Photon integrated broadband terahertz transmitting device based on TFLN

Abstract

The invention provides a photon integrated broadband terahertz transmitting device based on a TFLN, which comprises a TFLN integrated substrate and a plurality of components, the plurality of components comprise a ridge-shaped optical waveguide, a terahertz transmission line, a broadband transmitting antenna and an electro-optical modulation unit, the components in the plurality of components are integrated on the TFLN integrated substrate in a coplanar manner, and the ridge-shaped optical waveguide, the terahertz transmission line, the broadband transmitting antenna and the electro-optical modulation unit are integrated on the TFLN integrated substrate. And the integration level of the broadband terahertz transmitting device is improved.

Description

Technical Field

[0001] This invention relates to the field of terahertz radio communication technology, and more specifically to a photonic integrated broadband terahertz transmitting device based on TFLN. Background Technology

[0002] Thin-film lithium niobate (TFLN) possesses high second-order nonlinear coefficients and low optical losses, making integration possible. However, existing TFLN-based broadband terahertz emitting devices still have shortcomings: they have not achieved an integrated design of emission, control, and verification, requiring the construction of an additional detection system, and the integration level of existing broadband terahertz emitting devices is low. Summary of the Invention

[0003] This application provides a photonic integrated broadband terahertz transmitting device based on thin-film lithium niobate (TFLN), comprising a TFLN integrated substrate and multiple components, including a ridge optical waveguide, a terahertz transmission line, a broadband transmitting antenna, and an electro-optic modulation unit, wherein each of the multiple components is coplanarly integrated on the TFLN integrated substrate.

[0004] Optionally, the TFLN integrated substrate is a 600nm thick x-cut lithium niobate film bonded to a 4700nm thick thermally grown SiO2 / 500μm thick high-resistivity silicon substrate, and the second-order nonlinear coefficient χ of the TFLN is... (2) =360pm / V.

[0005] Optionally, the surface of the TFLN integrated substrate is covered with an 800nm ​​thick SiO2 cladding, and the cladding has laser avoidance holes with a diameter of 50μm. At the same time, a metal shielding film is embedded in the cladding.

[0006] Optionally, the ridge-shaped optical waveguide is a TFLN strip structure with a width of 2.2-2.6 μm and a height of 350-450 nm, used to transmit pump light in the 1560 nm band, and has a group refractive index of ng = 2.25 ± 0.02.

[0007] Optionally, the terahertz transmission line is a gold coplanar stripline wrapped around the outside of the ridge optical waveguide and integrated collinearly with the ridge optical waveguide, with a characteristic impedance of 65-75Ω, and its refractive index is matched with that of the ridge optical waveguide group.

[0008] Optionally, the broadband transmitting antenna is a dipole antenna with a length of 150-400μm and a width of 5-10μm, integrated at the end of the terahertz transmission line, with a 3dB radiation bandwidth of 200GHz-3.5THz.

[0009] Optionally, the electro-optic modulation unit is a Mach-Zehnder modulator connected in series at the input of the ridge-shaped optical waveguide, with an operating bandwidth > 10 GHz. The terahertz output amplitude is linearly controlled by applying a 0-0.7 V bias voltage, and the modulation efficiency η... mod =30.6V -1 ·m.

[0010] Optionally, grounding metal strips are provided on both sides of the terahertz transmission line.

[0011] Optionally, the terahertz transmission line is configured as an open strip cavity structure.

[0012] This application provides a method for fabricating a photonic integrated broadband terahertz emitting device based on TFLN, comprising the following steps:

[0013] S1: TFLN substrate preparation: A 600nm thick x-cut lithium niobate film was selected and bonded to a 4700nm SiO2 / 500μm high-resistivity silicon substrate by plasma-enhanced bonding process. O2 plasma treatment was performed to make the surface roughness Ra < 0.3nm.

[0014] S2: Ridge-shaped optical waveguide fabrication: fabricated using electron beam lithography and Ar... + Ion etching was used to fabricate a waveguide with a width of 3μm and a depth of 350nm, and the etching damage was repaired by O2 annealing at 450℃ for 30min.

[0015] S3: Terahertz transmission line fabrication: 15nm Ti / 300nm Au was deposited by electron beam evaporation, and a gold bar-shaped transmission line with a width of 80μm and a length of 2mm was formed by a lift-off process. The line was then vacuum annealed at 150℃ for 20min.

[0016] S4: Broadband transmitting antenna and electro-optic modulation unit integration: A 200μm long dipole antenna is fabricated using the same batch of Au deposition process, and the MZM modulator is connected to the ridge optical waveguide through an edge coupler;

[0017] S5: Cladding deposition and calibration: 800nm ​​SiO2 cladding was deposited by ICP-CVD, clearance holes were opened, and phase matching conditions were calibrated by a terahertz spectrum analyzer to complete device fabrication.

[0018] This application adopts an integrated coplanar architecture of "TFLN ridge waveguide-terahertz transmission line-wideband antenna", combined with dispersion compensation and electro-optic modulation modules, to achieve wideband terahertz generation and detection. Covering the 6 GHz core frequency band of terahertz communication (200 GHz-3.5 THz, expandable to 3.8 THz), it supports ultra-high bandwidth data transmission and improves the integration of wideband terahertz transmitting devices.

[0019] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a structural diagram of a photonic integrated broadband terahertz emitting device based on TFLN according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic flowchart of a method for fabricating a basic photonic integrated broadband terahertz emitting device according to an embodiment of the present invention.

[0023] Figure 3 This is a schematic flowchart of a method for fabricating a high-performance photonic integrated broadband terahertz emitting device according to an embodiment of the present invention. Detailed Implementation

[0024] To address the issue of low integration in existing broadband terahertz emitting devices, a photonic integrated broadband terahertz emitting device based on thin-film lithium niobate (TFLN) is provided.

[0025] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Furthermore, the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0026] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of the embodiments of the present invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein.

[0027] This invention relates to the field of terahertz radio communication technology, specifically to a photonic integrated broadband terahertz transmitting device based on TFLN, suitable for scenarios such as 6G short-range high-speed communication in the 200GHz-3.5THz frequency band, base station signal transmission, and core components of communication terminals.

[0028] Thin-film lithium niobate (TFLN) possesses high second-order nonlinear coefficients and low optical losses, making integration possible. However, existing TFLN-based broadband terahertz emitting devices still have shortcomings: They lack an integrated design for emission, control, and verification, requiring a separate detection system; grating coupling is commonly used, resulting in bandwidth loss and structural complexity; and there is a lack of optimization for the overall system size, making it difficult to meet the compact requirements of portable applications. Existing broadband terahertz emitting devices face three major technical bottlenecks:

[0029] Low integration: Traditional transmitting devices use discrete optical pump sources, nonlinear crystals, terahertz antennas, and transmission components, and their volume is typically >50cm². 3 This cannot meet the compact deployment requirements of communication terminals and base stations;

[0030] Bandwidth limitation: Electronic emission sources have a sharp drop in efficiency in the >1THz frequency band, and traditional optical emission devices have a bandwidth of <2THz due to phase mismatch, which cannot cover the core frequency band of terahertz communication.

[0031] High transmission loss: Terahertz signals are susceptible to dispersion and leakage during transmission. The connection loss between discrete transmission lines and transmitting devices is greater than 15%, which seriously affects communication distance and signal fidelity.

[0032] This invention solves the problems of low integration, limited bandwidth, and high transmission loss of traditional broadband terahertz transmitting devices, and provides a compact and high-fidelity transmitting device solution for 6G terahertz radio communication.

[0033] The photonic integrated broadband terahertz transmitter based on thin-film lithium niobate (TFLN) provided by this invention adopts an integrated coplanar architecture of "TFLN ridge waveguide-terahertz transmission line-broadband antenna", combined with dispersion compensation and electro-optic modulation modules to achieve broadband terahertz generation and detection. Using x-cut TFLN as the core functional material, broadband phase matching of 200GHz-3.5THz is achieved through transmission line size optimization. Optical-terahertz collinear phase matching is achieved through terahertz transmission line geometric modulation. The spatial overlap factor between the terahertz transmission line and the optical waveguide is ≥0.08, effectively suppressing dispersion and loss. The core size of the device is <5mm×3mm×0.5mm, the peak terahertz output electric field reaches 57V / m, it supports 100Gbps 64QAM modulated signal transmission, and the bit error rate is <1×10⁻⁶. -11 .

[0034] This invention takes the integration technology of TFLN-based optical waveguide and terahertz transmission line as its core, realizes the generation of broadband terahertz waves from 200 GHz to 3.5 THz through phase matching, and has electro-optic control capability, providing a core idea for solving the above problems.

[0035] The present invention provides a photonic integrated broadband terahertz transmitting device based on TFLN, which includes a TFLN integrated substrate and multiple components. The multiple components include a ridge optical waveguide, a terahertz transmission line, a broadband transmitting antenna and an electro-optic modulation unit. Each of the multiple components is coplanarly integrated on the TFLN integrated substrate.

[0036] Figure 1 This is a structural diagram of a photonic integrated broadband terahertz transmitting device based on TFLN disclosed in this invention. In the diagram: 1 is the TFLN integrated substrate; 2 is the ridge optical waveguide; 3 is the terahertz transmission line; 4 is the broadband transmitting antenna; and 5 is the THz wave.

[0037] The device provided by this invention achieves an integrated design of "optical waveguide-terahertz transmission line-wideband antenna". Using x-cut TFLN as a substrate, it generates a 200GHz-3.5THz wideband terahertz signal through phase matching technology, while integrating an electro-optic modulation unit to support high-speed amplitude control. The overall device size is <5mm×3mm×0.5mm, the terahertz signal dynamic range is >50dB (intensity), continuous operating stability is >1000h (temperature 22±1℃, humidity 50±5%RH), and it supports 100Gbps 64QAM modulated signal transmission, adapting to the needs of 200GHz-3.5THz terahertz radio communication.

[0038] Optionally, the TFLN integrated substrate is a 600nm thick x-cut lithium niobate film bonded to a 4700nm thick thermally grown SiO2 / 500μm thick high-resistivity silicon substrate (resistivity > 10). 4 Ω·cm), the second-order nonlinear coefficient χ of TFLN (2) =360pm / V.

[0039] Optionally, the surface of the TFLN integrated substrate is covered with an 800nm ​​thick SiO2 cladding, and the cladding has laser avoidance holes with a diameter of 50μm and a transmittance of >95%. At the same time, a metal shielding film is embedded in the cladding, with a shielding effectiveness of >40dB in the 200GHz-3.5THz frequency band, to avoid external electromagnetic interference from affecting the fidelity of communication signals.

[0040] Optionally, the ridge-shaped optical waveguide is a TFLN strip structure with a width of 2.2-2.6 μm and a height of 350-450 nm, used to transmit 1560 nm band pump light, with a group refractive index n. g =2.25±0.02, optical transmission loss in the 1550nm band <0.5dB / cm, group refractive index n g =2.25, supporting low-loss transmission of femtosecond lasers.

[0041] Optionally, the terahertz transmission line is a gold coplanar stripline wrapped around the outside of the ridge optical waveguide and integrated collinearly with the ridge optical waveguide, with a characteristic impedance of 65-75Ω and an effective refractive index n. TL =2.25-2.3, matching the refractive index of the ridge-shaped optical waveguide group to achieve collinear phase matching from 200GHz to 3.5THz. The terahertz transmission loss is ≤0.45dB / mm by matching the effective refractive index of the transmission line with the refractive index of the waveguide group. The width is 50-100μm and the thickness is 300nm (including a 15nm Ti adhesion layer), matching the refractive index of the optical waveguide group to achieve phase matching across the entire frequency band.

[0042] Optionally, the broadband transmitting antenna is a dipole antenna with a length of 150-400 μm and a width of 5-10 μm, integrated at the end of the terahertz transmission line, with a 3dB radiation bandwidth of 200 GHz-3.5 THz, radiating perpendicularly to the substrate.

[0043] Optionally, the electro-optic modulation unit is a Mach-Zehnder modulator (MZM), connected in series at the input of the ridge-shaped optical waveguide, with an operating bandwidth > 10 GHz. The terahertz output amplitude is linearly controlled by applying a 0-0.7 V bias voltage, and the modulation efficiency η... mod =30.6V -1 ·m.

[0044] Optionally, grounding metal strips are provided on both sides of the terahertz transmission line.

[0045] The terahertz transmission line is provided with grounding metal strips (20μm wide and 10μm apart from the transmission line) on both sides to form a coplanar waveguide structure, which suppresses the leakage of terahertz signals to the substrate, reduces leakage loss by 40%, and enhances the electromagnetic compatibility of the device, making it suitable for complex communication environments with multiple base stations.

[0046] Optionally, the terahertz transmission line is configured as an open strip cavity structure.

[0047] The terahertz transmission line can be configured as an open strip cavity structure (length 100-200μm), with a reflection coefficient S11 > 90% (< 1.7THz), supporting discrete terahertz mode generation, adapting to the narrowband signal transmission requirements of the local oscillator (LO) in terahertz communication, and a linewidth < 100MHz.

[0048] The broadband transmitting antenna can be replaced with a bow antenna (aperture angle 60-90°, edge radius 5μm), with a 3dB radiation bandwidth extended to 200GHz-3.8THz and a far-field beam half-power angle <30°, adapting to the directional transmission requirements of point-to-point terahertz communication.

[0049] Optionally, the present invention also provides a method for fabricating a photonic integrated broadband terahertz emitting device based on TFLN, comprising the following steps S1-S5:

[0050] S1: TFLN substrate preparation: A 600nm thick x-cut lithium niobate film was selected and bonded to a 4700nm SiO2 / 500μm high-resistivity silicon substrate by plasma-enhanced bonding process. O2 plasma treatment was performed to make the surface roughness Ra < 0.3nm.

[0051] S2: Ridge-shaped optical waveguide fabrication: fabricated using electron beam lithography and Ar... + Ion etching was used to fabricate a waveguide with a width of 3μm and a depth of 350nm, and the etching damage was repaired by O2 annealing at 450℃ for 30min.

[0052] S3: Terahertz transmission line fabrication: 15nm Ti / 300nm Au was deposited by electron beam evaporation, and a gold bar-shaped transmission line with a width of 80μm and a length of 2mm was formed by a lift-off process. The line was then vacuum annealed at 150℃ for 20min.

[0053] S4: Broadband transmitting antenna and electro-optic modulation unit integration: A 200μm long dipole antenna is fabricated using the same batch of Au deposition process. The MZM modulator is connected to the ridge optical waveguide through an edge coupler, with a coupling efficiency >13%.

[0054] S5: Cladding Deposition and Calibration: An 800nm ​​SiO2 cladding layer was deposited by ICP-CVD, and clearance vias were created. Phase matching conditions were calibrated using a terahertz spectrum analyzer. TL =2.25-2.3), and the device fabrication is completed.

[0055] The present invention can achieve the following technical effects:

[0056] (1) High integration and wide bandwidth coverage: It adopts an integrated coplanar architecture of "TFLN ridge waveguide-terahertz transmission line-wideband antenna", combined with dispersion compensation and electro-optic control modules to realize wideband terahertz generation and detection. 200GHz-3.5THz (expandable to 3.8THz), covering the core frequency band of 6G terahertz communication, and supporting ultra-large bandwidth data transmission.

[0057] (2) Low loss and high fidelity: Optical-terahertz collinear phase matching is achieved by utilizing the geometric control of the terahertz transmission line. The terahertz transmission loss is <0.45dB / mm, the signal dynamic range is >50dB, and 100Gbps 64QAM modulation is supported. The bit error rate is <1×10⁻⁶. -11 .

[0058] (3) Strong communication adaptability: It integrates an electro-optic modulation unit, supports high-speed coding, and has an electromagnetic shielding design to adapt to complex communication environments, providing a highly reliable transmission core for 6G terahertz radio communication.

[0059] This invention enables the generation of 200GHz-3.5THz wideband terahertz signals, while integrating an electro-optic modulation unit to support high-speed amplitude control. It solves the problems of low integration, limited bandwidth, and high transmission loss of traditional broadband terahertz transmitting devices, providing a compact and high-fidelity transmitting device solution for 6G terahertz radio communication.

[0060] This invention achieves an integrated design of "optical waveguide-terahertz transmission line-wideband antenna," using x-cut TFLN as a substrate and employing phase-matching technology to generate 200GHz-3.5THz wideband terahertz signals. Simultaneously, it integrates an electro-optic modulation unit to support high-speed amplitude control. This solves the problems of low integration, limited bandwidth, and high transmission loss in traditional broadband terahertz transmitters, providing a compact, high-fidelity transmitter solution for 6G terahertz radio communication.

[0061] like Figure 2 As shown, this invention provides a broadband terahertz transmitting device that meets the "compact, wideband, and high-speed" requirements of 6G short-range high-speed communication terminals. The flowchart illustrates a basic photonic integrated broadband terahertz transmitting device fabrication method that achieves wideband signal coverage and high-power transmission, specifically including the following steps S11-S15:

[0062] S11, Substrate pretreatment;

[0063] Substrate selection: A 500μm thick double-sided polished high-resistivity silicon substrate (resistivity > 10) was used. 4 Ω·cm), and a 4700nm thick thermal oxide layer (SiO2) is pre-grown on its surface for insulation and TFLN bonding buffer;

[0064] Cleaning process: The surface is ultrasonically cleaned sequentially with acetone (5 min), isopropanol (5 min), and deionized water (10 min), and then dried on a hot plate at 120℃ for 10 min to remove organic residues and moisture.

[0065] Bonding pretreatment: A 100 nm thick polyimide (PI) adhesive is spin-coated onto the SiO2 surface (3000 rpm, baking temperature 80℃ / 30 min) for subsequent low-temperature bonding of the TFLN film to the substrate.

[0066] Fabrication of S12 and TFLN ridge waveguides;

[0067] TFLN thin film transfer: A 600nm thick, tangentially composed TFLN thin film (second-order nonlinear coefficient d) was selected.33 =27pm / V), transferred to the surface of the PI layer on the pretreated silicon substrate using van der Waals force bonding technology, with bonding pressure controlled at 0.3MPa, temperature at 150℃, and holding for 2h to achieve dense interface bonding;

[0068] Waveguide patterning: Electron beam lithography (EBL) was used with Ma-N 2403 negative photoresist (spin coating speed 5000 rpm, resist thickness 800 nm) and exposure dose 80 μC / cm. 2 After development, a ridge waveguide pattern is formed (waveguide width 2.2-2.6μm, ridge height 400nm, spacing 10μm);

[0069] Dry etching: using Ar + Ion etching (Ar etching gas flow rate 20 sccm, power 100W, bias voltage 50V) was used to etch to a depth of 400 nm to the surface of the SiO2 layer, forming a TFLN ridge structure.

[0070] Annealing repair: The etched sample was placed in an O2 atmosphere annealing furnace, heated to 450℃, and held for 2 hours to repair the Ar. + Etching-induced TFLN lattice damage reduces optical loss (after repair, loss at 1550nm band <0.5dB / cm).

[0071] S13, fabrication of terahertz transmission lines;

[0072] Transmission line patterning: Ultraviolet lithography (UVL) process was adopted, using AZ 5214 positive photoresist (spin coating speed 4000rpm, photoresist thickness 1.2μm), exposure time 30s, and after development, a gold ribbon pattern was formed (line width 10μm, length 2mm, collinearly aligned with the ridge waveguide, offset <0.5μm).

[0073] Metal deposition: An electron beam evaporation system was used to first deposit a 15 nm thick Ti transition layer (to improve adhesion), followed by a 300 nm thick Au layer (99.99% purity). The evaporation rate of Ti was [missing information]. Au for Vacuum degree < 5 × 10 -5 Pa;

[0074] Stripping process: The sample is immersed in AZ 300MIF developer and ultrasonically (power 50W) for 10 minutes to remove residual photoresist and excess metal, forming a gold strip terahertz transmission line coplanar with the TFLN waveguide (characteristic impedance 65-75Ω, loss <1dB / mm in 1THz band).

[0075] S14, Fabrication of broadband dipole antenna;

[0076] Antenna patterning: EBL process was used with ZEP 520A photoresist (spin coating speed 6000 rpm, resist thickness 500 nm), and exposure dose 120 μC / cm. 2 After development, a dipole antenna pattern is formed (total length 200μm, arm width 5μm, feed end overlaps with the end of terahertz transmission line, overlap length 10μm).

[0077] Metal-enhanced deposition: A 300 nm thick Au layer was deposited using magnetron sputtering (sputtering power 200 W, Ar flow rate 30 sccm, vacuum degree < 3 × 10⁻⁶). -4 Pa), to ensure a low-resistance connection between the antenna and the transmission line (contact resistance < 5Ω);

[0078] Antenna passivation: A 200nm thick SiO2 passivation layer is spin-coated (using tetraethyl orthosilicate sol-gel method, baking temperature 200℃ / 1h) to cover the non-feed area of ​​the antenna and improve environmental stability.

[0079] S15, Module Integration and Packaging;

[0080] Dispersion compensation module integration: 11m single-mode fiber and 2 segments of PMDCFA5 dispersion compensation fiber (each segment 1.5m long) are coupled at the device input end, and coupled to the TFLN waveguide edge through fiber array (coupling efficiency 13%, using 5μm spot size lens fiber);

[0081] Electro-optic control module integration: An MXAN-LN-10-PD-P-PFA-FA type Mach-Zehnder modulator (MZM) is connected in series in the optical fiber link, and the output of the modulator is compensated for loss through a doped fiber amplifier (EDFA) (amplification gain 20dB).

[0082] Packaging: It adopts a ceramic shell and is filled with nitrogen (99.99% purity). The shell has reserved fiber optic interface and terahertz emission window (the window adopts a 1mm thick ZnTe crystal and the anti-reflection coating covers the 100GHz-4THz frequency band).

[0083] This invention provides a method for fabricating a high-performance photonic integrated broadband terahertz transmitting device, as described above, which can be used as a core transmitting device for terahertz base stations, achieving wideband signal coverage and high-power transmission. Figure 3 As shown, the main optimization steps are as follows: S111-S113:

[0084] S111, Terahertz transmission line process optimization (double-layer metal-dielectric structure);

[0085] Dielectric spacer layer fabrication: After the TFLN ridge waveguide is fabricated, a 200 nm thick Si3N4 dielectric layer is deposited using plasma-enhanced chemical vapor deposition (PECVD) (deposition temperature 300℃, SiH4 / NH3 flow ratio 1:5, power 150W) to cover both sides of the waveguide (width 5 μm) as a spacer between the transmission line metal layer and the TFLN.

[0086] Double-layer metal deposition: First, a 15nm Ti / 300nm Au bottom layer is deposited by electron beam evaporation, and then a 100nm thick Cu layer is deposited on the Si3N4 layer by magnetron sputtering (sputtering power 180W, Ar flow rate 25sccm) to form an "Au-Cu" double-layer metal structure, which reduces the transmission loss in the 1-3THz frequency band (optimized loss <0.8dB / mm).

[0087] Transmission line size fine-tuning: The transmission line width is optimized to 8μm through EBL, the characteristic impedance is matched to 48Ω, and the impedance matching degree with the antenna feed end is improved to 95%.

[0088] S112, Broadband antenna process optimization (gradient slot dipole antenna);

[0089] Antenna pattern optimization: A gradient slot design is adopted, with the antenna arm linearly tapering from the feed end (5μm wide) to the end end (2μm wide), and the slot width gradually increasing from 1μm to 3μm. Patterning is achieved through EBL (AR-P 6200 photoresist, spin coating speed 7000rpm, resist thickness 300nm, exposure dose 100μC / cm). 2 );

[0090] Slot etching: Ion beam etching (IBE) is used on the antenna metal layer with an etching gas flow rate of 15 sccm, a power of 80W, and an etching depth of 450nm (through the Au-Cu double metal layer) to form a gradient slot structure and expand the antenna bandwidth (after optimization, the reflection coefficient of the 100GHz-4THz band is <-15dB).

[0091] Antenna field enhancement treatment: A 50nm thick Al2O3 nanofilm is deposited at the end of the antenna (atomic layer deposition ALD process, temperature 120℃) to enhance the terahertz field radiation efficiency through surface plasmon resonance effect (radiation gain increased by 2dB).

[0092] S113, Substrate and bonding process optimization;

[0093] Substrate thinning: The thickness of the high-resistivity silicon substrate is reduced from 500μm to 300μm (using mechanical grinding + chemical mechanical polishing CMP process, the surface roughness Ra after polishing is <0.5nm), reducing the transmission loss of terahertz in the substrate;

[0094] Bonding interface optimization: 5 wt% nano-Al2O3 particles (20 nm in diameter) were incorporated into the PI binder, ultrasonically dispersed for 30 min, and then spin-coated. The bonding temperature was reduced to 120℃, and the holding time was extended to 3 h to improve the interfacial thermal conductivity (optimized interfacial thermal resistance < 10). -4 K·m 2 / W) to prevent the device from overheating during operation.

[0095] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0096] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A photonic integrated broadband terahertz emitting device based on thin-film lithium niobate (TFLN), characterized in that, It includes a TFLN integrated substrate and multiple components, including a ridge optical waveguide, a terahertz transmission line, a broadband transmitting antenna, and an electro-optic modulation unit, with each component coplanarly integrated on the TFLN integrated substrate.

2. The device as described in claim 1, characterized in that, The TFLN integrated substrate uses a 600nm thick x-cut lithium niobate thin film, bonded to a 4700nm thick thermally grown SiO2 / 500μm thick high-resistivity silicon substrate. The second-order nonlinear coefficient of TFLN is χ(2)=360pm / V.

3. The device as described in claim 1, characterized in that, The surface of the TFLN integrated substrate is covered with an 800nm ​​thick SiO2 cladding, and laser avoidance holes with a diameter of 50μm are formed in the cladding. At the same time, a metal shielding film is embedded in the cladding.

4. The device as claimed in claim 1, characterized in that, The ridge-shaped optical waveguide is a TFLN strip structure with a width of 2.2-2.6 μm and a height of 350-450 nm, used to transmit 1560 nm pump light, with a group refractive index n. g =2.

25.

5. The device as claimed in claim 1, characterized in that, The terahertz transmission line is a gold coplanar stripline wrapped around the outside of the ridge optical waveguide and integrated collinearly with the ridge optical waveguide. Its characteristic impedance is 65-75Ω and its refractive index is matched with that of the ridge optical waveguide group.

6. The device as claimed in claim 1, characterized in that, The broadband transmitting antenna is a dipole antenna with a length of 150-400μm and a width of 5-10μm. It is integrated at the end of the terahertz transmission line and has a 3dB radiation bandwidth of 200GHz-3.5THz.

7. The device as claimed in claim 1, characterized in that, The electro-optic modulation unit is a Mach-Zehnder modulator, connected in series at the input of the ridge-shaped optical waveguide, with an operating bandwidth > 10 GHz. The terahertz output amplitude is linearly controlled by applying a 0-0.7 V bias voltage, and the modulation efficiency ηmod = 30.6 V. -1 ·m.

8. The device as claimed in claim 1, characterized in that, The terahertz transmission line is provided with grounding metal strips on both sides.

9. The device as claimed in claim 1, characterized in that, The terahertz transmission line is configured as an open strip cavity structure.

10. A method for fabricating a photonic integrated broadband terahertz emitting device based on TFLN as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: TFLN substrate preparation: A 600nm thick x-cut lithium niobate film was selected and bonded to a 4700nm SiO2 / 500μm high-resistivity silicon substrate by plasma-enhanced bonding process. O2 plasma treatment was performed to make the surface roughness Ra < 0.3nm. S2: Ridge-shaped optical waveguide fabrication: fabricated using electron beam lithography and Ar... + Ion etching was used to fabricate a waveguide with a width of 3μm and a depth of 350nm, and the etching damage was repaired by O2 annealing at 450℃ for 30min. S3: Terahertz transmission line fabrication: 15nm Ti / 300nm Au was deposited by electron beam evaporation, and a gold bar-shaped transmission line with a width of 80μm and a length of 2mm was formed by a lift-off process. The line was then vacuum annealed at 150℃ for 20min. S4: Broadband transmitting antenna and electro-optic modulation unit integration: A 200μm long dipole antenna is fabricated using the same batch of Au deposition process, and the MZM modulator is connected to the ridge optical waveguide through an edge coupler; S5: Cladding Deposition and Calibration: An 800nm ​​SiO2 cladding was deposited by ICP-CVD, and clearance holes were opened. The phase matching conditions were calibrated by a terahertz spectrum analyzer to complete the device fabrication.

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