention. The present invention can also be implemented or applied through other specific implementation manners, and various details herein can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0076] The present invention is used to solve the performance bottleneck and power consumption requirements of current conventional traveling-wave electrode thin-film lithium niobate electro-optic modulators. By introducing a new electrode structure, a new type of silicon-based thin-film lithium niobate electro-optic modulator with ultra-wide bandwidth, ultra-low power consumption, and rapid DC bias adjustment can be realized.

[0077] In the first aspect of the present invention, a thin-film lithium niobate electro-optic modulator with DC bias embedded is provided. The thin-film lithium niobate electro-optic modulator of the present invention includes two structures, namely, a grounded upper and lower electrode connection and a signal upper and lower electrode insulation structure, and a grounded upper and lower electrode insulation and a signal upper and lower electrode connection structure.

[0078] As Figure 1 and Figure 17 shown, the thin-film lithium niobate electro-optic modulator of the present invention includes:

[0079] A base layer, on the upper surface of which a lithium niobate optical waveguide 4 is formed by etching. The lithium niobate optical waveguide 4 includes a Mach-Zehnder structure 17 arranged in the modulation region for transmitting optical signals; wherein, the Mach-Zehnder structure 17 includes two mutually parallel optical waveguide arms;

[0080] A cladding layer 5, covering the base layer for protecting the optical waveguide;

[0081] A capacitive load type T-structure electrode, arranged on the top surface of the cladding layer 5 and above the Mach-Zehnder structure 17, for modulating optical signals through a radio frequency modulation signal, specifically by changing the electric field distribution, thereby affecting the phase or intensity of the optical signal;

[0082] The traveling-wave electrode structure is arranged on the top surface of the cladding 5 and above the Mach-Zehnder structure 17, and is electrically connected to the capacitor-loaded T-structure electrode. It is used to load and transmit the radio-frequency modulation signal to the capacitor-loaded T-structure electrode, and to synchronously transmit the optical signal and the radio-frequency modulation signal in the modulation region. The traveling-wave electrode structure includes two pairs of grounding electrodes and a pair of signal electrodes. The grounding electrodes are mainly composed of an upper grounding electrode 12 and a lower grounding electrode 7 arranged vertically (stacked). The signal electrodes are mainly composed of an upper signal electrode 13 and a lower signal electrode 10 arranged vertically (stacked). The DC bias metal plate 6 is electrically connected to the lower signal electrode 10 or any one of the lower grounding electrodes 7;

[0083] The DC bias metal plate 6 is arranged on the top surface of the cladding 5 and is electrically connected to the traveling-wave electrode structure, and is used to load the DC bias signal to the traveling-wave electrode structure.

[0084] Preferably, the capacitor-loaded T-structure electrode and the traveling-wave electrode structure are correspondingly arranged above the modulation region. The DC bias metal plate 6 is correspondingly arranged above other regions except the modulation region.

[0085] Preferably, for the traveling-wave electrode structure, in each pair of grounding electrodes, the upper grounding electrode 12 and the lower grounding electrode 7 are arranged in alignment.

[0086] Preferably, for the traveling-wave electrode structure, in the signal electrodes, the upper signal electrode 13 and the lower signal electrode 10 are arranged in alignment.

[0087] Furthermore, the lithium niobate modulators of both structures also include an insulating layer 11. The insulating layer 11 separates the upper and lower layers of some structures in the traveling-wave electrode and is used to realize the embedded adjustment of the DC bias. Among them, the insulating layer 11 separating the upper and lower layers of some structures in the traveling-wave electrode means that the insulating layer 11 separates the upper and lower layers of the signal electrodes (the lower signal electrode 10 and the upper signal electrode 13) or the upper and lower layers of the grounding electrodes (the lower grounding electrode 7 and the upper grounding electrode 12).

[0088] Specifically, the following two implementation manners of the insulating layer 11 can both realize the embedded adjustment of the DC bias:

[0089] Such as Figure 1 and Figure 10As shown, in an electro-optic modulator with a grounded upper and lower electrode connection and a signal upper and lower electrode insulation structure, the signal lower electrode 10 and the signal upper electrode 13 are separated by an insulating layer 11. The grounded lower electrode 7 is connected to the grounded upper electrode 12, and the DC bias metal plate 6 is electrically connected to the signal lower electrode 10. Taking Embodiment 1 of the present invention as an example, by etching the insulating layer 11 above the two grounded lower electrodes 7, the grounded lower electrode 7 can be connected to the grounded upper electrode 12, and the insulating layer 11 covers the signal lower electrode 10, the grounded T-shaped electrode 8, and the signal T-shaped electrode 9. The signal upper electrode 13 is disposed on the insulating layer 11 directly above the signal lower electrode 10. An insulating layer 11 between the signal lower electrode 10 and the signal upper electrode 13 functions as a capacitor, isolating the DC bias signal but allowing the RF signal to be loaded between the signal lower electrode 10 and the grounded lower electrode 7, and then loaded onto the capacitor-loaded T electrode. In addition, this insulating structure isolates the signal lower electrode 10 from the 50-ohm resistor added between the signal upper electrode 13 and the grounded upper electrode 12 for load matching, so that the DC bias voltage loaded between the signal lower electrode 10 and the grounded lower electrode 7 does not consume power, thereby reducing the overall power consumption of the thin-film lithium niobate electro-optic modulator.

[0090] As Figure 17 and Figure 26 shown, in an electro-optic modulator with a grounded upper and lower electrode insulation and a signal upper and lower electrode connection structure, the grounded lower electrode 7 and the grounded upper electrode 12 are separated by an insulating layer 11. The signal lower electrode 10 is connected to the signal upper electrode 13, and the DC bias metal plate 6 is electrically connected to any one of the grounded lower electrodes 7. Taking Embodiment 2 of the present invention as an example, by etching the insulating layer 11 above the signal lower electrode 10, the signal lower electrode 10 can be connected to the signal upper electrode 13, and the insulating layer 11 covers the grounded lower electrode 7, the grounded T-shaped electrode 8, and the signal T-shaped electrode 9. The grounded upper electrode 12 is disposed on the insulating layer 11 directly above the grounded lower electrode 7. An insulating layer 11 between the grounded lower electrode 7 and the grounded upper electrode 12 functions as a capacitor, isolating the DC bias signal but allowing the RF signal to be loaded between the signal lower electrode 10 and the grounded lower electrode 7, and then loaded onto the capacitor-loaded T electrode. In addition, this insulating structure isolates the grounded lower electrode 7 from the 50-ohm resistor added between the signal upper electrode 13 and the grounded upper electrode 12 for load matching, so that the DC bias voltage loaded between the signal upper electrode 13 and the grounded lower electrode 7 does not consume power, reducing the overall power consumption of the thin-film lithium niobate electro-optic modulator.

[0091] Preferably, for the electro-optic modulators of the two structures, the insulating layer 11 is correspondingly arranged above the modulation region. More specifically, the insulating layer 11 covers the capacitive load type T-structure metal electrodes. More specifically, the insulating layer 11 is not provided above the DC bias metal plate 6.

[0092] Preferably, for the electro-optic modulators of the two structures, the insulating layer 11 can use a variety of insulating materials to achieve the insulating effect.

[0093] Preferably, for the electro-optic modulators of the two structures, the insulating layer 11 is made of silicon dioxide or aluminum oxide.

[0094] Preferably, for the electro-optic modulators of the two structures, the DC bias metal plate 6 is connected to the signal lower layer electrode 10 or the ground lower layer electrode 7 through metal, thereby realizing electrical connection.

[0095] Preferably, for the electro-optic modulators of the two structures, the signal electrodes are arranged above the inner sides of the two optical waveguide arms of the Mach-Zehnder structure 17, and the two pairs of ground electrodes are correspondingly arranged above the outer sides of the two optical waveguide arms. Among them, the outer sides of the two optical waveguide arms refer to the regions far from each other, and the inner sides of the two optical waveguide arms refer to the regions between them.

[0096] As Figure 11 and Figure 27 shown, for the capacitive load type T-structure electrodes of the two electro-optic modulators, a plurality of capacitive load type T-structure electrodes are arranged above each optical waveguide arm of the Mach-Zehnder structure 17. Above each optical waveguide arm, the respective capacitive load type T-structure electrodes are arranged at equal intervals along the length direction of the optical waveguide arm. The capacitive load type T-structure electrode is mainly composed of a ground T-shaped electrode 8 and a signal T-shaped electrode 9, and the two are symmetrically arranged with respect to the lower optical waveguide arm. The ground T-shaped electrode 8 is connected to the ground lower layer electrode 7 outside the optical waveguide arm, and the signal T-shaped electrode 9 is connected to the signal lower layer electrode 10.

[0097] Among them, the fact that the ground T-shaped electrode 8 and the signal T-shaped electrode 9 are symmetrically arranged with respect to the lower optical waveguide arm means that: the connection line between the intersections of the horizontal and vertical arms of the two T-shaped electrodes is perpendicular to the transmission path of the optical signal in the optical waveguide arm.

[0098] Preferably, for the two electro-optic modulators, the implementation manner of the capacitive load type T-structure electrode can be: the longitudinal arm end of the ground T-shaped electrode 8 is connected to the ground lower layer electrode 7, the longitudinal arm end of the signal T-shaped electrode 9 is connected to the signal lower layer electrode 10, the horizontal arm of the ground T-shaped electrode 8 and the horizontal arm of the signal T-shaped electrode 9 are respectively located on both sides of the corresponding optical waveguide arm and are parallel to the corresponding optical waveguide arm.

[0099] As Figure 1 and Figure 17As shown, for the base layers of the two electro-optic modulators, the base layer includes a substrate 1, a buried oxide layer 2, and a lithium niobate layer 3 arranged from bottom to top. The top surface of the lithium niobate layer 3 is formed with a lithium niobate optical waveguide 4 by etching. The substrate 1 is provided with two hollowing structures 14, and the two hollowing structures 14 are respectively arranged corresponding to the lower sides of the two optical waveguide arms of the Mach-Zehnder structure 17. The hollowing structures 14 are used to reduce the effective refractive index of the microwave signal.

[0100] Further, the width of the hollowing structure 14 is greater than the width of the corresponding optical waveguide arm.

[0101] Further, the center lines of the hollowing structures 14 and the optical waveguide arms are arranged in one-to-one correspondence and alignment in the vertical direction.

[0102] Further, there are two hollowing structures 14, and the center of the width of each of them is the center of each optical waveguide arm of the Mach-Zehnder structure 17. The hollowing structures 14 are located below the buried oxide layer 2, and the substrate 1 at the positions of the hollowing structures 14 is completely removed.

[0103] As Figure 1 and Figure 17 shown, for the lithium niobate optical waveguide 4 of the two electro-optic modulators, the lithium niobate optical waveguide 4 is mainly formed by sequentially connecting an input grating coupler 15, a 1*2 beam splitter 16, a Mach-Zehnder structure 17, a 2*1 beam splitter 18, and an output coupling grating 19.

[0104] The second aspect of the present invention provides a method for manufacturing a thin-film lithium niobate electro-optic modulator.

[0105] The manufacturing method includes the following steps:

[0106] S1) Form a lithium niobate optical waveguide 4 on the upper surface of a lithium niobate-on-insulator wafer by etching;

[0107] S2) Deposit a cladding layer 5 above the lithium niobate layer 3 containing the lithium niobate optical waveguide 4;

[0108] S3) Adopt a sputtering or evaporation method to form a grounded T-shaped electrode 8 and a signal T-shaped electrode 9, a DC bias metal plate 6, a grounded lower-layer electrode 7 and a signal lower-layer electrode 10, and a connecting metal for connecting the DC bias metal plate 6 and the grounded lower-layer electrode 7 or the signal lower-layer electrode 10 on the cladding layer 5, jointly forming a lower electrode layer;

[0109] S4) Deposit an insulating layer 11 on the lower electrode layer;

[0110] S5) Prepare a micro-nano pattern on the insulating layer 11 by using a photolithography or electron beam lithography method, and etch away the insulating layer 11 at the position of the grounded lower-layer electrode 7 or the signal lower-layer electrode 10 by using an etching method;

[0111] S6) A method of sputtering or evaporation is used to form the upper ground electrode 12 and the upper signal electrode 13.

[0112] S7) A method of lithography or electron beam exposure and etching is sequentially used to process a part of the substrate 1 structure under the buried oxide layer 2 to obtain a hollowed-out structure 14, completing the preparation of the thin-film lithium niobate electro-optic modulator.

[0113] Taking silicon dioxide as an example for the insulating layer 11, in the preparation process of the electro-optic modulator with a grounded upper and lower electrode connection and a signal upper and lower electrode insulation structure, in step S4, the insulating layer 11 is formed by depositing silicon dioxide, and in step S5, the silicon dioxide above the two lower ground electrodes 7 is etched away by an etching method.

[0114] Taking silicon dioxide as an example for the insulating layer 11, in the preparation process of the electro-optic modulator with a grounded upper and lower electrode insulation and a signal upper and lower electrode connection structure, in step S4, the insulating layer 11 is formed by depositing silicon dioxide, and in step S5, the silicon dioxide above the lower signal electrode 10 is etched away by an etching method.

[0115] Preferably, the lithography method includes using a stepper, a contact lithography machine, electron beam lithography, laser direct writing, etc.

[0116] Preferably, the etching method includes dry etching and wet etching.

[0117] Preferably, the dry etching includes focused ion beam etching and reactive ion etching.

[0118] Preferably, the deposition method includes chemical vapor deposition, magnetron sputtering, electron beam evaporation, electroplating, etc.

[0119] The third aspect of the present invention provides an electro-optic modulation system using the thin-film lithium niobate electro-optic modulator provided in the first aspect. The electro-optic modulation system includes the following devices:

[0120] A light source, connected to the input grating coupler 15 of the electro-optic modulator, for inputting the light to be modulated into the electro-optic modulator;

[0121] A DC source, the output terminal is electrically connected to the DC bias metal plate 6 of the electro-optic modulator, and the ground terminal is connected to the upper ground electrode 12, for inputting a DC bias signal into the electro-optic modulator;

[0122] An AC source, the output terminal is electrically connected to the upper signal electrode 13 of the electro-optic modulator, and the ground terminal is connected to the upper ground electrode 12, for inputting a radio frequency modulation signal into the electro-optic modulator.

[0123] The specific embodiments of the present invention are as follows:

[0124] Embodiment 1

[0125] As Figure 2 shown, this embodiment provides a thin-film lithium niobate electro-optic modulator with a grounded upper and lower layer electrode connection and a signal upper and lower layer electrode insulation structure.

[0126] In this embodiment, the substrate is made of silicon material; the buried oxide layer is made of silicon dioxide material with a thickness of 3 um; the lithium niobate layer is made of lithium niobate material with an overall thickness of 400 nm; the thin-film lithium niobate optical waveguide has a thickness of 200 nm and an inclination angle of 60 degrees; the cladding is made of silicon dioxide material with a thickness of 0.9 um; the insulating layer is made of silicon dioxide material with a thickness of 0.2 um.

[0127] In this embodiment, the grounded T-shaped electrode, the signal T-shaped electrode, the grounded lower layer electrode, the grounded upper layer electrode, the signal lower layer electrode, and the signal upper layer electrode are all made of metal gold material. The grounded T-shaped electrode, the signal T-shaped electrode, the grounded lower layer electrode, and the signal lower layer electrode are on the same horizontal plane with a thickness of 0.2 um each; the grounded upper layer electrode and the signal upper layer electrode have a thickness of 0.9 um; the grounded upper and lower layer electrodes are connected to each other, and the signal upper and lower layer electrodes are insulated from each other.

[0128] The width of the signal lower layer electrode is the same as that of the signal upper layer electrode, both being 80 um, and the distance between the signal lower layer electrode and the grounded lower layer electrode is 31.8 um. When ensuring the impedance matching between the traveling-wave electrode and the terminal load impedance, a larger signal electrode width can reduce the surface resistance of the traveling-wave signal electrode and reduce the microwave loss mainly caused by the traveling-wave electrode.

[0129] As Figure 11 shown, in this embodiment, the grounded T-shaped electrode and the signal T-shaped electrode have the same structure, both being capacitive load type T electrodes. The cross-arm width s of the capacitive load type T electrode is 2 um, the cross-arm length r is 47 um, the longitudinal arm width t is 2 um, and the longitudinal arm length h is 13 um; the distance c between the grounded T-shaped electrodes or the signal T-shaped electrodes on the same side is 3 um; the distance g between the grounded T-shaped electrode and the signal T-shaped electrode arranged oppositely is 1.8 um.

[0130] The distance between the cross-arms of the grounded T-shaped metal electrode and the signal T-shaped metal electrode arranged oppositely needs to be small to obtain a very small product of the half-wave voltage and the length, thus obtaining a high modulation efficiency. However, the distance also needs to be greater than the width of the optical waveguide arm, and the width of the optical waveguide arm is generally 1.5 um. At the same time, the extremely small electrode distance also confines the microwave field within a small range, ensuring that the radiation loss caused by the substrate at high frequencies can be largely reduced.

[0131] In this embodiment, the hollow structure in the substrate is located near the bottom of each optical waveguide arm of the Mach-Zehnder. The hollow structure is centered on each optical waveguide arm of the Mach-Zehnder and has a width of 70 um, completely hollowing out the substrate in this part and exposing the buried oxide layer above. The hollow structure around each optical waveguide arm can reduce the effective refractive index of the microwave signal and slow down the slow-wave effect caused by the capacitive load type T-structure electrode, thereby achieving efficient speed matching between microwaves and light waves.

[0132] As Figure 2 shown, the method for preparing the thin-film lithium niobate electro-optic modulator provided in this embodiment is prepared through the following steps:

[0133] (1) Prepare a lithium niobate-on-insulator wafer, which includes a substrate, a buried oxide layer, and a lithium niobate layer stacked in sequence, as Figure 3 shown;

[0134] (2) Use electron beam lithography to prepare micro-nano patterns on the lithium niobate layer, and use dry etching to obtain a thin-film lithium niobate optical waveguide, including an input grating coupler, a 1*2 beam splitter, a Mach-Zehnder structure, a 2*1 beam splitter, and an output coupling grating connected in sequence, as Figure 4 shown.

[0135] (3) Use plasma-enhanced chemical vapor deposition to deposit a silica cladding on the lithium niobate layer containing the lithium niobate optical waveguide, as Figure 5 shown.

[0136] (4) Use evaporation to form a first layer of thin metal on the silica cladding, including a grounded T-shaped electrode, a signal T-shaped electrode, a grounded lower electrode, a signal lower electrode, and a connecting metal for connecting the DC bias metal plate and the signal lower electrode, as Figure 6 shown.

[0137] (5) Use plasma-enhanced chemical vapor deposition again to deposit an insulating layer on the existing structure, as Figure 7 shown.

[0138] (6) Use photolithography to prepare micro-nano patterns on the insulating layer, and use etching to etch away the silica on the grounded lower electrode, as Figure 8 shown.

[0139] (7) Use evaporation again to form a second layer of metal, so that the grounded upper electrode is located above and connected to the grounded lower electrode, and form a signal upper electrode on the insulating layer, as Figure 9 shown.

[0140] (8) Prepare micro-nano patterns on a silicon substrate using photolithography, and obtain a hollowed-out structure on the substrate using etching to complete the preparation of a thin-film lithium niobate electro-optic modulator with a DC bias embedded, as Figure 10 shown.

[0141] Through simulation calculations, this thin-film lithium niobate electro-optic modulator with a DC bias embedded can achieve the simultaneous loading of DC signals and RF AC signals onto the modulator.

[0142] The process and results are as follows:

[0143] The circuit schematic diagram of the modulator is as Figure 12 shown. Among them, AC is an AC voltage source, DC is a DC voltage source. To achieve impedance matching, both resistor R1 and resistor R2 are 50Ω, and resistor R3 requires a relatively large resistance value to ensure the simultaneous loading of DC and AC voltages. Capacitor C1 is the capacitance generated by the insulating layer, and capacitor C2 is the total capacitance between the opposing capacitive load type T electrodes. GND1 - GND4 are grounding terminals. In this embodiment, GND1 - GND4 are all connected to the upper layer 12 of the grounding electrode through connection.

[0144] As Figure 13 shown, when an AC voltage with a peak-to-peak value of 12V and a frequency of 1MHz is applied to the traveling-wave electrode, and a DC bias voltage of 2V is applied to the DC bias electrode, after the voltage division of resistors R1 and R2, the voltage signal loaded on the electro-optic modulator (i.e., Figure 13 the voltage on the modulator in

[0145] To verify the influence of the AC signal frequency on the signal loaded on the electro-optic modulator, Figure 14 represents the frequency response curve of the electro-optic modulator when different frequencies of AC signals are loaded. After normalization, the closer the curve is to 1, the closer the effective value of the AC signal loaded on the electro-optic modulation region is to the set value, and the better the response. It can be seen that this electro-optic modulator has a good electro-optic response above 100kHz and can be applied to high-frequency modulation.

[0146] Due to the fact that this electro-optic modulator adopts the methods of increasing the width of the upper and lower signal electrodes, increasing the spacing between the upper and lower signal electrodes and the upper and lower grounding electrodes, setting capacitive load type T-structured electrodes, and thinning the substrate in its structure, this electro-optic modulator also has excellent performance:

[0147] As Figure 15 shown, the microwave loss of this electro-optic modulator is very low;

[0148] As Figure 16As shown, the bandwidth of this electro-optic modulator is also excellent. At a driving voltage of 1V, its electro-optic response bandwidth reaches 90GHz, and the bandwidth can be further improved if the driving voltage is increased.

[0149] Example 2

[0150] As Figure 17 shown, this example provides a thin-film lithium niobate electro-optic modulator with a grounded upper and lower layer electrode insulation and a signal upper and lower layer electrode connection structure.

[0151] In this example, the structure and size parameters of the electro-optic modulator are the same as those in Example 1. The difference is that in this example, the signal upper and lower layer electrodes are connected to each other, and the grounded upper and lower layer electrodes are insulated from each other. In this example, the DC bias metal plate 6 is connected to the grounded lower layer electrode 7 through a metal connection.

[0152] As Figure 18 shown, the preparation method of the thin-film lithium niobate electro-optic modulator provided in this example is prepared through the following steps:

[0153] (1) Prepare a lithium niobate on insulator wafer, which includes a substrate, a buried oxide layer, and a lithium niobate layer stacked in sequence, as Figure 19 shown;

[0154] (2) Use electron beam lithography to prepare micro-nano patterns on the lithium niobate layer, and use dry etching to obtain a thin-film lithium niobate optical waveguide, including an input grating coupler, a 1*2 beam splitter, a Mach-Zehnder structure, a 2*1 beam splitter, and an output coupling grating connected in sequence, as Figure 20 shown.

[0155] (3) Use plasma-enhanced chemical vapor deposition to deposit a silica cladding on the lithium niobate layer containing the lithium niobate optical waveguide, as Figure 21 shown.

[0156] (4) Use evaporation to form a first layer of thin metal on the silica cladding, including a grounded T-shaped electrode, a signal T-shaped electrode, a grounded lower layer electrode, a signal lower layer electrode, a DC bias metal plate, and a connection metal for connecting the DC bias metal plate and the grounded lower layer electrode, as Figure 22 shown.

[0157] (5) Use plasma-enhanced chemical vapor deposition to deposit an insulating layer again on the existing structure, as Figure 23 shown.

[0158] (6) Use lithography to prepare micro-nano patterns on the insulating layer, and use etching to etch away the silica on the signal lower layer electrode, as Figure 24 shown.

[0159] (7) The second layer of metal is formed again by evaporation, so that the signal upper electrode is located above the signal lower electrode and connected to each other, and the signal upper electrode is formed on the insulating layer, as Figure 25 shown.

[0160] (8) A micro-nano pattern is prepared on the silicon substrate by photolithography, and a hollowed-out structure on the substrate is obtained by etching, completing the preparation of the thin-film lithium niobate electro-optic modulator with DC bias embedded, as Figure 26 shown.

[0161] Through simulation calculations, the thin-film lithium niobate electro-optic modulator with DC bias embedded can load a DC signal and an RF AC signal onto the modulator at the same time. The circuit schematic diagram of the modulator is as Figure 28 shown, where AC is an AC voltage source, DC is a DC voltage source, the resistors are all 50Ω for impedance matching, capacitor C1 is the capacitance generated by the insulating layer, and capacitor C2 is the total capacitance between the opposing capacitor-loaded T electrodes. GND1 - GND4 are grounding terminals. In this embodiment, GND1 - GND4 are all grounded through connection to the upper layer 12 of the grounding electrode.

[0162] As Figure 29 shown, when an AC voltage with a peak-to-peak value of 12V and a frequency of 1MHz is applied to the traveling-wave electrode, and a DC bias voltage of 2V is applied to the DC bias electrode, after voltage division by resistors R1 and R2, the voltage signal loaded on the electro-optic modulator (i.e., the voltage on the modulator in Figure 29 ) is the sum of the DC bias voltage and an AC voltage with a peak-to-peak value of 6V, that is, the function of simultaneously loading a DC bias and an RF signal onto the electro-optic modulator is achieved.

[0163] In order to verify the influence of the AC signal frequency on the signal loaded on the electro-optic modulator, Figure 30 shows the frequency response curves of the electro-optic modulator under different frequencies of AC signals applied. After normalization, the closer the curve is to 1, the closer the effective value of the AC signal loaded on the electro-optic region is to the set value, and the better the response. It can be seen that this electro-optic modulator has a significant electro-optic response and can be applied to high-frequency modulation.

[0164] Since the structure of this electro-optic modulator adopts the methods of increasing the width of the traveling-wave signal electrode, increasing the distance between the traveling-wave signal electrode and the traveling-wave grounding electrode, setting the capacitor-loaded T-structured electrode, and thinning the substrate, this electro-optic modulator also has excellent performance:

[0165] As Figure 31 shown, the microwave loss of this electro-optic modulator is very low;

[0166] As Figure 32As shown, the bandwidth of this electro-optic modulator is also excellent. At a driving voltage of 1V, its electro-optic response bandwidth reaches 95GHz. If the driving voltage is increased, its bandwidth can be further improved.

[0167] The above embodiments are preferred embodiments of the present invention. However, the embodiments of the present invention are not limited to the above embodiments. Any other structure that conforms to the changes in structure, materials, thickness, etc., and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A DC bias embedded thin film lithium niobate electro-optic modulator, characterized in that: include: A substrate layer, an upper surface of which is formed a lithium niobate optical waveguide (4) for transmitting optical signals, wherein the lithium niobate optical waveguide (4) includes a Mach-Zehnder structure (17); A cladding layer (5), covering the base layer; A capacitive load type T-structure electrode, arranged on the top surface of the cladding (5), for modulating the optical signal by means of a radio frequency modulation signal; A traveling wave electrode structure, arranged on the top surface of the cladding (5), for loading a radio frequency modulated signal onto the capacitive load type T-structure electrode; A DC bias metal plate (6) is arranged on the top surface of the cladding (5), is electrically connected to the traveling wave electrode structure, and is used to load a DC bias signal onto the traveling wave electrode structure.

2. The DC bias embedded thin film lithium niobate electro-optic modulator according to claim 1, characterized in that: The traveling wave electrode structure comprises two pairs of grounded upper electrodes (12) and grounded lower electrodes (7) arranged vertically, and a pair of signal upper electrodes (13) and signal lower electrodes (10) arranged vertically; The DC bias metal plate (6) is electrically connected to a signal lower layer electrode (10) or a ground lower layer electrode (7).

3. The DC bias embedded thin film lithium niobate electro-optic modulator according to claim 2, characterized in that: The lithium niobate modulator also includes an insulating layer (11) for realizing embedded regulation of DC bias; When the signal lower electrode (10) and the signal upper electrode (13) are separated by the insulating layer (11), and the grounded lower electrode (7) and the grounded upper electrode (12) are connected, the DC bias metal plate (6) is electrically connected to the signal lower electrode (10); When the grounded lower electrode (7) and the grounded upper electrode (12) are separated by the insulating layer (11), and the signal lower electrode (10) and the signal upper electrode (13) are connected, the DC bias metal plate (6) is electrically connected to one of the grounded lower electrodes (7), and the two grounded lower electrodes (7) are electrically connected.

4. The DC bias embedded thin film lithium niobate electro-optic modulator according to claim 3, characterized in that: The insulating layer (11) covers the capacitive load type T-structure electrode.

5. The DC bias embedded thin film lithium niobate electro-optic modulator according to claim 2, characterized in that: The signal electrode is arranged above the inner sides of the two optical waveguide arms of the Mach-Zehnder structure (17), and two pairs of ground electrodes are arranged above the outer sides of the two optical waveguide arms respectively.

6. The DC bias embedded thin film lithium niobate electro-optic modulator according to claim 5, characterized in that: A plurality of capacitively loaded T-structure electrodes are arranged above each optical waveguide arm of the Mach-Zehnder structure (17), and the capacitively loaded T-structure electrodes are arranged at equal intervals along the length direction of the optical waveguide arm below; the capacitively loaded T-structure electrodes are mainly composed of a grounding T-type electrode (8) and a signal T-type electrode (9), and the grounding T-type electrode (8) and the signal T-type electrode (9) are arranged symmetrically with respect to the optical waveguide arm below, the grounding T-type electrode (8) is connected to a grounding lower layer electrode (7) outside the optical waveguide arm, and the signal T-type electrode (9) is connected to a signal lower layer electrode (10).

7. The DC bias embedded thin film lithium niobate electro-optic modulator according to claim 1, characterized in that: The base layer comprises a substrate (1), a buried oxide layer (2) and a lithium niobate layer (3) arranged from bottom to top, a lithium niobate optical waveguide (4) is formed on the top surface of the lithium niobate layer (3) by etching, and the substrate (1) is provided with two hollow structures (14), the two hollow structures (14) are respectively arranged below two optical waveguide arms of the Mach-Zehnder structure (17), and the hollow structures (14) are used to reduce the effective refractive index of microwave signals.

8. The DC bias embedded thin film lithium niobate electro-optic modulator according to claim 1, characterized in that: The lithium niobate optical waveguide (4) is mainly composed of an input grating coupler (15), a 1*2 beam splitter (16), a Mach-Zehnder structure (17), a 2*1 beam splitter (18) and an output coupling grating (19) which are connected in sequence.

9. A method for preparing a thin film lithium niobate electro-optic modulator as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: S1) forming a lithium niobate optical waveguide (4) on the upper surface of a lithium niobate wafer on an insulator by etching; S2) forming a cladding layer (5) by deposition on the lithium niobate layer (3) including the lithium niobate optical waveguide (4); S3) forming a ground T-type electrode (8), a signal T-type electrode (9), a DC bias metal plate (6), a ground lower electrode (7) and a signal lower electrode (10) on the cladding layer (5) by sputtering or evaporation to form a lower electrode layer; S4) depositing an insulating layer (11) on the lower electrode layer; S5) preparing a micro-nano pattern on the insulating layer (11) by photolithography or electron beam exposure, and etching away the insulating layer (11) at the grounding lower electrode (7) or the signal lower electrode (10) by etching; S6) forming a ground upper electrode (12) and a signal upper electrode (13) by sputtering or evaporation; S7) sequentially using photolithography or electron beam exposure and etching methods to process the partial substrate (1) structure under the buried oxide layer (2) to obtain a hollow structure (14), thereby completing the preparation of the thin film lithium niobate electro-optical modulator.

10. An electro-optic modulation system using the thin-film lithium niobate electro-optic modulator according to any one of claims 1 to 8, characterized in that: Also includes: A light source connected to an input grating coupler (15) of the electro-optic modulator and used for inputting light to be modulated into the electro-optic modulator; A direct current source, the output end of which is electrically connected to a direct current bias metal plate (6) of the electro-optic modulator, and is used to input a direct current bias signal to the electro-optic modulator; An alternating current source, the output end of which is electrically connected to the input end of the signal upper electrode (13) of the electro-optic modulator, is used to input a radio frequency modulated signal to the electro-optic modulator.

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