High-Q-value micro-ring resonator and filter based on free-form curve design

Abstract

The invention discloses a high-Q-value micro-ring resonator and filter based on free-form curve design. The high-Q-value micro-ring resonator comprises an annular waveguide formed by sequentially connecting a first bent waveguide, a first straight waveguide, a second bent waveguide and a second straight waveguide end to end; the bus waveguide is formed by sequentially connecting a third straight waveguide, a third bent waveguide and a fourth bent waveguide; the input waveguide and the output waveguide are formed by conical waveguides; the first bent waveguide, the second bent waveguide, the third bent waveguide and the fourth bent waveguide are all 180-degree bent waveguides and adopt free-form curve structures, and the overall curve can be discretized into equal-length cascade curve segments based on a generalized Euler curve model; and respectively optimizing the geometrical shape of each curve section by adopting an optimization algorithm model so as to reduce the bending loss. By optimizing the geometrical shape of the curve, scattering loss and bending loss of the rough side wall are reduced, and the high-Q-value micro-ring resonator which is compact in structure and easy to integrate is achieved.

Description

Technical Field

[0001] The present invention relates to the fields of optoelectronic integration technology, optical communication and optical sensing, and in particular to a high-Q value micro-ring resonator and filter based on free-form curve design. Background Art

[0002] The microring resonator consists of a closed ring waveguide and an adjacent bus-coupled waveguide. The input light is coupled to the ring cavity through the bus waveguide and propagates back and forth multiple times in the cavity to form an optical circuit. Since no additional reflection surface is required, the microring resonator is highly integrable and plays an important role in the field of integrated photonics. The Q value is defined as the ratio of the energy stored in the resonator to the energy dissipated per unit time, and is a key indicator for measuring the performance of a microring resonator. Microring resonators with high Q values ​​are widely used in microwave filtering, lasers, sensors, nonlinear optics, and quantum optics. Therefore, improving the Q value of microring resonators has always been the focus of integrated photonics research.

[0003] The main factors affecting the Q value of the microring resonator include: the coupling coefficient between the ring waveguide and the bus waveguide, the scattering loss caused by the roughness of the waveguide sidewall, and the bending loss of the ring waveguide. Among them, the coupling coefficient can be controlled by precise process manufacturing, but due to the inherent limitations of the exposure and etching processes, it is difficult to obtain an ideal smooth sidewall, which leads to increased scattering loss. A common optimization strategy is to increase the waveguide width to improve the mode confinement ability and confine the light field more inside the waveguide, thereby reducing the scattering loss. However, the increase in waveguide width may cause the waveguide to support multi-mode transmission, which in turn causes the mode field mismatch problem, causing the mode light to excite other high-order modes and radiation modes in the coupling waveguide and the ring waveguide, aggravating the scattering loss and bending loss, and reducing the Q value of the microring resonator. In addition, in application scenarios that require single-mode resonance (such as filters), the excitation of high-order modes will seriously affect the performance of the device. In order to suppress high-order modes, traditional designs usually use large bending radius to ensure single-mode transmission. However, this method significantly increases the size of the device and limits its application scenarios. Therefore, in order to achieve both high Q value and small size of microring resonators, it is urgent to develop new optimized design schemes. Summary of the invention

[0004] The present invention provides a high-Q micro-ring resonator and filter based on a free-form curve design (FFC), which is used to solve the problem that it is difficult for micro-ring resonators in the prior art to simultaneously achieve high Q value and small size. The 180° curved waveguide based on the FFC design ensures the mode field matching of the mode light during transmission, avoids the mode light from exciting other high-order modes and radiation modes in the coupling waveguide and the ring waveguide, and reduces the scattering loss and bending loss. Both the bus coupling waveguide and the ring waveguide use multi-mode waveguides to reduce the scattering loss of the waveguide sidewalls. The curved waveguide structure is designed based on the FFC, and the adiabatic transmission of the mode light is achieved by optimizing the trajectory curvature distribution. Specifically, the FFC structure is discretized into multiple curve segments based on the generalized Euler curve model, with the goal of reducing the bending loss of the mode light, and the geometric parameters of each curve segment are optimized.

[0005] In a first aspect, the present invention provides a high-Q microring resonator based on FFC design, including a ring waveguide, a bus waveguide, an input waveguide and an output waveguide:

[0006] The annular waveguide comprises a first curved waveguide, a first straight waveguide, a second curved waveguide, and a second straight waveguide connected end to end in sequence;

[0007] The bus waveguide includes a third straight waveguide and an S-shaped bent waveguide connected in sequence;

[0008] The S-shaped curved waveguide includes a third curved waveguide and a fourth curved waveguide connected in sequence;

[0009] The input waveguide is a first tapered waveguide; the output waveguide is a second tapered waveguide;

[0010] The input waveguide is connected to the third straight waveguide;

[0011] The S-shaped bending waveguide is connected to the output waveguide;

[0012] The third straight waveguide and the first straight waveguide form a coupling region;

[0013] The mode light is incident from the input port of the first tapered waveguide, enters the third straight waveguide from the output port, and is coupled in the coupling region. The light satisfying the resonance frequency in the mode light enters the ring waveguide to resonate. The other mode lights sequentially pass through the third curved waveguide and the fourth curved waveguide, enter the input port of the second tapered waveguide, and are output from the output port.

[0014] The first curved waveguide, the second curved waveguide, the third curved waveguide and the fourth curved waveguide are all 180°, and their geometric models are FFC structures, which are discretized as equal-length cascade curve segments based on a generalized Euler curve model;

[0015] The curvature distribution of the FFC is optimized by using an optimization algorithm model to ensure adiabatic transmission of the mode light in the ring waveguide and the bus waveguide, reduce bending loss, and improve the Q value of the microring resonator.

[0016] The present invention comprises a ring waveguide which is connected end to end in sequence by a first curved waveguide, a first straight waveguide, a second curved waveguide and a second straight waveguide; a bus waveguide which is connected end to end by a third straight waveguide, a third curved waveguide and a fourth curved waveguide; and an input waveguide and an output waveguide which are formed by tapered waveguides; the first curved waveguide, the second curved waveguide, the third curved waveguide and the fourth curved waveguide are all 180-degree curved waveguides, and a free-form curve structure is adopted, and the overall curve can be discretized into equal-length cascade curve segments based on a generalized Euler curve model; and an optimization algorithm model is adopted to respectively optimize the geometric shape of each curve segment to reduce bending loss.

[0017] The present invention can ensure efficient single-mode transmission in a multimode waveguide while reducing the size of the device, avoid the generation of other high-order modes and radiation modes, and reduce the scattering loss and bending loss of the rough sidewall by optimizing the geometric shape of the curve, thereby realizing a high-Q value microring resonator with a compact structure and easy integration.

[0018] Furthermore, the curve geometric models of the first curved waveguide, the second curved waveguide, the third curved waveguide and the fourth curved waveguide adopt a free-form curve structure, which is composed of a plurality of cascaded curve segments of equal length. The curve segments in the free-form curve structure adopt a generalized Euler curve model, and the curvature Use the following formula:

[0019]

[0020] Among them, RS is the adjustable starting point curvature radius, RT is the adjustable end point curvature radius, Δθ is the adjustable angle, ΔL is the constant length, θ is the angle variable, and l is the path length variable.

[0021] The traditional free-form curve (FFC) design usually adopts a series of equi-angle arc segments to achieve low-loss transmission of mode light by optimizing its radius. However, the curvature of each curve segment remains constant, and the control parameters are relatively single, which makes it difficult to fine-tune the local curvature distribution, thereby greatly limiting the optimization space of the overall structure. The FFC structure described in the present invention is based on the generalized Euler curve model, and introduces a series of curve segments with adjustable curvature, so that the curvature is no longer limited to a discrete constant value, but can be linearly changed in each curve segment according to the actual transmission loss. This design provides greater freedom. By combining the optimization algorithm model, the curve optimization can adapt to various evolution situations of the mode light, avoid the excitation of other high-order modes, and further improve the transmission efficiency. In addition, while maintaining the compactness of the traditional FFC structure, this method takes into account the requirements of high performance to achieve a compact design of a high-Q microring resonator.

[0022] Furthermore, the optimization algorithm model uses Lumerical simulation software to calculate the bending loss of each curve segment, sets the mode light source and waveguide structure, and optimizes the geometric parameters of each curve segment, including the starting curvature radius RS, the end curvature radius RT, and the angle Δθ, through a directional binary search algorithm, in order to reduce the bending loss of each curve segment and achieve the optimal design of the curvature distribution of the FFC.

[0023] Furthermore, the first tapered waveguide and the second tapered waveguide are both waveguides with linearly gradient widths, ensuring adiabatic transmission of mode light between the single-mode waveguide and the multi-mode waveguide, the input port cross-sectional width of the first tapered waveguide is a first width, and the output port cross-sectional width is a second width, the input port cross-sectional width of the second tapered waveguide is a second width, and the output port cross-sectional width is the first width, and the first width is smaller than the second width.

[0024] Furthermore, the coupling region adopts a standard directional coupling structure, that is, the third straight waveguide and the first straight waveguide have the same width, are parallel to each other and are placed at intervals, so as to achieve refractive index matching for mode coupling.

[0025] Further, the first curved waveguide, the second curved waveguide, the S-shaped curved waveguide, the first straight waveguide, the second straight waveguide and the third straight waveguide are all multimode waveguides, and have constant and equal widths, which are all the second width.

[0026] Furthermore, the mode light includes the TE fundamental mode and other high-order modes, the TM fundamental mode and other high-order modes, ensuring that the microring resonator is suitable for signal processing of different mode lights.

[0027] Furthermore, the lengths of the first straight waveguide and the second straight waveguide can be adjusted simultaneously, and different runway lengths correspond to different FSRs, thereby ensuring that the FSR is controllable to be applicable to a variety of application scenarios.

[0028] Furthermore, the lengths of the first straight waveguide and the third straight waveguide can be adjusted simultaneously, and different coupling lengths correspond to different coupling coefficients, thereby ensuring that the coupling coefficient is adjustable to control the coupling state of the microring resonator.

[0029] Further, the coupling coefficient is determined by the waveguide gap and the coupling length in the coupling region.

[0030] Further, applicable optical waveguide structures of the first curved waveguide, the second curved waveguide, the S-shaped curved waveguide, the first straight waveguide, the second straight waveguide, the third straight waveguide, the first tapered waveguide and the second tapered waveguide include strip waveguides, ridge waveguides and multilayer waveguides.

[0031] Further, suitable optical waveguide materials for the first curved waveguide, the second curved waveguide, the S-shaped curved waveguide, the first straight waveguide, the second straight waveguide, the third straight waveguide, the first tapered waveguide and the second tapered waveguide include silicon, silicon dioxide, indium phosphide, gallium arsenide, silicon nitride, lithium niobate or polymer.

[0032] In a second aspect, the present invention provides a bandpass filter, wherein the bandpass filter adopts a high-Q microring resonator based on FFC design as described in any one of the first aspects.

[0033] In a third aspect, the present invention provides a band-stop filter, wherein the band-stop filter adopts a high-Q microring resonator based on FFC design as described in any one of the first aspects.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. The present invention innovatively provides a high-Q microring resonator based on FFC design. By optimizing the curvature distribution of FFC, the generation of other high-order modes and radiation modes in the ring waveguide and bus waveguide is suppressed, the bending loss is reduced, the adiabatic transmission of the mode light is achieved, and the Q value of the microring resonator is improved.

[0036] 2. The present invention innovatively provides an FFC structure, which is composed of a cascade of equal-length curve segments based on a generalized Euler curve model, providing a new degree of freedom for the optimal design of the FFC.

[0037] 3. The high-Q microring resonator based on FFC design provided by the present invention adopts a standard directional coupling structure. The mode light maintains refractive index matching and stably transmits and couples in the coupling area. It is insensitive to process manufacturing and suppresses the generation of other high-order modes.

[0038] 4. The high-Q microring resonator based on FFC design provided by the present invention has simple process, compact structure and easy integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the structure of a high-Q microring resonator based on FFC design provided by the present invention;

[0040] Figure 2 A schematic diagram of a 180° curved waveguide structure based on an FFC structure design provided by the present invention;

[0041] Figure 3 It is a curvature parameter distribution diagram of a 180° curved waveguide based on FFC optimized in an embodiment of the present invention and a curvature parameter distribution diagram of a 180° curved waveguide based on Euler curve with the same size and waveguide structure;

[0042] Figure 4 It is a spectrum diagram of the net transmittance of the TE fundamental mode in the wavelength range of 1500nm to 1600nm obtained by the 180° curved waveguide based on FFC designed by numerical simulation in an embodiment of the present invention and the 180° curved waveguide based on Euler curve with the same size and waveguide structure;

[0043] Figure 5 It is a spectrum diagram of TE fundamental mode loop transmission loss in the wavelength range of 1500nm to 1600nm obtained by a ring waveguide based on FFC designed by numerical simulation in an embodiment of the present invention and a ring waveguide based on Euler curve with the same size and waveguide structure;

[0044] Figure 6 : is a TE fundamental mode coupling spectrum diagram of the coupling region of the high Q value microring resonator based on FFC design designed by numerical simulation in the embodiment of the present invention within the wavelength range of 1500nm to 1600nm ( Figure 6 (a)) and the electric field diagram of the mode light transmission profile at 1550nm ( Figure 6 (b)).

[0045] Figure 7 This is a spectrum diagram of a high-Q microring resonator based on FFC design designed by numerical simulation in an embodiment of the present invention ( Figure 7 (a)) and details of the resonance peak near 1550nm wavelength ( Figure 7(b)) and the spectrum of a high-Q microring resonator based on an Euler curve with the same size and waveguide structure ( Figure 7 (c)) and details of the resonance peak near 1550nm wavelength ( Figure 7 (d)). DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] like Figure 1 As shown, an embodiment of the present invention provides a high-Q microring resonator based on FFC design, including a ring waveguide, a bus waveguide, an input waveguide and an output waveguide;

[0048] The annular waveguide comprises a first curved waveguide 1, a first straight waveguide 2, a second curved waveguide 3, and a second straight waveguide 4 which are connected end to end in sequence;

[0049] The bus waveguide includes a third straight waveguide 6 and an S-shaped curved waveguide connected in sequence;

[0050] The S-shaped curved waveguide comprises a third curved waveguide 7 and a fourth curved waveguide 8 connected in sequence;

[0051] The input waveguide is a first tapered waveguide 5; the output waveguide is a second tapered waveguide 9;

[0052] The input waveguide is connected to the third straight waveguide 6;

[0053] The S-shaped bending waveguide is connected to the output waveguide;

[0054] The third straight waveguide 6 and the first straight waveguide 2 form a coupling region;

[0055] The mode light is incident from the input port of the first tapered waveguide 5, enters the third straight waveguide 6 from the output port, and is coupled in the coupling region. The light satisfying the resonance frequency in the mode light enters the ring waveguide to resonate. The other mode lights pass through the third curved waveguide 7 and the fourth curved waveguide 8 in sequence, enter the input port of the second tapered waveguide 9, and are output from the output port.

[0056] The first curved waveguide 1, the second curved waveguide 3, the third curved waveguide 7 and the fourth curved waveguide 8 are all 180 degrees, and their geometric model is an FFC structure, such as Figure 2As shown, the whole is discretized into equal-length cascade curve segments based on the generalized Euler curve model, and its curvature Use the following formula:

[0057]

[0058] Among them, RS is the adjustable starting point curvature radius, RT is the adjustable end point curvature radius, Δθ is the adjustable angle, ΔL is the constant length, θ is the angle variable, and l is the path length variable.

[0059] The curvature distribution of the FFC is optimized by using an optimization algorithm model to ensure adiabatic transmission of the mode light in the ring waveguide and the bus waveguide, reduce bending loss, and improve the Q value of the microring resonator.

[0060] In this embodiment, in order to demonstrate the compatibility of the material and waveguide structure of the high-Q microring resonator provided by the present invention, a strip waveguide structure of a lithium niobate platform is taken as an example:

[0061] This process platform uses commercial anisotropic lithium niobate on insulator wafers with a film thickness of 400nm and a buried oxide layer thickness of 4.7μm.

[0062] Furthermore, it is necessary to determine the multimode waveguide width of the microring resonator, that is, the second width. On the one hand, the wider the multimode waveguide, the lower the scattering loss of the rough sidewall to the mode light, and the higher the Q value that the microring resonator can achieve. On the other hand, the wider the multimode waveguide, the easier it is to excite other high-order modes at the bend, and the larger the size required to meet the mode matching. Taking all factors into consideration, the second width designed in this example is 1.8μm. The first curved waveguide 1, the second curved waveguide 3, the third curved waveguide 7 and the fourth curved waveguide 8, the first straight waveguide 2, the second straight waveguide 4 and the third straight waveguide 6 are all multimode waveguides with constant and equal widths, all of which are the second width, so as to reduce the mode mismatch loss caused by the change in waveguide width.

[0063] like Figure 2 As shown, the 180° curved waveguide is a structure symmetrical along the 90° angle bisector. Therefore, only the 0° to 90° portion of the FFC structure needs to be designed, which is discretized into multiple curve segments based on the generalized Euler curve model, and the 90° to 180° portion can be obtained directly along the 90° angle bisector. The finally designed 180° curved waveguide structure can be used for the first curved waveguide 1, the second curved waveguide 3, the third curved waveguide 7, and the fourth curved waveguide 8.

[0064] Furthermore, it is necessary to determine the length of the discrete curve segment of the FFC structure. The shorter the discrete curve segment length, the more sophisticated the structural design, but the higher the time cost of the design. Taking all factors into consideration, the length of the discrete curve segment designed in this example is 3μm. Since the total length of the 0° to 90° portion of the FFC structure is not necessarily equal to an integer multiple of the discrete curve segment length, the length of the last curve segment near the 90° angle bisector is changed according to the actual situation, as long as the end of the curve segment is at 90°.

[0065] The optimization algorithm model uses Lumerical simulation software to calculate the bending loss of each curve segment. In this example, a TE fundamental mode light source with a wavelength of 1550nm is set. Through the directional binary search algorithm, the geometric parameters of each curve segment are optimized, including the starting curvature radius RS, the end curvature radius RT and the angle Δθ, in order to reduce the bending loss of each curve segment and optimize the curvature distribution of the FFC. Finally, the optimized curve segments are cascaded in sequence to form a 180° curved waveguide, and the parameter distribution of its curvature is shown as follows: Figure 3 As shown, we also designed an Euler curve with the same size and waveguide structure for performance comparison. The parameter distribution of its curvature is shown in Figure 3 The total arc length is calculated to be about 52.93 μm and the effective radius is about 12 μm.

[0066] Furthermore, the numerical simulation of the designed 180° curved waveguide based on the FFC structure obtains the TE fundamental mode net transmittance ( Figure 4 Solid line). It can be found that the TE fundamental mode transmission efficiency is extremely high in the wavelength range of 1500nm to 1600nm, and no other high-order modes are generated. At the same time, the TE fundamental mode net transmittance of the Euler curve with the same size and waveguide structure is simulated ( Figure 4 The comparison with the dotted line shows that the adiabatic transmission performance of the mode light of the designed FFC curve is better than that of the Euler curve.

[0067] Furthermore, the lengths of the first straight waveguide 2 and the second straight waveguide 4 can be adjusted simultaneously, and different track lengths correspond to different FSRs. In this example, the lengths of the first straight waveguide 2 and the second straight waveguide 4 are both 20 μm, so the total length of the ring waveguide is about 145.86 μm.

[0068] Furthermore, the transmission loss of the ring waveguide based on the FFC design designed by numerical simulation includes the total loss of the first curved waveguide 1, the first straight waveguide 2, the second curved waveguide 3 and the second straight waveguide 4 ( Figure 5 The results show that the transmission loss of the mode optical loop at the working wavelength of 1550nm is 0.0001dB, and the corresponding average transmission loss is about 0.69dB / m. Compared with the Euler curve with the same size and waveguide structure ( Figure 5 The mode light loop transmission loss at the working wavelength of 1550nm is 0.0004dB, and the corresponding average transmission loss is about 2.74dB / m, indicating that the mode light adiabatic transmission performance of the designed FFC curve is much better than that of the Euler curve.

[0069] Furthermore, it is necessary to determine the single-mode waveguide width of the microring resonator, that is, the first width. The first tapered waveguide 5 and the second tapered waveguide 9 are both waveguides with linearly gradient widths, ensuring that the mode light is adiabatically transmitted between the single-mode waveguide and the multi-mode waveguide. The input port cross-sectional width of the first tapered waveguide 5 is the first width, and the output port cross-sectional width is the second width. The input port cross-sectional width of the second tapered waveguide 9 is the second width, and the output port cross-sectional width is the first width. According to the single-mode condition of the platform, the first width designed in this example is 0.9 μm.

[0070] Furthermore, it is necessary to determine the waveguide spacing and coupling length of the coupling region in the microring resonator. The coupling region adopts a standard directional coupling structure, that is, the width of the third straight waveguide 6 and the first straight waveguide 2 are constant and equal, and they are parallel to each other and spaced apart to achieve refractive index matching for mode coupling. The lengths of the third straight waveguide 6 and the first straight waveguide 2 are adjusted at the same time. Under the premise of a certain waveguide spacing, different coupling lengths correspond to different coupling coefficients. According to Figure 3 The loop loss simulation results show that in order to achieve the critical coupling condition of the microring resonator, the loop loss factor is required to be equal to the coupling coefficient. Therefore, the coupling coefficient of the microring resonator based on FFC design is set to 2.5×10 -5 The coupling coefficient of the microring resonator designed based on the Euler curve is 1×10 -4 . Considering the process conditions of the platform, the waveguide spacing designed in this example is 0.8μm. The simulation calculation shows that for the microring resonator based on FFC design, when the coupling length is 0μm (depending on the situation, the coupling length is not necessarily 0μm at other waveguide spacings), its coupling coefficient meets the design requirements. Using the above structural parameters, we designed the coupling region of the high-Q microring resonator based on FFC design, and simulated the spectrum of the directional coupling region ( Figure 6 (a)) and the electric field diagram of the mode light transmission profile at 1550nm ( Figure 6 (b)). Figure 6 (a) shows that the designed structure obtains the required coupling coefficient at 1550nm, and its coupling loss is as low as 1.6×10 -3 dB, and the coupling loss at 1550nm is almost 0dB, indicating that the mode light still maintains adiabatic transmission after coupling. Figure 6(b) shows that no other high-order modes are generated during the coupling process. A similar method can be used to obtain the structural parameters of the directional coupling region designed based on the Euler curve.

[0071] Furthermore, the simulation data was imported into Lumerical Interconnect software to perform link simulation of the microring resonator, and the spectrum diagrams of the microring resonator based on FFC were obtained respectively ( Figure 7 (a) and Figure 7 (b)) and the spectrum of the microring resonator based on the Euler curve ( Figure 7 (c) and Figure 7 (d)). Figure 7 As shown in (a) and 7(c), the FSR of the microring resonator in this embodiment is about 7.33nm, and the sizes of the microring resonators designed based on the two curves are similar. Figure 7 As shown in (b), the full width at half maximum (FWHM) of the microring resonator based on FFC design is about 61.66 fm, and the central wavelength is 1549.37 nm, from which Q can be calculated to be 2.51×10 7 , while the FWHM of the microring resonator designed based on the Euler curve is about 221fm, the central wavelength is 1549.37nm, and Q=7.01×10 6 ,like Figure 7 The results show that, under the same size, the Q value of the microring resonator based on FFC design is about one order of magnitude higher than that of the microring resonator based on Euler curve design, which reflects the advanced nature of the design of the present invention.

[0072] Furthermore, the first curved waveguide 1, the second curved waveguide 2, the first straight waveguide 3, the second straight waveguide 4, the third straight waveguide 6, the third curved waveguide 7, the fourth curved waveguide 8, the first tapered waveguide 5 and the second tapered waveguide 9 can all be strip waveguides, ridge waveguides and multi-layer waveguides, and are not limited to specific waveguide structures.

[0073] Furthermore, the first curved waveguide 1, the second curved waveguide 2, the first straight waveguide 3, the second straight waveguide 4, the third straight waveguide 6, the third curved waveguide 7, the fourth curved waveguide 8, the first tapered waveguide 5 and the second tapered waveguide 9 can all be made of silicon, silicon dioxide, indium phosphide, gallium arsenide, silicon nitride, lithium niobate or polymer, and are not limited to specific materials.

[0074] On the basis of the above embodiments, the present invention further provides a bandpass filter, wherein the bandpass filter adopts the high-Q microring resonator based on FFC design as described in any one of the above embodiments.

[0075] On the basis of the above embodiments, the present invention further provides a band-stop filter, wherein the band-stop filter adopts the high-Q micro-ring resonator based on FFC design as described in any one of the above embodiments.

[0076] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-Q microring resonator based on free-form curve design, characterized in that: Including ring waveguide, bus waveguide, input waveguide and output waveguide; The annular waveguide comprises a first curved waveguide, a first straight waveguide, a second curved waveguide, and a second straight waveguide connected end to end in sequence; The bus waveguide includes a third straight waveguide and an S-shaped bent waveguide connected in sequence; The S-shaped curved waveguide includes a third curved waveguide and a fourth curved waveguide which are connected in sequence.

2. The high-Q microring resonator based on free-form curve design according to claim 1, characterized in that: The input waveguide is connected to the third straight waveguide; The S-shaped bent waveguide is connected to the output waveguide.

3. The high-Q microring resonator based on free-form curve design according to claim 1, characterized in that: The geometric models of the curves of the first curved waveguide, the second curved waveguide, the third curved waveguide and the fourth curved waveguide adopt a free-form curve structure, and the curve segments in the free-form curve structure adopt a generalized Euler curve model, whose curvature Use the following formula: Among them, RS is the adjustable starting point curvature radius, RT is the adjustable end point curvature radius, Δθ is the adjustable angle, ΔL is the constant length, θ is the angle variable, and l is the path length variable.

4. The high-Q microring resonator based on free-form curve design according to claim 1, characterized in that: The input waveguide is a first tapered waveguide, and the output waveguide is a second tapered waveguide.

5. The high-Q microring resonator based on free-form curve design according to claim 4, characterized in that: The first tapered waveguide and the second tapered waveguide are both waveguides with linearly gradient widths. The first tapered waveguide has an input port cross-sectional width of a first width and an output port cross-sectional width of a second width. The second tapered waveguide has an input port cross-sectional width of a second width and an output port cross-sectional width of a first width. The first width is smaller than the second width.

6. The high-Q microring resonator based on free-form curve design according to claim 5, characterized in that: The third straight waveguide and the first straight waveguide form a coupling region; The first curved waveguide, the second curved waveguide, the third curved waveguide and the fourth curved waveguide are all 180°.

7. The high-Q microring resonator based on free-form curve design according to claim 6, characterized in that: The third straight waveguide has the same width as the first straight waveguide, and is parallel to and spaced apart from each other.

8. The high-Q microring resonator based on free-form curve design according to claim 6, characterized in that: The first curved waveguide, the second curved waveguide, the S-shaped curved waveguide, the first straight waveguide, the second straight waveguide and the third straight waveguide are all multimode waveguides, and have constant and equal widths, which are all the second width.

9. A bandpass filter, characterized in that: The bandpass filter adopts a high-Q microring resonator based on a free-form curve design according to any one of claims 1 to 8.

10. A band-stop filter, characterized in that: The band-stop filter adopts a high-Q micro-ring resonator based on a free-form curve design according to any one of claims 1 to 8.

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