Non-coplanar traveling wave electrode electro-optical modulator and sampling system

Abstract

The invention discloses a non-coplanar traveling wave electrode electro-optical modulator, and relates to the technical field of microwave photonic devices and photoelectric measurement. A non-coplanar patch antenna and a thin-film lithium niobate optical waveguide structure are constructed into one device, and the patch antenna is directly used as a traveling wave electrode of the modulator; and direct conversion between a free space terahertz signal and an optical signal in the waveguide can be realized. Meanwhile, due to the introduction of the non-coplanar traveling wave electrode structure, the electric field component of the terahertz wave in the vertical direction of the electro-optical crystal can be enhanced, the electro-optical conversion efficiency of the device is effectively improved, the working bandwidth of the device is enhanced, and the space phase modulation problem of the terahertz wave can be effectively solved. The electro-optical sampling system based on the non-coplanar traveling wave electrode electro-optical modulator has the advantages of being wide in frequency band, high in anti-interference capacity and the like, efficient detection of terahertz waves can be achieved, and the technical advantages are obvious.

Description

Technical Field

[0001] The invention relates to the field of microwave photonic devices and photoelectric measurement technology, and in particular to a non-coplanar traveling wave electrode electro-optical modulator and a sampling system. Background Art

[0002] In recent years, with the deepening of the concept of "photoelectric fusion", terahertz signal detection technology based on electro-optical sampling technology has gradually become a research hotspot. As the core component of the electro-optical sampling system, the performance indicators of the ultra-wideband electro-optical modulator directly affect the detection capability of the system.

[0003] Under the action of an external electric field, the chaotic polarons inside the lithium niobate crystal material can be instantly arranged in one direction in a femtosecond level through the electro-optic effect. Theoretically, the corresponding modulation rate can reach millions of gigahertz. And because of the strong binding of light by the optical waveguide, the electro-optic modulator based on thin-film lithium niobate can reduce the electrode spacing without increasing the metal's absorption loss of light, thereby achieving the purpose of enhancing the device's electro-optical efficiency. Not only that, because of the presence of the buried layer with a low dielectric constant in the middle, it can also effectively improve the phase velocity matching between the RF signal and the optical signal, effectively improving the device bandwidth. Therefore, the electro-optic modulator based on thin-film lithium niobate has gradually become the preferred solution for high-speed transmission measurement systems.

[0004] Based on this, the present invention provides a thin-film lithium niobate-based electro-optic modulator based on non-coplanar traveling wave electrodes and ridge-type optical waveguides, which can be used for spatial phase modulation of terahertz waves. Furthermore, by combining gain horn antennas and optical elements, an electro-optic sampling system is constructed to achieve efficient detection of terahertz waves. Summary of the invention

[0005] This specification provides a non-coplanar traveling wave electrode electro-optic modulator and a sampling system to solve the spatial phase modulation problem of terahertz waves.

[0006] The present invention provides a non-coplanar traveling wave electrode electro-optic modulator, comprising:

[0007] A lithium niobate substrate layer; a grounding metal layer, the grounding metal layer is arranged on the top of the lithium niobate substrate layer; a silicon dioxide buried insulating layer, the silicon dioxide buried insulating layer is arranged on the top of the grounding metal layer; a lower electrode metal layer, the lower electrode metal layer is buried inside the silicon dioxide buried insulating layer; a lithium niobate waveguide film layer, the lithium niobate waveguide film layer is arranged on the top of the silicon dioxide buried insulating layer;

[0008] The lithium niobate waveguide film layer has an optical waveguide with a ridge-type cross-sectional structure, and the optical waveguide includes an input waveguide, a first 3dB beam splitter, waveguide interference arms arranged in parallel up and down, a second 3dB beam combiner, and an output waveguide connected in sequence, wherein the first 3dB beam splitter and the second 3dB beam combiner adopt a Y-shaped branch structure of a rising cosine curve;

[0009] An upper electrode metal layer, the upper electrode metal layer is arranged on the top of the lithium niobate waveguide thin film layer; a silicon dioxide insulating isolation layer, the silicon dioxide insulating isolation layer is arranged on the top of the upper electrode metal layer; wherein the upper electrode metal layer and the lower electrode metal layer are both rectangular structures, the edges of the upper electrode metal layer and the lower electrode metal layer are respectively located directly above and directly below the optical waveguide, and the upper electrode metal layer and the lower electrode metal layer are alternately arranged on both sides of the waveguide interference arm to form a plurality of traveling wave electrodes.

[0010] In an optional embodiment, the characteristic dimension of the optical waveguide cross section of the lithium niobate waveguide film layer meets the single-mode dimension requirement at the wavelength of the transmitted light;

[0011] The first 3dB beam splitter and the second 3dB beam combiner use a 12-multimode interference coupler structure;

[0012] The silicon dioxide buried insulating layer is used to fixedly connect the lithium niobate waveguide film layer and the grounding metal layer to achieve bonding of the composite epitaxial wafer.

[0013] In an optional implementation, the upper electrode metal layer and the lower electrode metal layer may also be of a T-shaped structure;

[0014] The linear period of the upper electrode metal layer and the lower electrode metal layer on both sides of the waveguide interference arm is 80 microns to 120 microns;

[0015] The dielectric constant of the silicon dioxide insulating isolation layer is less than 4.0.

[0016] In an optional embodiment, the widths of the input waveguide, the first 3dB beam splitter, the waveguide interference arm, the second 3dB beam combiner and the output waveguide in the lithium niobate waveguide film layer are all 2 microns to 4 microns;

[0017] The length of the waveguide interference arm is 15 mm to 25 mm;

[0018] The thickness of the upper electrode metal layer and the lower electrode metal layer is 200 nanometers to 500 nanometers.

[0019] The present invention also provides a method for preparing a non-coplanar traveling wave electrode electro-optic modulator, comprising:

[0020] The steps of preparing the ultra-thin lithium niobate wafer are as follows: cleaning the ultra-thin lithium niobate wafer and drying it; depositing a silicon dioxide layer on the lower surface of the ultra-thin lithium niobate wafer by a plasma enhanced chemical vapor deposition process; preparing a ridge-type optical waveguide structure on the upper surface of the ultra-thin lithium niobate wafer by photolithography, development, hardening and dry etching processes; depositing a silicon dioxide buffer layer on the top of the ridge-type optical waveguide structure; sputtering an AuGeNi / Au lower metal electrode on the silicon dioxide layer on the lower surface of the ultra-thin lithium niobate wafer, wherein the thickness of the lower metal electrode is 100 nanometers; preparing an upper metal electrode on the silicon dioxide buffer layer; and depositing an insulating isolation layer on the surface of the upper metal electrode by a plasma enhanced chemical vapor deposition process.

[0021] The supporting layer wafer preparation steps include: cleaning the supporting layer wafer and drying it; depositing a silicon dioxide layer on the upper surface of the supporting layer wafer by a plasma enhanced chemical vapor deposition process; polishing the upper surface of the supporting layer wafer and the lower surface of the ultra-thin lithium niobate wafer by a chemical mechanical polishing process, so that the surface roughness of the upper surface of the supporting layer wafer and the lower surface of the ultra-thin lithium niobate wafer is less than 0.5 nanometers;

[0022] Wafer bonding step: using argon ions, oxygen ions or nitrogen ions to activate the upper surface of the support layer wafer and the lower surface of the ultra-thin lithium niobate wafer, the activation treatment time is 20 seconds to 300 seconds, and the plasma power of the activation treatment is 150 watts to 600 watts; in a bonding chamber with a vacuum degree less than 10-5 Pa, the upper surface of the support layer wafer and the lower surface of the ultra-thin lithium niobate wafer are wafer-bonded, the bonding force of the wafer bonding is 5 kN to 100 kN, and the bonding time of the wafer bonding is 10 seconds to 100 seconds.

[0023] The present invention also provides an electro-optical sampling system based on a non-coplanar traveling wave electrode electro-optical modulator, comprising:

[0024] Optical links and terahertz wave links;

[0025] The optical link includes an ultrafast femtosecond laser sampling source, a polarization control module, an end coupling module, an electro-optic modulator on-chip optical waveguide structure, a photodetector and a signal acquisition module connected in sequence;

[0026] The terahertz wave link comprises a terahertz signal source, a gain horn antenna and an on-chip metal electrode structure of an electro-optic modulator which are connected in sequence.

[0027] In an optional embodiment, the terahertz signal source includes a continuous terahertz wave signal source and a pulsed terahertz signal source;

[0028] The continuous terahertz wave signal source is composed of a low-frequency signal source and a frequency doubling module;

[0029] The pulsed terahertz signal source is composed of an ultrafast femtosecond laser pump source and a high-speed photodetector, and the repetition frequency difference between the ultrafast femtosecond laser pump source and the ultrafast femtosecond laser sampling source is 1 kHz.

[0030] In an optional embodiment, the gain horn antenna is located above the on-chip metal electrode structure of the electro-optic modulator;

[0031] The spacing between the gain horn antenna and the metal electrode structure on the electro-optic modulator chip is greater than or equal to the far-field distance of the gain horn antenna;

[0032] The far-field distance is calculated by the formula 2D2 / λ, where D is the aperture size of the gain horn antenna and λ is the wavelength of the terahertz wave signal.

[0033] In an optional embodiment, the system further includes:

[0034] Small rubidium clock and power divider;

[0035] The short-term stability of the time base of the small rubidium clock is better than 10-1 1;

[0036] The power divider distributes the reference clock signal generated by the small rubidium clock to the terahertz signal source, the ultrafast femtosecond laser sampling source and the signal acquisition module;

[0037] The test trigger signal generated by the small rubidium clock is a square wave signal or a sine wave signal with a repetition frequency of 1 kHz, and the amplitude of the test trigger signal is 500 mV to 1 V.

[0038] At least one of the above technical solutions adopted in the embodiments of this specification can achieve the following beneficial effects:

[0039] 1. Technical effects of hierarchical structure design:

[0040] The lithium niobate substrate layer provides mechanical support for the entire device and ensures structural stability; the setting of the grounding metal layer realizes the effective grounding of the RF signal and reduces the parasitic capacitance; the silicon dioxide buried insulating layer reduces the dielectric loss of the device and improves the modulation efficiency; the lower electrode metal layer buried in the buried insulating layer can reduce the interaction between the metal and the light wave and reduce the light transmission loss.

[0041] 2. Technical effects of waveguide structure design:

[0042] The ridge-type cross-section structure provides stronger light field confinement capability and reduces mode loss. The Mach-Zehnder interference structure (input waveguide-beam splitter-interference arm-beam combiner-output waveguide) realizes phase modulation of the optical signal. The Y-type branch uses a rising cosine curve to reduce optical loss at the branch and improve splitting / combining efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0044] Figure 1 This is a schematic diagram of the structure of a non-coplanar traveling wave electrode electro-optic modulator based on a thin film lithium niobate substrate according to the present invention;

[0045] Figure 2 This is a schematic diagram of the cross-sectional structure of a non-coplanar traveling wave electrode electro-optic modulator based on a thin-film lithium niobate substrate according to the present invention, wherein (a) the signal electrode is located below the waveguide, and (b) the signal electrode is located above the waveguide, and (a) and (b) together constitute a traveling wave electrode cycle;

[0046] Figure 3 This is a schematic diagram of a top view structure of a non-coplanar traveling wave electrode of an electro-optic modulator based on a thin-film lithium niobate substrate according to the present invention, (a) is a rectangular metal electrode, and (b) is a T-shaped metal electrode;

[0047] Figure 4 This is a simulation comparison diagram of the vertical electric field component of a coplanar traveling wave electrode and a non-coplanar traveling wave electrode of an electro-optic modulator based on a thin-film lithium niobate substrate of the present invention, (a) is a non-coplanar traveling wave electrode, (b) is a coplanar traveling wave electrode;

[0048] Figure 5 This is a schematic diagram of an optical waveguide structure of an electro-optic modulator in a waveguide thin film layer of a non-coplanar traveling wave electrode electro-optic modulator based on a thin film lithium niobate substrate according to the present invention;

[0049] Figure 6 The present invention provides a method for preparing an electro-optic modulator in a waveguide thin film layer of a non-coplanar traveling wave electrode electro-optic modulator based on a thin film lithium niobate substrate;

[0050] Figure 7 This is a schematic diagram of a continuous terahertz wave electro-optical sampling system based on a non-coplanar traveling wave electrode electro-optical modulator according to the present invention;

[0051] Figure 8 The present invention is a schematic diagram of a pulsed terahertz wave electro-optical sampling system based on a non-coplanar traveling-wave electrode electro-optical modulator.

[0052] Reference numerals

[0053] 1. Substrate layer; 2. Ground metal layer; 3. Buried insulator layer; 4. Waveguide film layer; 5. Single-mode ridge waveguide; 6. Buffer layer; 7. Lower electrode metal layer; 8. Upper electrode metal layer; 9. Insulation isolation layer; 10. Ultrafast femtosecond laser sampling source; 11. Polarization control module; 12. End coupling module; 13. On-chip optical waveguide structure of electro-optic modulator; 14. Photodetector; 15. Signal acquisition and analysis module; 16. Low-frequency signal source; 17. Spread spectrum module; 18. Gain horn antenna; 19. Small rubidium clock; 20. Power divider; 21. Trigger signal source; 22. Ultrafast femtosecond laser pump source; 23. High-speed photodetector; 24. Input waveguide; 25. 1x2 multimode interference coupler; 26. Parallel transmission waveguide interference arm; 27. Output waveguide. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0055] The following is combined with Figure 1 To Attachment Figure 8 , describe in detail the technical solutions provided by each embodiment of the present application.

[0056] like Figure 1 As shown, the present invention discloses a non-coplanar traveling wave electrode electro-optic modulator based on a thin film lithium niobate substrate. The modulator constructs a non-coplanar patch antenna and a thin film lithium niobate optical waveguide structure into one device, and uses the patch antenna directly as the traveling wave electrode of the modulator, so as to realize the direct conversion between the free space terahertz signal and the optical signal in the waveguide. Figure 2The device cross-section is shown, which includes a substrate layer, a grounding metal layer, a buried insulator layer, a lower electrode metal layer, a waveguide film layer, a buffer layer, an upper electrode metal layer and an insulating isolation layer from bottom to top. The substrate layer is used to support the overall device structure, and the material can be lithium niobate or silicon. The grounding metal layer is located on the top of the substrate layer, and is a Ti / Au alloy with a thickness of about 100nm. The buried insulating layer is located on the top of the grounding metal layer, and the material is preferably a low dielectric constant such as SiO2 or Si3N4, and a material with low absorption loss for terahertz waves. It is mainly used to fix the connection between the waveguide film layer and the grounding metal layer to achieve bonding of the composite epitaxial wafer, and the thickness is about 1000nm to 4000nm. The waveguide film layer is located above the buried insulating layer, and the material is preferably an x-cut y-conducting or z-cut y-conducting lithium niobate crystal, which is mainly used to prepare a single-mode transmission ridge optical waveguide structure. The upper and lower metal layers are located on the upper and lower sides of the waveguide film layer, respectively. The top layer of the device is an insulating isolation layer, the material of which is preferably a material with low dielectric constant and low absorption loss for terahertz waves, such as SiO2 or Si3N4. It is mainly used to reduce the effective refractive index of microwaves and passivate the flagship surface for protection.

[0057] Figure 3 (a) shows the structure of the upper and lower metal electrodes with a rectangular structure. It can be seen that the traveling wave electrodes are placed on both sides relative to the waveguide interference arm, and the edges of the metal electrodes are located directly above and below the optical waveguide respectively. The structural parameters of the metal electrodes and their relative distance to the optical waveguide are obtained through COMSOL simulation. Figure 3 (b) The electric field mode profile of the thin film lithium niobate waveguide obtained by electromagnetic field simulation using COMSOL.

[0058] Figure 4 (a) shows the structure of the upper and lower metal electrodes with a T-shaped structure. Similarly, the traveling wave electrodes are placed on both sides relative to the waveguide interference arm, and the edges of the metal electrodes are located directly above and below the optical waveguide respectively. The structural parameters of the metal electrode and its relative distance to the optical waveguide are obtained through COMSOL simulation, and its electric field mode profile can also be obtained through COMSOL simulation.

[0059] Figure 5 The optical waveguide structure of the electro-optic modulator in the waveguide film layer is given, and the characteristic dimensions of all optical waveguide cross sections meet the single-mode dimensions at the wavelength of the transmitted light, including the sequentially connected input waveguide, 3dB beam splitter, parallel transmission waveguide interference arm, 3dB beam combiner and output waveguide, wherein the 3dB beam splitter / combiner can be a Y-type branch with a rising cosine bend or a 1x2 multimode interference coupler or a directional coupler. The non-coplanar traveling wave electrode is located in the parallel transmission waveguide interference arm region.

[0060] like Figure 6The figure shows a method for preparing a non-coplanar traveling-wave electrode electro-optic modulator, which is mainly divided into two steps. First, the non-coplanar traveling-wave electrode electro-optic modulator is prepared on an ultra-thin lithium niobate wafer, and then the support layer wafer and the ultra-thin lithium niobate wafer are bonded.

[0061] like Figure 7 The figure shows a continuous terahertz wave electro-optic sampling system based on a non-coplanar traveling wave electrode electro-optic modulator, which can be divided into two parts: an optical link and a terahertz wave link according to different propagation media. The optical link includes an ultrafast femtosecond laser sampling source with a central wavelength of 1550nm, a repetition frequency of 50MHz, a pulse width of 100fs, and an output power of 100mW, a polarization control module, an end coupling module, an electro-optic modulator on-chip optical waveguide structure, a photodetector, and a signal acquisition and analysis module; the terahertz link includes a continuous terahertz wave signal source composed of a low-frequency signal source and a spectrum expansion module, a gain horn antenna, and an electro-optic modulator on-chip metal electrode structure. The sampling light emitted by the ultrafast femtosecond laser sampling source is efficiently incident on the input optical waveguide of the electro-optic modulator through the end coupling module after the polarization direction of the light is adjusted by the polarization control module. After being transmitted on the electro-optic modulator, it is emitted by the output optical waveguide and then efficiently incident on the photodetector through the end coupling module. The photodetector converts the optical signal into an electrical signal, and finally it is converted into waveform data by the data acquisition and analysis module. At the same time, the radio frequency signal radiated by the low-frequency signal source generates a terahertz wave signal with a frequency range of 110GHz to 500GHz after passing through the spectrum spread module. It is radiated in a direction in space to the traveling wave electrode on the electro-optic modulator through the gain horn antenna. After receiving the terahertz wave in the far field, the traveling wave electrode is transmitted in the same direction as the optical wave in the electro-optic crystal, and the terahertz wave signal is loaded onto the optical signal due to the electro-optic effect. After subsequent demodulation and other work, the extraction of the terahertz wave signal is realized. During the system test, a small rubidium clock with a short-term stability of better than 10-11 is used to provide a reference clock to each instrument through a power divider. The test trigger signal is a square wave signal with a repetition frequency of 1kHz and an amplitude of about 500mV to 1V.

[0062] like Figure 8 The figure shows a continuous wave terahertz electro-optic sampling system based on non-coplanar traveling wave electrode electro-optic modulator. Its basic working principle is similar to Figure 7The continuous terahertz wave electro-optic sampling system based on non-coplanar traveling wave electrode electro-optic modulator is similar to the one shown in the figure. The optical link includes an ultrafast femtosecond laser sampling source with a central wavelength of 1550nm, a repetition frequency of 100MHz, and a pulse width of 100fs, a polarization control module, an end coupling module, an electro-optic modulator on-chip optical waveguide structure, a photodetector, and a signal acquisition and analysis module, which are connected in sequence; the terahertz link includes another ultrafast femtosecond laser pump source with a central wavelength of 1550nm, a pulse width of 100fs, and a repetition frequency of 100MHz+1kHz, and its output laser is connected to a high-speed photodetector to stimulate the generation of a high-speed pulsed terahertz wave signal.

[0063] The above is only the embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. Non-coplanar traveling wave electrode electro-optic modulator, characterized in that: include: Lithium niobate substrate layer; A grounding metal layer, the grounding metal layer being arranged on top of the lithium niobate substrate layer; A buried silicon dioxide insulating layer, wherein the buried silicon dioxide insulating layer is disposed on top of the grounding metal layer; A lower electrode metal layer, wherein the lower electrode metal layer is buried in the silicon dioxide buried insulating layer; a lithium niobate waveguide film layer, wherein the lithium niobate waveguide film layer is arranged on top of the silicon dioxide buried insulating layer; The lithium niobate waveguide film layer has an optical waveguide with a ridge-type cross-sectional structure, and the optical waveguide includes an input waveguide, a first 3dB beam splitter, waveguide interference arms arranged in parallel up and down, a second 3dB beam combiner, and an output waveguide connected in sequence, wherein the first 3dB beam splitter and the second 3dB beam combiner adopt a Y-shaped branch structure of a rising cosine curve; An upper electrode metal layer, the upper electrode metal layer is arranged on the top of the lithium niobate waveguide thin film layer; a silicon dioxide insulating isolation layer, the silicon dioxide insulating isolation layer is arranged on the top of the upper electrode metal layer; wherein the upper electrode metal layer and the lower electrode metal layer are both rectangular structures, the edges of the upper electrode metal layer and the lower electrode metal layer are respectively located directly above and directly below the optical waveguide, and the upper electrode metal layer and the lower electrode metal layer are alternately arranged on both sides of the waveguide interference arm to form a plurality of traveling wave electrodes.

2. The modulator according to claim 1, characterized in that The characteristic dimensions of the optical waveguide cross section of the lithium niobate waveguide film layer meet the single-mode dimension requirements at the wavelength of the transmitted light; The first 3dB beam splitter and the second 3dB beam combiner use a 12-multimode interference coupler structure; The silicon dioxide buried insulating layer is used to fixedly connect the lithium niobate waveguide film layer and the grounding metal layer to achieve bonding of the composite epitaxial wafer.

3. The modulator according to claim 1, characterized in that The upper electrode metal layer and the lower electrode metal layer may also adopt a T-shaped structure; The linear period of the upper electrode metal layer and the lower electrode metal layer on both sides of the waveguide interference arm is 80 microns to 120 microns; The dielectric constant of the silicon dioxide insulating isolation layer is less than 4.

0.

4. The modulator according to claim 1, characterized in that The widths of the input waveguide, the first 3dB beam splitter, the waveguide interference arm, the second 3dB beam combiner and the output waveguide in the lithium niobate waveguide film layer are all 2 microns to 4 microns; The length of the waveguide interference arm is 15 mm to 25 mm; The thickness of the upper electrode metal layer and the lower electrode metal layer is 200 nanometers to 500 nanometers.

5. A method for preparing a non-coplanar traveling wave electrode electro-optic modulator, characterized in that: include: Ultra-thin lithium niobate wafer preparation steps: clean the ultra-thin lithium niobate wafer and dry it; A silicon dioxide layer is deposited on the lower surface of the ultra-thin lithium niobate wafer by a plasma enhanced chemical vapor deposition process; a ridge-type optical waveguide structure is prepared on the upper surface of the ultra-thin lithium niobate wafer by photolithography, development, hardening and dry etching processes; a silicon dioxide buffer layer is deposited on the top of the ridge-type optical waveguide structure; an AuGeNi / Au lower metal electrode is sputtered on the silicon dioxide layer on the lower surface of the ultra-thin lithium niobate wafer, and the thickness of the lower metal electrode is 100 nanometers; an upper metal electrode is prepared on the silicon dioxide buffer layer; and an insulating isolation layer is deposited on the surface of the upper metal electrode by a plasma enhanced chemical vapor deposition process; Support layer wafer preparation steps: cleaning the support layer wafer and drying it; A silicon dioxide layer is deposited on the upper surface of the support layer wafer by a plasma enhanced chemical vapor deposition process; the upper surface of the support layer wafer and the lower surface of the ultra-thin lithium niobate wafer are polished by a chemical mechanical polishing process, so that the surface roughness of the upper surface of the support layer wafer and the lower surface of the ultra-thin lithium niobate wafer is less than 0.5 nanometers; Wafer bonding step: using argon ions, oxygen ions or nitrogen ions to activate the upper surface of the support layer wafer and the lower surface of the ultra-thin lithium niobate wafer, the activation treatment time is 20 seconds to 300 seconds, and the plasma power of the activation treatment is 150 watts to 600 watts; in a bonding chamber with a vacuum degree less than 10-5 Pa, the upper surface of the support layer wafer and the lower surface of the ultra-thin lithium niobate wafer are wafer-bonded, the bonding force of the wafer bonding is 5 kN to 100 kN, and the bonding time of the wafer bonding is 10 seconds to 100 seconds.

6. The electro-optic sampling system based on the non-coplanar traveling wave electrode electro-optic modulator according to claim 1, characterized in that: include: Optical links and terahertz wave links; The optical link includes an ultrafast femtosecond laser sampling source, a polarization control module, an end coupling module, an electro-optic modulator on-chip optical waveguide structure, a photodetector and a signal acquisition module connected in sequence; The terahertz wave link comprises a terahertz signal source, a gain horn antenna and an on-chip metal electrode structure of an electro-optic modulator which are connected in sequence.

7. The system according to claim 6, characterized in that The terahertz signal source includes a continuous terahertz wave signal source and a pulsed terahertz signal source; The continuous terahertz wave signal source is composed of a low-frequency signal source and a frequency doubling module; The pulsed terahertz signal source is composed of an ultrafast femtosecond laser pump source and a high-speed photodetector, and the repetition frequency difference between the ultrafast femtosecond laser pump source and the ultrafast femtosecond laser sampling source is 1 kHz.

8. The system according to claim 7, characterized in that The gain horn antenna is located above the on-chip metal electrode structure of the electro-optic modulator; The spacing between the gain horn antenna and the metal electrode structure on the electro-optic modulator chip is greater than or equal to the far-field distance of the gain horn antenna; The far-field distance is calculated by the formula 2D2 / λ, where D is the aperture size of the gain horn antenna and λ is the wavelength of the terahertz wave signal.

9. The system according to claim 7, characterized in that The system further comprises: Small rubidium clock and power divider; The short-term stability of the time base of the small rubidium clock is better than 10-11; The power divider distributes the reference clock signal generated by the small rubidium clock to the terahertz signal source, the ultrafast femtosecond laser sampling source and the signal acquisition module; The test trigger signal generated by the small rubidium clock is a square wave signal or a sine wave signal with a repetition frequency of 1 kHz, and the amplitude of the test trigger signal is 500 mV to 1 V.

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