Real-time tunable dispersion wave generation system and method based on thin-film lithium niobate waveguide

Abstract

The present invention discloses a real-time tunable dispersion wave generation system and method based on a thin-film lithium niobate waveguide. The present invention utilizes the mode hybridization characteristics in a high refractive index contrast waveguide to cause a sudden change in the dispersion characteristics at a specific wavelength, and in the supercontinuum spectrum finally generated, a high-power, narrow-bandwidth, spectrally isolated mode hybridization dispersion wave can be obtained at this wavelength. At the same time, combined with the thermo-optical birefringence effect of the lithium niobate crystal, the real-time tuning of the mode hybridization dispersion wave is achieved by thermoelectrically regulating the temperature of the waveguide. The present invention is implemented by an ultrashort pulse laser, an adjustable DC regulated power supply, a polarization controller, a lens fiber, a thin-film lithium niobate chip, a metal heating electrode, an optical spectrum analyzer, and optical fibers and wires connecting them. The present invention utilizes an ultrashort pulse laser to efficiently and directionally transfer energy to a target wavelength range on a single thin-film lithium niobate waveguide, generating a high-power, spectrally isolated, real-time tunable mode hybridization dispersion wave.

Description

Technical Field

[0001] The present invention relates to nonlinear optics, nonlinear frequency conversion, mode hybridization phenomenon in high refractive index waveguides, dispersive wave generation, and supercontinuum generation, and in particular to a real-time tunable dispersive wave generation system and method based on a thin-film lithium niobate waveguide. Background Art

[0002] In the past decade, many important applications have put forward higher requirements for the working band of coherent light sources, and the existing laser gain media still cannot fully cover new bands such as ultraviolet, visible light, and mid-infrared. Using nonlinear effects is a necessary means to effectively expand the light source to new bands. Among the various mechanisms and methods for generating coherent laser sources in bands outside the traditional telecommunications band, supercontinuum generation, as a key branch of optical nonlinear processes, has been widely used in optical coherence tomography, spectroscopy, optical communications, photometry and other fields because it can efficiently transfer pump energy to an extremely wide frequency band. Dispersive waves, as an important intermediate process in the generation of supercontinuum, have the advantages of good directionality and more energy-concentrated localized spectral structure, which has attracted widespread interest from researchers and scientific research institutions.

[0003] Dispersive waves can not only achieve efficient energy conversion, but also maintain the coherence of the pump source well. Dispersive waves are mainly generated by high-order dispersive perturbations. Therefore, in the reported work, the central wavelength of the dispersive waves can be controlled by dispersion engineering through geometric structure adjustment or periodic polarization of the waveguide. Obviously, it is very challenging to tune dispersive waves on a single waveguide in real time in this way, because it requires an integrated waveguide array composed of multiple waveguides with different geometric structures and cumbersome and complex waveguide switching and waveguide end-face coupling operations. Waveguide end-face coupling relies on multiple calibration experiments, and the switching and end-face coupling of multiple waveguides cannot be effectively operated in real time.

[0004] One possible solution for real-time tunable dispersive wave generation is to use highly nonlinear material waveguides with strong electro-optic or thermo-optic effects. The thin-film lithium niobate on insulator platform has the advantages of strong optical field confinement, wide transparency window (0.4-5μm), large second-order and third-order nonlinear coefficients, and the ability to achieve multi-physical field coupling such as acoustic field, optical field and electric field, and has attracted widespread attention in the industry. Based on this platform, researchers have developed many active and passive devices with superior performance. Compared with the electro-optic effect, the thermo-optic effect of thin-film lithium niobate is stronger and is not affected by DC drift. However, since the absolute change in the effective refractive index caused by the thermo-optic effect is not large enough, it is still difficult to effectively tune conventional dispersive waves.

[0005] In recent years, studies have reported the phenomenon of mode hybridization found on waveguide platforms with different high refractive index contrasts, especially since 2017, when Hickstein et al. of the National Institute of Standards and Technology of the United States experimentally observed the phenomenon of mode hybridization in aluminum nitride strip waveguides. This mode hybridization phenomenon occurs in waveguides with high refractive index contrasts whose cross-sectional geometry is asymmetric in the vertical or horizontal direction. One of the notable features is that the two orthogonal polarization modes have similar effective refractive indices and similar mode field distributions at the hybridization wavelength, which causes a sudden change in the group velocity dispersion near this wavelength. Therefore, in the region near the hybridization wavelength, the original anomalous dispersion will become normal dispersion, thereby achieving the phase matching conditions required for the generation of dispersive waves and exciting "mode hybridization dispersive waves". Compared with conventional dispersive waves, mode hybridization dispersive waves have higher spectral intensity and spectral isolation structure, which is conducive to energy concentration and spectral positioning. Summary of the invention

[0006] The purpose of the present invention is to provide a real-time tunable dispersion wave generation system and method based on thin-film lithium niobate waveguides in view of the deficiencies of the prior art. The mode hybridization phenomenon is used to efficiently and directionally generate high-power, narrow-bandwidth, and spectrally isolated mode hybrid dispersion waves; by thermoelectrically regulating the temperature of the waveguide, real-time tuning of the mode hybrid dispersion waves can be achieved.

[0007] The present invention proposes a method for generating real-time tunable dispersive waves based on thin-film lithium niobate waveguides. The mode hybridization characteristics in high-refractive-index contrast waveguides are utilized to cause a sudden change in the dispersion characteristics at a specific wavelength, so that in the final supercontinuum spectrum, a high-power, narrow-bandwidth, spectrally isolated mode hybridized dispersive wave can be obtained at this wavelength; at the same time, combined with the thermo-optical birefringence effect of the suspended lithium niobate ridge waveguide, the temperature of the suspended lithium niobate ridge waveguide is thermoelectrically controlled to tune the wavelength at which the mode hybridization phenomenon occurs in the waveguide, and ultimately achieve real-time tuning of the mode hybridized dispersive wave. Specifically, the asymmetric structure of the suspended lithium niobate ridge waveguide in the vertical direction is utilized. The effective refractive indexes of the TE fundamental mode and the TM first-order mode cross at the mode hybridization wavelength; the wavelength that produces the mode hybridization phenomenon is very sensitive to the relative change of the effective refractive index between the two polarization modes. Combined with the unique thermo-optical birefringence effect of the lithium niobate material itself, the two polarized lights polarized along the optical axis and polarized along the perpendicular optical axis have a great difference in thermo-optical coefficients. Therefore, the refractive index of the TE mode polarized along the optical axis is more sensitive to temperature changes than the refractive index of the TM mode polarized along the perpendicular optical axis. Therefore, the mode hybridization and thermo-optical effects are combined to realize the real-time thermal tuning of the wavelength of the mode hybridization dispersion wave.

[0008] The real-time tunable dispersion wave generation system based on thin-film lithium niobate waveguide is realized by an ultrashort pulse laser, an adjustable DC regulated power supply, a polarization controller, a lens fiber, a thin-film lithium niobate chip, a metal heating electrode, an optical spectrum analyzer, and a single-mode fiber and a metal wire connecting them. The output end of the ultrashort pulse laser is connected to the input end of the polarization controller through a single-mode fiber; the output end of the polarization controller is connected to the lens fiber through a single-mode fiber; the lens fiber couples the light field to the input end of the suspended waveguide of the thin-film lithium niobate chip through end-face coupling; the adjustable DC regulated power supply is connected to the metal heating electrode through a wire; on the thin-film lithium niobate chip, the metal heating electrode is parallel and close to the suspended waveguide, and the waveguide is heated by the thermal effect of the current flowing through the metal electrode; the light field is output from the other end of the suspended waveguide and coupled to the input end of the lens fiber through end-face coupling; the output end of the lens fiber is connected to one end of the single-mode fiber; the other end of the single-mode fiber is connected to the input end of the optical spectrum analyzer.

[0009] Furthermore, the light pulse emitted by the ultrashort pulse light source passes through the polarization controller, and its polarization direction is adjusted to be parallel to the optical axis direction of the lithium niobate waveguide. After passing through the single-mode optical fiber and the lens optical fiber in sequence, the light pulse is coupled to the waveguide with a light spot of a size similar to the cross-sectional size of the lithium niobate suspended waveguide. When transmitted in the waveguide, the nonlinear effect of the lithium niobate material is excited by the high-intensity light pulse, so that the light field interacts with the medium, so that the light pulse undergoes a series of changes in the time domain and frequency domain, and finally forms a supercontinuum spectrum and a mode hybrid dispersion wave. The wavelength of the generated mode hybrid dispersion wave can be adjusted by the waveguide temperature, and finally coupled to the lens optical fiber through the output end of the lithium niobate waveguide, and input into the optical spectrum analyzer through the single-mode optical fiber for observation. The adjustable DC regulated power supply inputs current to the heating electrode on the lithium niobate chip, and uses the thermal effect of the current to heat the waveguide to achieve the purpose of controlling the waveguide temperature. The current size can be controlled by the adjustable DC regulated power supply, and then the heating power and the waveguide temperature can be controlled until the mode hybrid dispersion wave observed by the optical spectrum analyzer is in the required wavelength range.

[0010] The thin-film lithium niobate chip is based on an X-cut lithium niobate on insulator platform, wherein the substrate is lithium niobate or silicon, the buried oxide layer is a silicon dioxide layer, and the covering layer is air; due to the processing technology, there is an inclination angle on the side wall of the waveguide; the waveguide adopts a suspended structure to obtain a better thermal insulation effect, and the realization of the suspended structure can utilize the buffer oxide etching technology to remove part of the silicon dioxide material under the lithium niobate waveguide to obtain an air insulation layer; since the lithium niobate material has a birefringent property, when the light field mode is a TE mode, its polarization is mainly along the optical axis direction, and when the light field mode is a TM mode, its polarization is mainly along the direction perpendicular to the optical axis.

[0011] The ultrashort pulse laser has a pulse width of sub-picosecond or femtosecond order and a peak power of kilowatts. Its higher peak power and shorter laser pulse width can effectively excite the third-order nonlinear optical effect in nonlinear materials, which is beneficial to enhancing energy conversion efficiency and plays an important role in mode hybridization dispersion waves, excitation and energy conversion.

[0012] The polarization controller is used to control the polarization state of the light field at the output end of the lens optical fiber; when the light field is coupled from the lens optical fiber to the suspended structure lithium niobate ridge waveguide of the thin film lithium niobate chip through the end face coupling, only the TE fundamental mode in the waveguide is excited, and the TM fundamental mode or the higher-order modes of the TE and TM modes are not excited.

[0013] The metal heating electrode on the thin-film lithium niobate chip is used to control the temperature of the waveguide. The temperature of the waveguide can be controlled by using the current passing through the metal electrode, and the current size is controlled by an adjustable DC regulated power supply connected to the metal electrode by a wire. The width of the two ends of the metal heating electrode gradually increases and gradually moves away from the lithium niobate suspension waveguide, making it easier to connect with the metal wire and avoiding the loss of the light field in the waveguide at the connection part. The middle section of the metal heating electrode is parallel to and close to the lithium niobate suspension waveguide, and the distance between the two can be determined according to the balance between the heating efficiency and the loss of the light field in the waveguide caused by the metal.

[0014] The lithium niobate waveguide has an asymmetric refractive index distribution in the horizontal or vertical direction, so that it meets the conditions for the generation of mode hybridization phenomenon; and the waveguide has an anomalous dispersion characteristic at the pump wavelength, so that the pump pulse maintains a soliton form during transmission, maintains the high peak power and narrow pulse width characteristics of the pulse, is conducive to improving the intensity of the nonlinear effect, so that lower pump energy can achieve pulse broadening, and improve the flatness of the supercontinuum spectrum.

[0015] The metal heating electrode on the thin-film lithium niobate chip is used to adjust the waveguide temperature and must have the characteristic of having a large resistivity. The heating power can be controlled by the current passing through, and the current is controlled by an adjustable DC regulated power supply. The metal heating electrode and the lithium niobate waveguide should be kept parallel so that the waveguide temperature remains uniform in the direction of light field propagation, and the distance between the two should achieve a balance between light loss and heating efficiency.

[0016] The optical spectrum analyzer is used to detect and record the frequency domain results of the generated mode hybridization dispersion wave and supercontinuum spectrum so as to explore its spectral characteristics.

[0017] The present invention proposes that by utilizing the mode hybridization phenomenon of thin-film lithium niobate, the generation of dispersive waves with isolated spectral structures can be achieved, thereby generating a high-power, narrow-bandwidth coherent laser source at a desired frequency in a directionally and efficiently manner; by utilizing the thermo-optical birefringence characteristics of thin-film lithium niobate, the wavelength position of the mode hybridized dispersive wave can be tuned in real time, without the need for an integrated waveguide array composed of multiple waveguides of different geometric structures and cumbersome and complex waveguide switching and waveguide end-face coupling operations; by combining the generation of dispersive waves based on mode hybridization with real-time thermal tuning characteristics, the generation of high-power, isolated spectral structures, and real-time tunable frequency signals can be achieved on a thin-film lithium niobate platform.

[0018] Beneficial effects of the present invention:

[0019] (1) The present invention adopts an X-cut thin-film lithium niobate platform, which has the advantages of strong light field confinement, large transparent window, and large thermo-optic coefficient; it can support the transmission of a wide range of spectra and the generation of mode hybridization and thermo-optical birefringence effects, which is conducive to the excitation of mode hybridization dispersion waves and thermal tuning operations;

[0020] (2) Hollowing out part of the buried oxide layer to form an air insulation layer can greatly improve thermal efficiency, thereby greatly reducing the power consumption required during the tuning process;

[0021] (3) The present invention utilizes the mode hybridization phenomenon existing in the X-cut thin-film lithium niobate waveguide to produce a large dispersion mutation at the mode hybridization wavelength, thereby achieving phase matching between the dispersion wave and the pump wave at this wavelength, and finally obtaining a dispersion wave with high power, narrow bandwidth and isolated spectral structure;

[0022] (4) The present invention utilizes the thermo-optical birefringence effect of thin-film lithium niobate waveguides to achieve the purpose of real-time tuning of mode hybridization dispersion waves, thereby solving the problem that when using traditional methods to tune dispersion waves, multiple calibration experiments are required to achieve waveguide end-face coupling, resulting in the inability to effectively perform real-time operations for switching and end-face coupling of multiple waveguides. This method only requires a single waveguide, an ultrashort pulse laser with a fixed wavelength, and a DC adjustable voltage-regulated power supply to generate high-power narrowband dispersion waves at the desired wavelength, and the dispersion wave wavelength can be tuned in real time by the current size. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a system schematic diagram of a method for generating real-time tunable dispersive waves based on thin-film lithium niobate waveguides.

[0024] Figure 2 This is a schematic diagram of the structure on a thin-film lithium niobate chip.

[0025] Figure 3 It is a schematic cross-sectional view of a suspended ridge waveguide on a thin-film lithium niobate chip.

[0026] Figure 4 It is the effective refractive index curve of TE0 and TM1 modes at different wavelengths in thin film lithium niobate waveguide when the waveguide temperature is 25℃.

[0027] Figure 5 It is the integrated dispersion curve of TE0 mode at different wavelengths in thin film lithium niobate waveguide when the waveguide temperature changes from 25℃ to 500℃ with 95℃ intervals.

[0028] Figure 6 This is the frequency domain evolution diagram of the real-time tunable dispersive wave based on thin-film lithium niobate waveguide when the waveguide temperature is 25°C.

[0029] Figure 7 Frequency domain results of real-time tunable dispersive waves based on thin-film lithium niobate waveguide when the waveguide temperature is 25°C.

[0030] Figure 8 This is the frequency domain result of real-time tunable dispersive wave based on thin-film lithium niobate waveguide when the waveguide temperature is 500℃. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and an implementation example of a method for generating real-time tunable dispersion waves based on a thin-film lithium niobate optical waveguide.

[0032] The present invention utilizes the structural asymmetry of the ridge waveguide in the vertical direction, so that the effective refractive index of the TE fundamental mode and the TM first-order mode cross at the mode hybridization wavelength. The wavelength that produces the mode hybridization phenomenon is very sensitive to the relative change of the effective refractive index between the two polarization modes, and the unique thermo-optical birefringence effect of the lithium niobate material itself makes the two polarized lights polarized along the optical axis and polarized along the perpendicular optical axis have a great difference in thermo-optical coefficients. Specifically, the refractive index of the TE mode polarized along the optical axis is more sensitive to temperature changes than the refractive index of the TM mode polarized along the perpendicular optical axis. Therefore, the combination of mode hybridization and thermo-optical effect can realize real-time thermal tuning of the wavelength of the mode hybridization dispersion wave.

[0033] Figure 1The system schematic diagram of the method for generating real-time tunable dispersive waves based on thin-film lithium niobate optical waveguide is shown. The system includes an ultrashort pulse laser 1, a polarization controller 3, an adjustable DC voltage-stabilized power supply 6, a thin-film lithium niobate chip 7, and an optical spectrum analyzer 11; specifically: the output end of the ultrashort pulse laser 1 is connected to the input end of the polarization controller 3 through a first single-mode optical fiber 2; the output end of the polarization controller 3 is connected to the first lens optical fiber 5 through a second single-mode optical fiber 4; the first lens optical fiber 5 couples the light field to the input end of the suspended structure lithium niobate ridge waveguide 15 of the thin-film lithium niobate chip 7 through end face coupling; the adjustable DC voltage-stabilized power supply 6 is connected to the metal heating electrode 16 in the thin-film lithium niobate chip 7 through a wire 8; the light field is output from the other end of the suspended structure lithium niobate ridge waveguide 15, and is coupled to the input end of the second lens optical fiber 9 through an end face; the output end of the second lens optical fiber 9 is connected to one end of the third single-mode optical fiber 10; the output end of the third single-mode optical fiber 10 is connected to the input end of the optical spectrum analyzer 11.

[0034] Figure 2 It is a top view of the structure on the thin-film lithium niobate chip. On the thin-film lithium niobate chip, the metal heating electrode 13 is parallel and close to the suspended structure lithium niobate ridge waveguide 12 (the distance between the two is determined according to the actual situation, and it is only necessary to balance the heating efficiency and the loss of the metal to the light field in the waveguide). The suspended structure lithium niobate ridge waveguide 12 is heated by the thermal effect of the current flowing through the metal heating electrode 13.

[0035] Figure 3 It is a schematic cross-sectional view of a thin-film lithium niobate chip. The substrate 18 is lithium niobate or silicon, the buried oxide layer 17 is silicon dioxide, the thermal insulation channel 16 is air, the waveguide layer 15 is a lithium niobate film, the metal heating electrode 13 is a nickel-chromium alloy, and the cover layer 14 is air; due to the processing technology, the side wall of the suspended structure lithium niobate ridge waveguide 12 is allowed to have a tilt angle.

[0036] In the simulation calculation, the height of the suspended structure lithium niobate ridge waveguide 12 is 0.9μm, the etching depth is 0.3μm, and the width of the waveguide top is 1.2μm, because this is easy to achieve in the actual process; the refractive index simulation is based on the Sellmeier equation. The simulation of dispersive waves and supercontinuum is based on the nonlinear Schrödinger equation, which is as follows:

[0037]

[0038] where A(z,τ) is the slowly varying amplitude of the pulse envelope, is the Fourier transform of A(z,τ), is the Fourier transform symbol, ω is the transmission light pulse frequency, ω0 is the pump frequency, T represents the waveguide temperature, and the dispersion of each order β nIt is derived from the effective refractive index, where n is the dispersion order, and the integer greater than or equal to 2 is used in the formula, τ s =1 / ω0 is the light impact time, γ=0.8 is the nonlinear coefficient, α=0.1 is the waveguide loss coefficient, R(τ) is the nonlinear response function, and the integral term represents the energy transfer caused by Raman scattering within the pulse; the peak power of the ultrashort pulse laser pump is P0=3kW, the pulse width is T0=80fs, the wavelength is λ0=1550nm, and the Raman effect is not considered for the time being.

[0039] Figure 4 is the effective refractive index of the TE0 and TM1 modes when the temperature of the suspended structure lithium niobate ridge waveguide 12 is 25°C. It can be seen that near the mode hybridization point (about 1130nm), the effective refractive index of the TE0 and TM1 modes is similar and has similar mode field distribution, and the closer to the hybridization wavelength, the more similar the TE0 and TM1 mode field distributions are; this method numerically evaluates the hybridization strength by calculating the following formula:

[0040]

[0041] Among them, E x and E y are the electric field components in the horizontal and vertical directions respectively. TE When the value is close to 1, it represents the quasi-TE mode, when it is close to 0, it represents the quasi-TM mode, and when it is 0.5, it represents the maximum hybridization intensity. The wavelength at this time is called the mode hybridization point.

[0042] Figure 5 is the integrated dispersion curve of the TE0 mode when the temperature of the suspended structure lithium niobate ridge waveguide 12 changes from 25°C to 500°C at equal intervals. In the figure, T represents the waveguide temperature. The integrated dispersion is calculated by the following formula:

[0043]

[0044] In the formula, β int is the integrated dispersion, β1 is the first-order dispersion, β is the propagation constant, and each order of dispersion is derived from the effective refractive index. As can be seen from the figure, the integrated dispersion zero point moves toward the shorter wavelength direction as the temperature increases, which means that the phase matching wavelength between the dispersion wave and the pump wave blue shifts as the temperature increases.

[0045] Figure 6 This is a frequency domain evolution diagram of real-time tunable dispersion waves based on thin-film lithium niobate optical waveguides when the waveguide temperature is 25°C. The incident pump pulse is symmetrically broadened due to self-phase modulation in the early stage of propagation, and the spectrum is rapidly broadened in the second stage due to the soliton splitting effect, and conventional dispersion waves and mode hybrid dispersion waves are generated; the wavelength of the mode hybrid dispersion wave is about 1149nm, which is located on the long-wave side of the conventional dispersion wave, and is generated slightly earlier than the conventional dispersion wave.

[0046] Figure 7 , 8 The frequency domain results of the real-time tunable dispersion wave based on thin-film lithium niobate optical waveguide when the waveguide temperature is 25℃ and 500℃ respectively. The existence of conventional dispersion waves and mode hybrid dispersion waves can be clearly seen in the frequency domain. The mode hybrid dispersion wave is located on the long-wave side of the conventional dispersion wave. The spectral width of the mode hybrid dispersion wave is about 10nm, and its intensity exceeds that of the conventional dispersion wave. When the waveguide temperature is 500℃, the wavelength of the mode hybrid dispersion wave moves toward the short-wave direction compared with that at 25℃, and unlike the multi-peak structure of the spectrum of the conventional dispersion wave, the mode hybrid dispersion wave still maintains an isolated spectral structure similar to that at 25℃, as well as almost the same spectral intensity and spectral width.

[0047] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A real-time tunable dispersive wave generation system based on thin-film lithium niobate waveguide, characterized by The system comprises an ultrashort pulse laser (1), a polarization controller (3), an adjustable direct current voltage-stabilized power supply (6), a thin-film lithium niobate chip (7) and an optical spectrum analyzer (11); the output end of the ultrashort pulse laser (1) is connected to the input end of the polarization controller (3) through a first single-mode optical fiber (2); the output end of the polarization controller (3) is connected to a first lens optical fiber (5) through a second single-mode optical fiber (4); the first lens optical fiber (5) couples the light field to the input end of the thin-film lithium niobate chip (7) through end-face coupling; the adjustable direct current voltage-stabilized power supply (6) is connected to the thin-film lithium niobate chip (7) through a wire (8), and the mode hybridization characteristics in the high refractive index contrast waveguide are utilized to make the color at a specific wavelength The dispersion characteristics suddenly change, so that in the supercontinuum spectrum finally generated, a high-power, narrow-bandwidth, spectrally isolated mode hybrid dispersion wave can be obtained at this wavelength; a metal heating electrode (13), a suspended structure lithium niobate ridge waveguide (12), a substrate (18), a buried oxide layer (17), a thermal insulation channel (16), a waveguide layer (15) and a covering layer (14) are arranged on the thin-film lithium niobate chip (7); the light field is output from the thin-film lithium niobate chip (7) and coupled to the input end of the second lens optical fiber (9) through the end face; the output end of the second lens optical fiber (9) is connected to one end of the third single-mode optical fiber (10); the output end of the third single-mode optical fiber (10) is connected to the input end of an optical spectrum analyzer (11); On a thin-film lithium niobate chip (7), a metal heating electrode (13) is parallel to a suspended structure lithium niobate ridge waveguide (12), and the distance between the two is set according to actual needs; the suspended structure lithium niobate ridge waveguide (12) is heated by the thermal effect of current flowing through the metal heating electrode (13).

2. The real-time tunable dispersive wave generation system based on thin-film lithium niobate waveguide according to claim 1 is characterized in that The first lens optical fiber (5) couples the light field to the input end of the suspended structure lithium niobate ridge waveguide (12) of the thin film lithium niobate chip (7) through end face coupling; the light field is output from the other end of the suspended structure lithium niobate ridge waveguide (12) and coupled to the input end of the second lens optical fiber (9) through the end face.

3. The real-time tunable dispersive wave generation system based on thin-film lithium niobate waveguide according to claim 1 is characterized in that The adjustable DC regulated power supply (6) is connected to the metal heating electrode (13) in the thin-film lithium niobate chip (7) via a wire (8).

4. The real-time tunable dispersive wave generation system based on thin-film lithium niobate waveguide according to claim 2 is characterized in that The substrate (18) is lithium niobate or silicon, the buried oxide layer (17) is silicon dioxide, the thermal insulation channel (16) is air, the waveguide layer (15) is a lithium niobate film, the metal heating electrode (13) is a nickel-chromium alloy, and the cover layer (14) is air.

5. The method for realizing a real-time tunable dispersive wave generating system based on a thin-film lithium niobate waveguide according to claim 1, 2 or 3, characterized in that The mode hybridization characteristics in the high refractive index contrast waveguide are used to cause a sudden change in the dispersion characteristics at a specific wavelength, so that a high-power, narrow-bandwidth, spectrally isolated mode hybridization dispersion wave can be obtained at the wavelength in the ultimately generated supercontinuum spectrum; at the same time, the temperature of the suspended lithium niobate ridge waveguide (12) is thermoelectrically controlled in combination with the thermo-optical birefringence effect of the suspended lithium niobate ridge waveguide (12), so as to tune the wavelength at which the mode hybridization phenomenon occurs in the waveguide, and finally achieve real-time tuning of the mode hybridization dispersion wave. Specifically, the suspended lithium niobate ridge waveguide (12) is structurally inhomogeneous in the vertical direction. The symmetric characteristics make the effective refractive indices of the TE fundamental mode and the TM first-order mode cross at the mode hybridization wavelength; the wavelength that produces the mode hybridization phenomenon is very sensitive to the relative change of the effective refractive index between the two polarization modes. Combined with the unique thermo-optical birefringence effect of the lithium niobate material itself, the two polarized lights polarized along the optical axis and polarized along the perpendicular optical axis have a huge difference in thermo-optical coefficients. Therefore, the refractive index of the TE mode polarized along the optical axis is more sensitive to temperature changes than the refractive index of the TM mode polarized along the perpendicular optical axis. Therefore, the mode hybridization and thermo-optical effects are combined to realize the real-time thermal tuning of the wavelength of the mode hybridization dispersion wave.

6. The method for realizing the real-time tunable dispersive wave generation system based on thin-film lithium niobate waveguide according to claim 1, 2 or 3, characterized in that When the temperature of the suspended structure lithium niobate ridge waveguide (12) is T°C, within the setting range of the mode hybridization point, the effective refractive indexes of the TE0 and TM1 modes are similar and have similar mode field distributions. The closer to the hybridization wavelength, the more similar the TE0 and TM1 mode field distributions are. The hybridization strength is numerically evaluated by calculating the following formula: Among them, E x and E y are the electric field components in the horizontal and vertical directions respectively. TE When the value is close to 1, it represents the quasi-TE mode, when it is close to 0, it represents the quasi-TM mode, and when it is 0.5, it represents the maximum hybridization intensity. The wavelength at this time is called the mode hybridization point.

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