On-chip all-optical wavelength converter and method of fabricating the same

Abstract

This application relates to an on-chip all-optical wavelength converter and its fabrication method. The on-chip all-optical wavelength converter includes: a silicon-containing substrate, and a WDM input coupler, a TFLN waveguide, an EDWA, and a WDM output coupler located on the silicon-containing substrate; the TFLN waveguide includes a tip coupling structure; the tip of the tip coupling structure of the TFLN waveguide is wrapped in the EDWA to form a heterogeneous thermally adiabatic coupling section; the TFLN waveguide and EDWA connected by the heterogeneous thermally adiabatic coupling section are bent on the silicon-containing substrate to form a micro-ring resonator; the WDM input coupler is connected to the TFLN waveguide and is used to couple signal light and pump light into the TFLN waveguide; the micro-ring resonator is used to convert pump light and signal light into amplified signals; the WDM output coupler is connected to the EDWA and is used to output amplified signals, thereby solving the technical problems of excessively large structure and excessively high power consumption of the all-optical wavelength converter.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to an on-chip all-optical wavelength converter and its fabrication method. Background Technology

[0002] As intelligent computing centers continue to grow in scale, the optical interconnection scale of the WDM (Wavelength Division Multiplexing) optical communication network they adopt is also increasing. Therefore, data exchange at network nodes of the optical communication network is facing an increasingly serious "optical-electrical-optical" conversion bottleneck.

[0003] To address the aforementioned conversion bottlenecks, all-optical wavelength conversion technology, which can directly change wavelengths without electrical domain processing, has become a core technology for achieving flexible all-optical routing and reducing network latency in WDM optical communication networks.

[0004] However, if all-optical wavelength conversion is achieved based on the cross-gain modulation or four-wave mixing effect of SOA (Semiconductor Optical Amplifier), pattern effect interference will occur when processing high-speed digital signals due to the short recovery time of SOA carriers, resulting in severe pulse distortion and channel crosstalk.

[0005] If full-wavelength conversion is achieved based on the second-order nonlinear cascade effect of periodically polarized nonlinear crystals, such as PPLN (Periodically Poled Lithium Niobate), extremely high pump power is required to obtain considerable conversion efficiency.

[0006] If a macroscopic fiber loop is constructed using an EDFA (Erbium-Doped Fiber Amplifier) ​​and a PPLN waveguide, allowing the pump light to resonate in the fiber cavity, extremely high local pump power can be generated at the PPLN waveguide, thereby achieving cascaded wavelengths. However, since this structure requires a fiber cavity several meters long, it is bulky and can only exist as a rack-mount device. Moreover, the mode field mismatch during the resonance process of the light in the fiber cavity is severe, and the gain provided by the EDFA is significantly depleted. Therefore, the typical power consumption of this structure is as high as 8-10 watts, which is too high.

[0007] How to achieve low-power all-optical wavelength conversion with a smaller all-optical wavelength conversion structure, while avoiding pulse distortion and channel crosstalk, has become a technical challenge that urgently needs to be solved in the field of WDM optical communication networks. Summary of the Invention

[0008] Based on this, an on-chip all-optical wavelength converter and its fabrication method are provided to solve the technical problems of excessively large structure and high power consumption of all-optical wavelength converters.

[0009] In a first aspect, embodiments of this application provide an on-chip all-optical wavelength converter, comprising:

[0010] A silicon-containing substrate, and a wavelength division multiplexing (WDM) input coupler, a thin-film lithium niobate (TFLN) waveguide, an erbium-doped waveguide amplifier (EDWA), and a WDM output coupler located on the silicon-containing substrate;

[0011] TFLN waveguides include tip-coupled structures;

[0012] The tip of the TFLN waveguide's tip coupling structure is wrapped in the EDWA to form a heterogeneous thermally adiabatic coupling segment. The TFLN waveguide and EDWA connected by the heterogeneous thermally adiabatic coupling segment are bent on a silicon-containing substrate to form a micro-ring resonant cavity.

[0013] The WDM input coupler is connected to the TFLN waveguide and is used to couple the signal light and pump light into the TFLN waveguide.

[0014] Microring resonators are used to convert pump light and signal light into amplified signals;

[0015] The WDM output coupler is connected to the EDWA and is used to output amplified signals.

[0016] In one embodiment, the tip coupling structure is located at the center of the microring resonant cavity, and the tip coupling structure includes at least one of the following forms:

[0017] Linear gradient inverted cone structure, nonlinear gradient inverted cone structure, parabolic gradient inverted cone structure.

[0018] In one embodiment, the outer side of the tip coupling structure is covered with an erbium-doped oxide coating layer, and the width of the tip coupling structure is reduced from the TFLN single-mode width to the tip width along the light transmission direction, so that the effective refractive index of the TFLN at the tip decreases to match the erbium-doped oxide coating layer.

[0019] In one embodiment, the TFLN single-mode width includes 600 nm to 1000 nm, the tip width includes 100 nm to 200 nm, the thickness of the erbium-doped oxide coating layer includes 1.2 μm to 2.0 μm, and the concentration of erbium-doped oxide in the erbium-doped oxide coating layer is 2 to 3 mol.

[0020] In one embodiment, the length of the tapered inverted portion of the tip coupling structure ranges from 50 μm to 300 μm.

[0021] In one embodiment, the silicon-containing substrate is a rigid substrate of silicon or silicon-on-insulator.

[0022] Secondly, embodiments of this application also provide a method for fabricating an on-chip all-optical wavelength converter, comprising:

[0023] A lithium niobate TFLN thin film layer was fabricated on a silicon-containing substrate, and the TFLN layer was etched to obtain a TFLN waveguide including a tip coupling structure.

[0024] Erbium-doped oxide cladding is applied over a silicon substrate and a TFLN waveguide using reactive magnetron sputtering.

[0025] Erbium-doped oxide cladding is etched to obtain erbium-doped waveguide amplifier (EDWA). The tip of the tip-coupled structure is clad in EDWA. The TFLN waveguide and EDWA are bent on a silicon-containing substrate to form a micro-ring resonator.

[0026] In one embodiment, the TFLN layer is etched to obtain a TFLN waveguide including a tip-coupled structure, comprising:

[0027] The width of the TFLN layer is reduced from the TFLN single-mode width to the tip width along the light transmission direction, so that the effective refractive index of the TFLN at the tip of the tip coupling structure decreases to be consistent with EDWA.

[0028] In one embodiment, the tip coupling structure is located at the center of the microring resonant cavity, and the tip coupling structure includes at least one of the following forms:

[0029] Linear gradient inverted cone structure, nonlinear gradient inverted cone structure, parabolic gradient inverted cone structure.

[0030] The tapered portion of the tip-coupled structure has a length ranging from 50 μm to 300 μm, a single-mode width ranging from 600 nm to 1000 nm, a tip width ranging from 100 nm to 200 nm, and a thickness of erbium-doped oxide coating ranging from 1.2 μm to 2.0 μm.

[0031] In one embodiment, etching the TFLN layer includes:

[0032] The TFLN layer was etched using photolithography and argon-ion dry etching techniques;

[0033] Etching an erbium-doped oxide cladding layer yields an erbium-doped waveguide amplifier (EDWA), including:

[0034] EDWA was obtained by etching the erbium-doped oxide coating layer using photolithography and argon-ion dry etching techniques.

[0035] The erbium-doped oxide coating is made of erbium-doped aluminum oxide with an erbium concentration of 2 to 3 mol.

[0036] This application provides an on-chip all-optical wave converter. By encapsulating the tip coupling structure in a TFLN waveguide with a higher refractive index within a low-refractive index EDWA, a thermally adiabatic evolution of the mode field from the TFLN waveguide to the EDWA is achieved. This allows the gain that would otherwise require several meters of optical fiber to be achieved on a silicon-containing substrate, thus avoiding the random polarization drift and phase mismatch caused by ambient temperature or mechanical vibration on several meters of optical fiber. In addition, the TFLN waveguide and EDWA are bent on the silicon-containing substrate to form an integrated micro-ring resonator. When the injected pump light wavelength is aligned with the resonance peak of the micro-ring resonator, the light circulates and superimposes within the micro-ring resonator. This allows the gain of the EDWA to offset the circumference loss and coupling loss of the light within the micro-ring resonator, thereby achieving near-critical coupling all-optical wavelength conversion with extremely low power consumption and minimal external optical power required. The rigid structure of the silicon-containing substrate fundamentally improves anti-interference capability, phase matching accuracy, and long-term reliability in engineering applications. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of the on-chip all-optical wavelength converter provided in the embodiments of this application;

[0039] Figure 2 This is a schematic diagram of the structure of the on-chip all-optical wavelength converter provided in the embodiments of this application;

[0040] Figure 3 This is a schematic diagram of the structure of the on-chip all-optical wavelength conversion system provided in the embodiments of this application;

[0041] Figure 4 This is a schematic diagram of a linear gradient inverted cone structure according to an embodiment of this application;

[0042] Figure 5 This is a schematic diagram of a parabolic gradient inverted cone structure according to an embodiment of this application;

[0043] Figure 6 This is a schematic diagram of the fabrication process of an on-chip all-optical wavelength converter provided in an embodiment of this application. Detailed Implementation

[0044] To facilitate understanding of this application, it will be described in more detail below. However, it should be understood that this application can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular implementations or embodiments only and is not intended to be limiting of this application. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0046] See Figure 1 As shown, this application embodiment provides an on-chip all-optical wavelength converter, including:

[0047] A silicon-containing substrate 101, and a WDM input coupler 102, a TFLN waveguide 103, an erbium-doped waveguide amplifier EDWA 104, and a WDM output coupler 105 located on the silicon-containing substrate;

[0048] TFLN waveguide 103 includes a tip coupling structure;

[0049] The tip of the tip coupling structure of the TFLN waveguide 103 is wrapped in the EDWA 104 to form a heterogeneous thermally adiabatic coupling section 106. The TFLN waveguide and EDWA connected by the heterogeneous thermally adiabatic coupling section 106 are bent on a silicon-containing substrate to form a micro-ring resonant cavity.

[0050] WDM input coupler 102 is connected to TFLN waveguide 103 and is used to couple signal light and pump light into TFLN waveguide 103.

[0051] Microring resonators are used to convert pump light and signal light into amplified signals;

[0052] WDM output coupler 105 is connected to EDWA104 and is used to output amplified signals.

[0053] The WDM output coupler 105 can also be used to output pump residue while simultaneously amplifying the output signal.

[0054] By wrapping the tip coupling structure in the higher refractive index TFLN waveguide within the low refractive index EDWA gain section, adiabatic mode field evolution from the TFLN waveguide to the EDWA is achieved. This allows the gain that would otherwise require several meters of fiber to be realized at the micro / nano waveguide level, thus avoiding the random polarization drift and phase mismatch caused by ambient temperature or mechanical vibration on several meters of fiber. In addition, the TFLN waveguide and the EDWA gain section are connected end-to-end on the substrate through trenches to form an integrated micro-ring resonator. When the injected pump light wavelength is aligned with the resonance peak of the micro-ring resonator, the light circulates and superimposes within the micro-ring resonator, allowing the gain of the EDWA to offset the circumference loss and coupling loss of the light within the micro-ring resonator. This achieves near-critical coupling or lossless all-optical wavelength conversion, resulting in extremely low power consumption and extremely low required externally injected optical power.

[0055] See Figure 2 As shown, the heterogeneous thermally adiabatic coupling section 106 includes a tip coupling structure 201 of the TFLN waveguide 103 and an erbium-doped oxide cladding layer 202 covering the outside of the tip coupling structure 201. The erbium-doped oxide cladding layer 202 can be the gain section of the EDWA 104.

[0056] The aforementioned tip coupling structure can adopt a three-dimensional gradient inverted cone structure (3D Adiabatic Taper).

[0057] For example, a linear tapered inverted cone structure, a nonlinear tapered inverted cone structure, or a parabolic tapered inverted cone joint can be used.

[0058] See Figure 2 As shown, the tip coupling structure includes a tapered inverted cone section with a length that can be, but is not limited to, 50 μm to 300 μm.

[0059] The tip of the gradient inverted cone section can be arc-shaped, bell-shaped, or tapered rounded, etc. The length of the gradient inverted cone section can be the straight-line distance from the bottom plane of the gradient inverted cone section to the top of the tip.

[0060] The outer side of the tip coupling structure is covered with an erbium-doped oxide cladding layer. The width of the tip coupling structure is reduced from the TFLN single-mode width to the tip width along the optical transmission direction, so that the effective refractive index of the TFLN at the tip decreases to match the erbium-doped oxide cladding layer. This allows the optical field to escape from the TFLN in the form of an escape wave and couple into the erbium-doped oxide cladding layer, thereby reducing the fiber length and greatly reducing power consumption.

[0061] The single-mode width of the TFLN core layer can be, but is not limited to, 600 nm to 1000 nm, the tip width can be, but is not limited to, 100 nm to 200 nm, and the thickness of the erbium-doped oxide coating layer can be, but is not limited to, 1.2 μm to 2.0 μm.

[0062] For example, if the tip of the tapered inverted cone is a tapered round head, then the tip width can be the maximum diameter of the tapered round head.

[0063] In the heterogeneous thermally coupled section, the tip coupling structure of the TFLN waveguide serves as the core layer, and the gain section of the EDWA serves as the erbium-doped oxide cladding layer. If the length of the tapered section of the tip coupling structure is too short (e.g., 10 μm or 20 μm), the contraction angle of the tapered section will be too large and too steep, causing the effective refractive index of the tip coupling structure of the TFLN waveguide as the core layer to decrease too quickly, thus disrupting the thermal evolution conditions of the optics.

[0064] Setting the lower limit of the length of the gradient inverted cone section to 50 μm ensures that the change in refractive index gradient is sufficiently gentle, ensuring that the 1480 nm pump light and 1550 nm signal light escape completely in the form of evanescent waves without loss, and controlling the coupling insertion loss of the heterostructure interface (the interface between the tip coupling structure and the erbium-doped oxide coating layer) to a low level (such as below 0.2 dB).

[0065] In the process of micro-nano fabrication, nanoscale roughness is inevitably left on the sidewalls of the waveguide. The longer the light travels in the tapered section, the greater the intrinsic scattering loss due to the accumulated sidewall roughness. Excessive transmission distance will consume valuable pump energy. Therefore, setting the upper limit of the length of the tapered section to 300 μm can effectively block the accumulation of scattering loss caused by the etching of sidewall roughness. While maximizing the retention of pump light energy for nonlinear conversion, it greatly compresses the physical size of passive devices, enabling the entire on-chip all-optical wavelength converter to be embedded in a high-density photonic chip network at the square millimeter level.

[0066] The single-mode width of the TFLN core can refer to the initial waveguide width of the TFLN layer, that is, the width of the TFLN core layer before it enters the tip coupling structure and before it begins to decrease.

[0067] See Figure 3As shown, an optional embodiment of this application provides an on-chip all-optical wavelength conversion system, including: a pump laser, an external bus waveguide, and an on-chip all-optical wavelength converter. The on-chip all-optical wavelength converter includes: a silicon-containing substrate 101, and a WDM input coupler 102, a TFLN waveguide 103, an erbium-doped waveguide amplifier EDWA 104, and a WDM output coupler 105 located on the silicon-containing substrate; the TFLN waveguide 103 includes a tip coupling structure; the tip of the tip coupling structure of the TFLN waveguide 103 is wrapped in the EDWA 104 to form a heterogeneous thermally adiabatic coupling section 106, and the TFLN waveguide 103 and EDWA 104 connected by the heterogeneous thermally adiabatic coupling section 106 are bent on the silicon-containing substrate to form a micro-ring resonator; one end of the WDM input coupler 102 is connected to the TFLN waveguide 103, and the other end is divided into two branches, the first branch receives signal light, and the second branch is connected to the pump laser through the external bus waveguide to receive the pump light output by the pump laser. The WDM input coupler couples the pump light and signal light into the micro-ring resonator (through the EDWA, heterogeneous thermal coupling section, and TFLN waveguide) to achieve all-optical wavelength conversion and obtain the amplified signal. The WDM output coupler outputs the amplified signal and pump residue.

[0068] For example, see Figure 4 As shown, in an on-chip all-optical wave converter, when the tip coupling structure is a standard linearly tapered inverted cone structure, the single-mode width of the TFLN core layer can be 800 nm, the tip width is 150 nm, and the length of the tapered inverted cone portion is between 150 μm and 200 μm. The sidewalls of the profile shape of the standard linearly tapered inverted cone structure exhibit a linear contraction (linear function shape), and the deposition thickness of the erbium-doped oxide (Er:Al2O3) in the erbium-doped oxide coating layer covering the outside of the tip coupling structure is 1.5 μm to 2.0 μm. The total perimeter of the microring resonator can be 2 cm.

[0069] In this on-chip all-optical-wave converter, a silicon dioxide cladding (SiO2) can be deposited on top of the TFLN waveguide and EDWA, with a deposition thickness of up to 2 μm.

[0070] The embodiments of this application can smoothly extrude the mold field and stably control the heterogeneous interface coupling loss to about 0.2dB to 0.3dB. The length of the gradient inverted cone portion is more than 150μm, which can ensure that the mold field maintains adiabatic conditions during the refractive index jump from the TFLN core layer to the erbium-doped oxide coating layer (Er:Al2O3).

[0071] Using the standard EBL (Electron Beam Lithography) process to fabricate the gradient tapered section can stabilize its production yield.

[0072] See Figure 5As shown, in an on-chip all-optical wave converter, when the tip coupling structure is a parabolic tapered inverted cone structure, the single-mode width of the TFLN core layer can be 800 nm, the tip width is 100 to 120 nm, and the length of the tapered inverted cone portion is between 50 μm and 80 μm. The width of the parabolic tapered inverted cone structure decreases paraboically or exponentially with the length, and the erbium-doped oxide (Er:Al2O3) deposition thickness in the erbium-doped oxide coating layer covering the outside of the tip coupling structure is 1.2 μm. Compared with the standard linear tapered inverted cone structure, the nonlinear design of the parabolic tapered inverted cone structure can shorten the device length of the tip coupling structure by more than half. The extremely narrow tip design with a tip width of less than 120 nm ensures that the residual reflection is close to zero. Since the mode field overflow critical region provides sufficient adiabatic evolution space, the heterojunction coupling loss can even be reduced to below 0.15 dB.

[0073] In the design of nonlinear gradient inverted cone structures, since the contraction slope at the end of the inverted cone is smaller than that at the front end, extremely low insertion loss can be achieved within a shorter coupling length (e.g., <100μm) of the gradient inverted cone section. In order to ensure that the overflow optical field is completely contained by the erbium-doped oxide coating layer, the erbium-doped oxide coating layer needs to provide sufficient stimulated emission gain volume. Therefore, the thickness of the erbium-doped oxide coating layer can be from 1.0μm to 2.5μm, thereby reducing the single coupling loss of the heterojunction to below 0.2dB.

[0074] In this on-chip all-optical-wave converter, a silicon dioxide cladding (SiO2) can be deposited on top of the TFLN waveguide and EDWA, with a deposition thickness of up to 2 μm.

[0075] Using standard EBL process to fabricate the tapered section can stabilize the fabrication yield of the tapered section of the on-chip all-wavelength transducer.

[0076] In this embodiment, the conversion efficiency of linear wavelength conversion is proportional to the square of the pump light power. When the injected pump light wavelength is aligned with the resonance peak of the micro-ring resonator, the light circulates and superimposes within the micro-ring resonator. At this time, the gain provided by EDWA just offsets the encirclement loss and coupling loss of the micro-ring resonator, reaching a near-critical coupling or lossless state. This causes a surge in the quality factor (Q value) and fineness (Finesse) of the micro-ring resonator. The relationship between the pump light intensity Icirc circulating within the micro-ring resonator and the input light intensity Iin is greatly increased. Therefore, only a very low external pump light power (e.g., 20mW) is needed to accumulate a high-intensity local pump field at the watt level inside the micro-ring resonator, thereby exciting a highly efficient nonlinear polarization effect in the TFLN waveguide region, achieving low-power, high-efficiency wavelength conversion. Because this embodiment uses a high concentration of erbium-doped oxide (2 to 3 mol%) as the active gain medium in the microring resonator, it can handle high-speed digital optical signals up to 40 Gbps or 100 Gbps, and the Er in EDWA... 3+ The ion's upper energy level lifetime is on the order of milliseconds (ms), which allows the EDWA's gain state to maintain absolute gain clamping (inertia) in the face of picosecond-level pulse signals, fundamentally immune to pattern effects and ensuring high fidelity of the signal after wavelength conversion.

[0077] See Figure 6 As shown in the embodiments of this application, a method for fabricating an on-chip all-optical wavelength converter is also provided, comprising:

[0078] S601: A TFLN lithium niobate thin film layer is prepared on a silicon-containing substrate, and the TFLN layer is etched to obtain a TFLN waveguide including a tip coupling structure;

[0079] S602: Erbium-doped oxide cladding layer is applied over a silicon substrate and a TFLN waveguide using reactive magnetron sputtering.

[0080] S603: Etching the erbium-doped oxide cladding layer yields the erbium-doped waveguide amplifier (EDWA). The tip of the tip-coupled structure is clad within the EDWA. The TFLN waveguide and EDWA are bent on a silicon-containing substrate to form a micro-ring resonator.

[0081] In an optional embodiment of this application, after S603, a WDM input coupler can be embedded at the input end of the micro-ring resonator, and a WDM output coupler can be embedded at the output end of the micro-ring resonator.

[0082] In an optional embodiment of this application, S601 can be implemented in the following manner:

[0083] The width of the TFLN layer is reduced from the TFLN single-mode width to the tip width along the light transmission direction, so that the effective refractive index of the TFLN at the tip of the tip coupling structure decreases to be consistent with EDWA.

[0084] The tip coupling structure is located at the center of the microring resonator, and the tip coupling structure includes at least one of the following forms:

[0085] Linear gradient inverted cone structure, nonlinear gradient inverted cone structure, parabolic gradient inverted cone structure.

[0086] The tapered portion of the tip-coupled structure has a length ranging from 50 μm to 300 μm, a single-mode width ranging from 600 nm to 1000 nm, a tip width ranging from 100 nm to 200 nm, and a thickness of erbium-doped oxide coating ranging from 1.2 μm to 2.0 μm.

[0087] On-chip all-optical wavelength converters can be directly etched onto rigid substrates of silicon or silicon-on-insulator (SOI) using lithography technology, and the overall size of the on-chip all-optical wavelength converter can be less than 5mm. 2 Its cross-sectional area is on the submicron scale. Due to the absolute rigidity and consistency of the waveguide geometry ensured by the photolithography process, the silicon-containing substrate provides excellent mechanical support and heat conduction path. Therefore, this all-solid-state micro-physically constrained on-chip all-optical wavelength converter locks the polarization state of the light wave. It can be designed to support single TE (Transverse Electric) or TM (Transverse Magnetic) transmission, so that the pump light and signal light always maintain phase lock in the entire micro-ring resonant cavity. This ensures the ultimate stability of the system during long-term operation and avoids the strong stress birefringence caused by extremely small temperature gradient changes or acoustic mechanical vibrations on optical fibers that are several meters long. This would lead to random evolution of the polarization state of the light wave, thereby destroying the phase match and causing the output power to fluctuate drastically.

[0088] For example, photolithography and argon-ion dry etching techniques can be used to etch the TFLN layer;

[0089] For example, EDWA can be obtained by etching the erbium-doped oxide coating layer using photolithography and argon-ion dry etching techniques.

[0090] The material of the erbium-doped oxide coating layer can be erbium-doped aluminum oxide with an erbium concentration of 2 to 3 mol.

[0091] Using standard EBL technology to fabricate the tapered section can stabilize the fabrication yield of the on-chip all-optical wavelength converter.

[0092] Embodiment 1 of this application provides an on-chip all-optical wavelength conversion system, including: a pump laser, an external bus waveguide, and an on-chip all-optical wavelength converter.

[0093] In the on-chip all-optical wavelength conversion system of Example 1, the tip-coupled structure of the TFLN waveguide is inserted as the core layer into the EDWA to form a heterogeneous thermally adiabatic coupling section. The TFLN waveguide and EDWA are bent on a silicon-containing substrate to form a microring resonator. When the tip-coupled structure is a standard linearly tapered inverted cone structure, the single-mode width of the TFLN core layer can be 800 nm, the tip width is 150 nm, and the length of the tapered inverted cone portion is between 150 μm and 200 μm. The sidewalls of the standard linearly tapered inverted cone structure exhibit a linear contraction (linear function shape), and the deposition thickness of the erbium-doped oxide (Er:Al2O3) in the erbium-doped oxide cladding layer covering the outside of the tip-coupled structure is 1.5 μm to 2.0 μm. The total perimeter of the microring resonator can be 2 cm.

[0094] Continuous 1480nm pump light (20 mW power) and 1535nm signal light carrying 40Gbps data (1 mW power) were injected into the on-chip all-optical wavelength converter of Example 1. The pump light resonated and surged within the micro-ring resonant cavity, and the on-chip all-optical wavelength converter stably output a new wavelength data stream near 1550nm through the WDM output coupler. Since the coupling loss within the on-chip all-optical wavelength converter is only 0.2dB, and the micro-ring resonant cavity effectively enhances the local optical field, the net conversion efficiency of the on-chip all-optical wavelength conversion system reaches -5dB, with a clear eye diagram and no pattern distortion. After 100 hours of continuous operation, there was no significant drift in polarization state or conversion efficiency.

[0095] In the macroscopic all-optical wave conversion system of Comparative Example 1 of this application, a 5-meter erbium-doped fiber EDFA (Erbium-Doped Fiber Amplifier) ​​and a discrete PPLN crystal module are used, which are connected to an FBT (Fused Biconical Taper) coupler through a single-mode fiber to form a macroscopic all-optical wave conversion system.

[0096] The single-pass insertion loss of Comparative Example 1, from the single-mode fiber entering the PPLN crystal module to its return, is as high as 4dB. To achieve the same conversion efficiency as Example 1, Comparative Example 1 requires an additional 500mW of electrical power to drive the EDFA. When operating at room temperature without a vibration damping platform, Comparative Example 1 experiences periodic and severe fluctuations in output converted optical power due to airflow and minor vibrations, with fluctuation amplitudes exceeding 3dB.

[0097] Table 1: Experimental data of Example 1 and Comparative Example 1

[0098] The on-chip all-optical waveguide conversion system of Example 1 physically fuses EDWA and TFLN waveguides at the sub-micrometer scale to form a millimeter-scale all-solid-state microring resonator. Because Example 1 uses EDWA, its Er... 3+ The ions have a millisecond-level lifetime in their upper energy level and exhibit a stable gain clamping state in the face of picosecond-level digital pulses. Therefore, Example 1 is completely immune to pattern effects and maintains extremely high signal fidelity even at high speeds. The difference in the underlying structure between Example 1 and Comparative Example 1 directly leads to a generational gap in physical performance. The heterogeneous thermally adiabatic coupling section of Example 1 eliminates the up to 4.0dB mode field mismatch insertion loss in Comparative Example 1, enabling the on-chip all-optical wave converter system to achieve resonance enhancement at extremely low pump power (20mW). At the same time, the micron-level rigid solid-state structure used in Example 1 fundamentally eliminates the sensitivity of the long fiber cavity of Comparative Example 1 to environmental vibrations and temperature gradients. The output jitter of Comparative Example 1 is higher than 13.0dB, while the output jitter of Example 1 is less than 0.1dB, breaking through the physical bottleneck of high-speed optical communication and completely breaking the volume barrier. This allows the wavelength converter to be integrated as an on-chip integrated element and densely integrated into the optical interconnect network nodes of the next-generation intelligent computing center.

[0099] This application also provides a method for fabricating an on-chip all-optical wavelength conversion system, including:

[0100] A lithium niobate TFLN thin film layer was fabricated on a silicon-containing substrate, and the TFLN layer was etched to obtain a TFLN waveguide including a tip coupling structure.

[0101] Erbium-doped oxide cladding is applied over a silicon substrate and a TFLN waveguide using reactive magnetron sputtering.

[0102] Erbium-doped oxide cladding layer is etched to obtain erbium-doped waveguide amplifier EDWA. The tip of the tip coupling structure is clad in EDWA. The TFLN waveguide and EDWA are bent on a silicon-containing substrate to form a micro-ring resonant cavity.

[0103] WDM input couplers and WDM output couplers are fabricated on a silicon-containing substrate and connected to the input and output terminals of a microring resonator, respectively.

[0104] The WDM input coupler is connected to the pump laser via an external bus waveguide.

[0105] This application embodiment achieves thermal evolution of the mode field from the TFLN waveguide to the EDWA by encasing the tip coupling structure in the higher refractive index TFLN waveguide within the low refractive index EDWA. This allows the gain that would otherwise require several meters of optical fiber to be achieved on a silicon-containing substrate, thus avoiding the random polarization drift and phase mismatch caused by ambient temperature or mechanical vibration on several meters of optical fiber. Furthermore, the TFLN waveguide and EDWA are bent on the silicon-containing substrate to form an integrated micro-ring resonator. When the injected pump light wavelength is aligned with the resonant peak of the micro-ring resonator, the light circulates and superimposes within the micro-ring resonator, allowing the gain of the EDWA to offset the circumference loss and coupling loss of the light within the micro-ring resonator. This achieves near-critical coupling all-optical wavelength conversion with extremely low power consumption and minimal external optical power required. The rigid structure of the silicon-containing substrate fundamentally improves anti-interference capability, phase matching accuracy, and long-term reliability for engineering applications.

[0106] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application.

Claims

1. An all-optical wavelength converter on a chip, characterized by, include: A silicon-containing substrate, and a wavelength division multiplexing (WDM) input coupler, a thin-film lithium niobate (TFLN) waveguide, an erbium-doped waveguide amplifier (EDWA), and a WDM output coupler located on the silicon-containing substrate; The TFLN waveguide includes a tip-coupled structure; The tip of the tip coupling structure of the TFLN waveguide is wrapped in the EDWA to form a heterogeneous thermally adiabatic coupling segment. The TFLN waveguide and EDWA connected by the heterogeneous thermally adiabatic coupling segment are bent on the silicon-containing substrate to form a micro-ring resonant cavity. The WDM input coupler is connected to the TFLN waveguide and is used to couple the signal light and pump light into the TFLN waveguide. The micro-ring resonant cavity is used to convert the pump light and the signal light into an amplified signal; The WDM output coupler is connected to the EDWA and is used to output the amplified signal.

2. The on-chip all-optical wavelength converter according to claim 1, characterized in that, The tip coupling structure is located at the center of the microring resonant cavity, and the tip coupling structure includes at least one of the following forms: Linear gradient inverted cone structure, nonlinear gradient inverted cone structure, parabolic gradient inverted cone structure.

3. The on-chip all-optical wavelength converter according to claim 1, characterized in that, The outer side of the tip coupling structure is covered with an erbium-doped oxide coating layer. The width of the tip coupling structure is reduced from the TFLN single-mode width to the tip width along the light transmission direction, so that the effective refractive index of the TFLN at the tip decreases to match the erbium-doped oxide coating layer.

4. The on-chip all-optical wavelength converter according to claim 3, characterized in that, The TFLN single-mode width includes 600nm to 1000nm, the tip width includes 100nm to 200nm, the thickness of the erbium-doped oxide coating layer includes 1.2μm to 2.0μm, and the concentration of erbium-doped oxide in the erbium-doped oxide coating layer is 2 to 3 mol.

5. The on-chip all-optical wavelength converter according to claim 3, characterized in that, The length of the tapered inverted portion of the tip coupling structure ranges from 50 μm to 300 μm.

6. The on-chip all-optical wavelength converter according to claim 1, characterized in that, The silicon-containing substrate is a rigid substrate of silicon or silicon on an insulator.

7. A method for fabricating an on-chip all-optical wavelength converter, characterized in that, include: A lithium niobate TFLN thin film layer is prepared on a silicon-containing substrate, and the TFLN layer is etched to obtain a TFLN waveguide including a tip coupling structure. An erbium-doped oxide cladding layer is applied over the silicon substrate and the TFLN waveguide using reactive magnetron sputtering. The erbium-doped oxide cladding layer is etched to obtain an erbium-doped waveguide amplifier (EDWA). The tip of the tip-coupled structure is clad in the EDWA. The TFLN waveguide and the EDWA are bent on the silicon-containing substrate to form a micro-ring resonator.

8. The method as described in claim 7, characterized in that, Etching the TFLN layer yields a TFLN waveguide including a tip-coupled structure, comprising: The width of the TFLN layer is reduced from the TFLN single-mode width to the tip width along the light transmission direction, so that the effective refractive index of the TFLN at the tip of the tip coupling structure decreases to be consistent with the EDWA.

9. The method as described in claim 8, characterized in that, The tip coupling structure is located at the center of the microring resonant cavity, and the tip coupling structure includes at least one of the following forms: Linear gradient inverted cone structure, nonlinear gradient inverted cone structure, parabolic gradient inverted cone structure. The length of the tapered inverted portion of the tip coupling structure ranges from 50 μm to 300 μm, the width of the TFLN single-mode ranges from 600 nm to 1000 nm, the tip width ranges from 100 nm to 200 nm, and the thickness of the erbium-doped oxide coating layer ranges from 1.2 μm to 2.0 μm.

10. The method as described in claim 7, characterized in that, The etching of the TFLN layer includes: The TFLN layer was etched using photolithography and argon-ion dry etching techniques; The etching of the erbium-doped oxide cladding layer to obtain the erbium-doped waveguide amplifier (EDWA) includes: The erbium-doped oxide coating layer was etched using photolithography and argon-ion dry etching techniques to obtain EDWA. The erbium-doped oxide coating is made of erbium-doped aluminum oxide with an erbium concentration of 2 to 3 mol.

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