A lithium niobate thin film electro-optic modulator

Abstract

The disclosure provides a lithium niobate thin film electro-optic modulator, which comprises: a one-dimensional photonic crystal, which is a single-row structure composed of a plurality of first structure units and second structure units arranged along an X-axis passing through a center point of the one-dimensional photonic crystal; the first and second structure units are respectively located on the left and right sides of the center line of the one-dimensional photonic crystal; the first structure unit is formed by etching a region A1 on the first basic unit; the second structure unit is formed by etching a region A2 on the second basic unit, which has a different distribution form from the region A1; the size of the region A1 on the single first and second structure units is equal to that of the region A2; input waveguides and output waveguides are arranged along a Y-axis perpendicular to the X-axis and connected to the upper and lower sides of the one-dimensional photonic crystal respectively; and modulation electrodes are arranged along the X-axis and located on the upper and lower sides of the one-dimensional photonic crystal respectively. The disclosure can improve the integration and stability of the electro-optic modulator and reduce the modulation energy consumption.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of electro-optic modulators, and in particular to a lithium niobate thin film electro-optic modulator. BACKGROUND

[0002] Electro-optic modulators are the core devices of optical communication systems, which modulate the amplitude or phase characteristics of the output light by changing the applied electric field. Lithium niobate material is widely used in the field of electro-optic modulation due to its superior electro-optic coefficient. However, the currently commercialized bulk lithium niobate electro-optic modulator is facing problems such as large size and power consumption, low integration, high manufacturing cost, and difficulty in expansion, which makes it difficult to meet the growing demand for data transmission in the future.

[0003] Lithium niobate thin film not only has superior electro-optic performance, but also can limit light transmission to a smaller area, and has better performance than traditional bulk material devices in many aspects. Modulators based on one-dimensional photonic crystals are more compact than other structures. The latest research progress (Li, M., Ling, J., He, Y. et al. Lithium niobate photonic-crystal electro-optic modulator. Nat Commun 11, 4123 (2020).) verifies that a single row structure can achieve modulation in a very small area, and the energy consumption of a single bit of modulation is far below the current device. However, this structure is actually based on photonic crystal defects to achieve high-quality factor optical localization states, and each unit in the single row structure needs to be changed slightly in size or position to achieve this function. This design increases the ultra-high precision requirement of the device in the actual processing process. In contrast, topologically protected photonic crystal structures are not sensitive to structural defects or deviations, and are expected to be used to realize similar single row structures to achieve corresponding electro-optic modulators. SUMMARY

[0004] The present disclosure aims to at least partially solve one of the technical problems in the related art.

[0005] To this end, the lithium niobate thin film electro-optic modulator provided by the embodiments of the present disclosure realizes a very small device size and reduces the required modulation energy consumption, and the device design structure is topologically protected and not sensitive to processing defects, especially the units in the structure that need to be processed have only two sizes to be processed and etched, greatly improving the stability of the device. The lithium niobate thin film electro-optic modulator provided by the present disclosure comprises:

[0006] A one-dimensional photonic crystal, which is a single-row structure composed of a plurality of first structural units and second structural units arranged in sequence along an X axis passing through a center point of the one-dimensional photonic crystal, a left side portion of the one-dimensional photonic crystal being composed of all the first structural units, a right side portion of the one-dimensional photonic crystal being composed of all the second structural units, the first structural units being formed by etching a region A1 on a first basic unit, the second structural units being formed by etching a region A2 on a second basic unit, the region A1 on a single first structural unit being equal in size to the region A2 on a single second structural unit, and the region A1 on a single first structural unit being symmetrically arranged with respect to the X axis and the Y axis, the region A2 on a single second structural unit being symmetrically arranged with respect to the X axis and the Y axis;

[0007] An input waveguide and an output waveguide, which are arranged along a Y axis perpendicular to the X axis and are connected to upper and lower sides of the one-dimensional photonic crystal, respectively; and

[0008] A modulation electrode, which is arranged along the X axis and is located on the upper and lower sides of the one-dimensional photonic crystal, respectively.

[0009] In some embodiments, the one-dimensional photonic crystal, the input waveguide and the output waveguide are made of X-cut lithium niobate, the X axis is arranged along the Y direction of the lithium niobate crystal axis, and the Y axis is arranged along the Z direction of the lithium niobate crystal axis.

[0010] In some embodiments, the one-dimensional photonic crystal is located in an electric field formed by the modulation electrode, and an optical signal to be modulated is coupled into a central region of the one-dimensional photonic crystal vertically through the input waveguide.

[0011] In some embodiments, the region A1 of a single first structural unit and the region A2 of a single second structural unit are one or more independent sub-regions formed by etching, and all the sub-regions formed on a single structural unit are symmetric with respect to the X axis and the Y axis.

[0012] Further, the region A1 of a single first structural unit is composed of at least two independent sub-regions, and the region A2 of a single second structural unit is composed of one sub-region.

[0013] In some embodiments, the periods of the first structural units and the second structural units are equal, the number of the first structural units and the second structural units should be ensured to form a physical boundary of the one-dimensional photonic crystal to form a localized state of the optical field; and / or

[0014] The first structural units and the second structural units have the same lattice constant to form a required energy band distribution.

[0015] Further, the intrinsic frequency of the optical field localization state of the lithium niobate thin film electro-optic modulator is 1660 nm, the period of the first structural unit and the second structural unit is 600 nm, the height is 300 nm, and the width is 750 nm, and the size of the etching region on a single structural unit is 350 nm*500 nm; the structure parameters of other working wavelengths are scaled in proportion.

[0016] In some embodiments, the number of the first structural unit and the second structural unit is at least 8, and each adjacent two structural units are arranged without a gap.

[0017] In some embodiments, the input waveguide and the output waveguide are single-mode TE polarization, the input waveguide and the output waveguide are directly connected with the upper and lower boundaries of the one-dimensional photonic crystal, and the position of the input and output waveguides deviates by no more than the width of one waveguide at the joint of the left part and the right part of the one-dimensional photonic crystal.

[0018] In some embodiments, the lithium niobate thin film electro-optic modulator further comprises a substrate and an insulating layer formed on the substrate, the one-dimensional photonic crystal, the input waveguide, the output waveguide and the modulation electrode are all formed on the insulating layer, and the insulating layer directly below the one-dimensional photonic crystal is removed.

[0019] The lithium niobate thin film electro-optic modulator provided by the embodiments of the present disclosure has the following characteristics and beneficial effects:

[0020] The design scheme fully utilizes the advantages of the one-dimensional topological photonic crystal structure, such as high-quality factor optical field localization state, small influence on structural defects, and small structure area, and can realize a small-size modulator (the entire modulation structure width only needs a few microns) that is easy to process on a thin film lithium niobate platform, which has great significance for improving the device integration and reducing the energy consumption of single modulation of the device in practical applications. Moreover, only two sizes (small rectangles and large square regions in the embodiment structure) of the units in the structure that need to be processed and etched are needed to be processed in the device, which greatly improves the stability of the device. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a top view of the lithium niobate thin film electro-optic modulator provided by the embodiments of the present disclosure, wherein the one-dimensional photonic crystal region is partially divided;

[0022] Figure 2 (a) and (b) in are respectively Figure 1 the sectional view at A-A in Figure 1 the side view of

[0023] Figure 3(a) and (b) are schematic diagrams of the first structural unit 11 and the second structural unit 12 that make up the left and right sides of the photonic crystal in the lithium niobate thin film electro-optic modulator provided in the embodiments of this disclosure.

[0024] Figure 4 In the examples of this disclosure, (a) and (b) are the structural parameters of the first structural unit formed by the lithium niobate thin film and the corresponding one-dimensional photonic crystal band, respectively.

[0025] Figure 5 The structural eigenstates obtained by simulating the structural parameters used in the embodiments of this disclosure are arranged according to the disclosed design and are located within the bandgap frequency range of the photonic crystal.

[0026] Figure 6 (a) shows the electric field distribution of the electro-optic modulator provided in this embodiment after excitation by the input waveguide (excitation frequency corresponds to...). Figure 5 (Eigenstates) Figure 6 (b) shows the transmission spectrum of the electro-optic modulator provided in the embodiments of this disclosure before and after an electric field is applied. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0028] Conversely, this application covers any alternatives, modifications, equivalent methods, and schemes made within the spirit and scope of this application as defined by the claims. Furthermore, to provide the public with a better understanding of this application, certain specific details are described in detail below. However, this application can be fully understood by those skilled in the art even without these detailed descriptions.

[0029] In the description of the disclosure, it needs to be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the disclosure and simplifying the description, and do not indicate or imply that the indicated basis or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the disclosure. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the disclosure, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0030] In the description of the disclosure, it needs to be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the disclosure can be understood according to the specific circumstances.

[0031] In the disclosure, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "upper", "above" and "on" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The "below", "under" and "under" of the first feature to the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0032] Referring to Figure 1 The lithium niobate thin film electro-optical modulator provided by the embodiment of the disclosure comprises:

[0033] The one-dimensional photonic crystal 10 is a single-row structure composed of a plurality of first structure units 11 and second structure units 12 arranged along the X axis passing through the center point of the one-dimensional photonic crystal 10, the left part PhC1 of the one-dimensional photonic crystal 10 is composed of all the first structure units 11, the right part PhC2 of the one-dimensional photonic crystal 10 is composed of all the second structure units 12, the first structure units 11 are formed by etching the region A1 on the first basic unit, the second structure units 12 are formed by etching the region A2 on the second basic unit, the size of the region A1 on the single first structure unit 11 is equal to the size of the region A2 on the single second structure unit 12, the region A1 on the single first structure unit 11 is symmetrically arranged with respect to the X axis and the Y axis, the region A2 on the single second structure unit 12 is symmetrically arranged with respect to the X axis and the Y axis;

[0034] The input waveguide 20 and the output waveguide 21 are arranged along the Y axis perpendicular to the X axis and are connected to the upper and lower sides of the one-dimensional photonic crystal 10, respectively; and

[0035] The modulation electrode is arranged along the X axis and is located on the upper and lower sides of the one-dimensional photonic crystal 10, respectively.

[0036] In some embodiments, referring to Figure 2 (a) and (b) (wherein, Figure 2 (b) only shows a partial side view of the electro-optical modulator in the X axis direction), the lithium niobate thin film electro-optical modulator provided by the present disclosure further comprises a substrate and an insulating layer formed on the substrate, the one-dimensional photonic crystal 10, the input waveguide 20, the output waveguide 21 and the modulation electrode are formed on the insulating layer. The insulating layer can be made of silicon dioxide with a thickness of several hundred nanometers to several microns, and the substrate can be made of silicon to support the structure layers thereon.

[0037] In some embodiments, the one-dimensional photonic crystal 10, the input waveguide 20 and the output waveguide 21 serve as the optical structure of the present embodiment electro-optical modulator for guiding the traveling direction of the input optical signal in the present electro-optical modulator and modulating the input optical signal (specifically, the input optical signal to be modulated is coupled into the center region of the one-dimensional photonic crystal 10 through the input waveguide 20, and then outputted after the signal modulation process is completed through the output waveguide 21 located at the other side of the single-row structure and consistent with the input waveguide 20 in position and direction), and the optical structure is made of X-cut lithium niobate, with the X axis (i.e. the layout direction of the one-dimensional photonic crystal 10 and the modulation electrode) arranged along the Y direction of the lithium niobate crystal axis, and the Y axis (i.e. the layout direction of the input waveguide 20 and the output waveguide 21) arranged along the Z direction of the lithium niobate crystal axis. The modulation electrode serves as the electrical structure of the present embodiment electro-optical modulator, which can change the refractive index of the thin-film lithium niobate material under the action of the electric field by using the electro-optic effect, so as to cause the change of the transmission performance of the device and realize high-performance electro-optical modulation. The modulation electrode is made of conductive material, preferably gold, and can also be made of platinum, titanium, ITO and other materials. It is required that the one-dimensional photonic crystal 10 should be partially or entirely located in the electric field formed by the modulation electrode. According to the structure shown in FIG. 1, there are two pairs of modulation electrodes, one pair of modulation electrodes 30 and 31 symmetrically arranged on the upper and lower sides of the left part PhC1 of the one-dimensional photonic crystal 10, and the other pair of modulation electrodes 32 and 33 symmetrically arranged on the upper and lower sides of the right part PhC2 of the one-dimensional photonic crystal 10. The length (i.e. the size along the X axis) of the modulation electrode is P~n*P (n is the number of periods of the structural unit 11 or 12, and P is the period of the structural unit), and the width (i.e. the size along the Y axis) is 5 μm~10 μm. The net distance between the modulation electrode and the one-dimensional photonic crystal 10 along the Y axis should be more than 4 μm. Figure 1

[0038] In some embodiments, the input waveguide 20 and the output waveguide 21 are both single-mode TE polarization, the input waveguide 20 and the output waveguide 21 are directly connected to the upper and lower boundaries of the one-dimensional photonic crystal 10, respectively, and the position of the input waveguide 20 and the output waveguide 21 deviates from the joint of the left part PhC1 and the right part PhC2 of the one-dimensional photonic crystal 10 by no more than one waveguide width. The width of the input waveguide 20 and the output waveguide 21 is 300 nm~500 nm.

[0039] In some embodiments, the one-dimensional photonic crystal 10 is composed of two structural units 11 and 12, and the two structural units are arranged without gap along the center line of the one-dimensional photonic crystal 10. Figure 1 ​The left part PhC1 and the right part PhC2 of the one-dimensional photonic crystal 10 are formed on the left and right sides of the region A, respectively. The first structure unit 11 and the second structure unit 12 have the same lattice constant to form the required energy band distribution. The distribution of the region A1 on the single first structure unit 11 is different from the distribution of the region A2 on the single second structure unit 12. The region A1 on the single first structure unit 11 and the region A2 on the single second structure unit 12 can be one or more independent sub-regions formed by etching, and all the sub-regions formed on the single structure unit are required to be symmetrical about the X axis and the Y axis. The present disclosure does not have special requirements for the shape of the etched region on the single first structure unit 11 and the single second structure unit 12, which can be regular or irregular shape, as long as the actual total etched region A1 of the single first structure unit 11 is equal in size to the actual total etched region A2 of the single second structure unit 12. The periods P of the two structure units are equal, and the number of the two structure units can be equal or unequal. In order to ensure that the light field can be confined in the one-dimensional photonic crystal 10, the number of the structure units constituting the left part PhC1 and the right part PhC2 of the one-dimensional photonic crystal 10 should not be less than 8, that is, the number of the first structure units 11 constituting the left part PhC1 should be greater than or equal to 8, and the number of the second structure units 12 constituting the right part PhC2 should be greater than or equal to 8.

[0040] Optionally, referring to Figure 3 In (a) and (b), the region A1 on the first structure unit 11 is composed of two rectangular sub-regions 110 and 111 which are independent of each other and equal in size, and the sub-regions 110 and 111 are symmetrically arranged about the X axis and the Y axis. The region A2 on the second structure unit 12 is composed of a rectangular sub-region 120 located at the center of the second structure unit 12, and the size of the sub-region 120 is equal to the sum of the sizes of the sub-regions 110 and 111, that is, the sub-regions 110 and 111 are the uniform distribution structure of the sub-region 120.

[0041] More specifically, in the designed thin-film lithium niobate electro-optical modulator, the commonly used X-cut thin-film lithium niobate material is selected as the design raw material to fully utilize its superior electro-optical performance. The thickness of the lithium niobate thin film layer is 300 nm, and below it there are a 3-micron-thick silicon dioxide layer and a thicker silicon substrate layer. When the eigenfrequency of the optical field localization state is 1660 nm, the structure parameters of the first structure unit 11 are optimized according to the selected materials. Referring to Figure 3 Figure 4 Figure 4 ​​In (a), the structure size of the optimized first structure unit 11 is shown, the period P of the first structure unit 11 is 600 nm (i.e. the size of the first structure unit 11 along the X axis), the height H is 300 nm, the width W is 750 nm (i.e. the size of the first structure unit 11 along the Y axis), and the etching region of lithium niobate is 175 nm*500 nm (corresponding to the size of the sub-region 110 in the first structure unit 11, which is equal to the size of the sub-region 111). Correspondingly, the period, height and width of the second structure unit 12 are the same as those of the first structure unit 11, and the etching region of the second structure unit 12 is 350 nm*500 nm (corresponding to the size of the sub-region 120 in the second structure unit 12). Both the first structure unit 11 and the second structure unit 12 are arranged along the Y direction of the lithium niobate crystal axis (i.e. the X axis direction in the schematic diagram). In order to obtain better device performance, the silicon dioxide insulating layer below the lithium niobate thin film layer forming the one-dimensional photonic crystal 10 is removed (in actual processing, it can be realized by chemical treatment) to form a suspended structure. The corresponding one-dimensional photonic crystal band structure of the structure is simulated and calculated as shown in Figure 4 In (b), a light transmission forbidden band can be formed near the frequency of 180 THz (the frequency at which the forbidden band is located can be adjusted to other required frequencies by changing the structure parameters in proportion). Further, based on the one-dimensional SSH model in the solid physical topology model, the corresponding one-dimensional photonic crystal band structure of the structure is simulated and calculated as shown in Figure 4 When the first structure unit 11 and the second structure unit 12 with the structure parameters shown in (a) are arranged on the left and right sides of the one-dimensional photonic crystal 10 respectively, a light field localization state can be formed at the physical junction of the two structure units, as shown in Figure 5 The localization state is located in the forbidden band of the one-dimensional photonic crystal.

[0042] The above-mentioned localization state is located in the forbidden band of the photonic crystal, and there is no similar localization state near the frequency in the entire forbidden band range. When the single-mode input and output waveguides are connected to the center line of the one-dimensional structure (the light is transmitted along the Z direction of the lithium niobate crystal axis, i.e. the Y axis direction in the schematic diagram, as shown in Figure 6 (a)), the light will be mostly transmitted through the output waveguide 21 due to the unlimited transmission outside the forbidden band range of the structure. However, in the forbidden band of the photonic crystal, the transmission rate will decrease due to the absence of light transmission state, especially, due to the existence of the optical localization state of the structure, the lowest transmission rate will be formed at the frequency (compared with the localization state in Figure 5 and the transmission light of the light field localization in (a) of Figure 6 will be suppressed). Therefore, the unique transmission characteristics of the structure can be used to realize electro-optic modulation. The selected lithium niobate material can obtain a refractive index change after applying an electric field, and the change corresponds to the corresponding movement of the transmission peak, as shown in Figure 6As shown in (b), high performance modulation can be achieved by using the electro-optic effect. In particular, since the designed electro-optic modulator is only about 10 microns long, the energy consumption required when the electro-optic modulator is modulating is extremely small.

[0043] In summary, the present disclosure combines the advantages of high quality factor, small influence of structural defects, and small structure area of one-dimensional photonic crystals to greatly reduce the size of the electro-optic modulator, improve the integration level, and reduce the energy consumption required by the millimeter-level size of ordinary devices. Moreover, only two sizes of etching structures need to be prepared in the actual preparation process of the device, which can greatly improve the performance stability in the actual preparation process.

[0044] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0045] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A lithium niobate thin film electro-optic modulator, characterized by, The lithium niobate thin film electro-optical modulator comprises: a one-dimensional photonic crystal formed by etching a lithium niobate thin film, the one-dimensional photonic crystal being a single-row structure composed of a plurality of first structure units and second structure units arranged along an X axis passing through a center point of the one-dimensional photonic crystal, a left part of the one-dimensional photonic crystal being composed of all the first structure units, and a right part of the one-dimensional photonic crystal being composed of all the second structure units, the first structure unit being formed by etching a region A1 on a first basic unit, the second structure unit being formed by etching a region A2 on a second basic unit, the region A1 on a single first structure unit being equal in size to the region A2 on a single second structure unit, the region A1 on a single first structure unit being symmetrically arranged with respect to the X axis and the Y axis, and the region A2 on a single second structure unit being symmetrically arranged with respect to the X axis and the Y axis; an input waveguide and an output waveguide arranged along a Y axis perpendicular to the X axis and connected to upper and lower sides of the one-dimensional photonic crystal, respectively; and a modulation electrode arranged along the X axis and located on the upper and lower sides of the one-dimensional photonic crystal, respectively.

2. The lithium niobate thin film electro-optic modulator of claim 1, wherein, The one-dimensional photonic crystal, the input waveguide and the output waveguide are made of X-cut lithium niobate, the X axis is arranged along the Y direction of the lithium niobate crystal axis, and the Y axis is arranged along the Z direction of the lithium niobate crystal axis.

3. The lithium niobate thin film electro-optic modulator of claim 1, wherein, The one-dimensional photonic crystal is located in an electric field formed by the modulation electrode, and an optical signal to be modulated is coupled into a central region of the one-dimensional photonic crystal through the input waveguide.

4. The lithium niobate thin film electro-optic modulator of claim 1, wherein, The region A1 of a single first structure unit and the region A2 of a single second structure unit are one or more independent sub-regions formed by etching, and all the sub-regions formed on a single structure unit are symmetric with respect to the X axis and the Y axis.

5. The lithium niobate thin film electro-optic modulator of claim 4, wherein, The region A1 of a single first structure unit is composed of at least two independent sub-regions, and the region A2 of a single second structure unit is composed of one sub-region.

6. The lithium niobate thin film electro-optic modulator of claim 1, wherein, The first structure unit and the second structure unit have the same period, the number of the first structure units and the second structure units should be ensured to form a physical boundary of the one-dimensional photonic crystal to form a localized optical field state; and / or The first structure unit and the second structure unit have the same lattice constant to form a required energy band distribution.

7. The lithium niobate thin film electro-optic modulator of claim 6, wherein, When the intrinsic frequency of the localized optical field state of the lithium niobate thin film electro-optical modulator is 1660 nm, the period of the first structure unit and the second structure unit is 600 nm, the height is 300 nm, the width is 750 nm, and the size of the etched region on a single structure unit is 350 nm*500 nm; the structure parameters of other working wavelengths are scaled proportionally.

8. The lithium niobate thin film electro-optic modulator of claim 1, wherein, The number of the first structure units and the second structure units is at least 8, and there is no gap between adjacent two structure units.

9. The lithium niobate thin film electro-optic modulator of claim 1, wherein, The input waveguide and the output waveguide are both single-mode TE polarization, the input waveguide and the output waveguide are directly connected with the upper and lower boundaries of the one-dimensional photonic crystal respectively, and the position of the input and output waveguide deviates from the joint of the left part and the right part of the one-dimensional photonic crystal by not more than the width of one waveguide.

10. The lithium niobate thin film electro-optic modulator of any one of claims 1-9, wherein, Further comprising a substrate and an insulating layer formed on the substrate, the one-dimensional photonic crystal, the input waveguide, the output waveguide and the modulation electrode are all formed on the insulating layer, and the insulating layer directly below the one-dimensional photonic crystal is removed.

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