Dispersion compensating device and method of manufacturing the same

Abstract

The application discloses a dispersion compensation device and a preparation method thereof. The dispersion compensation device comprises a substrate, an insulating layer arranged on the substrate, a lithium niobate film arranged on the insulating layer, a first multimode interferometer, a plurality of same chirped Bragg gratings, a plurality of optical waveguides, an incident waveguide cross section and an outgoing waveguide cross section arranged on the lithium niobate film. The first multimode interferometer is provided with a plurality of ports at two ends. Two ports of a first end of the first multimode interferometer are connected to the incident waveguide cross section and the outgoing waveguide cross section through transmission optical waveguides respectively. A plurality of ports of a second end of the first multimode interferometer are connected to input optical waveguides of the plurality of chirped Bragg gratings through transmission optical waveguides respectively. The period of the chirped Bragg grating linearly changes from a first period to a second period, and dispersion compensation is provided. The embodiment of the application can reduce loss, reduce the preparation process requirement, and can be widely applied to the technical field of photonic devices.

Description

Technical Field

[0001] This invention relates to the field of photonic device technology, and in particular to an on-chip dispersion compensation device and its fabrication method. Background Technology

[0002] In fiber optic communication systems, especially long-distance communication, dispersion causes pulse broadening and intersymbol interference (ISI), necessitating dispersion compensation. Furthermore, time-lens systems used to generate ultrashort pulses also require dispersion compensators for pulse compression. Current dispersion compensation methods suffer from drawbacks such as high loss or demanding fabrication processes. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a dispersion compensation device and its fabrication method, which can reduce losses and lower the requirements for fabrication processes.

[0004] In a first aspect, embodiments of the present invention provide a dispersion compensation device, comprising a substrate, an insulating layer disposed on the substrate, a lithium niobate thin film disposed on the insulating layer, a first multimode interferometer disposed on the lithium niobate thin film, a plurality of identical chirped Bragg gratings, a plurality of optical waveguides, an incident waveguide cross section, and an exit waveguide cross section; the first multimode interferometer has a plurality of ports distributed at both ends, the two ports at the first end of the first multimode interferometer are respectively connected to the incident waveguide cross section and the exit waveguide cross section through transmission optical waveguides, and the plurality of ports at the second end of the first multimode interferometer are respectively connected to the input optical waveguides of the plurality of chirped Bragg gratings through transmission optical waveguides, the period of the chirped Bragg gratings linearly changing from a first period to a second period.

[0005] Optionally, the width of the transmission optical waveguide is equal to the width of the input optical waveguide.

[0006] Optionally, the dispersion compensation device also includes a second multimode interferometer, wherein the output waveguide of the chirped Bragg grating is connected to the port of the first end of the second multimode interferometer via a transmission waveguide, and the width of the input waveguide is greater than or equal to the width of the transmission waveguide.

[0007] Optionally, when the width of the input optical waveguide is greater than the width of the transmission optical waveguide, the dispersion compensation device further includes a tapered waveguide, which is connected to the port of the second end of the second multimode interferometer, and the width of the tapered waveguide increases from the width of the transmission optical waveguide to the width of the input optical waveguide.

[0008] Optionally, the width of the input optical waveguide is greater than or equal to the width of the transmission optical waveguide, and the dispersion compensation device further includes a dissipative tapered waveguide, with the output optical waveguides respectively connected to the dissipative tapered waveguides.

[0009] Optionally, when the width of the input optical waveguide is greater than the width of the transmission optical waveguide, the width of the dissipative tapered waveguide increases from the width of the transmission optical waveguide to the width of the input optical waveguide.

[0010] Optionally, the surfaces of the components on the lithium niobate film and the lithium niobate film are covered with a cladding material, the cladding material including silicon dioxide.

[0011] Optionally, when the dispersion is positive, the first period is smaller than the second period; when the dispersion is negative, the first period is larger than the second period.

[0012] Optionally, the spacing between the chirped Bragg gratings is greater than 10 μm.

[0013] Secondly, embodiments of the present invention provide a method for fabricating a dispersion compensation device, comprising:

[0014] A substrate is provided, and a lithium niobate thin film is prepared on the substrate;

[0015] Photoresist is coated on a lithium niobate film, and all component structures are transferred onto the photoresist according to preset requirements. Unnecessary photoresist is removed according to all component structures to obtain a mask structure. All components include a first multimode interferometer, several identical chirped Bragg gratings, several optical waveguides, an incident waveguide cross section, and an outgoing waveguide cross section.

[0016] The mask structure was transferred onto a lithium niobate film using an etching method.

[0017] The implementation of this invention provides the following advantages: The dispersion compensation device in this embodiment includes a first multimode interferometer and a chirped Bragg grating. The two ports at the first end of the first multimode interferometer are connected to the incident waveguide section and the exit waveguide section respectively through transmission optical waveguides. The ports at the second end of the first multimode interferometer are connected to the input optical waveguide of the chirped Bragg grating respectively through transmission optical waveguides. An on-chip dispersion compensation structure with no intrinsic loss is constructed between the first multimode interferometer and the chirped Bragg grating, eliminating the need for an optical circulator. Furthermore, the device structure is only on the order of millimeters, achieving low loss. In addition, the fabrication method is simple, reducing the requirements for fabrication processes and facilitating mass production. Attached Figure Description

[0018] Figure 1 This is a perspective view of a dispersion compensation device provided in an embodiment of the present invention;

[0019] Figure 2 This is a top view of a dispersion compensation device provided in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the structure of a chirped Bragg grating provided in an embodiment of the present invention;

[0021] Figure 4This is a perspective view of another dispersion compensation device provided in an embodiment of the present invention;

[0022] Figure 5 This is a top view of another dispersion compensation device provided in an embodiment of the present invention;

[0023] Figure 6 This is a comparison chart of simulation data and test data provided in an embodiment of the present invention;

[0024] Figure 7 This is a perspective view of another dispersion compensation device provided in an embodiment of the present invention;

[0025] Figure 8 This is a top view of another dispersion compensation device provided in an embodiment of the present invention;

[0026] Figure 9 This is a schematic flowchart of the fabrication method of a dispersion compensation device provided in an embodiment of the present invention.

[0027] In the figure: 1. Substrate, 2. Insulating layer, 3. Lithium niobate thin film, 4. 2×2 multimode interferometer, 5. Optical waveguide, 6. Chirped Bragg grating, 7. Incident waveguide cross section, 8. Reflection output waveguide cross section, 9. Dissipative tapered waveguide. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0029] In the following description, references are made to “some embodiments,” which describe a subset of all possible embodiments. However, it is understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0030] In the following description, the terms "first, second, third" are used merely to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first, second, third" may be interchanged in a specific order or sequence where permitted, so that the embodiments of the invention described herein can be implemented in an order other than that illustrated or described herein.

[0031] Unless otherwise defined, all technical and scientific terms used in the embodiments of this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in the embodiments of this invention is for descriptive purposes only and is not intended to limit the invention.

[0032] This invention provides a dispersion compensation device, comprising a substrate, an insulating layer disposed on the substrate, a lithium niobate thin film disposed on the insulating layer, a first multimode interferometer disposed on the lithium niobate thin film, a plurality of identical chirped Bragg gratings, a plurality of optical waveguides, an incident waveguide cross section, and an exit waveguide cross section; the first multimode interferometer has a plurality of ports distributed at both ends, the two ports at the first end of the first multimode interferometer are respectively connected to the incident waveguide cross section and the exit waveguide cross section through transmission optical waveguides, and the plurality of ports at the second end of the first multimode interferometer are respectively connected to the input optical waveguides of the plurality of chirped Bragg gratings through transmission optical waveguides, the period of the chirped Bragg gratings linearly changing from a first period to a second period.

[0033] It should be noted that the materials used for the first multimode interferometer, chirped Bragg gratings, optical waveguides, incident waveguide cross-sections, and exit waveguide cross-sections are all lithium niobate. The number of ports in the first multimode interferometer is determined based on the actual application; for example, the first multimode interferometer may be a 2×2 multimode interferometer. The number of chirped Bragg gratings is determined based on the number of ports in the first multimode interferometer. For example, in a 2×2 multimode interferometer, two ports are used to connect the incident and exit waveguide cross-sections, and the other two ports are used to connect the chirped Bragg gratings, resulting in two chirped Bragg gratings.

[0034] See Figure 1 and Figure 2 , Figure 1 A 3D diagram showing a dispersion compensation device. Figure 2 The diagram shows a top view of a dispersion compensation device, which includes a substrate 1, an insulating layer 2 disposed on the substrate 1, a lithium niobate thin film 3 disposed on the insulating layer 2, a 2×2 multimode interferometer 4 fabricated on the lithium niobate thin film 3, two identical chirped Bragg gratings 6, and a transmission waveguide 5 fabricated on the lithium niobate thin film for transmitting the light beam, with an incident waveguide cross-section 7 and an exit waveguide cross-section 8. The two output ports of the 2×2 multimode interferometer 4 are respectively connected to the input waveguides of the two chirped Bragg gratings 6 through two S-shaped transmission waveguides.

[0035] The incident beam enters through the incident waveguide section 7 of the 2×2 multimode interferometer and is split into two beams. The two beams are output from the two right ports of the 2×2 multimode interferometer and enter two chirped Bragg gratings respectively. The beam whose wavelength meets the Bragg condition set by the chirped Bragg grating (wavelength = 2 × effective refractive index × period) will be reflected back and enter the 2×2 multimode interferometer again. Then it is output from the exit waveguide section 8, and the reflected light is given a set dispersion value.

[0036] The substrate material includes silicon or quartz. For optoelectronic platforms, silicon-based materials are currently the mainstream material due to their lower cost and compatibility with CMOS (Complementary Metal Oxide Semiconductor) processes. Lithium niobate, on the other hand, has become the preferred material for electro-optic modulators due to its excellent linear electro-optic (Pockels) effect.

[0037] The refractive index modulation of the chirped Bragg grating employs an apodization process. The width of the grating teeth of the two chirped Bragg gratings is suppressed by apodization design to suppress group delay ripple. The apodization function can be selected as needed, such as a sine function, raised cosine function, hyperbolic tangent function, or super-Gaussian function. In this embodiment, the chirped Bragg grating operates in the C-band with a center wavelength of 1550 nm; the period linearly varies from 429 nm to 445 nm, thus imparting a quadratic phase shift to the reflected light. This quadratic phase shift results in a linear group delay, which provides constant group delay dispersion with a duty cycle of 50%. The average waveguide width is 1 μm, and the modulation depth is 0.65 μm. The length of the chirped Bragg grating is 0.54 mm, and both the input and output waveguide widths are 1 μm. The Bragg grating employs an apodization process, which reduces the refractive index modulation at the input end of the Bragg grating and decreases the resonance between the front and back ends of the reflected light, thereby reducing the ripple jitter of the group delay. The apodization function can be selected as needed.

[0038] The optical waveguides are all monolithic ridge waveguides, consisting of a lower lithium niobate thin film planar layer and an upper ridge structure.

[0039] Optionally, when the dispersion is positive, the first period is smaller than the second period; when the dispersion is negative, the first period is larger than the second period.

[0040] Specifically, the sizes of the first and second periods are determined based on the dispersion requirements; see [reference needed]. Figure 3 , Figure 3 A schematic diagram showing the structure of a chirped Bragg grating. Figure 3 The first period is smaller than the second period, and the first period increases linearly to the second period.

[0041] Optionally, the spacing between the chirped Bragg gratings is greater than 10 μm.

[0042] If the spacing between chirped Bragg gratings is too small, it may cause crosstalk; setting the spacing between chirped Bragg gratings to be greater than 10 μm can reduce crosstalk between two gratings and ensure spectral quality.

[0043] Alternatively, the substrate may be silicon or quartz.

[0044] Optionally, the surfaces of the components on the lithium niobate film and the lithium niobate film are covered with a cladding material, the cladding material including silicon dioxide.

[0045] Specifically, the cladding layer serves to protect the device and improve spectral quality. The material of the cladding layer is determined according to the actual application, and this embodiment does not impose specific limitations. The cladding layer material includes, but is not limited to, silicon dioxide, and the silicon dioxide cladding layer thickness is greater than 1 μm.

[0046] Optionally, the width of the transmission optical waveguide is equal to the width of the input optical waveguide.

[0047] The widths of the transmission waveguide and the input waveguide are determined based on the actual application, and this embodiment does not impose specific limitations. In one specific embodiment, the widths of both the transmission waveguide and the input waveguide of the chirped Bragg grating are 1 μm.

[0048] Optionally, the dispersion compensation device also includes a second multimode interferometer, wherein the output waveguide of the chirped Bragg grating is connected to the port of the first end of the second multimode interferometer via a transmission waveguide, and the width of the input waveguide is greater than or equal to the width of the transmission waveguide.

[0049] The second multimode interferometer can be the same as the first multimode interferometer; for example, both the first and second multimode interferometers can be 2×2 multimode interferometers. The output ports of the two chirped Bragg gratings can be connected to the two input ports of the 2×2 multimode interferometer, respectively.

[0050] Optionally, when the width of the input optical waveguide is greater than the width of the transmission optical waveguide, the dispersion compensation device further includes a tapered waveguide, which is connected to the port of the second end of the second multimode interferometer, and the width of the tapered waveguide increases from the width of the transmission optical waveguide to the width of the input optical waveguide.

[0051] See Figure 4 and Figure 5 , Figure 4 A 3D diagram showing a dispersion compensation device. Figure 5The diagram shows a top view of a dispersion compensation device. The device includes a substrate 1, an insulating layer 2 disposed on the substrate 1, a lithium niobate thin film 3 disposed on the insulating layer 2, two 2×2 multimode interferometers 4, two identical chirped Bragg gratings 6, and a transmission waveguide 5 disposed on the lithium niobate thin film for transmitting the light beam. The two output ports of the 2×2 multimode interferometer A are connected to the input waveguides of the two chirped Bragg gratings via two S-shaped transmission waveguides, respectively. The output waveguides of the two chirped Bragg gratings are connected to the two input ports of the 2×2 multimode interferometer B via two S-shaped transmission waveguides, respectively. When the width of the input waveguide of the chirped Bragg grating is greater than that of the transmission waveguide, a tapered waveguide is used to connect them. The width of the tapered waveguide gradually increases from the width of the transmission waveguide to the width of the input waveguide of the chirped Bragg grating, and its waveguide length is set to ensure adiabatic transmission of the ground state mode. It should be noted that the widths of the left and right waveguides of the tapered waveguide are the same as the widths of the adjacent waveguides.

[0052] In this embodiment, the input beam enters from the input end of the optical waveguide, passes through the incident waveguide section 7 of the 2×2 multimode interferometer A, and is then input into interferometer A. The beam is split into two identical beams, which pass through two chirped Bragg gratings A and B, respectively. The light whose wavelength meets the Bragg condition is reflected back and re-enters the 2×2 multimode interferometer A. The two reflected beams interfere within the multimode interferometer and are output at the exit waveguide section 8, obtaining all reflected light containing the desired dispersion. The remaining light exits from the Bragg grating output waveguide, passes through the 2×2 multimode interferometer B, and is output as transmitted light from the lower right port. Alternatively, it can directly enter two dissipative tapered waveguides. As the width of the waveguides gradually decreases, the waveguides' restriction on the optical mode field weakens, and the light is dissipated outside the sheet.

[0053] See Figure 6 ,like Figure 6 (a) shows the simulation results of this embodiment, and (b) shows the experimental results of this embodiment. In this embodiment, the length of the chirped Bragg grating is 0.54 mm. The grating reflection spectrum and group delay curve obtained by numerical simulation are shown below. Figure 6 As shown in (a): the solid line R is the spectral curve, with a bandwidth covering 1530-1575nm, exhibiting near total internal reflection; the dashed line is the group delay curve GD, whose linear portion has a bandwidth of 45nm, covering 1530-1575nm, and the dotted line represents the linear fit of this portion, with a slope of 0.2219ps / nm, representing the group delay. Experimental results are shown in the figure below. Figure 6As shown in (b), experimental measurements revealed that the device's reflection spectrum R (solid line) covers a 45nm bandwidth of 1520-1565nm in the C-band, achieving a GD group delay of 0.2111ps / nm (cross symbol), corresponding to a dispersion value of 390ps / nm / m. This is 2.1 × 10⁴ times higher than the dispersion value of single-mode fiber SMF-28 (0.018ps / nm / m). The on-chip insertion loss in the reflection spectrum is less than 1dB, with no intrinsic loss. (Compared with simulation data) Figure 6 (a) In comparison, the chromatic dispersion data are basically consistent with the experimental data, with a blue shift of about 10 nm in the spectrum, which is presumably due to the error in the duty cycle of the grating teeth. The overall device size is about 0.8 mm. The on-chip dispersion compensation device in this embodiment can achieve on-chip dispersion compensation in the C-band 45 nm bandwidth range, with high compactness and low loss.

[0054] Optionally, the width of the input optical waveguide is greater than or equal to the width of the transmission optical waveguide, and the dispersion compensation device further includes a dissipative tapered waveguide, with the output optical waveguides respectively connected to the dissipative tapered waveguides.

[0055] Dissipative conical waveguides are used to dissipate the light output from chirped Bragg gratings.

[0056] Optionally, when the width of the input optical waveguide is greater than the width of the transmission optical waveguide, the width of the dissipative tapered waveguide increases from the width of the transmission optical waveguide to the width of the input optical waveguide.

[0057] See Figure 7 and Figure 8 , Figure 7 A 3D diagram showing a dispersion compensation device. Figure 8 The diagram shows a top view of a dispersion compensation device. The dispersion compensation device includes a substrate 1, an insulating layer 2 disposed on the substrate 1, a lithium niobate thin film 3 disposed on the insulating layer 2, a 2×2 multimode interferometer 4, two identical chirped Bragg gratings 6, two identical dissipative tapered waveguides 9, and a transmission waveguide 5 for transmitting the light beam, all fabricated on the lithium niobate thin film 3. The two output ports of the 2×2 multimode interferometer 4 are respectively connected to the input waveguides of the two chirped Bragg gratings 6 through two S-shaped transmission waveguides. The output waveguides of the two chirped Bragg gratings 6 are respectively connected to the two dissipative tapered waveguides 9. The width of the transmission waveguide is 1 μm, and the width of the input waveguide of the chirped Bragg grating is set to be greater than or equal to the width of the transmission waveguide. When the input waveguide width of the chirped Bragg grating is greater than that of the transmission waveguide, a tapered waveguide is used to connect the two. The width of the tapered waveguide gradually increases from the width of the transmission waveguide to the width of the input waveguide of the chirped Bragg grating, and its waveguide length is set to ensure adiabatic transmission of the ground state mode. Here, the widths of both the transmission waveguide and the input waveguide of the chirped Bragg grating are set to 1 μm.

[0058] In this embodiment, the light beam enters from the input end of the optical waveguide, passes through the incident waveguide section 7 of the 2×2 multimode interferometer, and is input into the interferometer. The light beam is split into two identical beams, which pass through two chirped Bragg gratings A and B, respectively. The light whose wavelength meets the Bragg condition is reflected back and re-enters the 2×2 multimode interferometer A, and then exits from the output waveguide section 8. The reflected light is given a set dispersion value, and the remaining light is output from the Bragg grating output waveguide and enters two dissipative tapered waveguides, and is finally dissipated off-chip.

[0059] Implementing the embodiments of the present invention has the following beneficial effects: The dispersion compensation device in this embodiment includes a first multimode interferometer and a chirped Bragg grating. The two ports at the first end of the first multimode interferometer are respectively connected to the incident waveguide section and the exit waveguide section through transmission optical waveguides. The ports at the second end of the first multimode interferometer are respectively connected to the input optical waveguide of the chirped Bragg grating through transmission optical waveguides. A dispersion compensation structure with no intrinsic loss is constructed between the first multimode interferometer and the chirped Bragg grating, eliminating the need for an optical circulator. Furthermore, the device structure is only on the order of millimeters, achieving low loss.

[0060] See Figure 9 This invention provides a method for fabricating a dispersion compensation device, comprising:

[0061] S100: Provide a substrate and prepare a lithium niobate thin film on the substrate.

[0062] The substrate material is determined based on the actual application, and lithium niobate thin films are prepared on the substrate by sputtering or other methods.

[0063] S200. Photoresist is applied to a lithium niobate film. All component structures are transferred onto the photoresist according to preset requirements. Unnecessary photoresist is removed based on all component structures to obtain a mask structure. All components include a first multimode interferometer, several identical chirped Bragg gratings, several optical waveguides, an incident waveguide cross section, and an outgoing waveguide cross section.

[0064] The distribution, shape, size, and connection relationships of all components are determined according to application requirements. A high-speed spin coating method is used to coat a lithium niobate film with photoresist. Electron beam exposure is then used to transfer the optical structure onto the photoresist, and development is used to remove unwanted portions of the photoresist to obtain the mask structure.

[0065] S300: An etching method is used to transfer the mask structure onto a lithium niobate film.

[0066] In an inductively coupled plasma system, dry etching of lithium niobate is performed using an etching gas to transfer optical structures onto a thin lithium niobate film. The etching gas includes argon plasma or a sulfur hexafluoride / argon mixed gas plasma, and the etching depth of lithium niobate is less than the film thickness.

[0067] Implementing the embodiments of the present invention has the following beneficial effects: a lithium niobate thin film is prepared on a substrate, then a mask is prepared by photoresist, and the mask structure is transferred to the lithium niobate thin film by etching, thereby preparing the dispersion compensation device in this embodiment. The preparation method is simple, reduces the preparation process requirements, and is convenient for mass production.

[0068] It is evident that the content of the above method embodiments is applicable to this system embodiment. The specific functions implemented in this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0069] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A dispersion compensation device, characterized in that, The device includes a substrate, an insulating layer disposed on the substrate, a lithium niobate thin film disposed on the insulating layer, a first multimode interferometer disposed on the lithium niobate thin film, several identical chirped Bragg gratings, several optical waveguides, an incident waveguide cross section, and an exit waveguide cross section. Several ports are distributed at both ends of the first multimode interferometer. The two ports at the first end of the first multimode interferometer are respectively connected to the incident waveguide cross section and the exit waveguide cross section through transmission optical waveguides. Several ports at the second end of the first multimode interferometer are respectively connected to the input optical waveguides of several chirped Bragg gratings through transmission optical waveguides. The period of the chirped Bragg gratings changes linearly from a first period to a second period.

2. The dispersion compensation device according to claim 1, characterized in that, The width of the transmission optical waveguide is equal to the width of the input optical waveguide.

3. The dispersion compensation device according to claim 1, characterized in that, The dispersion compensation device also includes a second multimode interferometer. The output waveguide of the chirped Bragg grating is connected to the port of the first end of the second multimode interferometer through the transmission waveguide. The width of the input waveguide is greater than or equal to the width of the transmission waveguide.

4. The dispersion compensation device according to claim 3, characterized in that, When the width of the input optical waveguide is greater than the width of the transmission optical waveguide, the dispersion compensation device also includes a tapered waveguide. The tapered waveguide is connected to the port of the second end of the second multimode interferometer, and the width of the tapered waveguide increases from the width of the transmission optical waveguide to the width of the input optical waveguide.

5. The dispersion compensation device according to claim 1, characterized in that, The width of the input optical waveguide is greater than or equal to the width of the transmission optical waveguide. The dispersion compensation device also includes a dissipative tapered waveguide, and the output optical waveguide is connected to the dissipative tapered waveguide.

6. The dispersion compensation device according to claim 5, characterized in that, When the width of the input optical waveguide is greater than the width of the transmission optical waveguide, the width of the dissipative tapered waveguide increases from the width of the transmission optical waveguide to the width of the input optical waveguide.

7. The dispersion compensation device according to any one of claims 1-6, characterized in that, The surfaces of the components on both lithium niobate films and lithium niobate films are covered with a cladding material, which includes silicon dioxide.

8. The dispersion compensation device according to any one of claims 1-6, characterized in that, When dispersion is positive, the first period is smaller than the second period; when dispersion is negative, the first period is larger than the second period.

9. The dispersion compensation device according to any one of claims 1-6, characterized in that, The spacing between chirped Bragg gratings is greater than 10 μm.

10. A method for fabricating a dispersion compensation device, characterized in that, For preparing the dispersion compensation device according to any one of claims 1-9, comprising: A substrate is provided, and a lithium niobate thin film is prepared on the substrate; Photoresist is coated on a lithium niobate film, and all component structures are transferred onto the photoresist according to preset requirements. Unnecessary photoresist is removed according to all component structures to obtain a mask structure. All components include a first multimode interferometer, several identical chirped Bragg gratings, several optical waveguides, an incident waveguide cross section, and an outgoing waveguide cross section. The mask structure was transferred onto a lithium niobate film using an etching method.

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