Microring resonator structure based on three-stage cascaded nested U-shaped waveguides

Abstract

The present invention discloses a microring resonator structure based on a three-stage cascaded nested U-shaped waveguide. The structure comprises a first straight waveguide, a second straight waveguide, and a third straight waveguide arranged in parallel, with the output end of the second straight waveguide connected to the input end of the U-shaped waveguide, which in turn is connected to the input end of the third straight waveguide. A first racetrack-shaped microring resonator and a circular-ring microring resonator are arranged between the first straight waveguide, the second straight waveguide, and the U-shaped waveguide, respectively. The second racetrack-shaped microring resonator is arranged in the U-shaped waveguide and between the second and third straight waveguides. The center of the first racetrack-shaped microring resonator, the center of the circular-ring microring resonator, the connection between the second straight waveguide and the U-shaped waveguide, the center of the second racetrack-shaped microring resonator, and the connection between the third straight waveguide and the U-shaped waveguide are all located on the same straight line. The present invention can achieve a steep resonance peak while effectively increasing the FSR, and is easy to integrate and miniaturize.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic integrated devices, and in particular relates to a micro-ring resonator structure based on a three-stage cascaded nested U-shaped waveguide. Background Art

[0002] With the rapid development of information technology, traditional integrated circuits can no longer meet the speed and quality requirements for information transmission. The emergence of integrated optics technology has provided new insights into certain research areas. Integrated optics requires optical devices that are small, dense, and perform well. Microring resonators, with their simple structure, high integration density, and low cost, perfectly meet the requirements of integrated optical devices and have therefore become a research hotspot in the field.

[0003] In recent years, with the development of materials with excellent optical properties and optical waveguide fabrication technology, a growing number of versatile microring resonators have been fabricated using these new materials and advanced processes. As a result, through continuous development, microring resonators now boast advantages such as compact structure, ease of integration, and immunity to electromagnetic interference. They can also be integrated on a single substrate on a large scale, enabling system-on-a-chip (SoC) implementations. Furthermore, microring resonators have a wide range of applications in optical modulators, optical switches, optical delay lines, sensors, optical frequency combs, and filters, making them highly promising multifunctional integrated optical devices.

[0004] The microring resonator was first proposed by Marcatili. It is a ring structure based on micro-nano optical waveguides that can resonate and enhance specific wavelengths, and the direction of light transmission is controllable. The free spectral range (FSR) refers to the difference between two adjacent resonant wavelengths (frequencies), and FSR is an important optimization parameter. A large FSR can prevent crosstalk between channels, and in dense wavelength division multiplexing systems, only when the FSR of the filter is greater than the total wavelength range of the system can the optical signals of each wavelength be accurately separated into their respective channels. However, the FSR of a single microring resonator is too small, so how to widen the limited FSR is an important research direction. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to propose a microring resonator structure based on a three-stage cascaded nested U-shaped waveguide, which can achieve a steep resonance peak while effectively increasing the FSR and facilitates integration and miniaturization.

[0006] A microring resonator structure based on a three-stage cascaded nested U-shaped waveguide according to an embodiment of the present invention includes:

[0007] substrate layer;

[0008] A silicon core layer, wherein the silicon core layer is stacked on one side surface of the substrate layer, and comprises a first straight waveguide, a second straight waveguide, a third straight waveguide, a U-shaped waveguide, a first racetrack-type microring resonator, a circular microring resonator, and a second racetrack-type microring resonator; wherein the first straight waveguide, the second straight waveguide, and the third straight waveguide are sequentially spaced and arranged in parallel, the output end of the second straight waveguide is connected to the input end of the U-shaped waveguide, and the output end of the U-shaped waveguide is connected to the input end of the third straight waveguide; the first racetrack-type microring resonator and the circular microring resonator are spaced apart and arranged between the first straight waveguide, the second straight waveguide, and the U-shaped waveguide, a straight section on one side of the first racetrack-type microring resonator is adjacent to and parallel to the first straight waveguide, and the first racetrack-type microring resonator The straight section on the other side of the resonator is adjacent to the circular microring resonator, and the circular microring resonator is located between the first racetrack microring resonator and the second straight waveguide and the U-shaped waveguide; the second racetrack microring resonator is arranged in the U-shaped waveguide and is located between the second straight waveguide and the third straight waveguide, the straight section on one side of the second racetrack microring resonator is adjacent to and parallel to the second straight waveguide, and the straight section on the other side of the second racetrack microring resonator is adjacent to and parallel to the third straight waveguide; the center of the first racetrack microring resonator, the center of the circular microring resonator, the connection between the second straight waveguide and the U-shaped waveguide, the center of the second racetrack microring resonator, and the connection between the third straight waveguide and the U-shaped waveguide are all located on the same straight line.

[0009] During operation, an optical signal is input by the first straight waveguide, an optical signal that does not meet the resonance condition is output by the first straight waveguide, and an optical signal that meets the resonance condition enters the first racetrack-type microring resonator in sequence in the coupling region between the first straight waveguide and the first racetrack-type microring resonator, and then enters the circular microring resonator in the coupling region between the first racetrack-type microring resonator and the circular microring resonator. The optical signal entering the circular microring resonator serves as the input light of the second straight waveguide. Based on the different arc radius of the first racetrack-type microring resonator and the radius of the circular microring resonator, it can be seen from the vernier effect that the FSR of the input light of the second straight waveguide at this time is the least common multiple of the FSR of a single first racetrack-type microring resonator and the FSR of a single circular microring resonator. Among the input light entering the second straight waveguide, the optical signal that does not meet the resonance condition enters the U-shaped waveguide from the output end of the second straight waveguide, produces a phase change after passing through the U-shaped waveguide and enters the third straight waveguide, and interferes with the optical signal that meets the resonance condition and passes through the second racetrack-type microring resonator and enters the third straight waveguide. Constructive interference suppresses the optical signal at the resonant wavelength, which is reflected in the output spectrum line as the output spectrum FSR of the output end of the third straight waveguide is doubled relative to the FSR of the third racetrack-type microring resonator.

[0010] The microring resonator structure based on the third-order cascaded nested U-shaped waveguide in the embodiment of the present invention can obtain a steep resonance peak while effectively increasing the FSR compared to the conventional second-order microring cascade structure. It can also be manufactured using mature microelectronic CMOS processing technology and has the advantages of easy integration, miniaturization, and a wide range of applications.

[0011] In some embodiments, the first racetrack microring resonator and the second racetrack microring resonator are the same size.

[0012] In some embodiments, the arc radius of the first racetrack-type microring resonator and the arc radius of the second racetrack-type microring resonator are both larger than the radius of the annular microring resonator.

[0013] In some embodiments, the circumference of the first racetrack microring resonator is greater than the circumference of the toroidal microring resonator.

[0014] In some embodiments, the length of the U-shaped waveguide, the perimeter of the first racetrack-type microring resonator, and the perimeter of the second racetrack-type microring resonator are all equal.

[0015] In some embodiments, the coupling spacing between the first racetrack-type microring resonator and the first straight waveguide, the coupling spacing between the second racetrack-type microring resonator and the second straight waveguide, and the coupling spacing between the second racetrack-type microring resonator and the third straight waveguide are all equal; the coupling spacing between the circular ring microring resonator and the first racetrack-type microring resonator and the coupling spacing between the circular ring microring resonator and the second straight waveguide are equal; the coupling spacing between the circular ring microring resonator and the first racetrack-type microring resonator is smaller than the coupling spacing between the first racetrack-type microring resonator and the first straight waveguide.

[0016] In some embodiments, the layer height of the first straight waveguide, the layer height of the second straight waveguide, the layer height of the third straight waveguide, the layer height of the U-shaped waveguide, the layer height of the first racetrack-type microring resonator, the layer height of the annular microring resonator, and the layer height of the second racetrack-type microring resonator are all equal.

[0017] In some embodiments, the thickness of the first straight waveguide, the thickness of the second straight waveguide, the thickness of the third straight waveguide, and the thickness of the U-shaped waveguide are all equal.

[0018] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0020] Figure 1 1 is a top view of a microring resonator structure based on a three-stage cascaded nested U-shaped waveguide according to an embodiment of the present invention;

[0021] Figure 2 1 is a side view of a microring resonator structure based on a three-stage cascaded nested U-shaped waveguide according to an embodiment of the present invention;

[0022] Figure 3 This is an experimental effect diagram of a simulation experiment of a microring resonator structure based on a three-stage cascaded nested U-shaped waveguide according to an embodiment of the present invention;

[0023] Figure 4 This is a top view of the conventional second-order microring resonator cascade structure;

[0024] Figure 5 This is a side view of a conventional second-order microring resonator cascade structure;

[0025] Figure 6 This is an experimental effect diagram of a simulation experiment of a conventional second-order microring resonator cascade structure.

[0026] Reference numerals:

[0027] A microring resonator structure 1000 based on a three-stage cascaded nested U-shaped waveguide 204; a substrate layer 1; a silicon core layer 2; a first straight waveguide 201; a second straight waveguide 202; a third straight waveguide 203; a U-shaped waveguide 204; a first racetrack-type microring resonator 205; a circular microring resonator 206; and a second racetrack-type microring resonator 207.

[0028] Conventional second-order microring resonator cascade structure 2000; large circular microring resonator 3; small circular microring resonator 4; fourth straight waveguide 5; fifth straight waveguide 6. DETAILED DESCRIPTION

[0029] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0030] The following combination Figures 1 to 3 A microring resonator structure 1000 based on three-stage cascaded nested U-shaped waveguides according to an embodiment of the present invention is described.

[0031] like Figure 1 and Figure 2As shown, a microring resonator structure 1000 based on a three-stage cascaded nested U-shaped waveguide according to an embodiment of the present invention includes a substrate layer 1 and a silicon core layer 2. The substrate layer 1 may be a silicon dioxide substrate layer, and the silicon core layer 2 is stacked on one side surface of the substrate layer 1. The silicon core layer 2 includes a first straight waveguide 201, a second straight waveguide 202, a third straight waveguide 203, a U-shaped waveguide 204, a first racetrack-type microring resonator 205, a toroidal microring resonator 206, and a second racetrack-type microring resonator 207. Specifically, the first straight waveguide 201, the second straight waveguide 202 and the third straight waveguide 203 are arranged in parallel at intervals in sequence, the output end of the second straight waveguide 202 is connected to the input end of the U-shaped waveguide 204, that is, the second straight waveguide 202 is connected to the straight section on one side of the U-shaped waveguide 204 end-to-end, the output end of the U-shaped waveguide 204 is connected to the input end of the third straight waveguide 203, that is, the third straight waveguide 203 is connected to the straight section on the other side of the U-shaped waveguide 204 end-to-end; the first racetrack-type microring resonator 205 and the annular microring resonator 206 are arranged at intervals between the first straight waveguide 201 and the second straight waveguide 202 and the U-shaped waveguide 204, wherein the straight section on one side of the first racetrack-type microring resonator 205 is connected to the input end of the third straight waveguide 203, that is, the straight section on the other side of the U-shaped waveguide 204 is connected to the input end of the third straight waveguide 203; The segment is adjacent to and parallel to the first straight waveguide 201. Thus, the length of the coupling region between the first racetrack-type microring resonator 205 and the first straight waveguide 201 is equal to the length of the straight segment on one side of the first racetrack-type microring resonator 205. If the length of the straight segment on one side of the first racetrack-type microring resonator 205 is not zero, the coupling region between the first racetrack-type microring resonator 205 and the first straight waveguide 201 is a line segment coupling region, that is, a non-point coupling region. The coupling length of the line segment coupling region can be 2.6 μm to 2.65 μm, for example, 2.6 μm, 2.633 μm, or 2.65 μm, which is conducive to obtaining a large FSR. Preferably, the length of the line segment coupling region is 2.633 μm, if the length of the straight section on one side of the first racetrack-type microring resonator 205 is zero, the coupling region between the first racetrack-type microring resonator 205 and the first straight waveguide 201 is a point coupling region; the straight section on the other side of the first racetrack-type microring resonator 205 is close to the annular microring resonator 206, so that the coupling region between the annular microring resonator 206 and the first racetrack-type microring resonator 205 is a point coupling region; the annular microring resonator 206 is located between the first racetrack-type microring resonator 205 and the second straight waveguide 202 and the U-shaped waveguide 204, so that the coupling region between the annular microring resonator 206 and the second straight waveguide 202 is a point coupling region. The domain is also a point coupling region; the second racetrack microring resonator 207 is arranged in the U-shaped waveguide 204 and is located between the second straight waveguide 202 and the third straight waveguide 203. The straight segment on one side of the second racetrack microring resonator 207 is adjacent to and parallel to the second straight waveguide 202, and the straight segment on the other side of the second racetrack microring resonator 207 is adjacent to and parallel to the third straight waveguide 203. In this way, the length of the coupling region between the second racetrack microring resonator 207 and the second straight waveguide 202 and the U-shaped waveguide 204 is equal to the length of the straight segment on one side of the second racetrack microring resonator 207. If the length of the straight segment on one side of the second racetrack microring resonator 207 is not zero, then The coupling region between the second racetrack-type microring resonator 207 and the second straight waveguide 202 and the U-shaped waveguide 204 is a line segment coupling region, that is, a non-point coupling region. The coupling length of the line segment coupling region can be 2.6 to 2.65 μm, for example, 2.6 μm, 2.633 μm, or 2.65 μm, which is conducive to obtaining a large FSR. Preferably, the length of the line segment coupling region is 2.633 μm. If the length of the straight segment on one side of the second racetrack-type microring resonator 207 is zero, the coupling region between the second racetrack-type microring resonator 207 and the second straight waveguide 202 and the U-shaped waveguide 204 is a point coupling. Similarly, the second racetrack-type microring resonator The length of the coupling region between the resonator 207 and the third straight waveguide 203 and the U-shaped waveguide 204 is equal to the length of the straight segment on the other side of the second racetrack-type microring resonator 207. If the length of the straight segment on the other side of the second racetrack-type microring resonator 207 is not zero, the coupling region between the second racetrack-type microring resonator 207 and the third straight waveguide 203 and the U-shaped waveguide 204 is a line segment coupling region, that is, a non-point coupling region. The coupling length of the line segment coupling region can be 2.6 to 2.65 μm, for example, 2.6 μm, 2.633 μm, or 2.65 μm, which is conducive to obtaining a large FSR. Preferably, the length of the line segment coupling region is 2.633μm. If the length of the straight segment on the other side of the second racetrack-type microring resonator 207 is zero, then the coupling region between the second racetrack-type microring resonator 207 and the third straight waveguide 203 and the U-shaped waveguide 204 is point coupling. The center of the first racetrack-type microring resonator 205, the center of the annular microring resonator 206, the connection between the second straight waveguide 202 and the U-shaped waveguide 204, the center of the second racetrack-type microring resonator 207, and the connection between the third straight waveguide 203 and the U-shaped waveguide 204 are all located on the same straight line, which facilitates accurate calculation of the FSR.

[0032] During operation, an optical signal is input by the first straight waveguide 201, and an optical signal that does not meet the resonance condition is output by the first straight waveguide 201. The optical signal that meets the resonance condition enters the first racetrack microring resonator 205 in the coupling region between the first straight waveguide 201 and the first racetrack microring resonator 205 in sequence, and then enters the annular microring resonator 206 in the coupling region between the first racetrack microring resonator 205 and the annular microring resonator 206. The optical signal entering the annular microring resonator 206 serves as the input light of the second straight waveguide 202. Based on the different radii of the arc of the first racetrack microring resonator 205 and the annular microring resonator 206, it can be seen from the vernier effect that the FSR of the input light of the second straight waveguide 202 at this time is the least common multiple of the FSR of a single first racetrack microring resonator 205 and the FSR of a single annular microring resonator 206. Among the input light entering the second straight waveguide 202, the optical signal that does not meet the resonance condition enters the U-shaped waveguide 204 from the output end of the second straight waveguide 202, produces a phase change after passing through the U-shaped waveguide 204 and enters the third straight waveguide 203, and interferes with the optical signal that meets the resonance condition and passes through the second racetrack-type microring resonator 207 and enters the third straight waveguide 203. Constructive interference suppresses the optical signal at the resonant wavelength, which is reflected in the output spectrum line as the output spectrum FSR of the output end of the third straight waveguide 203 is doubled relative to the FSR of the third racetrack-type microring resonator.

[0033] The following describes the micro-ring resonator structure 1000 based on the third-order cascaded nested U-shaped waveguide according to the embodiment of the present invention and the conventional second-order micro-ring resonator cascade structure 2000 (such as Figure 4 and Figure 5 Here, the conventional second-order micro-ring resonator cascade structure 2000 and its working principle are described to more clearly describe the comparative simulation experiment.

[0034] like Figure 4 and Figure 5As shown, the large circular microring resonator 3 and the small circular microring resonator 4 (the radius ratio is 3:2) are arranged between the fourth straight waveguide 5 and the fifth straight waveguide 6 which are parallel to each other, wherein the coupling region between the fourth straight waveguide 5 and the large circular microring resonator 3, the coupling region between the large circular microring resonator 3 and the small circular microring resonator 4, and the coupling region between the small circular microring resonator 4 and the fifth straight waveguide 6 are all point coupling regions.

[0035] like Figure 4 and Figure 5 As shown, the working process of the conventional second-order microring resonator cascade structure 2000 is as follows: when a beam of light waves enters the conventional second-order microring resonator cascade structure 2000 from the fourth straight waveguide 5, as the light waves propagate, a coupling effect occurs at a point close to the fourth straight waveguide 5 and the large circular microring resonator 3, so that part of the light wave energy is coupled from the fourth straight waveguide 5 to the large circular microring resonator 3, while the remaining light wave energy is still transmitted along the fourth straight waveguide 5. When the light wave coupled into the large circular microring resonator 3 propagates clockwise along the large circular microring resonator 3, after half a cycle, some of the light wave energy is coupled from the large circular microring resonator 3 to the small circular microring resonator 4. The remaining light wave energy in the large circular microring resonator 3 continues to propagate clockwise along the microring. After another half cycle of propagation, the remaining light wave in the large circular microring resonator 3 interferes with the light wave in the fourth straight waveguide 5. When the light wave meets the resonance condition of the large circular microring resonator 3, it resonates in the large circular microring resonator 3. When the light wave coupled into the small circular microring resonator 4 propagates clockwise along the microring, after half a cycle of propagation, some of the light wave energy is coupled from the small circular microring resonator 4 to the fifth straight waveguide 6. The remaining light wave energy in the small circular microring resonator 4 continues to propagate clockwise along the small circular microring resonator 4. After another half cycle of propagation, the remaining light wave in the small circular microring resonator 4 interferes with the light wave in the large circular microring resonator 3. At this time, the light wave that meets the resonance condition of the small circular microring resonator 4 will resonate in the small circular microring resonator 4 .

[0036] In the comparative simulation experiment, the micro-ring resonator structure 1000 based on the three-stage cascaded nested U-shaped waveguide according to the embodiment of the present invention is mainly simulated for its output spectrum. In the simulation experiment, it is found that: Figure 3 As shown, the resonance peak of the micro-ring resonator structure 1000 based on the third-order cascaded nested U-shaped waveguide according to the embodiment of the present invention is steeper, with only one resonance peak in the wavelength range of 1.5μm to 1.6μm, and a larger FSR. The simulation results comparing the output spectrum of the micro-ring resonator structure 1000 based on the third-order cascaded nested U-shaped waveguide and the output spectrum of the conventional second-order micro-ring cascade structure 2000 are shown in Figure 2. Figure 3 and Figure 6 shown.

[0037] from Figure 3 and Figure 6 It can be seen from the figure that the resonance peak of the micro-ring resonator structure 1000 based on the third-order cascaded nested U-shaped waveguide according to the embodiment of the present invention is steeper and the FSR is larger than that of the conventional second-order micro-ring cascade structure. Figure 3 It can also be seen in FIG. 1 that the resonant wavelength of the microring resonator structure 1000 based on the third-order cascaded nested U-shaped waveguide according to the embodiment of the present invention undergoes an obvious red shift.

[0038] In summary, the microring resonator structure 1000 based on the third-order cascaded nested U-shaped waveguide in the embodiment of the present invention can obtain a steep resonance peak while effectively increasing the FSR compared to the conventional second-order microring cascade structure 2000. It can also be manufactured using mature microelectronic CMOS processing technology, and has the advantages of easy integration, miniaturization, and a wide range of applications.

[0039] In some embodiments, the first racetrack microring resonator 205 and the second racetrack microring resonator 207 are of the same size. In this way, the microring resonator structure 1000 based on the three-stage cascaded nested U-shaped waveguide is relatively symmetrical, which facilitates accurate calculation of FSR.

[0040] In some embodiments, the arc radius of the first racetrack-type microring resonator 205 and the arc radius of the second racetrack-type microring resonator 207 are both larger than the radius of the annular microring resonator 206. In this way, the vernier effect can be utilized to enable the microring resonator structure 1000 based on the third-order cascaded nested U-shaped waveguide to obtain a large FSR.

[0041] In some embodiments, the ratio of the circumference of the first racetrack-type microring resonator 205 and the circumference of the second racetrack-type microring resonator 207 to the circumference of the annular microring resonator 206 is 3:2. For example, the circumference of the first racetrack-type microring resonator 205 and the arc radius of the second racetrack-type microring resonator 207 are both 6 μm, and the radius of the annular microring resonator 206 is 4.56 μm. This is conducive to obtaining a larger FSR.

[0042] In some embodiments, the perimeter of the first racetrack microring resonator 205 is greater than the perimeter of the annular microring resonator 206. This can utilize the Vernier effect to enable the microring resonator structure 1000 based on the three-stage cascaded nested U-shaped waveguide to obtain a large FSR.

[0043] In some embodiments, the length of the U-shaped waveguide 204 and the circumference of the second racetrack-type microring resonator 207 are equal, for example, both are a number between 45 μm and 46 μm, for example, 45 μm, 45.42 μm or 46 μm, preferably 45.42 μm. In this way, the optical signals in the second racetrack-type microring resonator 207 and the U-shaped waveguide 204 undergo constructive interference, and the constructive interference suppresses the optical signal at the resonant wavelength, thereby doubling the FSR.

[0044] In some embodiments, the coupling spacing between the first racetrack microring resonator 205 and the first straight waveguide 201, the coupling spacing between the second racetrack microring resonator 207 and the second straight waveguide 202, and the coupling spacing between the second racetrack microring resonator 207 and the third straight waveguide 203 are all equal, for example, they are all a number between 0.09 and 0.11 μm, such as 0.09 μm, 0.1 μm, and 0.11 μm. Preferably, the coupling spacing is 0.1 μm; the coupling spacing between the annular microring resonator 206 and the first straight waveguide 201 is equal to the coupling spacing between the second racetrack microring resonator 207 and the second straight waveguide 202. The coupling spacing between the racetrack-type microring resonators 205 and the coupling spacing between the annular microring resonator 206 and the second straight waveguide 202 are equal, for example, both are a number between 0.24 and 0.26 μm, such as 0.24 μm, 0.25 μm, or 0.26 μm. Preferably, the coupling spacing is 0.25 μm. The coupling spacing between the annular microring resonator 206 and the first racetrack-type microring resonator 205 is smaller than the coupling spacing between the first racetrack-type microring resonator 205 and the first straight waveguide 201. In this way, the microring resonator structure 1000 based on the three-stage cascaded nested U-shaped waveguide is relatively symmetrical, which facilitates accurate calculation of the FSR.

[0045] In some embodiments, the layer height of the first straight waveguide 201, the layer height of the second straight waveguide 202, the layer height of the third straight waveguide 203, the layer height of the U-shaped waveguide 204, the layer height of the first racetrack-type microring resonator 205, the layer height of the annular microring resonator 206, and the layer height of the second racetrack-type microring resonator 207 are all equal. In this way, the overall microring resonator structure 1000 based on the three-stage cascaded nested U-shaped waveguides is relatively symmetrical, which facilitates accurate calculation of the FSR.

[0046] In some embodiments, the layer height of the first straight waveguide 201, the layer height of the second straight waveguide 202, the layer height of the third straight waveguide 203, the layer height of the U-shaped waveguide 204, the layer height of the first racetrack-type microring resonator 205, the layer height of the annular microring resonator 206 and the layer height of the second racetrack-type microring resonator 207 are all 0.3 to 0.50 μm. For example, they can be 0.3 μm, 0.4 μm, 0.5 μm, etc., and a large FSR can be obtained. When it is preferably 0.4 μm, an even larger FSR can be obtained.

[0047] In some embodiments, the thickness of the first straight waveguide 201, the thickness of the second straight waveguide 202, the thickness of the third straight waveguide 203, and the thickness of the U-shaped waveguide 204 are all equal. In this way, the microring resonator structure 1000 based on the three-stage cascaded nested U-shaped waveguides is relatively symmetrical, facilitating accurate calculation of the FSR.

[0048] In some embodiments, the thickness of the first straight waveguide 201, the thickness of the second straight waveguide 202, the thickness of the third straight waveguide 203, and the thickness of the U-shaped waveguide 204 are all a number between 0.16 and 0.20 μm, for example, they can be 0.16 μm, 0.18 μm, 0.20 μm, etc., to obtain a large FSR, and preferably 0.18 μm, to obtain a larger FSR.

[0049] In summary, the microring resonator structure based on the three-stage cascaded nested U-shaped waveguide implemented in the present invention can effectively increase the FSR of the resonance peak.

[0050] Throughout this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" indicate that the specific features, structures, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0051] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A microring resonator structure based on a three-stage cascaded nested U-shaped waveguide, characterized in that: include: substrate layer; A silicon core layer, wherein the silicon core layer is stacked on one side surface of the substrate layer, and comprises a first straight waveguide, a second straight waveguide, a third straight waveguide, a U-shaped waveguide, a first racetrack-type microring resonator, a circular microring resonator, and a second racetrack-type microring resonator; wherein the first straight waveguide, the second straight waveguide, and the third straight waveguide are sequentially spaced and arranged in parallel, the output end of the second straight waveguide is connected to the input end of the U-shaped waveguide, and the output end of the U-shaped waveguide is connected to the input end of the third straight waveguide; the first racetrack-type microring resonator and the circular microring resonator are spaced apart and arranged between the first straight waveguide, the second straight waveguide, and the U-shaped waveguide, a straight section on one side of the first racetrack-type microring resonator is adjacent to and parallel to the first straight waveguide, and the first racetrack-type microring resonator The straight section on the other side of the resonator is adjacent to the circular microring resonator, and the circular microring resonator is located between the first racetrack microring resonator and the second straight waveguide and the U-shaped waveguide; the second racetrack microring resonator is arranged in the U-shaped waveguide and is located between the second straight waveguide and the third straight waveguide, the straight section on one side of the second racetrack microring resonator is adjacent to and parallel to the second straight waveguide, and the straight section on the other side of the second racetrack microring resonator is adjacent to and parallel to the third straight waveguide; the center of the first racetrack microring resonator, the center of the circular microring resonator, the connection between the second straight waveguide and the U-shaped waveguide, the center of the second racetrack microring resonator, and the connection between the third straight waveguide and the U-shaped waveguide are all located on the same straight line.

2. The microring resonator structure based on a three-stage cascaded nested U-shaped waveguide according to claim 1, characterized in that: The first racetrack microring resonator and the second racetrack microring resonator have the same size.

3. The microring resonator structure based on three-stage cascaded nested U-shaped waveguides according to claim 2, characterized in that: The arc radius of the first racetrack-type microring resonator and the arc radius of the second racetrack-type microring resonator are both larger than the radius of the annular microring resonator.

4. The microring resonator structure based on three-stage cascaded nested U-shaped waveguides according to claim 3, characterized in that: The circumference of the first racetrack microring resonator is greater than the circumference of the annular microring resonator.

5. The microring resonator structure based on three-stage cascaded nested U-shaped waveguides according to claim 2, characterized in that: The length of the U-shaped waveguide and the circumference of the second racetrack-type microring resonator are equal.

6. The microring resonator structure based on three-stage cascaded nested U-shaped waveguides according to claim 2, characterized in that: The coupling spacing between the first racetrack microring resonator and the first straight waveguide, the coupling spacing between the second racetrack microring resonator and the second straight waveguide, and the coupling spacing between the second racetrack microring resonator and the third straight waveguide are all equal; the coupling spacing between the annular microring resonator and the first racetrack microring resonator and the coupling spacing between the annular microring resonator and the second straight waveguide are equal; The coupling distance between the annular microring resonator and the first racetrack microring resonator is smaller than the coupling distance between the first racetrack microring resonator and the first straight waveguide.

7. The microring resonator structure based on three-stage cascaded nested U-shaped waveguides according to claim 2, characterized in that: The layer height of the first straight waveguide, the layer height of the second straight waveguide, the layer height of the third straight waveguide, the layer height of the U-shaped waveguide, the layer height of the first racetrack microring resonator, the layer height of the annular microring resonator and the layer height of the second racetrack microring resonator are all equal.

8. The microring resonator structure based on three-stage cascaded nested U-shaped waveguides according to claim 2, characterized in that: The thickness of the first straight waveguide, the thickness of the second straight waveguide, the thickness of the third straight waveguide, and the thickness of the U-shaped waveguide are all equal.

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