A thin-film lithium niobate phase modulator

Abstract

This application discloses a thin-film lithium niobate phase modulator, including a radio frequency modulation electrode, a DC bias electrode, and an optical waveguide. The DC bias electrode includes a first electrode and a second electrode. The first electrode is an open rectangle with one long side and two wide sides. The open rectangle also includes multiple sets of symmetrical first comb electrodes. Two first comb electrodes in each set are connected to the two wide sides respectively. The second electrode is axially symmetrical and includes multiple sets of second comb electrodes. The number of sets of second comb electrodes is the same as the number of sets of first comb electrodes. Each set of first comb electrodes in the first electrode and each set of second comb electrodes in the second electrode are arranged in a staggered manner. Any set of first comb electrodes in the first electrode and a set of second comb electrodes at the corresponding position in the second electrode form a comb group. The winding of the optical waveguide passes between the first and second comb electrodes in each comb group.

Description

Technical Field

[0001] This application relates to the field of phase modulator technology, and in particular to a thin-film lithium niobate phase modulator. Background Technology

[0002] Electro-optic phase modulators play an important role in fields such as optical fiber communication, optical fiber sensing, quantum communication, and laser frequency stabilization. Among them, electro-optic phase modulators based on thin-film lithium niobate not only utilize the excellent electro-optic modulation performance of lithium niobate, but also confine the optical field to the sub-micron scale, thereby greatly improving the overlap between the optical and electric fields. This is highly beneficial for improving electro-optic modulation efficiency, and therefore, the application of thin-film lithium niobate phase modulators is becoming increasingly widespread.

[0003] Thin-film lithium niobate phase modulators typically consist of an RF traveling-wave electrode, a DC bias electrode, and an optical waveguide. The RF traveling-wave electrode is used to rapidly modulate the phase change of the light wave in the optical waveguide, while the DC bias electrode is used to adjust the operating point of the phase modulator. However, in existing thin-film lithium niobate phase modulators, reducing the voltage applied to the electrodes requires increasing the electrode length, which in turn increases the chip length, hindering the development of thin-film lithium niobate phase modulators towards smaller size and higher integration. Therefore, how to reduce the voltage required to be applied to the DC bias electrode within a limited chip length is a pressing technical problem to be solved in this field. Summary of the Invention

[0004] In view of this, this application provides a thin-film lithium niobate phase modulator. By arranging each group of first comb electrodes in the first electrode and each group of second comb electrodes in the second electrode in a crosswise manner, the length of the DC bias electrode can be greatly increased within a limited chip length, thereby reducing the voltage applied to the DC bias electrode. This is simple and convenient, and is conducive to the development of thin-film lithium niobate phase modulators towards smaller size and higher integration.

[0005] According to one aspect of this application, a thin-film lithium niobate phase modulator is provided, including a radio frequency modulation electrode, a DC bias electrode, and an optical waveguide. The DC bias electrode includes a first electrode and a second electrode, wherein the first electrode is a signal electrode and the second electrode is a ground electrode, or the first electrode is a ground electrode and the second electrode is a signal electrode.

[0006] The first electrode is an open rectangle including one long side and two wide sides. The open rectangle also includes multiple sets of symmetrical first comb electrodes. Two first comb electrodes in each set of first comb electrodes are respectively connected to the two wide sides.

[0007] The second electrode is axially symmetrical comb-shaped and includes multiple sets of second comb-tooth electrodes. The number of sets of the second comb-tooth electrodes is the same as the number of sets of the first comb-tooth electrodes.

[0008] Each group of first comb-tooth electrodes in the first electrode and each group of second comb-tooth electrodes in the second electrode are arranged in a cross pattern. Any group of first comb-tooth electrodes in the first electrode and a group of second comb-tooth electrodes at the corresponding position in the second electrode form a comb-tooth group.

[0009] The winding of the optical waveguide passes between the first comb electrode and the second comb electrode in each comb tooth group.

[0010] Optionally, the electric field direction generated between the first and second comb electrodes in each comb group remains unchanged relative to the optical axis direction of the lithium niobate crystal of the optical waveguide.

[0011] Optionally, the width of the first comb electrode is a first width, and the width of the second comb electrode is a second width;

[0012] The first spacing between any two groups of adjacent first comb-tooth electrodes of the first electrode is greater than the target distance, which is twice the sum of the first width and the second width;

[0013] The second spacing between every two groups of adjacent second comb electrodes of the second electrode is greater than the target distance, which is twice the sum of the first width and the second width.

[0014] Optionally, the bottom layer of the cross section corresponding to each comb tooth group is a silicon substrate layer, and the middle layer is a silicon dioxide insulating layer.

[0015] Optionally, the core material of the optical waveguide is the lithium niobate thin film, which is etched to form a ridge waveguide structure.

[0016] Optionally, the first comb electrode and the second comb electrode in each comb tooth group are symmetrically distributed on both sides of the ridge waveguide structure of the optical waveguide.

[0017] Optionally, the upper layer of the cross section corresponding to each comb tooth group is one of a silicon dioxide insulating layer, an air layer, and a resin layer.

[0018] Optionally, the signal electrode and the ground electrode are gold electrodes.

[0019] Optionally, the first effective length of the DC bias electrode is positively correlated with the second effective length of each comb tooth group and positively correlated with the number of comb tooth groups.

[0020] Optionally, the number of comb teeth groups is at least two.

[0021] By employing the above technical solution, this application provides a thin-film lithium niobate phase modulator, which may include an RF modulation electrode, a DC bias electrode, and an optical waveguide. The DC bias electrode may include two types of electrodes: a first electrode and a second electrode. These two electrodes are a signal electrode and a ground electrode, respectively. When the first electrode is a signal electrode, the second electrode is a ground electrode; conversely, when the first electrode is a ground electrode, the second electrode is a signal electrode. The outermost shape of the first electrode is an open rectangle, which may include three sides, including one long side and two short sides. Furthermore, the open rectangle may include multiple sets of symmetrically distributed first comb-tooth electrodes, each set including two first comb-tooth electrodes, which are respectively connected to the two wide sides of the open rectangle. The second electrode has a comb-tooth shape that is symmetrical about an axis. The second electrode also includes multiple sets of second comb-tooth electrodes, each set including two second comb-tooth electrodes, both of which are connected to the axis of symmetry. Moreover, the number of sets of second comb-tooth electrodes in the second electrode is the same as the number of sets of first comb-tooth electrodes in the first electrode. After arranging the first and second electrodes, each group of first comb electrodes in the first electrode and each group of second comb electrodes in the second electrode are arranged in a staggered manner. Specifically, a group of second comb electrodes is arranged between every two adjacent groups of first comb electrodes, and a group of first comb electrodes is arranged between every two adjacent groups of second comb electrodes. Furthermore, any group of first comb electrodes in the first electrode can form a comb group with a corresponding group of second comb electrodes in the second electrode. The optical waveguide can be wound between the first and second comb electrodes in each comb group. This embodiment of the application, by arranging each group of first comb electrodes in the first electrode and each group of second comb electrodes in the second electrode in a staggered manner, can significantly increase the length of the DC bias electrode within a limited chip length, thereby reducing the voltage applied to the DC bias electrode, which is simple and convenient.

[0022] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0024] Figure 1 This illustration shows a schematic diagram of a DC bias electrode and optical waveguide provided in an embodiment of this application.

[0025] Figure 2 This illustration shows a schematic diagram of the structure of a first electrode provided in an embodiment of this application;

[0026] Figure 3 This illustration shows a schematic diagram of the structure of a first electrode provided in an embodiment of this application;

[0027] Figure 4 This illustration shows a schematic diagram of the structure of a second electrode provided in an embodiment of this application;

[0028] Figure 5 This illustration shows a schematic diagram of a DC bias electrode and optical waveguide provided in an embodiment of this application.

[0029] Figure 6 This illustration shows a schematic diagram of the electric field direction between a first comb electrode and a second comb electrode according to an embodiment of this application.

[0030] Figure 7 This illustration shows a schematic diagram of a DC bias electrode and optical waveguide provided in an embodiment of this application.

[0031] Figure 8 This illustration shows a cross-sectional schematic diagram of a comb tooth assembly provided in an embodiment of this application;

[0032] Figure 9 This paper shows the TE mode optical field distribution in a thin-film lithium niobate optical waveguide according to an embodiment of this application.

[0033] Figure 10 The diagram shows the electric field distribution around the waveguide structure provided in the embodiment of this application. Detailed Implementation

[0034] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0035] This embodiment provides a thin-film lithium niobate phase modulator, including an RF modulation electrode, a DC bias electrode, and an optical waveguide, such as... Figure 1 As shown, the DC bias electrode includes a first electrode and a second electrode, wherein the first electrode is a signal electrode and the second electrode is a ground electrode, or the first electrode is a ground electrode and the second electrode is a signal electrode.

[0036] The first electrode is an open rectangle including one long side and two wide sides. The open rectangle also includes multiple sets of symmetrical first comb electrodes. Two first comb electrodes in each set of first comb electrodes are respectively connected to the two wide sides.

[0037] The second electrode is axially symmetrical comb-shaped and includes multiple sets of second comb-tooth electrodes. The number of sets of the second comb-tooth electrodes is the same as the number of sets of the first comb-tooth electrodes.

[0038] Each group of first comb-tooth electrodes in the first electrode and each group of second comb-tooth electrodes in the second electrode are arranged in a cross pattern. Any group of first comb-tooth electrodes in the first electrode and a group of second comb-tooth electrodes at the corresponding position in the second electrode form a comb-tooth group.

[0039] The winding of the optical waveguide passes between the first comb electrode and the second comb electrode in each comb tooth group.

[0040] The thin-film lithium niobate phase modulator provided in this application embodiment may include an RF modulation electrode, a DC bias electrode, and an optical waveguide. The RF modulation electrode can be configured using existing methods. The DC bias electrode adjusts the operating point of the phase modulator, and the optical waveguide is the medium that guides light waves to propagate therein. The DC bias electrode may include two types of electrodes: a first electrode and a second electrode. These two electrodes are a signal electrode and a ground electrode, respectively. When the first electrode is the signal electrode, the second electrode is the ground electrode; when the first electrode is the ground electrode, the second electrode is the signal electrode.

[0041] The outermost shape of the first electrode is an open rectangle, such as... Figure 2 As shown, the open rectangle may include three sides, including one long side and two short sides. Furthermore, the open rectangle may also include multiple sets of symmetrically distributed first comb electrodes, each set containing two first comb electrodes, which are respectively connected to the two wide sides of the open rectangle. It should be noted that the long side of the open rectangle can also be considered as a set of first comb electrodes. Figure 3 As shown, assuming that the first comb electrode in the first group includes a first comb electrode A and a first comb electrode B, and the two wide sides of the unclosed rectangle are wide side 1 and wide side 2 respectively, then when the first comb electrode A is connected to wide side 1, the first comb electrode B is connected to wide side 2.

[0042] The second electrode has a comb-like shape that is symmetrical about the axis, such as... Figure 4 As shown, similarly, the second electrode also includes multiple sets of second comb-tooth electrodes, wherein each set of second comb-tooth electrodes includes two second comb-tooth electrodes, both of which are connected to the axis of symmetry. Furthermore, the number of sets of second comb-tooth electrodes in the second electrode is the same as the number of sets of first comb-tooth electrodes in the first electrode.

[0043] The arrangement of the first electrode and the second electrode is as follows: Figure 1As shown. After arranging the first and second electrodes, each group of first comb-tooth electrodes in the first electrode and each group of second comb-tooth electrodes in the second electrode are arranged alternately. Specifically, a group of second comb-tooth electrodes is arranged between every two adjacent groups of first comb-tooth electrodes; and a group of first comb-tooth electrodes is arranged between every two adjacent groups of second comb-tooth electrodes. Furthermore, any group of first comb-tooth electrodes in the first electrode can form a comb-tooth group with a corresponding group of second comb-tooth electrodes in the second electrode. For example, as... Figure 5 As shown, the first group of first comb teeth electrodes in the first electrode and the first group of second comb teeth electrodes in the second electrode form a comb tooth group, the second group of first comb teeth electrodes in the first electrode and the second group of second comb teeth electrodes in the second electrode form a comb tooth group, and so on, multiple comb tooth groups can be obtained.

[0044] The optical waveguide can be wound between the first and second comb electrodes in each comb tooth group, such as... Figure 1 As shown.

[0045] By applying the technical solution of this embodiment, the thin-film lithium niobate phase modulator can include an RF modulation electrode, a DC bias electrode, an optical waveguide, etc. The DC bias electrode can include two types of electrodes: a first electrode and a second electrode. These two electrodes are a signal electrode and a ground electrode, respectively. When the first electrode is a signal electrode, the second electrode is a ground electrode; when the first electrode is a ground electrode, the second electrode is a signal electrode. The outermost shape of the first electrode is an open rectangle, which can include three sides, including one long side and two short sides. Furthermore, the open rectangle can also include multiple sets of symmetrically distributed first comb-tooth electrodes, each set including two first comb-tooth electrodes, which are respectively connected to the two wide sides of the open rectangle. The second electrode has a comb-tooth shape that is symmetrical about an axis. The second electrode also includes multiple sets of second comb-tooth electrodes, each set including two second comb-tooth electrodes, both of which are connected to the axis of symmetry. Furthermore, the number of sets of second comb-tooth electrodes in the second electrode is the same as the number of sets of first comb-tooth electrodes in the first electrode. After arranging the first and second electrodes, each group of first comb electrodes in the first electrode and each group of second comb electrodes in the second electrode are arranged in a staggered manner. Specifically, a group of second comb electrodes is arranged between every two adjacent groups of first comb electrodes, and a group of first comb electrodes is arranged between every two adjacent groups of second comb electrodes. Furthermore, any group of first comb electrodes in the first electrode can form a comb group with a corresponding group of second comb electrodes in the second electrode. The optical waveguide can be wound between the first and second comb electrodes in each comb group. This embodiment of the application, by arranging each group of first comb electrodes in the first electrode and each group of second comb electrodes in the second electrode in a staggered manner, can significantly increase the length of the DC bias electrode within a limited chip length, thereby reducing the voltage applied to the DC bias electrode, which is simple and convenient.

[0046] Optionally, in this embodiment of the application, the electric field direction generated between the first comb electrode and the second comb electrode in each comb tooth group remains unchanged relative to the optical axis direction of the lithium niobate crystal of the optical waveguide.

[0047] In this embodiment, in each group of comb teeth, an electric field can be generated between the first comb tooth electrode and the second comb tooth electrode. The direction of the electric field can be from the first comb tooth electrode to the second comb tooth electrode, or from the second comb tooth electrode to the first comb tooth electrode. When the first comb tooth electrode is a signal electrode and the second comb tooth electrode is a ground electrode, the direction of the electric field is from the first comb tooth electrode to the second comb tooth electrode; when the first comb tooth electrode is a ground electrode and the second comb tooth electrode is a signal electrode, the direction of the electric field is from the second comb tooth electrode to the first comb tooth electrode. The relative direction between the direction of the electric field generated between the first and second comb tooth electrodes and the optical axis of the lithium niobate crystal in the optical waveguide remains unchanged. Generally, the optical axis of the lithium niobate crystal has three directions: X, Y, and Z. The Z direction can be divided into the +Z direction and the -Z direction. The direction of the electric field generated between the first and second comb tooth electrodes is either along the +Z direction, the -Z direction, or a direction that forms a certain angle with the Z-axis. In existing technologies, some thin-film lithium niobate phase modulators use folded radio frequency traveling-wave electrodes to reduce chip length. Since the electric field direction in the traveling-wave electrode needs to remain constant with the optical axis direction in the lithium niobate waveguide to maintain the accumulation of phase changes, after folding the traveling-wave electrode, either the electrodes cross over (i.e., the signal electrode and ground electrode are swapped vertically), or the lithium niobate optical waveguide needs polarization reversal to maintain the relative relationship between the electric field direction and the optical axis direction of the lithium niobate crystal after folding. However, the crossing of traveling-wave electrodes introduces high-frequency signal noise and degrades performance, and polarization reversal of the optical waveguide requires additional process steps for material polarization. In the embodiments of this application, as shown... Figure 6 As shown, an electric field direction is illustrated, where the first comb electrode is the signal electrode and the second comb electrode is the ground electrode. The electric field direction is from top to bottom, i.e., from the signal electrode to the ground electrode. Therefore, the electrodes do not need to cross, and the optical waveguide does not need to perform polarization domain reversal, resulting in better performance.

[0048] In addition, such as Figure 1 As shown, in this embodiment, the first comb electrode, the second comb electrode, and the optical waveguide arranged symmetrically on the left and right sides can also make the input and output of the optical waveguide at the same horizontal position, which can facilitate the subsequent overall packaging and meet the subsequent overall packaging requirements.

[0049] In this embodiment of the application, optionally, the width of the first comb electrode is a first width, and the width of the second comb electrode is a second width; the first spacing between every two groups of adjacent first comb electrodes of the first electrode is greater than a target distance, the target distance being twice the sum of the first width and the second width; the second spacing between every two groups of adjacent second comb electrodes of the second electrode is greater than a target distance, the target distance being twice the sum of the first width and the second width.

[0050] In this embodiment, the width of the first comb electrode can be set to a first width, and the width of the second comb electrode can be set to a second width. The first width and the second width may be equal or unequal. The first spacing between any two adjacent groups of first comb electrodes in the first electrode can be greater than a target distance, and the second spacing between any two adjacent groups of second comb electrodes in the second electrode can be greater than the target distance. Here, the target distance can be twice the sum of the first width and the second width. Figure 7 As shown, assuming the first width is d1 and the second width is d2, the first spacing between two adjacent sets of first comb electrode teeth is greater than 2*(d1+d2), and the second spacing between two adjacent sets of second comb electrode teeth is greater than 2*(d1+d2). This embodiment of the application, by setting the first and second spacings, ensures that each set of first and second comb electrode teeth does not interfere with each other, thus avoiding interference.

[0051] In this embodiment of the application, optionally, the bottom layer of the cross section corresponding to each group of comb teeth is a silicon substrate layer, and the middle layer is a silicon dioxide insulating layer.

[0052] In this embodiment, the cross-section corresponding to each group of comb teeth is as follows: Figure 8 As shown in the figure. The bottom layer material in the cross-section can be silicon (Si), and the middle layer material can be silicon dioxide insulating material (SiO2).

[0053] In this embodiment of the application, optionally, the core material of the optical waveguide is the lithium niobate thin film, and the lithium niobate thin film is etched to form a ridge waveguide structure.

[0054] In this embodiment, such as Figure 8 As shown, the lithium niobate thin film is etched into a ridge waveguide structure with a trapezoidal shape.

[0055] Optionally, in each comb tooth group, the first comb tooth electrode and the second comb tooth electrode are symmetrically distributed on both sides of the ridge waveguide structure of the optical waveguide.

[0056] In this embodiment, each comb tooth group includes a first comb tooth electrode and a second comb tooth electrode. The first and second comb tooth electrodes are symmetrically located on both sides of the ridge waveguide structure of the optical waveguide. Figure 8 As shown, in the cross-section corresponding to each group of comb teeth, the optical waveguide can be composed of a lithium niobate film of a ridge waveguide structure, a filling material between the first electrode and the ridge waveguide structure, a filling material between the second electrode and the ridge waveguide structure, and a filling material on the upper part of the ridge waveguide structure. Figure 8As can be seen, the first and second comb electrodes are symmetrically located on both sides of the ridge waveguide structure. Furthermore, the RF modulation electrodes are also symmetrically distributed on both sides of the optical waveguide, and the DC bias electrodes are respectively located on different sections of the optical waveguide.

[0057] In this embodiment of the application, optionally, the upper layer of the cross section corresponding to each group of comb teeth is one of a silicon dioxide insulating layer, an air layer, and a resin layer.

[0058] In this embodiment, the cross-section corresponding to each group of comb teeth includes not only the bottom silicon substrate layer and the middle silicon dioxide insulating layer, but also an upper layer material. The upper layer material can be a silicon dioxide insulating layer, an air layer, or a resin material. This is because silicon dioxide, air, and resin all have a lower refractive index than lithium niobate films, and therefore can be used as cladding materials for optical waveguides.

[0059] In this embodiment of the application, optionally, the signal electrode and the ground electrode are gold electrodes.

[0060] In this embodiment, both the signal electrode and the ground electrode can be made of gold (Au). Gold electrodes have a series of advantages, such as stable electrochemical properties and low defect density. Therefore, choosing gold as the material for both the signal electrode and the ground electrode can ensure more stable performance of the thin-film lithium niobate phase modulator.

[0061] Optionally, in an embodiment of this application, the first effective length of the DC bias electrode is positively correlated with the second effective length of each comb tooth group and positively correlated with the number of comb tooth groups.

[0062] In this embodiment, the second effective length of each comb tooth group can be determined. The first effective length of the DC bias electrode is actually approximately equal to the product of the second effective length and the number of comb tooth groups. The second effective length can be the length of the corresponding space, and the first effective length can be the total length of the actual electrode. That is, if the second effective length increases, the first effective length also increases accordingly; there is a positive correlation between the first and second effective lengths. Similarly, if the number of comb tooth groups increases, the first effective length also increases accordingly; there is also a positive correlation between the first effective length and the number of comb tooth groups. Figure 7 As shown, assuming the second effective length is L and the number of comb tooth groups is 4, then the first effective length is actually approximately equal to 4L. Therefore, the total voltage applied to the left electrode port only needs to be 1 / 4 of the original, achieving a reduction in the applied DC bias voltage within a finite length. Here, the number of comb tooth groups can be increased or decreased according to actual conditions.

[0063] Optionally, in this embodiment of the application, the number of comb teeth groups is at least two groups.

[0064] In this embodiment, in order to ensure that the length of the DC bias electrode can be increased within the limited chip length, the number of comb groups should be at least two, so as to achieve the effect of increasing the length of the DC bias electrode.

[0065] Furthermore, to fully illustrate this embodiment, a cross-sectional schematic diagram of a set of comb teeth is provided, as shown below. Figure 8 As shown, the bottom layer of the cross-section is a silicon substrate (Si), the middle layer is a silicon dioxide insulating layer (SiO2), and the top layer is a lithium niobate thin film (LiNbO3). The total thickness of the lithium niobate thin film can be 550 nm (from the top of the trapezoid to the boundary between the lithium niobate thin film and the middle layer). The lithium niobate thin film is etched to form a ridge waveguide structure. The etching depth h' = 275 nm. The top width of the optical waveguide w = 1 μm. The first and second comb electrodes are symmetrically distributed on the left and right sides of the optical waveguide. The electrode spacing between the first and second comb electrodes is g = 5 μm, d1 = d2 = 20 μm, and the electrode height is h = 900 nm. The materials of the first and second comb electrodes and the upper layer of the optical waveguide can be air, silicon dioxide (SiO2), or other resin materials as protective layers. Here, an x-cut lithium niobate thin film is used, with the electric field direction along the Z direction and the waveguide transmission direction along the Y direction.

[0066] The optical field distribution of the TE mode in the thin-film lithium niobate optical waveguide obtained by simulation calculation under the above embodiment at a working wavelength of 1550nm is shown in the figure below. Figure 9 As shown, the electric field distribution around the waveguide structure is as follows: Figure 10 As shown. The photoelectric overlap integral factor calculated from the above photoelectric field is 0.63, and the calculated half-wave voltage length product is 4.1 V·cm. That is to say, when the bias electrode length L is set to 1 cm, a voltage of 4.1 V needs to be applied to the electrode ports of the ordinary straight-line signal electrode and ground electrode to achieve the π phase change. With the thin-film lithium niobate phase modulator provided in this application embodiment, with the chip length unchanged, the voltage applied to the electrode ports of the phase modulator signal electrode and ground electrode only needs to be about 1.1 V to achieve the π phase change. If the applied voltage is kept constant at 4.1 V, the electrode length L can be shortened to 0.25 cm by setting the thin-film lithium niobate phase modulator provided in this application embodiment, thereby significantly shortening the overall chip length.

[0067] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of any particular implementation scenario. The above disclosures are merely a few specific implementation scenarios of this application; however, this application is not limited thereto, and any variations conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A thin film lithium niobate phase modulator comprising a radio frequency modulation electrode, a direct current bias electrode and an optical waveguide, characterised in that, The direct current bias electrode comprises a first electrode and a second electrode, the first electrode is a signal electrode, and the second electrode is a ground electrode, or the first electrode is a ground electrode, and the second electrode is a signal electrode; The first electrode is in the shape of an open rectangle comprising one long side and two wide sides, and the open rectangle further comprises a plurality of groups of symmetrical first comb-shaped electrodes, two first comb-shaped electrodes in each group of first comb-shaped electrodes are connected to the two wide sides respectively; The second electrode is in the shape of an axisymmetric comb, comprising a plurality of groups of second comb-shaped electrodes, and the number of groups of second comb-shaped electrodes is the same as the number of groups of first comb-shaped electrodes; Each group of first comb-shaped electrodes in the first electrode and each group of second comb-shaped electrodes in the second electrode are arranged in a cross manner, and any group of first comb-shaped electrodes in the first electrode and a corresponding group of second comb-shaped electrodes in the second electrode form a group of comb-shaped groups; The winding-through position of the optical waveguide comprises the first comb-shaped electrodes and the second comb-shaped electrodes in each group of comb-shaped groups.

2. The thin-film lithium niobate phase modulator of claim 1, wherein, The relative direction between the electric field direction in which the electric field is generated between the first comb-shaped electrodes and the second comb-shaped electrodes in each group of comb-shaped groups and the direction of the optical axis of the lithium niobate crystal of the optical waveguide remains unchanged.

3. The thin-film lithium niobate phase modulator of claim 2, wherein, The width of the first comb-shaped electrodes is a first width, and the width of the second comb-shaped electrodes is a second width; The first distance between every two adjacent groups of first comb-shaped electrodes of the first electrode is greater than a target distance, and the target distance is twice the sum of the first width and the second width; The second distance between every two adjacent groups of second comb-shaped electrodes of the second electrode is greater than a target distance, and the target distance is twice the sum of the first width and the second width.

4. The thin-film lithium niobate phase modulator of claim 2 or 3, wherein, The bottom layer of the cross section corresponding to each group of comb-shaped groups is a silicon substrate layer, and the middle layer is a silicon dioxide insulating layer.

5. The thin-film lithium niobate phase modulator of claim 4, wherein, The core layer material of the optical waveguide is a lithium niobate film, and the lithium niobate film is etched to form a ridge waveguide structure.

6. The thin-film lithium niobate phase modulator of claim 5, wherein, The first comb-shaped electrodes and the second comb-shaped electrodes in each group of comb-shaped groups are symmetrically distributed on both sides of the ridge waveguide structure of the optical waveguide.

7. The thin-film lithium niobate phase modulator of claim 4, wherein, The upper layer of the cross section corresponding to each group of comb-shaped groups is one of a silicon dioxide insulating layer, an air layer, and a resin layer.

8. The thin-film lithium niobate phase modulator of claim 4, wherein, The signal electrode and the ground electrode are gold electrodes.

9. The thin-film lithium niobate phase modulator of claim 1, wherein, The first effective length of the direct current bias electrode is positively correlated with the second effective length of each group of comb-shaped groups and is positively correlated with the number of groups of comb-shaped groups.

10. The thin-film lithium niobate phase modulator of claim 9, wherein, The number of groups of comb-shaped groups is at least two.

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