Waveguide coupling structure, microring resonator and optical chip

Abstract

The application relates to the field of photonic integrated circuits, in particular to a waveguide coupling structure, a micro-ring resonator and an optical chip, and aims to solve the technical problem of how to improve the design of a waveguide coupling structure, reduce the dependence on advanced processes, and enable a micro-ring resonator to achieve high coupling efficiency under a larger coupling pitch. To this end, the micro-ring resonator comprises a coupling area of the micro-ring resonator composed of a curved waveguide with a gradually changing width and a straight waveguide with a gradually changing width. The coupling structure composed of the waveguide with a gradually changing width is used in the design of the micro-ring resonator, which is more conducive to achieving critical coupling of the micro-ring resonator, achieving the best regulation state of optical power, and having high ER and Q values; meanwhile, the process tolerance of the micro-ring resonator can be increased, thereby reducing the process difficulty and reducing the dependence on advanced processes.

Description

Technical Field

[0001] This application relates to the field of photonic integrated circuits, specifically to a waveguide coupling structure, a microring resonator, and an optical chip. Background Technology

[0002] Microring resonators are a core component in silicon-based optoelectronics. They utilize the resonant characteristics of light in a miniature circular waveguide to achieve selective filtering, modulation, sensing, and delay of light at specific wavelengths. Due to their compact structure, microring resonators can achieve extremely high device density, making them particularly suitable for large-scale photonic integrated circuits. They are widely used in optical communication, optical interconnect, and optical sensing systems.

[0003] A typical microring resonator consists of a straight waveguide of uniform width and a circular waveguide of uniform width, which are close to each other to form a waveguide coupling structure. When the coupling coefficient of the optical coupling into the circular waveguide equals the loss coefficient of the circular waveguide (reaching the critical coupling state), the microring resonator is in the optimal energy modulation state. At this point, the optical field inside the circular waveguide cavity is strongest, and the highest extinction ratio (ER) and quality factor (Q) can be obtained. According to the evanescent wave theory, to improve the coupling efficiency of the microring resonator, the spacing between the coupled waveguides must be small enough, typically in the range of tens to three hundred nanometers. Correspondingly, the gap size (i.e., coupling spacing) between the circular and straight waveguides in the waveguide coupling structure needs to be strictly controlled, which places higher demands on processes such as photolithography and etching. Therefore, how to improve the waveguide coupling structure design, reduce the dependence on advanced process technology, and enable the microring resonator to achieve high coupling efficiency with a larger coupling spacing has become an urgent problem to be solved. Utility Model Content

[0004] To overcome the above-mentioned shortcomings, this application is proposed to address the technical problem of achieving high coupling efficiency in microring resonators with a large coupling spacing by improving the waveguide coupling structure and reducing dependence on advanced process technology.

[0005] In a first aspect, a waveguide coupling structure is provided, comprising: A straight waveguide, comprising a first tapered waveguide and a second tapered waveguide connected together; A curved waveguide, comprising a first curved waveguide and a second curved waveguide connected to each other, wherein the widths of the first curved waveguide and the second curved waveguide are gradually changed. A coupling region is formed between the straight waveguide and the curved waveguide; the narrow ends of the first tapered waveguide and the second tapered waveguide intersect at the centerline of the coupling region; the narrow ends of the first curved waveguide and the second curved waveguide intersect at the centerline of the coupling region.

[0006] In one technical solution of the above waveguide coupling structure, the narrow ends of the first tapered waveguide, the second tapered waveguide, the first curved waveguide, and the second curved waveguide all have the same width. The widths of the wide ends of the first tapered waveguide, the second tapered waveguide, the first curved waveguide, and the second curved waveguide are all equal.

[0007] In one technical solution of the above waveguide coupling structure, the wide ends of the first tapered waveguide, the second tapered waveguide, the first curved waveguide, and the second curved waveguide are all located outside the coupling region.

[0008] In one technical solution of the aforementioned waveguide coupling structure, the central angle corresponding to the curved waveguide is less than 180 degrees.

[0009] In one technical solution of the above waveguide coupling structure, the first tapered waveguide and the first curved waveguide are located on one side of the centerline of the coupling region, and the second tapered waveguide and the second curved waveguide are located on the other side of the centerline of the coupling region. Within the coupling region, at corresponding positions equidistant from the centerline of the coupling region, the first tapered waveguide and the first curved waveguide have the same cross-sectional width; the second tapered waveguide and the second curved waveguide have the same cross-sectional width.

[0010] In one technical solution of the above waveguide coupling structure, the first tapered waveguide and the second tapered waveguide are symmetrically arranged relative to the centerline of the coupling region, and the first curved waveguide and the second curved waveguide are symmetrically arranged.

[0011] In a second aspect, a microring resonator is provided, comprising: Waveguide coupling structure of any of the above technical solutions; Third curved waveguide; The two ends of the third curved waveguide are respectively connected to the wide ends of the first curved waveguide and the wide ends of the second curved waveguide to form a circular ring waveguide.

[0012] In a third aspect, a microring resonator is provided, comprising: A symmetrically arranged first and second waveguide coupling structure; Second uniform waveguide; Third uniform waveguide; Among them, the first waveguide coupling structure and the second waveguide coupling structure are both waveguide coupling structures of any of the above technical solutions; The curved waveguide in the first waveguide coupling structure, the second uniform waveguide, the curved waveguide in the second waveguide coupling structure, and the third uniform waveguide are connected in sequence.

[0013] In one technical solution of the aforementioned microring resonator Both the second and third uniform waveguides are uniformly curved waveguides. The curved waveguide in the first waveguide coupling structure, the second uniform waveguide, the curved waveguide in the second waveguide coupling structure, and the third uniform waveguide form a circular ring waveguide.

[0014] In a fourth aspect, an optical chip is provided, comprising a waveguide coupling structure according to any of the above technical solutions, or a microring resonator according to any of the above technical solutions.

[0015] The above-described technical solutions of this application have at least one or more of the following beneficial effects: Compared with traditional waveguide coupling structures, under the premise of the same coupling spacing and coupling region length, the width-gradient waveguide coupling structure adopted in this application has higher coupling efficiency. Using this width-gradient waveguide coupling structure in microring resonator design is more conducive to achieving critical coupling of the microring resonator, reaching the optimal control state of optical power, and possessing both high ER and Q values; at the same time, it can also increase the process tolerance of the microring resonator. Even if the coupling spacing deviates slightly during processing, the coupling efficiency of the microring resonator will not decrease significantly, thereby reducing the process difficulty and the dependence on advanced process technology. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a waveguide coupling structure according to one embodiment of this application.

[0017] Figure 2 This is a schematic diagram of a microring resonator according to one embodiment of this application.

[0018] Figure 3 This is a schematic diagram of a microring resonator according to another embodiment of this application.

[0019] Figure 4 These are optical coupling simulation diagrams of traditional waveguide coupling structures and waveguide coupling structures in the embodiments of this application.

[0020] Figure 5 This is a simulation diagram of the coupling spacing and coupling efficiency of a traditional waveguide coupling structure. Detailed Implementation

[0021] Some embodiments of this application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this application and are not intended to limit the scope of protection of this application.

[0022] It should be noted that in the description of this application, terms such as "upper," "lower," "left," "right," "inner," and "outer," indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device, structure, or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, terms such as "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] Based on the evanescent wave theory, when the coupling region of a microring resonator uses uniform straight waveguides and uniform circular ring waveguides that are close to each other, it is usually necessary to strictly control the spacing between the uniform straight waveguides and uniform circular ring waveguides to make the spacing between the coupled waveguides small enough. This places high demands on the photolithography and etching processes.

[0024] According to the mode-spot conversion coupling theory, when the width of a single-mode waveguide decreases, the waveguide's ability to confine the transmitted light weakens, and most of the transmitted light overflows the waveguide and enters the external space. At this time, the proportion of light intensity confined inside the waveguide and the proportion of light intensity transmitted outside the waveguide are proportional to the cross-sectional width at the coupled waveguide. When the widths of both coupled waveguides decrease uniformly at the same time, the light overflowing from the waveguide resonates with the coupled waveguide in space, thus coupling into the coupled waveguide. Based on this, the coupling structure and micro-ring resonator technical solution proposed in this application are presented, thereby reducing the requirement for precise control of the coupling spacing between straight waveguides and circular ring waveguides (bent waveguides), and thus reducing the manufacturing difficulty.

[0025] Figure 1 This is a schematic diagram of a waveguide coupling structure according to one embodiment of this application. Figure 1 As shown, the waveguide coupling structure of this application includes a straight waveguide and a curved waveguide. The straight waveguide includes a first tapered waveguide 101 and a second tapered waveguide 102 connected together. The curved waveguide includes a first curved waveguide 201 and a second curved waveguide 202 connected together. Furthermore, a coupling region 30 is formed in the region where the straight waveguide and the curved waveguide are close together (shown in dashed boxes in the figure).

[0026] The two tapered waveguides each have a narrow end and a wide end. The narrow ends of the first tapered waveguide 101 and the second tapered waveguide 102 intersect at the centerline (coupled region centerline) AA' of the coupling region. The two curved waveguides have gradually changing widths and also have narrow ends and wide ends; the narrow ends of the first curved waveguide 201 and the second curved waveguide 202 intersect at the coupled region centerline AA'. Furthermore, the coupled region centerline AA' is also the point where the coupling distance between the straight waveguide and the curved waveguide is minimized.

[0027] In this embodiment, the narrow ends of the first tapered waveguide 101, the second tapered waveguide 102, the first curved waveguide 201, and the second curved waveguide 202 all have the same width. The wide ends of the first tapered waveguide 101, the second tapered waveguide 102, the first curved waveguide 201, and the second curved waveguide 202 all have the same width to ensure that the optical signal transmission in both the straight and curved waveguides remains in single-mode. Furthermore, the wide ends of both curved waveguides and both tapered waveguides are located outside the coupling region 30.

[0028] In this application, the straight waveguide and the curved waveguide have a symmetrical structure with respect to the centerline AA' of the coupling region. That is, the first tapered waveguide 101 and the second tapered waveguide 102 are symmetrical with respect to the centerline AA' of the coupling region, and the first curved waveguide 201 and the second curved waveguide 202 are symmetrical with respect to the centerline AA' of the coupling region.

[0029] Specifically, within the coupling region 30, the waveguide lengths of the width-gradient portions of the first tapered waveguide 101 and the second tapered waveguide 102 are the same; and the cross-sectional widths of the first tapered waveguide 101 and the second tapered waveguide 102 are the same at positions equidistant from the centerline AA' of the coupling region. Similarly, within the coupling region 30, the waveguide lengths of the width-gradient portions of the first curved waveguide 201 and the second curved waveguide 202 are the same; and the cross-sectional widths of the first curved waveguide 201 and the second curved waveguide 202 are the same at positions equidistant from the centerline AA' of the coupling region.

[0030] It should be noted that although the widths of the first curved waveguide 201 and the second curved waveguide 202 gradually change, i.e., the curved waveguides are "wide at both ends and narrow in the center", the central radius of the entire curved waveguide remains unchanged, that is, the curve located at the center of the curved waveguide is arc-shaped. Figure 1 The circle (marked with a white dashed line) has a center of O and a radius of R. The center O of the center circle lies on the coupling region's centerline AA'. Furthermore, throughout the entire curved waveguide, the central angle corresponding to the aforementioned arc can not exceed 180 degrees.

[0031] based on Figure 1 The waveguide coupling structure shown is constructed as follows: Figure 2The diagram shows an all-pass microring resonator. Specifically, based on the waveguide coupling structure, the microring resonator further includes a third curved waveguide 203, whose two ends are connected to the wide ends of the first curved waveguide 201 and the second curved waveguide 202, respectively. Furthermore, the widths of the third curved waveguide 203 as a whole, the wide ends of the first curved waveguide 201, and the wide ends of the second curved waveguide 202 are all equal. In fact, the third curved waveguide 203, the first curved waveguide 201, and the second curved waveguide 202 together constitute the circular waveguide of the microring resonator, with the central circle corresponding to this circular waveguide located at the middle position of the circular waveguide. Figure 1 and Figure 2 In the diagram, the central circle is marked with a white dashed line, the center of the central circle is marked with O, and the radius of the central circle is marked with R.

[0032] Further reference Figure 1 and Figure 2 Within the coupling region 30, the width of the cross-section defined by the perpendicular intersection of line BB' and the centerline AA' of the coupling region is h1. Line BB' intersects the central circle (center O, radius R) at point M. The width of the cross-section defined by line BB' and the first curved waveguide 201 along the radius direction (MO) of the central circle at point M is h2. Therefore, h1 equals h2. Considering that point M is on line BB', the distance from point M to the centerline AA' of the coupling region is equal to the distance between line BB' and line AA'. In other words, within the coupling region, at corresponding positions equidistant from the centerline of the coupling region, the cross-sectional widths of the first tapered waveguide 101 and the first curved waveguide 201 are the same.

[0033] Similarly, the width of the cross-section determined by the perpendicular intersection of line CC' and the centerline AA' of the coupling region is h3. Line CC' intersects the central circle (center O, radius R) at point N. The width of the cross-section determined by the line CC' and the second curved waveguide 202 along the radius direction (NO) of the central circle at point N is h4. Therefore, h3 equals h4. Considering that point N is a point on CC', the distance from point N to the centerline AA' of the coupling region is equal to the distance between CC' and AA'. In other words, within the coupling region, at corresponding positions equidistant from the centerline of the coupling region, the cross-sectional widths of the second tapered waveguide 102 and the second curved waveguide 202 are the same.

[0034] The design that the cross-sectional widths of the tapered waveguide and the curved waveguide at the corresponding positions within the coupling region are equal can maintain optical mode field matching when light propagates in the curved waveguide and the tapered waveguide, thereby helping to improve the coupling efficiency of the waveguide coupling structure.

[0035] As mentioned above, the straight waveguide and the curved waveguide of the waveguide coupling structure are symmetrical with respect to the centerline AA' of the coupling region. Correspondingly, the all-pass micro-ring resonator is also symmetrical with respect to the centerline AA' of the coupling region. That is, the third curved waveguide 203 is also symmetrical with respect to the centerline AA' of the coupling region.

[0036] Further reference Figure 2 The wide ends of the first tapered waveguide 101 and the second tapered waveguide 102 can also be connected to the first uniform straight waveguide 103 and the second uniform straight waveguide 104, respectively. Furthermore, the widths of the first uniform straight waveguide 103, the second uniform straight waveguide 104, the wide ends of the first tapered waveguide 101 and the second tapered waveguide 102 are all equal.

[0037] When the first uniform straight waveguide 103 is used as the optical signal input terminal of the all-pass micro-ring resonator, the second uniform straight waveguide 104 is the output terminal of the filtered optical signal; when the second uniform straight waveguide 104 is used as the optical signal input terminal of the all-pass micro-ring resonator, the first uniform straight waveguide 103 is the output terminal of the filtered optical signal.

[0038] Figure 3 This is a schematic diagram of a microring resonator according to another embodiment of this application, as shown below. Figure 3 As shown, in another embodiment of this application, the microring resonator is an add-drop type microring resonator, comprising two symmetrically placed waveguide coupling structures, denoted as the first waveguide coupling structure 10 and the second waveguide coupling structure 20, respectively. Both the first waveguide coupling structure 10 and the second waveguide coupling structure 20 are... Figure 1 The waveguide coupling structures shown are identical in size for corresponding parts of the two waveguide coupling structures.

[0039] In addition to the two sets of waveguide coupling structures, this add-drop microring resonator also includes a second uniform waveguide 204 and a third uniform waveguide 205. The curved waveguide of the first waveguide coupling structure 10, the second uniform waveguide 204, the curved waveguide of the second waveguide coupling structure 20, and the third uniform waveguide 205 are connected in sequence to form a closed ring waveguide. At this time, the second uniform waveguide 204 and the third uniform waveguide 205 are also symmetrical structures with respect to the centerline AA' of the coupling region.

[0040] In the embodiments of this application, such as Figure 3 As shown, both the second and third uniform waveguides are uniformly curved waveguides. The curved waveguide of the first waveguide coupling structure 10, the second uniform waveguide 204 (curved waveguide), the curved waveguide of the second waveguide coupling structure 20, and the third uniform waveguide 205 (curved waveguide) are connected in sequence to form a closed circular ring waveguide (circular micro-ring).

[0041] The add-drop microring resonator also includes uniform straight waveguides 105 and 106, which are respectively connected to the wide ends of the two tapered waveguides of the first waveguide coupling structure 10, and uniform straight waveguides 107 and 108, which are respectively connected to the wide ends of the two tapered waveguides of the second waveguide coupling structure 20. In this case, the widths of the two tapered waveguides of the first waveguide coupling structure 10, the two tapered waveguides of the second waveguide coupling structure 20, uniform straight waveguides 105, 106, 107, and 108, the second uniform waveguide 204, and the third uniform waveguide 205 are all the same.

[0042] When the uniform straight waveguide 105 is used as the optical signal input terminal of the add-drop type microring resonator, the optical signal that meets the microring wavelength resonance condition will be output from the uniform straight waveguide 107 (drop end), and the optical signals of other wavelengths will be output from the uniform straight waveguide 106 (through end).

[0043] It should be noted that the calculation of the radius of the microring and the design of the waveguide dimensions in the microring resonator are well-known technologies in the field, and this application does not limit them.

[0044] As an example, it can be based on , The formulas are used to calculate the values ​​of the radius and other related parameters of the micro-ring (circular ring waveguide), where, The central resonant wavelength is R, and the radius of the micro-ring is R. For the effective refractive index of the curved waveguide, denoted as the group refractive index of the resonant cavity of the microring resonator, m is a positive integer, and FSR is the free spectral region.

[0045] In another embodiment, both the second and third uniform waveguides are uniform straight waveguides. In this case, the first waveguide coupling structure, the second uniform waveguide, the second waveguide coupling structure, and the third uniform waveguide will form a racetrack-shaped microring resonator.

[0046] Furthermore, the aforementioned waveguide coupling structure and microring resonator can be implemented using semiconductor processes. To this end, this application also provides an optical chip that can be fabricated based on SOI silicon wafers or silicon substrates.

[0047] Taking SOI silicon wafers as an example, this optical chip includes a silicon substrate, a buried oxide layer (silicon dioxide layer), and a waveguide layer, where the buried oxide layer serves as the lower cladding layer of the waveguide. Figures 1 to 3The waveguide coupling structure and / or the various structures of the microring resonator are formed in a patterned form within the waveguide layer, i.e., the patterned waveguide layer serves as the core layer of the waveguide. A dielectric layer is then placed over the waveguide layer. This dielectric layer can be made of silicon dioxide or other materials suitable as waveguide cladding. The dielectric layer fills the gaps between the components of the waveguide coupling structure and covers each structure.

[0048] In this application, the materials of the straight waveguide and the microring in the microring resonator can be independently selected from one of Si, SiN, InP, LiNO3, BaTiO3 and organic polymers. In the embodiments of this application, the materials of both the straight waveguide and the microring are Si.

[0049] The width of a uniform waveguide can be set in the range of 450-500 nanometers, the width of the narrow end of a tapered straight waveguide and a curved waveguide with a gradually changing width can be set in the range of 200-380 nanometers, the thickness of the waveguide can be set in the range of 220-340 nanometers, and the coupling spacing can be set in the range of 100-400 nanometers.

[0050] As an example, optical signals applied to single-mode transmission in C-band communication. Figure 2 The widths of the first uniform straight waveguide 103, the second uniform straight waveguide 104, and the third curved waveguide 203 in the all-pass microring resonator shown are all 500 nm; the widths of the narrow ends of the first tapered waveguide 101, the second tapered waveguide 102, the first curved waveguide 201, and the second curved waveguide 202 are all 220 nm; the thickness of each waveguide is 220 nm; and the coupling spacing (the distance between the maximum distance between the ring waveguide and the straight waveguide in the coupling region, and the distance between the edge of the straight waveguide and the edge of the curved waveguide) is 200 nm.

[0051] The fabrication process of this all-pass microring resonator is as follows: After wet cleaning of the SOI substrate, an anti-reflective coating (BARC) and photoresist are spin-coated. Following photolithography and etching, a microring resonator is formed. Figure 2 The structure of the all-pass microring resonator is shown; then, the photoresist is removed by plasma and the residue is removed by wet cleaning, and a 2.5-micron silicon dioxide cladding layer is deposited; finally, a chemical mechanical planarization (CMP) process is used to grind away part of the silicon dioxide layer to make the surface of the cladding layer flat; thus, the all-pass microring resonator is fabricated.

[0052] Continue reading Figure 4 Figure (a) is a simulation diagram of optical coupling of a traditional waveguide coupling structure consisting of a straight waveguide of uniform width and a circular ring waveguide of uniform width; Figure (b) is a simulation diagram of optical coupling of a waveguide coupling structure in an embodiment of this application.

[0053] Figure 4In this embodiment, the coupling length of the coupling region of the two waveguide coupling structures is 14 micrometers. At this time, it can be approximately equivalent to the coupling of two straight waveguides. That is, the traditional waveguide coupling structure can be approximated as a coupling structure composed of two parallel uniform straight waveguides. The waveguide coupling structure in this embodiment can be approximated as a coupling structure composed of two gradually wide straight waveguides (the two center lines in the waveguide width direction are parallel).

[0054] When the coupling spacing is 200 nanometers, according to the simulation results, the proportion of light intensity coupled to the coupled waveguide is about 78.8% when using the traditional waveguide coupling structure, and about 89.8% when using the waveguide coupling structure in the embodiment of this application.

[0055] Depend on Figure 4 Simulation results show that, under the same coupling spacing and coupling region length, the waveguide coupling structure in this embodiment has higher coupling efficiency compared to the traditional waveguide coupling structure. Using the waveguide coupling structure in this application for a microring resonator will be more conducive to achieving critical coupling in the microring resonator, reaching the optimal control state of optical power, and possessing both high ER and Q values.

[0056] In other words, to achieve the same coupling efficiency, under the same conditions, the coupling spacing of a traditional microring resonator using a uniform-width waveguide needs to be much smaller than that of the microring resonator in this application, solely in terms of coupling spacing. Therefore, the waveguide coupling structure and microring resonator in this application are easier to fabricate, thus reducing reliance on advanced equipment to some extent.

[0057] Continue reading Figure 5 , Figure 5 This is a simulation diagram of the coupling spacing and coupling efficiency of a traditional waveguide coupling structure.

[0058] Depend on Figure 5 It is known that traditional waveguide coupling structures require coupling spacing of around 50 nm or 160 nm to achieve a coupling efficiency (light intensity distribution) of over 90%. However, when using the gradient-width waveguide coupling structure of this application (with a coupling efficiency of 89.8% at a coupling spacing of 200 nm), high-efficiency coupling can be achieved even with a larger coupling spacing. Using the waveguide coupling structure of this application in microring resonators can increase the fabrication tolerance of the microring resonator, so that even if there are slight deviations in the coupling spacing during fabrication, the coupling efficiency of the microring resonator will not decrease significantly.

[0059] It should be noted that the optical chip described in this application can be an optical chip that only includes the waveguide coupling structure or microring resonator described in this application, serving as a coupling device or filtering device; or it can be based on the waveguide coupling structure or microring resonator described in this application with the addition of other structures. Examples include wavelength division multiplexing structures, large-scale optical switch arrays, optical beam splitters / combiners, etc., to form an optical computing chip for use in data centers and other fields; or it can be integrated with high-speed modulators, SOA arrays, etc., to achieve on-chip transceiver integration, forming a high-speed optical communication chip, etc.

[0060] The technical solution of this application has been described above with reference to one embodiment shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. A waveguide coupling structure, characterized in that, include: A straight waveguide, comprising a first tapered waveguide and a second tapered waveguide connected together; A curved waveguide includes a first curved waveguide and a second curved waveguide connected to each other, wherein the widths of the first curved waveguide and the second curved waveguide are gradually changed. A coupling region is formed between the straight waveguide and the curved waveguide; the narrow ends of the first tapered waveguide and the second tapered waveguide intersect at the centerline of the coupling region; the narrow ends of the first curved waveguide and the second curved waveguide intersect at the centerline of the coupling region.

2. The waveguide coupling structure according to claim 1, characterized in that, The narrow ends of the first tapered waveguide, the second tapered waveguide, the first curved waveguide, and the second curved waveguide all have the same width. The widths of the wide ends of the first tapered waveguide, the second tapered waveguide, the first curved waveguide, and the second curved waveguide are all equal.

3. The waveguide coupling structure according to claim 1, characterized in that, The wide ends of the first tapered waveguide, the second tapered waveguide, the first curved waveguide, and the second curved waveguide are all located outside the coupling region.

4. The waveguide coupling structure according to claim 3, characterized in that, The central angle corresponding to the curved waveguide is less than 180 degrees.

5. The waveguide coupling structure according to claim 1, characterized in that, The first tapered waveguide and the first curved waveguide are located on one side of the centerline of the coupling region, and the second tapered waveguide and the second curved waveguide are located on the other side of the centerline of the coupling region; Within the coupling region, at corresponding positions equidistant from the centerline of the coupling region, the first tapered waveguide and the first curved waveguide have the same cross-sectional width; the second tapered waveguide and the second curved waveguide have the same cross-sectional width.

6. The waveguide coupling structure according to any one of claims 1-5, characterized in that, The first tapered waveguide and the second tapered waveguide are symmetrically arranged relative to the centerline of the coupling region, and the first curved waveguide and the second curved waveguide are symmetrically arranged.

7. A microring resonator, characterized in that, include: Waveguide coupling structure according to any one of claims 1 to 6; Third curved waveguide; The two ends of the third curved waveguide are respectively connected to the wide ends of the first curved waveguide and the wide ends of the second curved waveguide to form a circular ring waveguide.

8. A microring resonator, characterized in that, include: A symmetrically arranged first and second waveguide coupling structure; Second uniform waveguide; Third uniform waveguide; Wherein, the first waveguide coupling structure and the second waveguide coupling structure are both waveguide coupling structures according to any one of claims 1 to 6; The curved waveguide in the first waveguide coupling structure, the second uniform waveguide, the curved waveguide in the second waveguide coupling structure, and the third uniform waveguide are connected in sequence.

9. The microring resonator according to claim 8, characterized in that, Both the second uniform waveguide and the third uniform waveguide are uniformly curved waveguides; The curved waveguide in the first waveguide coupling structure, the second uniform waveguide, the curved waveguide in the second waveguide coupling structure, and the third uniform waveguide form a ring waveguide.

10. An optical chip, characterized in that, include: Waveguide coupling structure according to any one of claims 1 to 6; or, The microring resonator according to any one of claims 7 to 9.

Images