Wavelength division multiplexing / demultiplexing system and preparation method thereof

Abstract

The invention provides a wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation and a preparation method thereof, and belongs to the field of optical coupling devices. The wavelength division multiplexing / demultiplexing system comprises a substrate and a buried oxide layer which are stacked, and n (n is a positive integer greater than or equal to 2) micro-ring units and an upper cladding which are positioned on the upper surface of the buried oxide layer. And the upper cladding covers the n micro-ring units and is in contact with the buried oxide layer. Each micro-ring unit comprises a straight-through waveguide and at least one micro-ring waveguide. And the n micro-ring units are connected into a whole through the straight waveguide. The micro-ring waveguide includes a first ring waveguide and a second ring waveguide over the first ring waveguide. The second annular waveguide is made of a phase change material, and a fourth distance exists between the second annular waveguide and the first annular waveguide. The micro-ring waveguides are arranged at intervals along the extension direction of the straight waveguide. A first distance exists between the straight-through waveguide and the micro-ring waveguide. The wavelength division multiplexing / demultiplexing system has the properties of low energy consumption, low loss, non-volatility and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical coupling devices, and in particular relates to a wavelength division multiplexing / demultiplexing system based on a micro-ring structure and phase change material modulation and a preparation method thereof. Background Art

[0002] Wavelength division multiplexing (WDM) technology significantly increases the capacity of communication systems by multiplexing or demultiplexing optical signals carrying information at different wavelengths onto a single optical fiber for transmission. Current mainstream WDM technology solutions include microring resonators, arrayed waveguide gratings (AWGs), thin-film filters (TFFs), and fiber Bragg gratings (FBGs). AWGs and TFFs have fixed channel spacing, making dynamic wavelength allocation difficult. Their large size (approaching centimeters) hinders high-density integration. FBGs only support reflective filtering, resulting in low flexibility and complex multiplexing / demultiplexing structures. Microring resonators offer ultra-compact dimensions (on the order of tens of microns), but they still face challenges such as high tuning power consumption, limited tuning speed, and process sensitivity.

[0003] The resonant wavelengths of the sub-unit microrings in traditional WDM microring arrays are significantly affected by the silicon photonics fabrication process, making channel wavelengths prone to deviation from designed values. To compensate for these process variations, the industry typically employs wavelength thermal tuning, which requires continuous heating to maintain wavelength channel uniformity, leading to cumulative static energy consumption. Thermal optical tuning consumes tens of milliwatts per channel, making it difficult to scale up large arrays. Furthermore, wavelength thermal tuning has a millisecond response time, which cannot meet the demands of high-speed dynamic networks (such as microsecond-level switching).

[0004] Prior art CN118732172A discloses a wavelength-selective optical attenuator based on microring resonators. This device is constructed by serially connecting second-order microring resonators with Mach-Zehnder interference structures in the outer coupling region. Each second-order microring resonator can tunably attenuate light waves within a specific wavelength range. A single 2×2 unit applies wavelength-selective attenuation to multiple signals (i.e., different wavelengths experience different attenuation), balancing the light intensity across wavelengths. Furthermore, wavelength-selective attenuation of optical signals in a particular channel is independent of and independent of other channels, significantly improving the integration of silicon-based systems for long-distance, high-speed, error-free transmission in dense wavelength division multiplexing systems. However, this solution uses titanium nitride thermo-optical phase shifters to heat the Mach-Zehnder interference arms of the microrings to achieve uniform wavelength channel spacing. This solution also requires continuous temperature control of multiple regions, resulting in high energy consumption and a lack of low-energy performance.

[0005] Prior art CN116243427A discloses a multi-channel amplitude equalizer based on a microring resonator array. This multi-channel amplitude equalizer includes an upper cladding, a lower cladding, a bus input / output waveguide, and N microring resonator units. The bus input / output waveguide and the N microring resonator units are disposed between the upper and lower claddings, and the N microring resonator units are disposed to the sides of the bus input / output waveguide. The N microring resonator units are spaced sequentially along the transmission direction of the bus input / output waveguide. Multiple wavelength signals are input from the bus waveguide and output from the bus waveguide by simultaneously controlling multiple microring resonator units, achieving amplitude equalization of the multiple optical signals. This multi-channel amplitude equalizer has a compact design and high stability. It utilizes the inherent resonant characteristics of microring resonators to achieve simultaneous amplitude equalization of multiple wavelength signals, with low energy consumption and excess loss. It is suitable for multi-channel wavelength division multiplexing systems, optical computing and neural networks, and microwave photonics. However, this solution changes the state of the tuning electrode through the thermo-optical effect or the electro-optical effect, and is not non-volatile after the system loses power, and cannot maintain the channel state.

[0006] Prior art CN110286444A discloses a reconfigurable microring optical switch based on phase change material. This reconfigurable microring optical switch comprises two bus waveguides, a microring resonator, and a hybrid waveguide equipped with phase change material. The hybrid waveguide comprises a silicon waveguide and a phase change material disposed on the silicon waveguide. The hybrid waveguide is positioned outside or inside the microring resonator and arranged in an arc-shaped segment that aligns with the microring resonator. Lateral evanescent wave coupling occurs between the microring resonator and the input / output waveguides and the upload / download waveguides, generating optical field resonance within the microring resonator. Lateral evanescent wave coupling occurs between the microring resonator and the hybrid waveguide equipped with phase change material to regulate the optical field resonance within the microring, thereby achieving optical path switching. This reconfigurable microring optical switch boasts a compact and highly stable structure, overcoming the inherent high loss of phase change materials, reducing crosstalk and improving the extinction ratio. It achieves self-sustaining characteristics and low energy consumption, making it suitable for reconfigurable and tunable wavelength division multiplexing systems. However, this scheme places a hybrid waveguide equipped with phase-change material laterally alongside the microring. Due to the characteristics of the coupler, light must travel a very long coupling length before gradually transitioning from the microring to the hybrid waveguide. This results in a larger microring area under horizontal coupling, increased optical losses, and a lower quality factor. Furthermore, the introduction of a lateral coupling waveguide into the microring waveguide in this scheme inevitably introduces light field reflections, which can lead to significant fluctuations in the transmission spectrum. Furthermore, the phase-change material deposition area and the coupling area are located in the same location, making them susceptible to process errors.

[0007] In summary, the wavelength division multiplexing system composed of microring resonators in the existing technology has the following limitations: (1) High power consumption: Thermo-optical tuning relies on resistive heating, with power consumption as high as tens of milliwatts per channel, and large crosstalk between large-scale microring resonator arrays. (2) Limited tuning speed: The thermal tuning response time is in the millisecond range, which cannot meet the requirements of high-speed dynamic networks with microsecond switching. (3) Lack of non-volatility: After tuning, continuous power supply is required to maintain the refractive index, resulting in static energy consumption accumulation. (4) Process sensitivity: The microring resonant wavelength is easily affected by manufacturing process errors and temperature drift, requiring complex calibration procedures to compensate. Summary of the Invention

[0008] In order to solve the problems of narrow tuning range, slow tuning speed, high power consumption, lack of non-volatility, and large process errors of microring resonators in wavelength division multiplexing systems in the prior art, the present invention provides a wavelength division multiplexing / demultiplexing system based on microring structure and phase change material modulation and its preparation method.

[0009] Specifically, in order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A wavelength division multiplexing / demultiplexing system based on microring structure and phase change material modulation comprises a substrate, a buried oxide layer located on one surface of the substrate, n microring units located on a surface of the buried oxide layer facing away from the substrate, and an upper cladding layer; the upper cladding layer covers the n microring units and contacts the buried oxide layer; each microring unit comprises a straight waveguide and at least one microring waveguide; the n microring units are connected into a whole via the straight waveguide; the microring waveguide comprises a first ring waveguide and a second ring waveguide located above the first ring waveguide; a fourth spacing exists between the second ring waveguide and the first ring waveguide; the material of the second ring waveguide is phase change material; the microring waveguides are arranged at intervals along the direction in which the straight waveguide extends; a first spacing exists between the straight waveguide and the microring waveguide; and n is a positive integer ≥2.

[0010] In a preferred embodiment, the microring unit includes a download waveguide, which is arranged opposite to the straight waveguide; a third distance exists between the download waveguide and the microring waveguide; and the microring waveguide is arranged at intervals between the straight waveguide and the download waveguide.

[0011] In a further preferred embodiment, the third spacing is 130-500 nm.

[0012] In a further preferred solution, along the direction from the through waveguide to the download waveguide, the minimum spacing between two adjacent microring waveguides is 130-500 nm.

[0013] In a further preferred embodiment, the download waveguide is a straight waveguide or a curved waveguide.

[0014] In a preferred embodiment, the dimension of the second ring waveguide in the direction from the substrate to the upper cladding is 30-300 nm.

[0015] In a preferred solution, along the extending direction of the through waveguide, the ring width of the second ring waveguide is 350-1000 nm, and the distance between the center of the first ring waveguide and the center of the second ring waveguide is 100-600 nm.

[0016] In a preferred solution, the length of the center line of the projected circular ring of the first annular waveguide on the upper surface of the buried oxide layer is distributed in an arithmetic progression in the extending direction of the through waveguide.

[0017] In a preferred embodiment, the first spacing is 130-500 nm.

[0018] In a preferred embodiment, the fourth spacing is 30-300 nm.

[0019] In a preferred embodiment, the phase change material is selected from antimony sulfide, antimony selenide, germanium antimony telluride, and germanium antimony selenium telluride.

[0020] In a preferred solution, the straight-through waveguide is a straight waveguide or a curved waveguide.

[0021] The present invention also provides a method for preparing the wavelength division multiplexing / demultiplexing system based on the micro-ring structure and phase change material modulation, comprising the following steps: S1. Prepare a wafer, wherein the wafer includes a substrate, a buried oxide layer, and a waveguide layer stacked in sequence; S2. Etching the waveguide layer to form a through waveguide and a first ring waveguide; S3, forming a first upper cladding layer on the upper surface of the structure obtained in step S2; S4. Etching the first upper cladding layer above the first ring waveguide to form a groove, and stopping the etching at a position having a fourth distance from the first ring waveguide; S5, depositing a phase change material on the upper surface of the structure obtained in step S4, and etching to form a second ring waveguide in the groove; S6. Form a second upper cladding layer on the upper surface of the structure obtained in step S5. The second upper cladding layer and the first upper cladding layer are collectively referred to as an upper cladding layer.

[0022] In a preferred embodiment, the material of the waveguide layer is selected from silicon, silicon nitride, silicon carbide, lithium niobate, and gallium nitride.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: The present invention cascades microring units integrated with phase-change materials to achieve multi-channel wavelength optical signal multiplexing and demultiplexing. Phase-change materials have a significant difference in refractive index between their crystalline and amorphous states. Optical / electrical control of the non-volatile phase-change material integrated within the microrings allows for fine-tuning of the ratio of crystalline to amorphous phases, resulting in quasi-continuous refractive index tuning. This allows for reshaping of wavelength channel spacing, resulting in ultra-low energy consumption and low loss for wavelength division multiplexing / demultiplexing systems.

[0024] Specifically, the present invention has the following beneficial effects: (1) Low energy consumption: With the wavelength division multiplexing / demultiplexing system provided by the present invention, the power consumption of single-word tuning is as low as nanojoule (nJ) level.

[0025] (2) Dynamic Reconfiguration: The wavelength division multiplexing / demultiplexing system provided by the present invention can realize the rapid change between the crystalline and amorphous states of the phase change material by acting on the phase change material through electrical / optical pulses, thereby quickly (in microseconds) switching the wavelength channel.

[0026] (3) Non-volatility: The wavelength division multiplexing / demultiplexing system provided by the present invention does not require energy maintenance after tuning, which significantly reduces static power consumption.

[0027] (4) Low loss: The material of the second ring waveguide in the wavelength division multiplexing / demultiplexing system provided by the present invention is a phase change material. Due to the adoption of a ring structure, the phase change material forms a continuous structure in the upper cladding layer, which can avoid light reflection caused by the discontinuous structure of the phase change material.

[0028] (5) Compensation capability: The structure provided by the present invention in which there is a gap between the first ring waveguide and the second ring waveguide in the wavelength division multiplexing / demultiplexing system can calibrate the manufacturing error of the micro-ring waveguide during the preparation process, so that the wavelength alignment accuracy is <0.02nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 An exploded view of a three-dimensional structural schematic diagram of a wavelength division multiplexing / demultiplexing system based on a micro-ring structure and phase change material modulation provided by the present invention; Figure 2 A schematic diagram of the distribution of micro-ring units on the upper surface of a buried oxide layer in another wavelength division multiplexing / demultiplexing system based on a micro-ring structure and phase change material modulation provided by the present invention; Figure 3 The wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation provided by the present invention is along the section AA' (refer to Figure 2 )’s cross-sectional view; Figure 4A schematic structural diagram of a microring unit of another wavelength division multiplexing / demultiplexing system based on a microring structure and phase change material modulation provided by the present invention; Figure 5 for Figure 4 Schematic diagram of the distribution of micro-ring units on the upper surface of the buried oxide layer and the principle of wavelength division multiplexing; Figure 6 for Figure 4 Schematic diagram showing the distribution of micro-ring units on the upper surface of the buried oxide layer and the principle of wavelength division multiplexing; Figure 7 Schematic diagram of the center line of the first ring waveguide of the wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation in the present invention; Figure 8 When a wavelength division multiplexing / demultiplexing system based on a micro-ring structure and phase change material modulation provided by the present invention is used as a wavelength division multiplexing filter, light field diagrams of the phase change material in the amorphous state (Figure (a)) and the crystalline state (Figure (b)); Figure 9 A spectrum diagram of a wavelength division multiplexing / demultiplexing system based on a micro-ring structure and phase change material modulation provided by the present invention when used as a wavelength division multiplexing filter; Figure 10 A spectrum diagram of the download waveguide output of another wavelength division multiplexing / demultiplexing system based on a micro-ring structure and phase change material modulation provided by the present invention; Figure 11 Light field diagrams of the phase change material in the amorphous state (Figure (a)) and the crystalline state (Figure (b)) of another wavelength division multiplexing / demultiplexing system based on a micro-ring structure and phase change material modulation provided by the present invention; Figure 12 The figure is a schematic diagram of the process of preparing a wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation in the present invention.

[0030] In the figure: 1, substrate; 2, buried oxide layer; 3, microring unit; 31, straight waveguide; 32, microring waveguide; 33, download waveguide; 321, first ring waveguide; 3211, center line; 322, second ring waveguide; 4, upper cladding; gap1, first spacing; gap2, second spacing; gap3, third spacing; gap4, fourth spacing; AA', cross section. DETAILED DESCRIPTION

[0031] The following content clearly and completely describes the technical solution of the present application in conjunction with the embodiments so that those skilled in the art can fully understand the present application. Obviously, the embodiments described are only some preferred embodiments of the present application, rather than all embodiments. Any equivalent transformation or substitution made by those of ordinary skill in the art to the following embodiments without creative work falls within the scope of protection of the present application.

[0032] Directional terms used in this application, such as "upper," "lower," "inner," "outer," "bottom," and "upper surface," indicate positions or locations based on the figures in the specification or the positions or locations in which the product of this application is typically placed when in use. These terms are intended solely to facilitate description and understanding of the product structure of this application. Therefore, these directional terms should not be construed as limiting this application. In this application, unless otherwise expressly defined, expressions such as "upper," "above," "above," and "upper surface" of a first feature relative to a second feature indicate that the first and second features may be in direct contact or indirect contact through an intermediary; that the first feature may be directly above or obliquely above the second feature, or simply indicate that the first feature is at a higher level than the second feature. Expressions such as "lower," "below," "below," and "lower surface" of a first feature relative to a second feature indicate that the first and second features may be in direct contact or indirect contact through an intermediary; that the first feature may be directly below or obliquely below the second feature, or simply indicate that the first feature is at a lower level than the second feature. The ordinal numbers used in this application, such as "first" and "second," are used solely for descriptive purposes to distinguish similar objects and are not to be construed as indicating or implying relative importance or implicitly indicating the quantity of the technical features indicated. Methods not described in detail in the following examples are conventional methods well known to those skilled in the art.

[0033] Example 1 Reference Figures 1 to 6 A wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation includes a substrate 1, a buried oxide layer 2, a micro-ring unit 3 and an upper cladding layer 4. The buried oxide layer 2 is located on the upper surface of the substrate 1. A plurality of micro-ring units 3 (refer to Figure 2 、 Figure 5 , Figure 1Only one microring unit 3 is shown above) located on the upper surface of the buried oxide layer 2. The number n of microring units 3 is a positive integer ≥ 2. The upper cladding layer 4 covers the multiple microring units 3 and contacts the upper surface of the buried oxide layer 2. Each microring unit 3 includes a straight waveguide 31 and at least one microring waveguide 32. The multiple microring units 3 are connected into a whole through the straight waveguide 31. Each microring waveguide 32 includes a first ring waveguide 321 and a second ring waveguide 322 located above the first ring waveguide 321. The material of the second ring waveguide 322 is a phase change material. The annular structure of the second ring waveguide 322 avoids the light reflection problem caused by the segmented discontinuity of the phase change material. There is a fourth gap gap4 (see Figure 3 The fourth gap4 is the distance between the first ring waveguide 321 and the second ring waveguide 322 in the direction from the substrate 1 to the upper cladding 4 (or in the direction from the upper cladding 4 to the substrate 1). The micro-ring waveguides 32 are arranged at intervals along the direction in which the through waveguide 31 extends. The through waveguide 31 is coupled to the micro-ring waveguide 32 closest to the through waveguide 31, and the shortest distance between the two is the first gap1 (see Figure 4 ).

[0034] In some more specific embodiments, the micro-ring unit 3 further includes a download waveguide 33 (e.g. Figures 4-6 As shown, the download waveguide 33 is arranged opposite to the straight waveguide 31. The download waveguide 33 is coupled with the micro-ring waveguide 32 closest to the download waveguide 33, and the shortest distance between the two is the third gap 3 (see Figure 4 The micro-ring waveguide 32 is arranged between the straight waveguide 31 and the download waveguide 33, and the arrangement direction is the direction in which the straight waveguide 31 extends (such as Figure 2 、 5 Alternatively, the arrangement direction is the direction in which the through waveguide 31 extends and the direction in which the through waveguide 31 extends to the download waveguide 33 (as shown in FIG. Figures 4-6 shown).

[0035] In the direction from the through waveguide 31 to the down waveguide 33, the plurality of micro-ring waveguides 32 form a multi-stage cascaded micro-ring resonator (eg Figure 5 、 6 shown), and the center line of each first ring waveguide (reference Figure 7 The shortest distance between two adjacent micro-ring waveguides 32 is the second gap2 (see Figure 4 ).

[0036] By adjusting at least one of the first gap gap1, the second gap gap2, the third gap gap3, and the fourth gap gap4, the channel spacing and extinction ratio of the wavelength division multiplexing / demultiplexing system can be changed to optimize the performance of the wavelength division multiplexing / demultiplexing system.

[0037] As an example, the first spacing gap1 is 130~500nm, for example, 130nm, 131nm, 132nm, 135nm, 140nm, 145nm, 150nm, 160nm, 170nm, 180nm, 200nm, 201nm, 202nm, 205nm, 208nm, 210nm, 212nm, 215nm, 216nm, 220nm, 225nm...500nm.

[0038] As an example, the second gap gap2 is 130-500 nm, for example, 130 nm, 131 nm, 132 nm, 135 nm, 138 nm, 140 nm, 145 nm, 150 nm, 160 nm, 170 nm, . . . 500 nm.

[0039] As an example, the third gap gap3 is 130-500 nm, for example, 130 nm, 132 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm, 160 nm, . . . 500 nm.

[0040] As an example, the fourth gap gap4 is 30~300nm, for example, 30nm, 31nm, 32nm, 33nm, 35nm, 40nm, 45nm, 50nm, 60nm, 70nm, 80nm, 81nm, 82nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm, 120nm, 125nm...300nm.

[0041] In other more specific embodiments, by adjusting the dimension of the second ring waveguide 322 (i.e., the thickness of the second ring waveguide 322) along the direction from the substrate 1 to the upper cladding 4 (or from the upper cladding 4 to the substrate 1), vertical coupling between the second ring waveguide 322 and the first ring waveguide 321 can be achieved, the coupling coefficient between the second ring waveguide 322 and the first ring waveguide 321 can be changed, and the tuning range can be increased. By way of example, the dimension of the second ring waveguide 322 along the direction from the substrate 1 to the upper cladding 4 ranges from 30 to 300 nm, for example, 30 nm, 31 nm, 32 nm, 33 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 100 nm, ..., to 300 nm.

[0042] In other more specific embodiments, Figure 2 ( Figure 2 The upper cross section AA' is perpendicular to the upper surface of the buried oxide layer 2 and parallel to the extending direction of the straight waveguide 31, and cuts through the cross section of the first ring waveguide 321 and the second ring waveguide 322). Figure 3As shown, by adjusting the ring width W of the second ring waveguide 322 pcm The distance offset between the center of the first ring waveguide 321 and the center of the second ring waveguide 322 along the extension direction of the straight waveguide 31 can adjust the light field confinement factor and control the proportion of light entering the second ring waveguide 322. pcm It is the ring width of the projection of the second ring waveguide 322 on the upper surface of the buried oxide layer 2 along the extending direction of the through waveguide 31 .

[0043] As an example, the ring width W of the second ring waveguide 322 is pcm It is 350~1000nm, for example, 350nm, 351nm, 352nm, 355nm, 340nm, 350nm, 380nm, 400nm, 500nm, 600nm, 650nm, 651nm, 652nm, 653nm, 655nm, 660nm, 665nm, 670nm, 680nm, 690nm, 700nm, 710nm, 720nm, 725nm...1000nm.

[0044] As an example, along the extension direction of the straight waveguide 31, the distance offset between the center of the first ring waveguide 321 and the center of the second ring waveguide 322 is 100~600nm, for example, 100nm, 105nm, 110nm, 120nm, 150nm, 180nm, 200nm, 205nm, 210nm, 230nm, 260nm, 280nm, 300nm, 301nm, 302nm, 303nm, 305nm, 310nm, 315nm, 320nm, 325nm, 330nm, 335nm, 340nm, 345nm, 350nm...600nm.

[0045] In some more specific embodiments, in order to form wavelength channels with uniform spacing, a plurality of first ring waveguides 321 are arranged at intervals in the direction in which the through waveguide 31 extends, and the center line 3211 (see FIG. 3 ) of the projection of the first ring waveguide 321 on the upper surface of the buried oxide layer 2 is Figure 7 ) are distributed in an arithmetic progression.

[0046] As an example, the straight waveguide 31 is a straight waveguide (eg Figure 5 、 6 shown) or a curved waveguide (e.g., an Euler-bent waveguide, not shown).

[0047] As an example, the download waveguide 33 is a straight waveguide (eg Figure 1 ) or a curved waveguide (e.g., an Euler-bent waveguide, see Figure 5 and Figure 6).

[0048] In other more specific embodiments, the material of the second ring waveguide 322 is any one of antimony sulfide, antimony selenide, germanium antimony telluride, and germanium antimony selenide telluride. Changing the type of phase-change material can achieve wavelength division multiplexing (WDM) or demultiplexing, or WDM filtering. When using a phase-change material with a small loss difference between its crystalline and amorphous states (such as antimony sulfide and antimony selenide), WDM or demultiplexing can be achieved. When using a phase-change material with a large loss difference between its crystalline and amorphous states (such as germanium antimony telluride and germanium antimony selenide telluride), it can function as a WDM filter switch.

[0049] As an example, the material of the first ring waveguide 321 is any one of silicon, silicon nitride, and silicon carbide.

[0050] In other more specific embodiments, a micro-titanium / gold heating electrode with a resistance of 30 ohms can be integrated on the upper surface of the upper cladding. Applying an electrical pulse (typical parameters: 5V, 200ns) generates Joule heating. This heat energy is transferred from the metal electrode to the phase-change material layer (the second ring waveguide), driving the PCM to reversibly switch between an amorphous state (low refractive index) and a crystalline state (high refractive index). As the PCM gradually transitions to the crystalline state through pulse modulation, its refractive index changes the equivalent refractive index profile of the microring waveguide, redshifting the resonant wavelength by approximately 5nm. In the amorphous state, the PCM refractive index decreases, and the resonant wavelength returns to its initial value. By programming the crystallization degree of the phase-change material of the microring unit through electrothermal pulses, the wavelength of the microring unit's transmission spectrum can be shifted. For example, 1553nm and 1556nm channels can be demultiplexed to different output ports, or demultiplexed into a single light source output.

[0051] In any of the above solutions, the number of wavelengths of the input or / and output light waves of the wavelength division multiplexing / demultiplexing system corresponds to the number n of micro-ring units 3. As an example, Figure 2 As shown, the wavelength division multiplexing / demultiplexing system contains four cascaded microring units 3. This structure does not contain a download waveguide. The high loss characteristics of the Germanium Antimony Telluride (GST) crystal state are used to selectively "turn off" the filtering function of the wavelength division multiplexing system to achieve flexible spectrum adjustment. In the initial state, all GSTs are amorphous, and each microring waveguide 32 independently filters out a specific wavelength, such as Figure 2From left to right, the first microring waveguide 32 in the upper image filters out light with a wavelength of λ1, the second microring waveguide 32 filters out light with a wavelength of λ2, and so on. Specifically, when the material of the second ring waveguide 322 in the wavelength division multiplexing / demultiplexing system is GST, the system functions as a wavelength division multiplexing filter. Its operating principle is as follows: When GST is in an amorphous state, it has low loss and minimal impact on the optical field of the microring waveguide. The microring waveguide maintains a high quality factor (Q value > 1000). At this time, if the input optical signal wavelength matches the resonant wavelength of the microring waveguide, it is filtered out by the microring waveguide, while other wavelengths are output through the straight-through waveguide. When laser pulses are applied to the phase change material region to gradually crystallize the GST, the high loss characteristics of the GST significantly enhance the light absorption of the microring waveguide, causing the microring waveguide's Q value to drop sharply to <100, eliminating the resonance peak. The previously filtered wavelength signal passes directly through the straight-through waveguide, effectively disabling the filtering function of the microring waveguide. That is, after selectively crystallizing a portion of the GST of the microring waveguide 32, the corresponding wavelength channel will bypass the filter and transmit directly, thereby reconstructing the output spectrum. Figure 2 As shown, the width of the straight waveguide 31 ( Figure 1 The dimension of the straight waveguide 31 in the direction from the substrate 1 to the upper cladding 4 is 500 nm. The center line 3211 of the first ring waveguide 321 (refer to Figure 7 ) has a radius of 10 μm. The first gap gap1 is 250 nm. The ring width of the second ring waveguide 322 is 1000 nm, the thickness is 30 nm, and the offset between the center of the first ring waveguide 321 and the center of the second ring waveguide 322 is 600 nm. The fourth gap gap4 is 80 nm. The fourth gap can prevent the GST from directly contacting the first ring waveguide, thereby reducing optical loss. When a wavelength signal containing λ1, λ2, λ3, and λ4 is input to the through waveguide 31, Figure 2 The GST crystallization of the first micro-ring waveguide 32 and the second micro-ring waveguide 32 from left to right (the light field under different GST crystal states is shown in FIG. Figure 8 ), the light with wavelengths λ1 and λ2 passes directly through the straight waveguide 31; while the light with wavelengths λ3 and λ4 passes through Figure 2 The third and fourth micro-ring waveguides 32, which are not crystallized from left to right, are filtered out by the two micro-ring waveguides. Therefore, the light output from the output end of the through waveguide 31 is the light with wavelengths λ1 and λ2, realizing the selection of programmed wavelengths (the spectrum of the wavelength division multiplexing filter is shown in FIG. Figure 9(As shown). The wavelength-division multiplexing filter uses GST loss modulation to achieve on-off control of the microring waveguide, avoiding the crosstalk introduced by wavelength offset in traditional tuning. The high absorption properties of the GST crystal ensure that microring resonances are completely suppressed. Multiple cascaded microring units eliminate the need for complex coupling designs. Simply connecting them in series via straight-through waveguides creates a multichannel filter, supporting the combination of output spectra across multiple microring waveguides. This solution provides a highly flexible, low-power solution for applications such as elastic optical networks and dynamic spectrum allocation.

[0052] As an example, Figure 2 The phase change material of the second ring waveguide 322 of the micro-ring waveguide 32 shown is replaced with antimony sulfide with a thickness of 300 nm. The ring width of the second ring waveguide 322 is 1000 nm. The offset distance between the center of the first ring waveguide 321 and the center of the second ring waveguide 322 is 600 nm. The fourth gap 4 is 200 nm. In this case, the phase change material (PCM) can independently support light field transmission, rather than the cladding light field coupling of traditional PCM. By vertically coupling the thicker PCM layer (second ring waveguide 322) with the first ring waveguide 321, the tuning freedom limitations of a single ring waveguide can be overcome, and the resonant wavelength spacing can be flexibly designed by adjusting the size and coupling distance of the two ring waveguides. The thicker structure of the second ring waveguide 322 enhances the interaction depth between the light field and the phase change material, extending the wavelength tuning range to over 30 nm.

[0053] As an example, Figure 4 、 Figure 5 As shown, the wavelength division multiplexing / demultiplexing system includes a whole formed by n micro-ring units 3 connected by a straight waveguide 31, and multiple wavelengths (wavelengths are λ1, λ2...λ n ) is input from one end of the straight waveguide 31. The resonant wavelength of each microring unit 3 corresponds to a wavelength in the input light source. Therefore, when the multi-wavelength light passes through each microring unit 3 in sequence, the light corresponding to the resonant wavelength of the microring unit 3 is captured by the microring unit 3 and then output from the download waveguide 33, realizing the function of wavelength decomposition and multiplexing (the spectrum output from the download waveguide 33 is shown in FIG. Figure 10 Conversely, Figure 4 、 Figure 6 As shown, when multiple single wavelength lights (wavelengths are λ1, λ2...λ n) are input from the downlink waveguides 33 of different microring units 3, are coupled through n microring units 3, and are ultimately merged into the through waveguide 31, from which they are output, thus achieving wavelength division multiplexing. Specifically, the first ring waveguide 321 is made of silicon, with a ring width (the width of the circular ring projected by the first ring waveguide 321 on the upper surface of the buried oxide layer 2) of 450 nm, a radius of 10 μm, and a first gap 1 of 200 nm. A layer of phase change material (such as antimony sulfide or antimony selenide) is disposed in a specific continuous ring pattern in the upper cladding layer 4 above the first ring waveguide 321, partially overlapping the top of the second ring waveguide 322 in space, enabling evanescent field coupling between the second ring waveguide 322 and the first ring waveguide 321. The thickness of the phase change material layer (second ring waveguide 322) is 30nm, the ring width is 650nm, and the distance offset between the center of the first ring waveguide 321 and the center of the second ring waveguide 322 is 300nm, so as to enhance the interaction efficiency between the light field and the phase change material and balance the optical loss caused by the phase change material. At the same time, it has a large tolerance for process errors, ensuring that the phase change material layer covers the target area of ​​the upper cladding layer and does not cover the coupling area between the straight waveguide and the first ring waveguide due to process errors. In this solution, by partially overlapping the second ring waveguide (phase change material waveguide) with the first ring waveguide (silicon waveguide), the low loss characteristics of the first ring waveguide (silicon waveguide) are retained, and the additional absorption loss introduced by the phase change material waveguide is reduced through evanescent field tuning. In addition, the local crystalline state switching of the phase change material only requires sub-microsecond electrical pulses. After the tuning is completed, the spectral characteristics can be retained, and the static power consumption effect can be achieved (see the light field under different crystalline states of the phase change material). Figure 11 Furthermore, by cascading multiple independent microring units, a wavelength division multiplexing system with more than eight channels can be expanded. By replacing the electrically controlled phase change scheme (i.e., heating the phase change material with a heating electrode) with an optically controlled phase change scheme (i.e., using laser heating to induce a phase change in the phase change material), all-optical dynamic reconfiguration can be achieved. This structure has significant application potential in optical communications, reconfigurable photonic circuits, and intelligent optical sensing.

[0054] Example 2 Reference Figure 12 (Take section AA' as an example) A method for preparing a wavelength division multiplexing / demultiplexing system based on a micro-ring structure and phase change material modulation includes the following steps: S1. Prepare a wafer, which includes a substrate, a buried oxide layer, and a waveguide layer stacked in sequence; S2. Etching the waveguide layer to form a through waveguide and a first ring waveguide; S3, forming a first upper cladding layer on the upper surface of the structure obtained in step S2; S4. Etching the first upper cladding layer above the first ring waveguide to form a groove, and stopping the etching at a position having a fourth distance from the first ring waveguide; S5, depositing a phase change material on the upper surface of the structure obtained in step S4, and etching to form a second ring waveguide in the groove; S6. Form a second upper cladding layer on the upper surface of the structure obtained in step S5. The second upper cladding layer and the first upper cladding layer are collectively referred to as an upper cladding layer.

[0055] As an example, the substrate in step S1 is at least one of a silicon substrate, a silicon carbide substrate, a silicon nitride substrate, a lithium niobate substrate, and a gallium nitride substrate.

[0056] As an example, the material of the buried oxide layer in step S1 is at least one of silicon dioxide, silicon nitride, and aluminum oxide.

[0057] As an example, the material of the waveguide layer in step S1 is any one of silicon, silicon nitride, silicon carbide, lithium niobate, and gallium nitride.

[0058] As an example, the specific etching steps in step S2 are as follows: spin-coating photoresist on the waveguide layer surface, soft-baking, and then performing pattern exposure to define the straight waveguide and the first ring waveguide pattern. The photoresist is then developed to remove the exposed areas. The waveguide layer is then etched, stopping at the top surface of the buried oxide layer. Afterwards, the photoresist is removed and cleaned to form the straight waveguide and the first ring waveguide.

[0059] As an example, the material of the first upper cladding layer in step S3 is at least one of silicon dioxide, silicon nitride, and aluminum oxide.

[0060] As an example, the step of forming the first upper cladding layer in step S3 is: depositing silicon dioxide (or other materials for the first upper cladding layer) on the upper surface of the structure obtained in step S2 by plasma enhanced chemical vapor deposition (PECVD), and then performing chemical mechanical polishing to ensure that the silicon dioxide layer is flattened to obtain the first upper cladding layer.

[0061] As an example, the groove formation step in step S4 involves spin-coating photoresist on the upper surface of the first upper cladding layer, exposing and developing the photoresist to define a pattern of the annular groove. The first upper cladding layer is selectively etched using a buffered oxide etchant wet etch or RIE (reactive ion etching) dry etch. The etching is stopped at a position with a fourth spacing from the first ring waveguide to ensure the etching depth, thereby forming the annular groove.

[0062] As an example, the step of forming the second ring waveguide in step S5 is: depositing a phase change material film on the upper surface of the structure obtained in step S4 by magnetron sputtering, then removing the phase change material outside the groove, retaining the phase change material inside the groove, and obtaining the second ring waveguide.

[0063] As an example, the material of the second upper cladding layer is at least one of silicon dioxide, silicon nitride, and aluminum oxide.

[0064] As an example, the step of forming the second upper cladding layer in step S6 is: growing silicon dioxide (or other materials of the second upper cladding layer) on the upper surface of the structure obtained in step S5 by PECVD method, covering the upper surface of the second ring waveguide to protect the second ring waveguide.

[0065] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. It will be apparent to anyone skilled in the art that various modifications and variations of the present invention are possible. Any simple equivalent variations and modifications made in accordance with the scope of protection of the present application and the contents of the specification are intended to be included within the scope of protection of the present invention.

Claims

1. A wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation, characterized in that: The invention comprises a substrate, a buried oxide layer located on a surface of one side of the substrate, n microring units located on a surface of the buried oxide layer facing away from the substrate, and an upper cladding layer; the upper cladding layer covers the n microring units and contacts the buried oxide layer; each microring unit comprises a straight waveguide and at least one microring waveguide; the n microring units are connected into a whole through the straight waveguide; the microring waveguide comprises a first ring waveguide and a second ring waveguide located above the first ring waveguide; there is a fourth spacing between the second ring waveguide and the first ring waveguide; the material of the second ring waveguide is phase change material; the microring waveguides are arranged at intervals along the direction in which the straight waveguide extends; there is a first spacing between the straight waveguide and the microring waveguide; and n is a positive integer ≥2.

2. The wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation according to claim 1, characterized in that: The microring unit includes a download waveguide, which is arranged opposite to the straight waveguide; there is a third distance between the download waveguide and the microring waveguide; and the microring waveguide is arranged at intervals between the straight waveguide and the download waveguide.

3. The wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation according to claim 2, characterized in that: The third spacing is 130-500 nm.

4. The wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation according to claim 2, characterized in that: Along the direction from the through waveguide to the download waveguide, the minimum spacing between two adjacent microring waveguides is 130-500 nm.

5. The wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation according to claim 1, characterized in that: Along the direction from the substrate to the upper cladding, the size of the second ring waveguide is 30-300 nm.

6. The wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation according to claim 1, characterized in that: Along the extending direction of the through waveguide, the ring width of the second ring waveguide is 350-1000 nm, and the distance between the center of the first ring waveguide and the center of the second ring waveguide is 100-600 nm.

7. The wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation according to claim 1, characterized in that: The length of the center line of the projected circular ring of the first annular waveguide on the upper surface of the buried oxide layer is distributed in an arithmetic progression in the extending direction of the through waveguide.

8. The wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation according to claim 1, characterized in that: The first spacing is 130-500 nm; or / and the fourth spacing is 30-300 nm.

9. The wavelength division multiplexing / demultiplexing system based on micro-ring structure and phase change material modulation according to claim 1, characterized in that: The phase change material is selected from antimony sulfide, antimony selenide, germanium antimony telluride, and germanium antimony selenide telluride; or / and the through waveguide is a straight waveguide or a curved waveguide.

10. The method for preparing a wavelength division multiplexing / demultiplexing system according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Prepare a wafer, wherein the wafer includes a substrate, a buried oxide layer, and a waveguide layer stacked in sequence; S2. Etching the waveguide layer to form a through waveguide and a first ring waveguide; S3, forming a first upper cladding layer on the upper surface of the structure obtained in step S2; S4. Etching the first upper cladding layer above the first ring waveguide to form a groove, and stopping the etching at a position having a fourth distance from the first ring waveguide; S5, depositing a phase change material on the upper surface of the structure obtained in step S4, and etching to form a second ring waveguide in the groove; S6. Form a second upper cladding layer on the upper surface of the structure obtained in step S5. The second upper cladding layer and the first upper cladding layer are collectively referred to as an upper cladding layer.

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