Double-layer waveguide 2*2 micro-ring optical switch, optical switch array thereof and optical signal processing method

Abstract

The invention discloses a double-layer waveguide 2 * 2 microring optical switch, an optical switch array thereof and an optical signal processing method, and belongs to the technical field of optical communication devices. Aiming at the technical problem that a traditional micro-ring optical switch is difficult to realize a large free spectral range and low-loss transmission at the same time, the invention provides an innovative structure combining a silicon nitride micro-ring resonator and an annular Bragg grating, and the outer side of the silicon nitride micro-ring resonator is nested with the annular Bragg grating; and a light field forbidden band is constructed to suppress a light field radiated outwards by the resonator, so that strong light field constraint is realized to remarkably reduce bending loss. A silicon-silicon nitride double-layer waveguide interlayer coupling technology is adopted, the lower layer is a silicon coupling waveguide, the upper layer is a silicon nitride micro-ring resonator and concentric annular grating structure, and a titanium nitride micro-heater is integrated to adjust the resonant wavelength. The invention effectively solves the technical problem that the silicon nitride micro-ring optical switch is difficult to obtain in the aspects of large free spectral range and low loss at the same time, and is a key technical support for constructing a high-integration wavelength selection optical switching chip.

Description

Technical Field

[0001] The present invention relates to the technical field of optical communication devices, and specifically to a small-size, low-loss double-layer waveguide 2×2 micro-ring optical switch, an optical switch array thereof, and an optical signal processing method. The switch is suitable for highly integrated wavelength-selective optical switching chips and can be widely used in data centers and optical communication networks. Background Art

[0002] In recent years, with the rapid growth of data center capacity demands and the increasing complexity of optical communication networks, large-scale integrated optical switch chips have been widely researched and applied across a variety of platforms. Silicon-based optoelectronics, with its significant advantages such as perfect compatibility with complementary metal oxide semiconductor (CMOS) processes, compactness, and low power consumption, has become a key technology path for achieving high-performance integrated optical switches. Microring resonators, with their excellent wavelength selectivity and compact structure, have shown great potential for application in wavelength-granular optical switching, becoming a core component in the construction of highly integrated optical switching chips.

[0003] However, in the practical application of microring optical switches, a fundamental contradiction exists between expanding the free spectral range (FSR) and achieving low-loss transmission. The FSR refers to the difference between two adjacent resonant wavelengths of a microring resonator and directly determines the number of channels an optical switch system can accommodate. The traditional approach to increasing the FSR is to reduce the microring radius, leveraging the inverse relationship between radius and FSR to increase channel capacity. However, as the microring radius decreases, the curvature of the optical waveguide increases dramatically, making it difficult to effectively confine the light field at the bend. At smaller bend radii, the propagation direction of the light wave changes dramatically, reducing the waveguide's ability to confine the light field and causing more optical energy to radiate outward. The smaller the bend radius, the more severe this radiation loss becomes, resulting in a sharp increase in bending loss, making it difficult to achieve both high-capacity channels and low-loss transmission.

[0004] The microring in a microring optical switch typically adopts a circular structure with a constant radius of curvature and perfect central rotational symmetry. In such a circular microring, the bending loss of the optical waveguide is mainly determined by the waveguide's geometric parameters and material properties. It is important to note that special bending designs often mentioned in the literature, such as Euler bending [Vogelbacher F, Nevlacsil S, Sagmeister M, et al., Optics Express 2019, 27, 31394.], Euler-circular bending [Fujisawa T, Makino S, Sato T, et al., J. Lightwave Technol. 2017, 25, 9150-9159.], and Bessel bending [Bazargani HP, Flueckiger J, Chrostowski L, et al., OSA 2015.], are primarily used in the transition region between straight and curved waveguides. Their design goal is to achieve a smooth transition from zero curvature to the target curvature, thereby reducing the transition loss between the straight and curved waveguides, rather than directly reducing the bending loss of the curved waveguide itself. These special transition designs are not directly applicable to circular microring resonators because circular microrings already have a constant curvature and do not suffer from sudden changes in curvature.

[0005] To address the bending loss problem in small-sized microrings, researchers have proposed various technical approaches. For example, the Vernier effect, which employs two coupled microrings with slightly different radii [Liu Xin, Kong Mei, Wen Quan, Chinese J. Lasers 2010, 37, 2885.], can achieve tens or even hundreds of times higher FSR. This design effectively relaxes the strict bending radius requirements for a single ring, allowing for a larger bending radius to reduce bending loss. However, while the Vernier effect improves FSR, it also introduces other challenges. Compared to a single microring, a dual-ring coupled structure introduces additional transmission loss and inter-ring coupling loss. Because the optical signal must couple and transmit multiple times between the two rings, the total insertion loss of the system is typically much higher than that of a single-ring resonator. The Vernier effect design also generates a large number of spurious modes. These undesirable resonance peaks severely impact the performance of the microring resonator, reducing spectral purity and the device's wavelength selectivity. The presence of spurious modes makes it difficult to achieve ideal transmission characteristics in practical applications. To effectively suppress spurious modes and achieve good device performance, extremely precise control of the coupling coefficient between the two microrings is required. This not only requires the tiny dimensional differences between the two rings to be controlled within an extremely narrow tolerance, but also requires precise adjustment of the coupling strength, which greatly increases the difficulty of process manufacturing and system coordination. Any slight deviation in the manufacturing process can lead to significant deterioration in device performance, thus limiting the practicality of this method in large-scale production.

[0006] In addition to the aforementioned Vernier effect approach, researchers have also developed approaches based on waveguide Bragg gratings (WBGs) and photonic crystal defect cavities to achieve microcavities with large free spectral ranges [Solehmainen K, Aalto T, Dekker J, et al., J. Opt. A: Pure Appl. Opt. 2006, 8, S455-S460.]. Waveguide Bragg grating microcavities create a distributed feedback structure by periodically modulating the refractive index or geometry in a waveguide. This structure exploits the Bragg reflection principle to produce strong reflection at specific wavelengths, thereby constructing a resonant cavity. Unlike traditional ring resonators, the FSR of a Bragg grating resonator is primarily determined by the grating period and effective refractive index, rather than the geometric dimensions. Therefore, a large FSR can be achieved in a relatively compact structure. Waveguide Bragg grating resonators offer the advantages of high design flexibility and precise control of resonant characteristics by adjusting the grating parameters. Furthermore, their linear structure offers advantages in applications requiring high integration density. However, this approach also has significant limitations. First, the scattering and coupling losses introduced by the grating structure are typically high, affecting the overall performance of the device. Second, the reflected light and the incident light share the same physical port. This common port characteristic makes signal separation a new challenge. To effectively separate the reflected and incident signals, traditional solutions must rely on optical circulators. However, the implementation of on-chip circulators itself is a major technical challenge in the field of integrated optics.

[0007] Photonic crystal defect cavities form optical resonant cavities by introducing defects into a periodic photonic crystal structure (e.g., removing some periodic units or changing local structural parameters). This structure utilizes the photonic bandgap effect to strictly confine the light field to the defect region, achieving extremely high quality factors and compact mode volumes. Photonic crystal defect cavities have the potential for high quality factors and can theoretically achieve extremely high Q values. At the same time, due to the strong confinement effect of the photonic bandgap, ultra-small mode volumes can be achieved, resulting in extremely high light field enhancement effects. In addition, the large FSR characteristics of the photonic crystal structure make it particularly suitable for single-mode operation. Although photonic crystal defect cavities have excellent theoretical performance, they face many challenges in practical applications. The first problem is the difficulty of coupling. Due to the strong confinement characteristics of photonic crystals, external light fields are difficult to effectively couple into the defect cavity, resulting in low coupling efficiency in practical applications. The second problem is manufacturing complexity. Photonic crystal structures require precise periodic patterns at the nanometer scale, which places extremely high demands on the manufacturing process.

[0008] Therefore, there is an urgent need to develop an innovative design solution that can effectively resolve the technical contradiction between a large free spectral range and low bending loss in micro-ring optical switches. This design solution can fully utilize the principle of optical field confinement to achieve low-loss transmission while also solving the technical difficulties of traditional methods in terms of coupling efficiency and manufacturing feasibility. Summary of the Invention

[0009] The technical problem to be solved by the present invention is the technical contradiction that existing micro-ring optical switches find it difficult to simultaneously achieve a large free spectral range and low-loss transmission. The traditional method for increasing the free spectral range (FSR) is to reduce the micro-ring radius. However, as the micro-ring radius decreases, the curvature of the optical waveguide increases sharply, and the bending loss also increases sharply, making it difficult to achieve both high-capacity channels and low-loss transmission. Although methods such as the Vernier effect, waveguide Bragg gratings, and photonic crystal defect cavities can address this problem to a certain extent, they all suffer from technical limitations such as high insertion loss, pseudo-mode interference, low coupling efficiency, and complex manufacturing. The present invention proposes a small-sized, low-loss double-layer waveguide 2×2 micro-ring optical switch. By utilizing a double-layer waveguide structure in conjunction with a ring Bragg grating, this device overcomes the technical bottleneck of traditional micro-ring optical switches in achieving the three key characteristics of small size, low loss, and large FSR. This device provides a high-performance unit device for high-density integrated optical switching chips, with significant industrial application value.

[0010] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0011] A small-size, low-loss double-layer waveguide 2×2 micro-ring optical switch, comprising: an upper silicon nitride waveguide layer and a lower silicon waveguide layer;

[0012] The upper silicon nitride waveguide layer includes a microring resonator and a ring-shaped Bragg grating nested outside the microring resonator in a concentric circle manner to form a light field confinement;

[0013] The lower silicon waveguide layer includes an upper coupling waveguide and a lower coupling waveguide, which are respectively located below the microring resonator and maintain a certain distance to form a silicon-silicon nitride double-layer waveguide interlayer coupling structure;

[0014] It also includes a titanium nitride microheater arranged in an arc shape above the microring resonator, which changes the effective refractive index of the microring resonator through thermal tuning, thereby changing the phase of the microring resonator to achieve switching of the input optical signal between the through port and the download port.

[0015] The silicon nitride microring resonator is a ring waveguide with a uniform waveguide width, and is used to generate resonance for a specific wavelength to achieve frequency selection and routing switching functions.

[0016] The Bragg grating consists of periodically alternating waveguide segments and gap segments, wherein the waveguide segment width is 0.4-0.9 μm, the gap segment width is 0.2-0.65 μm, and the spacing between the innermost ring grating and the microring resonator is 1.2-2.5 μm.

[0017] The micro-ring resonator is a ring waveguide with a uniform waveguide width, and is used to generate resonance for a specific wavelength to achieve frequency selection and routing switching functions.

[0018] The uplink coupling waveguide and the downlink coupling waveguide have the same structure and the same waveguide height, and both include a wide waveguide, a tapered waveguide, a narrow waveguide, and a combination of a tapered waveguide and a wide waveguide. The narrow waveguide segment is used to couple with the microring resonator, and the wide waveguide structure is used to reduce the disturbance of the grating structure on the light field in the waveguide, thereby reducing loss.

[0019] The 2×2 micro-ring optical switch is an add-drop switch unit having four optical ports: an input port (In), a loading port (Add), a through port (Through), and a download port (Drop).

[0020] Parameters such as the grating period, duty cycle, and spacing between the grating and the resonator of the Bragg grating can be optimized and adjusted according to different application requirements. The light field ban constructed by Bragg resonance suppresses the outward radiation of the light field, which has little dependence on wavelength and can maintain good low-loss characteristics over a wide spectral range.

[0021] The interlayer coupling of the silicon-silicon nitride double-layer waveguide controls the coupling coefficient by adjusting the longitudinal and lateral spacing of the waveguide, thereby achieving transmission spectra and switching performances with different characteristics.

[0022] Second, the present invention also provides an optical switch array, which is characterized in that:

[0023] It is composed of a plurality of double-layer waveguide 2×2 micro-ring optical switch units as described above;

[0024] The array supports 4×4 or 8×8 scale optical signal routing, and each switch unit can be controlled independently.

[0025] Furthermore, the array is integrated on any one of silicon-based, silicon nitride-based, thin-film lithium niobate-based or indium phosphide-based material platforms; the titanium nitride microheaters of each switching unit in the array are cooperatively controlled by the same driving circuit.

[0026] Thirdly, the present invention also provides an optical signal processing method, which is characterized by: using the above-mentioned double-layer waveguide 2×2 micro-ring optical switch to implement optical signal routing through the following steps:

[0027] a) coupling the input optical signal into the microring resonator;

[0028] b) detecting whether the wavelength of the input optical signal matches the microring resonant wavelength;

[0029] c) If they match, the optical signal is output from the download port; if they do not match, the resonant wavelength of the microring is changed through thermal tuning so that the optical signal is output from the through port.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) Strong design flexibility: Parameters such as the grating period, duty cycle, and the distance between the grating and the resonator can be optimized and adjusted according to different application requirements. The bandgap of the optical field is constructed through Bragg resonance to suppress the outward radiation of the optical field. It has little dependence on wavelength and can maintain good low-loss characteristics over a wide spectral range.

[0032] (2) Solving technical contradictions: Effectively solving the key technical problem of silicon nitride microring optical switches in terms of large free spectral range and low loss, achieving a small-size microring resonator with a radius of 15μm, and low-loss transmission of the switch unit at 0.05dB on the through end and 0.2dB on the download end;

[0033] (3) Wide range of applications: This design is not only applicable to silicon photonic platforms, but can also be extended to various material system platforms such as thin-film lithium niobate and indium phosphide, and can meet the application requirements of large-scale micro-ring optical switch arrays;

[0034] (4) Friendly manufacturing process: The ring grating waveguide structure based on total internal reflection has the advantages of large bandwidth, large design and processing tolerance, and passive characteristics, which reduces the manufacturing difficulty and cost and improves the reliability of the device;

[0035] (5) System integration advantages: It provides important unit device technology support for the realization of highly integrated wavelength-selective optical switching chips, helps to build large-scale integrated optical switch arrays, and meets the development needs of data centers and optical communication networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the structure of a small-size, low-loss double-layer waveguide 2×2 micro-ring optical switch unit of the present invention;

[0037] Figure 2 This is a three-dimensional schematic diagram of a small-size, low-loss double-layer waveguide 2×2 micro-ring optical switch structure of the present invention;

[0038] Figure 3 is a schematic diagram of a microring resonator and a ring Bragg grating of the present invention;

[0039] Figure 4 is a side view of the microring resonator and the annular Bragg grating of the present invention;

[0040] Figure 5 Figure 2 is the relationship between the ring Bragg grating structure parameters and loss. (a) is the relationship between the resonator loss and the grating parameter w, (b) is the relationship between the resonator loss and the grating parameter gap, and (c) is the relationship between the resonator loss and the gap between the grating and the resonator, L.

[0041] Figure 6 is the loss bandwidth characteristic of the microring resonator under the Bragg grating structure;

[0042] Figure 7 This is a schematic diagram of the Si upload and download coupling waveguide structure;

[0043] Figure 8 is a schematic diagram of the coupling between silicon-silicon nitride waveguide layers;

[0044] Figure 9 is the coupled light field diagram between silicon-silicon nitride waveguide layers;

[0045] Figure 10 is the transmission spectrum of the microring resonator; DETAILED DESCRIPTION

[0046] The present invention is further described below with reference to the accompanying drawings and examples, but they should not be construed to limit the scope of protection of the present invention.

[0047] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of a small-size, low-loss double-layer waveguide 2×2 micro-ring optical switch unit of the present invention. As shown in the figure, the switch unit includes a micro-ring resonator 1.1, a ring Bragg grating 1.2, an uplink 1.3 and a downlink coupling waveguide 1.4, and a titanium nitride microheater 1.5. Figure 2 The figure below is a schematic diagram of its three-dimensional structure. The 2×2 microring optical switch array in this embodiment is implemented on a conventional 220nm silicon-based waveguide process platform, and can also implement a silicon-silicon nitride double-layer waveguide process. The microring resonator and ring Bragg grating utilize a silicon nitride waveguide layer, while the upload and download coupling waveguides utilize a silicon waveguide layer. The design and fabrication platform for this optical switch is not limited to silicon photonics platforms and is also applicable to various material systems, including thin-film lithium niobate and indium phosphide.

[0048] The optical switch in the embodiment is an add-drop switch. The device has four ports, where In is the input port, Add is the loading port, Through is the through port, and Drop is the download port. When the wavelength λ of the optical signal incident from In is consistent with the resonant wavelength of the microring, the optical signal is coupled into the microring and output from the Drop port. In this case, the state of the microring optical switch is defined as the on state. If the phase of the microring is adjusted so that the resonant wavelength of the microring shifts (redshift or blueshift), causing the wavelength λ of the optical signal incident from In to no longer be consistent with the resonant wavelength of the microring, the optical signal is directly output from the through port. In this case, the state of the microring optical switch is defined as the off state. For the phase adjustment of the microring, the present invention adds a titanium nitride microheater at a position 1.45μm above the microring resonator. Through the thermal effect of the heater, the refractive index of the microring resonator waveguide changes, thereby changing the resonant wavelength of the microring resonator and realizing output port switching. The phase shifting method is not limited to the titanium nitride heater heating method. An annular silicon waveguide structure can also be added to the silicon waveguide layer inside the microring resonator. By doping the silicon waveguide inside the microring resonator and utilizing the thermal effect of the doped silicon waveguide, the refractive index of the microring resonator waveguide changes, thereby achieving the adjustment of the resonant wavelength of the microring resonator.

[0049] The microring resonator and the ring Bragg grating structure in the embodiment are as follows Figure 3 As shown, Figure 4 The figure is a side view of the structure. The microring resonator is a silicon nitride waveguide with a width of 1μm, a height of 400nm, and a waveguide center radius of 15μm. At this time, the FSR of the microring resonator is about 15.18nm. The annular Bragg grating is nested on the outside of the microring in a concentric circle manner with the center of the microring resonator as the center. The annular Bragg grating forms a light field band gap, which confines the light field to the silicon nitride resonator waveguide in the center, thereby reducing the resonator loss. The effect of the Bragg grating in confining the light field depends on the grating period, duty cycle, grating order, and the distance between the grating and the resonator. In the embodiment, the parameters such as the grating waveguide width w, the grating spacing gap, and the distance L between the grating and the resonator are optimized and designed. The MODE module in LUMERICAL is used to analyze and optimize the loss of the curved waveguide under different structures. First, without the constraint of the Bragg grating on the outside of the resonator, the loss of a single silicon nitride ring resonator at a wavelength of 1550nm is 26.4dB / cm. After adding the ring Bragg grating, the above three parameters L, w, and gap can be optimized, such as Figure 5 As shown, Figure 5(a), (b), and (c) are the relationships between the resonator loss and the parameters w, gap, and L, respectively. It can be seen that the grating period and duty cycle greatly affect the resonator loss characteristics. Therefore, when the grating waveguide width w = 0.56μm and gap = 0.4μm under this structure, the grating has the strongest ability to confine the light field and the lowest resonator loss. At the same time, it is necessary to determine the spacing L between the grating and the silicon nitride ring waveguide. Figure 5 Figure (c) shows that when L = 1.76 μm, the lowest ring resonator loss of 2.9 dB / cm can be achieved. This result demonstrates that, compared to a single silicon nitride ring waveguide, adding a waveguide Bragg grating structure to the outside of the resonator effectively suppresses light field leakage out of the waveguide, strictly confining the light field within the microring and significantly reducing bending losses.

[0050] To more accurately verify the effect of the Bragg grating, we performed a 3D simulation using FDTD in LUMERICAL. The results showed that with the Bragg grating L = 1.76μm, w = 0.56μm, and gap = 0.4μm, the minimum loss of the ring resonator at 1550nm was 0.04dB, corresponding to a loss of 4.24dB / cm. This is slightly different from the results in MODE, which is due to the difference in simulation accuracy. At the same time, under the incident light of a wide spectrum, the bandwidth response of the simulated resonator loss is shown in Figure 2. Figure 6 As shown, the shorter the wavelength, the lower the loss. At 1330nm, the loss is approximately 0.01dB, achieving a small-radius, low-loss microring optical switch. Furthermore, the loss in the O-band is lower than in the C-band, resolving the conflict between the large FSR and the loss of microring resonators. The optimization in this embodiment of the present invention is limited to linear parameter sweep optimization. To achieve even lower loss, optimization methods such as particle swarm optimization can be used, including but not limited to particle swarm optimization.

[0051] After optimizing and determining the structural parameters of the Bragg grating circulator, it is necessary to design the interlayer coupling of the waveguide. Since the outer side of the silicon nitride ring waveguide is surrounded by the grating, it is difficult to couple in the same layer of waveguide. In this embodiment, the interlayer coupling of silicon-silicon nitride waveguide is used. Figure 7As shown, the Si coupled waveguide consists of five sections, each with a height of 220 nm. The first section is a straight waveguide 7.1 with a width of 1 μm, the second section is a tapered waveguide 7.2 with a waveguide width gradually changing from 1 μm to 0.3 μm, the third section is a straight waveguide 7.3 with a waveguide width of 0.3 μm, the fourth section is a tapered waveguide 7.4 with a waveguide width gradually changing from 0.3 μm to 1 μm, and the fifth section is a straight waveguide 7.5 with a width of 1 μm. This ensures that the light at the input and output ports does not cause optical mode perturbations when passing through the ring grating, while also reducing transmission loss. When the tapered waveguide length is 8 μm and the narrow waveguide length is 4 μm, the transmission loss of a single Si coupled waveguide is 0.04 dB. In the coupling region, the waveguide is a straight waveguide with a smaller width, which reduces the refractive index of the optical mode in the waveguide, matching the refractive index of the optical mode transmitted in the microring resonator, thereby achieving effective coupling. In this embodiment, the two Si coupled waveguides use exactly the same structure and parameters.

[0052] The switch transmission characteristics of this embodiment can be modified by adjusting the longitudinal and lateral spacing between the ring resonator waveguide and the upstream and downstream coupling waveguides, thereby adjusting the electric field coupling coefficient κ. Given a fixed microring resonator structure, i.e., a fixed loss factor, the electric field coupling coefficient κ must be specifically set to obtain transmission spectra with different characteristics. Figure 8 Figure 1 is a schematic diagram of the interlayer coupling structure, where the interlayer distance is h and the lateral distance is G. In the embodiment of the present invention, the interlayer distance between the silicon waveguide and the SiN waveguide is 0.25 μm. Too close an interlayer distance will result in an excessively large coupling coefficient κ, and the transmission spectrum characteristics suitable for switching cannot be obtained. When h is 0.25 μm, the electric field coupling coefficient κ is adjusted by adjusting the lateral spacing G between the Si coupled waveguide and the SiN resonator. When the lateral distance G is 0.15 m, the coupling coefficient κ is approximately 0.43, and the corresponding coupled light field diagram is Figure 9 As shown in Figure 2, a small amount of light is coupled into the microring resonator through the upper carrier waveguide without causing disturbances in the upper Bragg grating. Low-loss and efficient coupling is achieved through the silicon-silicon nitride double-layer waveguide. Figure 10 For the transmission spectrum obtained at this time, the through-end loss is 0.05dB, the download-end loss is 0.2dB, and the free spectral range is 15.1nm, which meets the requirements of low loss and large FSR in the micro-ring optical switch system.

Claims

1. A double-layer waveguide 2×2 micro-ring optical switch, characterized in that: comprising an upper silicon nitride waveguide layer and a lower silicon waveguide layer; The upper silicon nitride waveguide layer includes a microring resonator (1.1) and a ring-shaped Bragg grating (1.2) nested outside the microring resonator (1.1) in a concentric circle manner to form a light field confinement; The lower silicon waveguide layer comprises an upper coupling waveguide (1.3) and a lower coupling waveguide (1.4), which are respectively located below the microring resonator (1.1) and maintain a certain distance therebetween, forming a silicon-silicon nitride double-layer waveguide interlayer coupling structure; The invention also includes a titanium nitride microheater (1.5) arranged in an arc shape above the microring resonator, which changes the effective refractive index of the microring resonator by thermal tuning, thereby changing the phase of the microring resonator and realizing the switching of the input optical signal between the through port and the download port.

2. The double-layer waveguide 2×2 micro-ring optical switch according to claim 1, characterized in that: The Bragg grating (1.2) consists of periodically alternating waveguide segments and gap segments, wherein the waveguide segment width is 0.4-0.9 μm, the gap segment width is 0.2-0.65 μm, and the spacing between the innermost ring grating and the microring resonator is 1.2-2.5 μm.

3. The double-layer waveguide 2×2 micro-ring optical switch according to claim 1, characterized in that: The micro-ring resonator (1.1) is a ring waveguide with a uniform waveguide width, and is used to generate resonance for a specific wavelength and realize frequency selection and routing switching functions.

4. The double-layer waveguide 2×2 micro-ring optical switch according to claim 1, characterized in that: The uplink coupling waveguide and the downlink coupling waveguide both adopt a five-section structure, which comprises a first wide waveguide (7.1), a first tapered waveguide (7.2), a narrow waveguide (7.3), a second tapered waveguide (7.4), and a second wide waveguide (7.5) in the order along the light transmission direction. The narrow waveguide section is used for coupling with the microring resonator, and the first wide waveguide and the second wide waveguide are used for reducing the disturbance of the grating structure on the light field in the waveguide, thereby reducing the loss.

5. The double-layer waveguide 2×2 micro-ring optical switch according to claim 1, characterized in that: It includes optical ports, namely input port (In), load port (Add), through port (Through) and download port (Drop).

6. The double-layer waveguide 2×2 micro-ring optical switch according to claim 1, characterized in that: Parameters such as the grating period, duty cycle, and spacing between the grating and the resonator of the Bragg grating can be optimized and adjusted according to different application requirements. The light field ban constructed by Bragg resonance suppresses the outward radiation of the light field, which has little dependence on wavelength and can maintain good low-loss characteristics over a wide spectral range.

7. The double-layer waveguide 2×2 micro-ring optical switch according to claim 6, characterized in that: The interlayer coupling of the silicon-silicon nitride double-layer waveguide controls the coupling coefficient by adjusting the longitudinal and lateral spacing of the waveguide, thereby achieving transmission spectra and switching performances with different characteristics.

8. An optical switch array, characterized in that: Composed of a plurality of double-layer waveguide 2×2 micro-ring optical switch units according to any one of claims 1 to 7; The array supports 4×4 or 8×8 scale optical signal routing, and each switch unit can be controlled independently.

9. The optical switch array according to claim 8, wherein: The array is integrated on any one of silicon-based, silicon nitride-based, thin-film lithium niobate-based or indium phosphide-based material platforms; the titanium nitride microheaters of each switch unit in the array are cooperatively controlled by the same driving circuit.

10. A method for processing an optical signal, characterized in that: The double-layer waveguide 2×2 micro-ring optical switch according to any one of claims 1 to 6 is used to implement optical signal routing through the following steps: a) coupling the input optical signal into the microring resonator; b) detecting whether the wavelength of the input optical signal matches the microring resonant wavelength; c) If they match, the optical signal is output from the download port; if they do not match, the resonant wavelength of the microring is changed through thermal tuning so that the optical signal is output from the through port.

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