Micro-ring assisted MZI wavelength division multiplexer and chip

Abstract

This application discloses a microring-assisted MZ I wavelength division multiplexer and chip, which is disposed on a substrate. The substrate has a first cladding layer and a second cladding layer stacked on it, and a core layer located between the first cladding layer and the second cladding layer. The wavelength division multiplexer, located in the core layer, includes a Mach-Zehnder interferometer and at least one microring resonator. The Mach-Zehnder interferometer includes a first waveguide arm and a second waveguide arm arranged at relatively intervals. The microring resonator includes a waveguide microring, with at least one waveguide microring coupled to the side of at least one of the first waveguide arm and the second waveguide arm. The first cladding layer, the core layer, and the second cladding layer are all made of materials with positive thermo-optic coefficients. The second cladding layer has a cutout corresponding to the waveguide microring, and the cutout is filled with a material with a negative thermo-optic coefficient to form a negative thermo-optic cladding layer. The projection of the negative thermo-optic cladding layer onto the core layer at least covers the waveguide microring to compensate for the temperature drift caused by the core layer and the first cladding layer, so that the resonant wavelength of the microring resonator does not change with temperature.

Description

Technical Field

[0001] This application relates to the field of optical communication technology, specifically to a micro-ring assisted MZI wavelength division multiplexer and chip. Background Technology

[0002] Wavelength division multiplexing (WDM) devices are crucial components in optical communication systems, used for multiplexing and demultiplexing optical signals of different wavelengths. Among them, cascaded MZI WDM devices are ideal for on-chip integrated WDM devices due to their significant advantages such as low loss and wide flat passband. However, achieving a flat passband output in a WDM structure with cascaded Mach-Zehnder interferometers requires cascading multiple Mach-Zehnder interferometers, often resulting in large device size and high cost.

[0003] Furthermore, MZI wavelength division multiplexers based on microring-assisted structures exhibit superior low-loss and flat passband characteristics. Moreover, their more compact structure makes them more suitable for low-cost, highly integrated on-chip wavelength division multiplexing devices. However, microring-assisted MZI wavelength division multiplexers are susceptible to temperature variations in practical applications. Due to the thermo-optical effect of the materials, the operating wavelength of the device shifts with temperature changes, causing the wavelength division multiplexing device to malfunction. Summary of the Invention

[0004] The purpose of this application is to provide a micro-ring assisted MZI wavelength division multiplexer and chip, which reduces the impact of temperature on its operating wavelength and solves the problem that the operating wavelength of existing micro-ring assisted MZI wavelength division multiplexers is easily affected by temperature and thus cannot work properly.

[0005] To address the aforementioned technical problems, embodiments of the present invention disclose the following technical solutions:

[0006] On one hand, a microring-assisted MZI wavelength division multiplexer is provided, disposed on a substrate, wherein the substrate has a first cladding layer and a second cladding layer stacked on it, and a core layer located between the first cladding layer and the second cladding layer, and the microring-assisted MZI wavelength division multiplexer is located in the core layer; characterized in that the microring-assisted MZI wavelength division multiplexer includes: a Mach-Zehnder interferometer and at least one microring resonator, the Mach-Zehnder interferometer includes a beam splitter, a beam combiner, and a first waveguide arm and a second waveguide arm arranged at opposite intervals, the first waveguide arm and the second waveguide arm being respectively connected between the beam splitter and the beam combiner; the microring resonator includes a waveguide microring, at least one of the waveguide microrings is coupled to the side of at least one of the first waveguide arm and the second waveguide arm, the phase difference between the first waveguide arm and the second waveguide arm is half the phase of the microring resonator, and the resonant wavelength spacing of the microring resonator is the same as the channel wavelength spacing of the microring-assisted MZI wavelength division multiplexer;

[0007] The first cladding, the core layer, and the second cladding are all materials with positive thermo-optic coefficients. The second cladding has a hollow portion corresponding to the waveguide microring. The hollow portion is filled with a material with a negative thermo-optic coefficient to form a negative thermo-optic cladding. The projection of the negative thermo-optic cladding onto the core layer at least covers the waveguide microring to compensate for the temperature drift caused by the core layer and the first cladding, so that the resonant wavelength of the microring resonator does not change with temperature.

[0008] Furthermore, the negative thermo-optical cladding is configured such that the sum of the product of the field effect factor of the waveguide microring and the thermo-optical coefficient of the waveguide microring, the product of the field effect factor of the first cladding and the thermo-optical coefficient of the first cladding, and the product of the field effect factor of the negative thermo-optical cladding and the thermo-optical coefficient of the negative thermo-optical cladding is zero.

[0009] Furthermore, the material with a negative thermo-optic coefficient includes any one or more of TiO2, ZnO, magnesium-doped ZnO, PMMA, SU-8, and polystyrene.

[0010] Furthermore, the first waveguide arm and / or the second waveguide arm coupled to the waveguide microring includes a coupling segment coupled to the waveguide microring, and the projection of the negative thermo-optical cladding on the core layer at least covers the waveguide microring and the coupling segment coupled thereto; or, the projection of the negative thermo-optical cladding on the core layer covers the waveguide microring, as well as the first waveguide arm and / or the second waveguide arm.

[0011] Furthermore, the number of the microring resonators is one, the waveguide microring is coupled to the first waveguide arm, and the optical path of the second waveguide arm is greater than that of the first waveguide arm.

[0012] Furthermore, the number of microring resonators is multiple, and the phase of each microring resonator is the same;

[0013] The plurality of microring resonators are respectively coupled to the sides of the first waveguide arm and / or the second waveguide arm.

[0014] Furthermore, the coupling coefficients of the multiple microring resonators and their corresponding waveguide arms are different.

[0015] Furthermore, one or both of the first waveguide arm and the second waveguide arm include at least two waveguide segments with different widths, such that within the operating band of the microring-assisted MZI wavelength division multiplexer, the phase difference between the first waveguide arm and the second waveguide arm does not change with temperature; the width refers to the width of the cross-section of the waveguide arm.

[0016] Furthermore, the first waveguide arm includes a plurality of first waveguide segments having a first width W1, a plurality of second waveguide segments having a second width W2, and a first coupling segment having a third width W3. The first width W1 is not equal to the second width W2, and the third width W3 is equal to the first width W1 or the second width W2, or is not equal to either the first width W1 or the second width W2.

[0017] The second waveguide arm includes a fourth waveguide segment having a fourth width W4;

[0018] A first total length of several first waveguide segments is L1, a second total length of several second waveguide segments is L2, a third total length of a first coupling segment is L3, and a fourth total length of a fourth waveguide segment is L4. The total length and width of each waveguide segment are configured such that, within the operating band of the wavelength division multiplexer, the phase change of the first waveguide arm with temperature is equal to the phase change of the second waveguide arm with temperature; wherein,

[0019] The phase of the first waveguide arm changes with temperature as a sum of the following three factors: the product of the first total length L1 and the equivalent thermo-optic coefficient of the first waveguide segment, the product of the second total length L2 and the equivalent thermo-optic coefficient of the second waveguide segment, and the product of the third total length L3 and the equivalent thermo-optic coefficient of the first coupling segment.

[0020] The phase of the second waveguide arm changes with temperature as a product of the fourth total length L4 and the equivalent thermo-optic coefficient of the fourth waveguide segment.

[0021] The equivalent thermo-optic coefficient is the sum of the product of the field effect factor of the corresponding waveguide segment and its thermo-optic coefficient, the product of the field effect factor of the first cladding corresponding to the waveguide segment and its thermo-optic coefficient, and the product of the field effect factor of the second cladding corresponding to the waveguide segment and its thermo-optic coefficient. Waveguides of different widths have different field effect factors.

[0022] Furthermore, the second waveguide arm also includes a plurality of fifth waveguide segments with a fifth width W5 and a second coupling segment with a sixth width W6, wherein the fifth total length of the plurality of fifth waveguide segments is L5 and the sixth total length of the second coupling segment is L6;

[0023] The phase of the second waveguide arm changes with temperature as a sum of the following three factors: the product of the fourth total length L4 and the equivalent thermo-optic coefficient of the fourth waveguide segment, the product of the fifth total length L5 and the equivalent thermo-optic coefficient of the fifth waveguide segment, and the product of the sixth total length L6 and the equivalent thermo-optic coefficient of the second coupling segment.

[0024] Furthermore, waveguide segments of different widths are connected by tapered waveguides.

[0025] On the other hand, a chip is provided that includes any of the micro-ring assisted MZI wavelength division multiplexers disclosed above.

[0026] One of the above technical solutions has the following advantages or beneficial effects: The main difficulty in practical applications of micro-ring assisted MZI wavelength division multiplexers lies in the susceptibility of the micro-ring resonator to temperature influences. In the technical solution disclosed in this application, a hollow portion is provided in the second cladding corresponding to the waveguide micro-ring position, and filled with a material with a negative thermo-optic coefficient to form a negative thermo-optic cladding. The projection of the negative thermo-optic cladding onto the core layer at least completely covers the waveguide micro-ring. With this configuration, both the core layer where the waveguide micro-ring is located and the first cladding are made of materials with positive thermo-optic coefficients. The refractive index of these materials increases with temperature, leading to wavelength drift. However, the refractive index of the negative thermo-optic cladding decreases with temperature, compensating for the thermo-optic effect of materials with positive thermo-optic coefficients. Through the compensation mechanism of the negative thermo-optic cladding, the wavelength drift problem caused by the thermo-optic effect of the micro-ring resonator is solved, ensuring that the resonant wavelength of the micro-ring resonator does not change with temperature, thereby achieving temperature stability of the resonant wavelength.

[0027] Meanwhile, the output spectrum of the micro-ring assisted MZI wavelength division multiplexer is controlled by the phase difference between the first and second waveguide arms. By setting the phase difference between the first and second waveguide arms to half the phase of the micro-ring resonator, it can be ensured that the interference signals of the two arms and the output signal of the micro-ring resonator coherently superimpose at the channel wavelength. This effectively enhances the synergistic effect between the micro-ring resonator and the Mach-Zehnder interferometer, facilitates flat passband filtering, reduces insertion loss and crosstalk, and improves the overall performance of the micro-ring assisted MZI wavelength division multiplexer. The resonant wavelength spacing of the micro-ring resonator directly determines its selectivity for different wavelength optical signals. Setting the resonant wavelength spacing of the micro-ring resonator to be the same as the channel wavelength spacing of the micro-ring assisted MZI wavelength division multiplexer allows for precise matching of each channel, ensuring that the optical signal of the target wavelength correctly enters the corresponding channel and avoiding channel overlap or crosstalk problems caused by wavelength spacing mismatch. Attached Figure Description

[0028] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0029] Figure 1 This is a schematic diagram of the structure of a microring-assisted MZI wavelength division multiplexer provided in an embodiment of this application. Figure 1 ;

[0030] Figure 2 This is a schematic cross-sectional view of a microring-assisted MZI wavelength division multiplexer provided in an embodiment of this application. Figure 1 ;

[0031] Figure 3 This is a schematic diagram of the structure of a microring-assisted MZI wavelength division multiplexer provided in an embodiment of this application. Figure 2 ;

[0032] Figure 4 This is a schematic cross-sectional view of a microring-assisted MZI wavelength division multiplexer provided in an embodiment of this application. Figure 2 ;

[0033] Figure 5 This is a schematic diagram of the structure of a microring-assisted MZI wavelength division multiplexer provided in an embodiment of this application. Figure 3 ;

[0034] Figure 6 This is a schematic cross-sectional view of a microring-assisted MZI wavelength division multiplexer provided in an embodiment of this application. Figure 3 ;

[0035] Figure 7 This is a graph showing the variation of the effective refractive index of different waveguide arms with temperature, provided in the embodiments of this application.

[0036] Figure 8 This is a schematic diagram of the structure of a microring-assisted MZI wavelength division multiplexer provided in an embodiment of this application. Figure 4 ;

[0037] Figure 9 This is a schematic diagram of the structure of a microring-assisted MZI wavelength division multiplexer provided in an embodiment of this application. Figure 5 .

[0038] Key reference numerals:

[0039] 10. Substrate;

[0040] 20. First cladding layer;

[0041] 30. Core layer;

[0042] 40. Second cladding; 41. Negative thermo-optical cladding;

[0043] 50. Mach-Zehnder interferometer; 51. First waveguide arm; 511. First waveguide segment; 512. Second waveguide segment; 513. First coupling segment; 52. Second waveguide arm; 521. Fourth waveguide segment; 522. Fifth waveguide segment; 523. Second coupling segment; 53. Beam splitter; 54. Beam combiner; 55. Compensating waveguide;

[0044] 60. Microring resonator; 61. Waveguide microring;

[0045] 70. Hollowed-out section. Detailed Implementation

[0046] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described in this specification are merely for explaining the invention and are not intended to limit the invention.

[0047] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0048] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0050] This application discloses a micro-ring assisted MZI wavelength division multiplexer, which aims to reduce the influence of temperature on its operating wavelength and solve the problem that the operating wavelength of existing micro-ring assisted MZI wavelength division multiplexers is easily affected by temperature and thus cannot work properly.

[0051] Reference Figure 1 and Figure 2The microring-assisted MZI wavelength division multiplexer of this application embodiment is disposed on a substrate 10. The substrate 10 has a first cladding layer 20 and a second cladding layer 40 stacked on it, and a core layer 30 located between the first cladding layer 20 and the second cladding layer 40. The microring-assisted MZI wavelength division multiplexer is located in the core layer 30. Specifically, the microring-assisted MZI wavelength division multiplexer includes a Mach-Zehnder interferometer 50 and at least one microring resonator 60. The Mach-Zehnder interferometer 50 includes a beam splitter 53, a beam combiner 54, and a first waveguide arm 51 and a second waveguide arm 52 arranged at intervals. The first waveguide arm 51 and the second waveguide arm 52 are respectively connected between the beam splitter 53 and the beam combiner 54. The microring resonator 60 includes a waveguide microring 61. At least one waveguide microring 61 is coupled to the side of at least one of the first waveguide arm 51 and the second waveguide arm 52. The phase difference between the first waveguide arm 51 and the second waveguide arm 52 is half the phase of the microring resonator 60. The resonant wavelength spacing of the microring resonator 60 is the same as the channel wavelength spacing of the microring-assisted MZI wavelength division multiplexer. The first cladding 20, the core layer 30, and the second cladding 40 are all materials with positive thermo-optic coefficients. It is worth mentioning that the first waveguide arm 51, the second waveguide arm 52, and the waveguide microring 61 of the microring-assisted MZI wavelength division multiplexer located in the core layer 30 are all part of the core layer 30 and are materials with positive thermo-optic coefficients. The second cladding 40 has a hollow portion 70 corresponding to the waveguide microring 61. This hollow portion 70 is filled with a material with a negative thermo-optic coefficient to form a negative thermo-optic cladding 41. The projection of the negative thermo-optic cladding 41 onto the core layer 30 at least covers the waveguide microring 61 to compensate for the wavelength temperature drift caused by the core layer 30 and the first cladding 20, so that the resonant wavelength of the microring resonator 60 does not change with temperature. The phase of the microring resonator 60 is the phase shift of light propagating one revolution within its waveguide microring 61.

[0052] Specifically, microring-assisted MZI wavelength division multiplexers are easily affected by temperature in practical applications, leading to wavelength drift. The main challenge in avoiding wavelength drift lies in addressing the temperature sensitivity of the microring resonator 60. In the technical solution disclosed in this application, a hollow portion 70 is provided in the second cladding 40 corresponding to the waveguide microring 61, and filled with a material with a negative thermo-optic coefficient to form a negative thermo-optic cladding 41. The projection of the negative thermo-optic cladding 41 onto the core layer 30 at least completely covers the waveguide microring 61. Both the core layer 30 and the first cladding 20, where the waveguide microring 61 is located, are materials with positive thermo-optic coefficients. The refractive index of these materials increases with increasing temperature, leading to wavelength drift. This application provides a negative thermo-optic cladding 41 above the waveguide microring 61, utilizing the characteristic that the refractive index of the negative thermo-optic cladding 41 decreases with increasing temperature to compensate for the thermo-optic effect of materials with positive thermo-optic coefficients. The compensation mechanism of the negative thermo-optic cladding 41 solves the wavelength drift problem of the micro-ring resonator 60 caused by the thermo-optic effect, enabling the resonant wavelength of the micro-ring resonator 60 to remain unchanged with temperature, thereby achieving temperature stability of the resonant wavelength.

[0053] Meanwhile, the output spectrum of the micro-ring assisted MZI wavelength division multiplexer is controlled by the phase difference between the first waveguide arm 51 and the second waveguide arm 52. By setting the phase difference between the first waveguide arm 51 and the second waveguide arm 52 to half the phase of the micro-ring resonator 60, it can be ensured that the interference signals of the two arms and the output signal of the micro-ring resonator 60 coherently superimpose at the channel wavelength. This effectively enhances the synergistic effect between the micro-ring resonator 60 and the Mach-Zehnder interferometer 50, facilitates flat passband filtering, reduces insertion loss and crosstalk, and improves the overall performance of the micro-ring assisted MZI wavelength division multiplexer. The resonant wavelength spacing of the micro-ring resonator 60 directly determines its selectivity for different wavelength optical signals. Setting the resonant wavelength spacing of the micro-ring resonator 60 to be the same as the channel wavelength spacing of the micro-ring assisted MZI wavelength division multiplexer allows for precise matching of each channel, ensuring that the optical signal of the target wavelength correctly enters the corresponding channel and avoiding channel overlap or crosstalk problems caused by wavelength spacing mismatch.

[0054] It is worth noting that in a typical axisymmetric Mach-Zehnder interferometer, the length and width of the two waveguide arms are equal, and therefore the phases of the two waveguide arms are equal. When constructing a wavelength division multiplexer (WDM), a phase difference needs to be introduced into the two waveguide arms of the Mach-Zehnder interferometer to form a filter. Therefore, in a WDM, a phase compensation waveguide is introduced into one of the waveguide arms of the Mach-Zehnder interferometer, giving that waveguide arm a longer optical path than the other. In some embodiments of this application, a phase compensation waveguide 55 is introduced into the second waveguide arm 52, making the optical path of the second waveguide arm 52 greater than that of the first waveguide arm 51, and the phase difference between the second waveguide arm 52 and the first waveguide arm 51 is half the phase of the microring resonator 60.

[0055] like Figure 1 and 2 In the illustrated embodiment, there is one microring resonator 60, with its waveguide microring 61 coupled to the first waveguide arm 51, which has a shorter optical path. The optical path of the uncoupled second waveguide arm is greater than that of the coupled first waveguide arm. In this way, the losses of the two optical paths transmitted through the two waveguide arms can be balanced, minimizing the difference in losses between the two optical paths.

[0056] It should be noted that, in some embodiments disclosed in this application, materials with negative thermo-optic coefficients include any one or more of TiO2, ZnO, magnesium-doped ZnO, PMMA, SU-8, and polystyrene. Materials with positive thermo-optic coefficients include any one or more of Si, SiO2, SiN, SiON, and TFLN.

[0057] Specifically, the negative thermo-optical cladding 41 can compensate for the thermo-optical effects of the first cladding and core layer, solving the wavelength drift problem. This ensures that the phase of the microring resonator 60 does not change with temperature, and therefore its resonant wavelength also does not change with temperature, thus realizing a temperature-insensitive microring resonator. The specific principle is as follows: without considering the influence of the coefficient of thermal expansion, the phase of the microring resonator 60 changes with temperature... It can be expressed by the following formula:

[0058]

[0059] Where k0 is the wave number and L is the microring length. Characterized by the equivalent thermo-optical coefficient. Γ: is the field effect factor, characterizing the proportion of the light field distribution in the corresponding layer; in the above formula, Γ core Γ represents the field effect factor of core layer 30. upcladding Γ represents the field effect factor of the second cladding layer 40. lowcladding : Characterizes the field effect factor of the first cladding layer 20. The thermo-optic coefficient characterizes the core layer 30, representing the rate at which the effective refractive index of the core layer 30 changes with temperature; The thermo-optic coefficient characterizes the second cladding 40 and represents the rate at which the effective refractive index of the second cladding 40 changes with temperature. The thermo-optic coefficient characterizes the first cladding layer 20 and represents the rate at which the effective refractive index of the first cladding layer 20 changes with temperature.

[0060] Therefore, in order to ensure that the phase of the microring resonator 60 does not change with temperature, it is only necessary to make the equivalent thermo-optic coefficient of the microring resonator 60 zero (i.e., This allows its phase to change with temperature to be zero (i.e., This application introduces a negative thermo-optical cladding 41 on the side of the waveguide microring 61 away from the first cladding 20, thereby replacing the second cladding 40 that originally covered the waveguide microring 61 with the negative thermo-optical cladding 41. In this case, the core layer 30 is the waveguide microring 61. The thermo-optic coefficient characterizes waveguide microring 61, representing the rate at which the effective refractive index of waveguide microring 61 changes with temperature. Both the core layer and the lower cladding layer have positive thermo-optic coefficients, and the effective refractive index of both increases with increasing temperature. and All are positive numbers. The thermo-optic coefficient characterizes the negative thermo-optic cladding 41, representing the rate at which its effective refractive index changes with temperature. Since the thermo-optic coefficient of the negative thermo-optic cladding 41 is negative, its effective refractive index decreases with increasing temperature. This allows the negative thermo-optic cladding 41 to compensate for the temperature drift of the waveguide microring 61 and the first cladding 20, i.e., by configuring a suitable Γ... core ,Γupcladding ,Γ lowcladding (It should be noted that at this time Γ) core Γ is the field effect factor of waveguide microring 61. upcladding By considering the field effect factor (of the negative thermo-optical cladding 41) and the negative thermo-optical coefficient, the sum of the product of the field effect factor and the thermo-optical coefficient of the waveguide microring 61, the product of the field effect factor and the thermo-optical coefficient of the first cladding 20, and the product of the field effect factor and the thermo-optical coefficient of the negative thermo-optical cladding 41 can be made zero, thus achieving the above... The value is zero, thus realizing a temperature-insensitive microring resonator.

[0061] In a microring-assisted MZI wavelength division multiplexer, the phase of the two waveguide arms of the Mach-Zehnder interferometer is also affected by temperature. This application also provides a design scheme for the Mach-Zehnder interferometer to ensure that the phase difference between the first waveguide arm 51 and the second waveguide arm 52 does not change with temperature, thus ensuring that the phase difference is always half the phase of the microring resonator. The rate of change of the effective refractive index of the first waveguide arm 51 and the second waveguide arm 52 with temperature is related to their own waveguide width (waveguide width refers to the width of the cross-section of the waveguide arm). (Refer to...) Figure 7 , Figure 7 This illustrates the temperature-dependent characteristics of the effective refractive index of waveguide modes for waveguides of different widths. (Through...) Figure 7 It is known that when the waveguide arm width is small (e.g., 200 nm), the rate of change of the effective refractive index of the mode with temperature is approximately half that when the waveguide arm width is large (e.g., 400 nm). Therefore, in the embodiments of this application, by designing a combination of a wider and a narrower waveguide segment in the waveguide arm, the phase difference between the first waveguide arm 51 and the second waveguide arm 52 does not change with temperature, thereby making the micro-ring assisted MZI wavelength division multiplexer as a whole temperature-insensitive.

[0062] Specifically, in some embodiments disclosed in this application, one or both of the first waveguide arm 51 and the second waveguide arm 52 include at least two waveguide segments with different widths, such that the phase difference between the first waveguide arm 51 and the second waveguide arm 52 does not change with temperature within the operating band range of the microring-assisted MZI wavelength division multiplexer. To facilitate the explanation of the solutions in this application, the structures of the first waveguide arm 51 and the second waveguide arm 52 disclosed in the following embodiments are provided as examples.

[0063] like Figure 1 and 2In the first embodiment shown, the first waveguide arm 51 includes a plurality of first waveguide segments 511 having a first width W1, a plurality of second waveguide segments 512 having a second width W2, and a first coupling segment 513 having a third width W3. The first width W1 is not equal to the second width W2, and the third width W3 is equal to the first width W1 or the second width W2, or is not equal to either the first width W1 or the second width W2 (e.g., ...). Figure 1 For example, Figure 1 (This illustration shows the case where the third width W3 of the first coupling segment 513 is equal to the first width W1 of the first waveguide segment 511). The second waveguide arm 52 includes a fourth waveguide segment 521 with a fourth width W4. The first total length of a plurality of first waveguide segments 511 is L1, the second total length of a plurality of second waveguide segments 512 is L2, the third total length of the first coupling segment 513 is L3, and the fourth total length of the fourth waveguide segment 521 is L4. The total length and width of each waveguide segment are configured such that, within the operating band of the wavelength division multiplexer, the phase change of the first waveguide arm 51 with temperature is equal to the phase change of the second waveguide arm 52 with temperature, thereby ensuring that the phase difference between the first waveguide arm 51 and the second waveguide arm 52 does not change with temperature.

[0064] Furthermore, the phase change of the first waveguide arm 51 with temperature is the sum of the following three factors: the first total length L1 is the product of the equivalent thermo-optical coefficient of the first waveguide segment 511; the second total length L2 is the product of the equivalent thermo-optical coefficient of the second waveguide segment 512; and the third total length L3 is the product of the equivalent thermo-optical coefficient of the first coupling segment 513. The phase change of the second waveguide arm 52 with temperature is the product of the fourth total length L4 and the equivalent thermo-optical coefficient of the fourth waveguide segment 521. That is, the following formula condition needs to be satisfied:

[0065]

[0066] Furthermore, within the operating band, the above requirements must be met for each operating wavelength. Therefore, the design of each waveguide segment must also satisfy the following formula conditions:

[0067]

[0068] in, The equivalent refractive index of each waveguide segment is differentiated with respect to temperature and wavelength, that is, the equivalent thermo-optic coefficient of each waveguide segment is differentiated with respect to wavelength, to ensure that the phase difference between the first waveguide arm 51 and the second waveguide arm 52 does not change with temperature within the working wavelength range.

[0069] The equivalent thermo-optic coefficients for each waveguide segment are the sum of the product of the field effect factor and the thermo-optic coefficient of the corresponding waveguide segment, the product of the field effect factor and the thermo-optic coefficient of the first cladding 20 corresponding to the waveguide segment, and the product of the field effect factor and the thermo-optic coefficient of the second cladding 40 corresponding to the waveguide segment. Waveguide segments of different widths have different field effect factors, similar to the formula for the equivalent thermo-optic coefficient of the aforementioned waveguide microring 61. It should be noted that this application... Figure 1 and 2 In the first disclosed embodiment, the projection of the negative thermo-optical cladding 41 onto the core layer 30 only covers the waveguide microring 61. That is, the cladding of the first coupling segment 513 is the same as the cladding of the first waveguide segment 511, and the third width W3 of the first coupling segment 513 is equal to the first width W1 of the first waveguide segment 511. Therefore, the field effect factors of the first cladding 20, core layer 30, and second cladding 40 of the first waveguide segment 511 and the first coupling segment 513 are the same. In some other embodiments, the widths of the first coupling segment 513 and the first waveguide segment 511 are different, and the corresponding field effect factors of the core layer 30 and cladding are also different. Alternatively, when the first coupling segment 513 or the first waveguide segment 511 is covered by the negative thermo-optical cladding, the specific value of its field effect factor is also affected by the effective refractive index of the negative thermo-optical cladding 41. In this application, the equivalent thermo-optic coefficients corresponding to different waveguide segments can be determined first, and then appropriate first total lengths L1, L2, L3, and L4 can be determined so that the phase change of the first waveguide arm 51 with temperature is equal to the phase change of the second waveguide arm 52 with temperature, so that the phase difference between the first waveguide arm 51 and the second waveguide arm 52 does not change with temperature, that is, the phase difference between the first waveguide arm 51 and the second waveguide arm 52 with temperature is zero. In some other embodiments, waveguide segments of different widths can also be designed to make the phase change of the first waveguide arm 51 and the phase change of the second waveguide arm 52 with temperature zero, respectively.

[0070] In this embodiment, the negative thermo-optical cladding 41 covers only the waveguide microring 61, focusing on addressing the temperature drift problem of the microring resonator 60 without affecting the optical performance of other areas. When there are multiple microring resonators 60, each microring resonator 60 is equipped with independent negative thermo-optical compensation, allowing for optimized design based on the specific thermo-optical requirements of different microring resonators 60, avoiding undercompensation or overcompensation problems caused by a general design. Simultaneously, by reducing the coverage area of ​​the negative thermo-optical material, the interference of the negative thermo-optical material on the waveguide arm or other optical structures is minimized, maintaining the low-loss performance of the entire waveguide system.

[0071] like Figure 3 and Figure 4The second embodiment shown in the diagram has the same structure as the first waveguide arm 51 and the second waveguide arm 52 as in the first embodiment, and will not be described again here. The difference between the second and first embodiments is that the projection of the negative thermal cladding 41 onto the core layer 30 also covers the first coupling segment 513. Therefore, the specific value of the field effect factor of the first coupling segment 513 is also affected by the effective refractive index of the negative thermal cladding 41, and differs from the specific value in the first embodiment. This, in turn, affects the width and total length of each waveguide segment in the first and second waveguide arms. However, the above requirement still needs to be met: the phase change of the first waveguide arm 51 with temperature is equal to the phase change of the second waveguide arm 52 with temperature, thereby ensuring that the phase difference between the first and second waveguide arms 51 does not change with temperature. Therefore, similarly, after determining the equivalent thermo-optic coefficients corresponding to different waveguide segments, appropriate first total lengths L1, second total lengths L2, third total lengths L3, and fourth total lengths L4 can be determined so that the phase change of the first waveguide arm 51 with temperature is equal to the phase change of the second waveguide arm 52 with temperature, ensuring that the phase difference between the first waveguide arm 51 and the second waveguide arm 52 does not change with temperature, i.e., the phase difference between the first waveguide arm 51 and the second waveguide arm 52 is zero with temperature. In some cases, the spacing between the waveguide microring 61 and the coupling segment is usually small, possibly less than 500 nm. Making the negative thermo-optic cladding 41 cover only the waveguide microring 61 is difficult and costly in terms of manufacturing process. Furthermore, simultaneously covering the coupling segment and the microring resonator 60 helps stabilize the coupling coefficient between the microring resonator and the waveguide arm, reducing fluctuations. In Embodiment 2 of this application, after expanding the coverage of the negative thermo-optic cladding 41, it is not necessary to strictly distinguish the boundary between the microring and the coupling segment, reducing the manufacturing difficulty.

[0072] It should be noted that in both Embodiment 1 and Embodiment 2, the number of waveguide microrings 61 is one. When the number of waveguide microrings is one, the coupling coefficient between the waveguide microring and the corresponding waveguide arm is usually set to around 0.8. The schemes of Embodiment 1 and Embodiment 2 are also applicable to microring-assisted MZI wavelength division multiplexers with multiple waveguide microrings, i.e., when the number of microring resonators 60 is multiple. The arrangement of multiple waveguide microrings can be referred to in the following embodiments.

[0073] As in this application Figure 5 and 6In the disclosed embodiment three, the structures of the first waveguide arm 51 and the second waveguide arm 52 are the same as in embodiment one, and will not be described again. The difference between embodiment three and embodiment one is that the projection of the negative thermo-optical cladding 41 onto the core layer 30 not only covers the waveguide microring 61, but also the entire first waveguide arm 51 and the entire second waveguide arm 52. Therefore, the specific values ​​of the field effect factors of each waveguide segment and coupling segment of the first and second waveguide arms are also affected by the effective refractive index of the negative thermo-optical cladding, and are different from the specific values ​​in embodiment one, thus also affecting the width and total length of each waveguide segment in the first and second waveguide arms. However, the above requirement still needs to be met: the phase change of the first waveguide arm 51 with temperature is equal to the phase change of the second waveguide arm 52 with temperature, thereby ensuring that the phase difference between the first waveguide arm 51 and the second waveguide arm 52 does not change with temperature.

[0074] In some other embodiments, when the waveguide microring 61 is coupled only to the first waveguide arm 51, the negative thermo-optical cladding 41 can also cover the waveguide microring 61 and the entire first waveguide arm 51 (not shown in the figure); or, the waveguide microring 61 is coupled only to the second waveguide arm 52, and the negative thermo-optical cladding 41 covers the waveguide microring 61 and the entire second waveguide arm 52 (not shown in the figure), so the field effect factor of each waveguide segment has different values ​​in different cases. The scheme of Embodiment 3 is also applicable to microring-assisted MZI wavelength division multiplexers with multiple waveguide microrings, that is, when the number of microring resonators 60 is multiple. The arrangement of multiple waveguide microrings can be referred to in the following embodiments.

[0075] When the negative thermo-optical cladding 41 covers the waveguide arm coupled to the waveguide microring 61 or covers all of the waveguide arm, the negative thermo-optical cladding 41 can compensate for the temperature sensitivity of the positive thermo-optical coefficient material of the covered waveguide arm. This provides greater design freedom for the waveguide width difference, allowing for the selection of smaller width differences to simplify waveguide design. Reducing the waveguide width difference helps achieve lower-loss optical transmission and avoids the problem of increased transmission loss due to unreasonable waveguide size design.

[0076] like Figure 8The fourth embodiment shown differs from the second embodiment in that it employs two microring resonators 60. The first waveguide arm 51 and the second waveguide arm 52 are each coupled to a microring resonator 60. Similar to the second embodiment, the projection of the negative thermo-optical cladding 41 onto the core layer 30 covers both the waveguide microring 61 and the coupling segment coupled to the corresponding waveguide microring 61. Of course, in other embodiments, the projection of the negative thermo-optical cladding 41 onto the core layer 30 may only cover the waveguide microring 61, or it may cover the waveguide microring 61, the entire first waveguide arm 51, and the entire second waveguide arm 52. The structure of the first waveguide arm 51 is the same as in the second embodiment and will not be described again. The difference between the fourth and second embodiments is that the second waveguide arm 52 further includes several fifth waveguide segments 522 with a fifth width W5 and second coupling segments 523 with a sixth width W6. The fourth width W4 is not equal to the fifth width W5, and the sixth width W6 is equal to the fourth width W4 or the fifth width W5, or is not equal to either the fourth width W4 or the fifth width W5 (in other words...). Figure 8 For example, Figure 8 (This illustration shows the case where the sixth width W6 of the second coupling segment 523 is equal to the fourth width W4 of the fourth waveguide segment 521). The fifth total length of several fifth waveguide segments 522 is L5, and the sixth total length of the second coupling segment 523 is L6. Therefore, in this embodiment, the phase change of the second waveguide arm 52 with temperature is the sum of the following three factors: the product of the fourth total length L4 and the equivalent thermo-optical coefficient of the fourth waveguide segment 521, the product of the fifth total length L5 and the equivalent thermo-optical coefficient of the fifth waveguide segment 522, and the product of the sixth total length L6 and the equivalent thermo-optical coefficient of the second coupling segment 523.

[0077] It should be noted that when there are multiple microring resonators 60, the phases of each microring resonator 60 are the same, and each waveguide microring 61 and its coupled segment are covered by a negative thermo-optical cladding layer 41. In the fourth embodiment disclosed in this application, the second cladding layer 40 has a cutout 70 at the position corresponding to each waveguide microring 61 and its coupled segment, and the cutout 70 is filled with a negative thermo-optical material, so that the side of each waveguide microring 61 and its corresponding coupled segment facing away from the first cladding layer 20 is covered by the negative thermo-optical cladding layer 41.

[0078] In various embodiments of this application, when there are multiple microring resonators 60, the coupling coefficients of the multiple microring resonators 60 with their corresponding waveguide arms can be different. Specifically, in this embodiment, the optical path length of the second waveguide arm is greater than that of the first waveguide arm. Therefore, the coupling coefficient of the waveguide microring 61 coupled to the first waveguide arm 51 can be set to approximately 0.95, and the coupling coefficient of the waveguide microring 61 coupled to the second waveguide arm 52 can be set to approximately 0.6.

[0079] When multiple microring resonators 60 are coupled to the same waveguide arm, the waveguide arm also has a corresponding number of coupling segments, specifically as follows: Figure 9 The difference between Embodiment 5 and Embodiment 4 is that this embodiment uses three microring resonators. Two microring resonators 60 are coupled to the first waveguide arm 51, and the other microring resonator 60 is coupled to the second waveguide arm. Therefore, the first waveguide arm 51 has two first coupling segments 513, and the third width W3 of the two first coupling segments 513 can be the same or different. Figure 9 The illustration shows the case where the third width W3 of the two first coupling segments 513 is equal and also equal to the first width W1. Therefore, in this embodiment, the total length of the first coupling segment 513 is the sum of the lengths of the two first coupling segments 513. In some other embodiments, the widths of the two first coupling segments 513 in the first waveguide arm 51 may be different. In this case, the phase change of the first waveguide arm 51 needs to take into account both the phase change and the length of the two first coupling segments 513.

[0080] In Embodiment 5 disclosed in this application, among the three waveguide microrings 61, one of the two waveguide microrings 61 coupled to the first waveguide arm 51 has the largest coupling coefficient, and the other has the smallest coupling coefficient. The coupling coefficient of the waveguide microring 61 coupled to the second waveguide arm 52 is between the two mentioned above.

[0081] Embodiments 4 and 5 respectively employ two and three microring resonators 60. In other embodiments, even more microring resonators 60 may be used. Using multiple microring resonators 60 can significantly improve the filtering effect, especially facilitating flat-top filtering and thus extending the passband bandwidth of the filter. Embodiments of this application also optimize the coupling positions and corresponding coupling coefficients of the multiple microring resonators to reduce the losses and crosstalk of the aforementioned wavelength division multiplexer.

[0082] It is worth mentioning that in the above embodiments, waveguide segments of different widths can be connected by tapered waveguides with gradually changing widths. This arrangement can reduce optical signal loss. Furthermore, in the embodiments of this application, the same tapered waveguide can be used in the first waveguide arm 51 and the second waveguide arm 52. Therefore, the tapered waveguide will not affect its temperature characteristics or other properties, but will only reduce the mode adaptation loss when connecting waveguides of different widths.

[0083] This application also discloses a chip including any of the micro-ring assisted MZI wavelength division multiplexers disclosed above.

[0084] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A micro-ring assisted MZI wavelength division multiplexer, disposed on a substrate (10), wherein the substrate (10) has a first cladding layer (20) and a second cladding layer (40) stacked on it, and a core layer (30) located between the first cladding layer (20) and the second cladding layer (40), wherein the micro-ring assisted MZI wavelength division multiplexer is located in the core layer (30); characterized in that, The microring-assisted MZI wavelength division multiplexer includes a Mach-Zehnder interferometer (50) and at least one microring resonator (60). The Mach-Zehnder interferometer (50) includes a beam splitter (53), a beam combiner (54), and a first waveguide arm (51) and a second waveguide arm (52) arranged at opposite intervals. The first waveguide arm (51) and the second waveguide arm (52) are respectively connected between the beam splitter (53) and the beam combiner (54). The microring resonator (60) includes a waveguide microring (61). At least one waveguide microring (61) is coupled to the side of at least one of the first waveguide arm (51) and the second waveguide arm (52). The phase difference between the first waveguide arm (51) and the second waveguide arm (52) is half the phase of the microring resonator (60). The resonant wavelength spacing of the microring resonator (60) is the same as the channel wavelength spacing of the microring-assisted MZI wavelength division multiplexer. The first cladding layer (20), the core layer (30), and the second cladding layer (40) are all materials with positive thermo-optic coefficients. The second cladding layer (40) has a hollow portion (70) corresponding to the waveguide microring (61). The hollow portion (70) is filled with a material with a negative thermo-optic coefficient to form a negative thermo-optic cladding layer (41). The projection of the negative thermo-optic cladding layer (41) onto the core layer (30) at least covers the waveguide microring (61) to compensate for the temperature drift caused by the core layer (30) and the first cladding layer (20), so that the resonant wavelength of the microring resonator (60) does not change with temperature.

2. The micro-ring assisted MZI wavelength division multiplexer according to claim 1, characterized in that, The negative thermo-optic cladding (41) is configured such that the sum of the product of the field effect factor of the waveguide microring (61) and the thermo-optic coefficient of the waveguide microring (61), the product of the field effect factor of the first cladding (20) and the thermo-optic coefficient of the first cladding (20), and the product of the field effect factor of the negative thermo-optic cladding (41) and the thermo-optic coefficient of the negative thermo-optic cladding (41) is zero.

3. The micro-ring assisted MZI wavelength division multiplexer according to claim 1, characterized in that, The material with a negative thermo-optic coefficient includes any one or more of TiO2, ZnO, magnesium-doped ZnO, PMMA, SU-8, and polystyrene.

4. The micro-ring assisted MZI wavelength division multiplexer according to claim 1, characterized in that, The first waveguide arm (51) and / or the second waveguide arm (52) coupled to the waveguide microring (61) includes a coupling segment coupled to the waveguide microring (61), and the projection of the negative thermo-optical cladding (41) onto the core layer (30) at least covers the waveguide microring (61) and the coupling segment coupled thereto; or, The projection of the negative thermal-optical cladding (41) onto the core layer (30) covers the waveguide microring (61), as well as the first waveguide arm (51) and / or the second waveguide arm (52).

5. The micro-ring assisted MZI wavelength division multiplexer according to claim 1, characterized in that, The number of microring resonators (60) is one, the waveguide microring (61) is coupled to the first waveguide arm (51), and the optical path of the second waveguide arm (52) is greater than that of the first waveguide arm (51).

6. The micro-ring assisted MZI wavelength division multiplexer according to claim 1, characterized in that, The number of microring resonators (60) is multiple, and the phase of each microring resonator (60) is the same; The plurality of microring resonators (60) are respectively coupled to the sides of the first waveguide arm (51) and / or the second waveguide arm (52).

7. The micro-ring assisted MZI wavelength division multiplexer according to claim 6, characterized in that, The coupling coefficients of the multiple microring resonators (60) and their corresponding waveguide arms are different.

8. The micro-ring assisted MZI wavelength division multiplexer according to claim 1, characterized in that, One or both of the first waveguide arm (51) and the second waveguide arm (52) include at least two waveguide segments with different widths, such that the phase difference between the first waveguide arm (51) and the second waveguide arm (52) does not change with temperature within the operating band range of the micro-ring assisted MZI wavelength division multiplexer; the width refers to the width of the cross-section of the waveguide arm.

9. The micro-ring assisted MZI wavelength division multiplexer according to claim 8, characterized in that, The first waveguide arm (51) includes a plurality of first waveguide segments (511) having a first width W1, a plurality of second waveguide segments (512) having a second width W2, and a first coupling segment (513) having a third width W3. The first width W1 is not equal to the second width W2, and the third width W3 is equal to the first width W1 or the second width W2, or is not equal to either the first width W1 or the second width W2. The second waveguide arm (52) includes a fourth waveguide segment (521) having a fourth width W4; The first total length of a plurality of first waveguide segments (511) is L1, the second total length of a plurality of second waveguide segments (512) is L2, the third total length of the first coupling segment (513) is L3, and the fourth total length of the fourth waveguide segment (521) is L4. The total length and width of each waveguide segment are configured such that within the operating band of the micro-ring assisted MZ I wavelength division multiplexer, the phase change of the first waveguide arm (51) with temperature is equal to the phase change of the second waveguide arm (52) with temperature. The phase of the first waveguide arm (51) changes with temperature as a sum of the following three factors: the product of the first total length L1 and the equivalent thermo-optic coefficient of the first waveguide segment (511), the product of the second total length L2 and the equivalent thermo-optic coefficient of the second waveguide segment (512), and the product of the third total length L3 and the equivalent thermo-optic coefficient of the first coupling segment (513). The phase of the second waveguide arm (52) changes with temperature as a product of the fourth total length L4 and the equivalent thermo-optic coefficient of the fourth waveguide segment (521); The equivalent thermo-optic coefficient is the sum of the product of the field effect factor of the corresponding waveguide segment and its thermo-optic coefficient, the product of the field effect factor of the first cladding (20) corresponding to the waveguide segment and its thermo-optic coefficient, and the product of the field effect factor of the second cladding (40) corresponding to the waveguide segment and its thermo-optic coefficient. Waveguides of different widths have different field effect factors.

10. The micro-ring assisted MZI wavelength division multiplexer according to claim 9, characterized in that, The second waveguide arm (52) further includes a plurality of fifth waveguide segments (522) with a fifth width W5 and a second coupling segment (523) with a sixth width W6. The total fifth length of the plurality of fifth waveguide segments (522) is L5, and the total sixth length of the second coupling segment (523) is L6. The fourth width W4 is not equal to the fifth width W5, and the sixth width W6 is equal to the fourth width W4 or the fifth width W5, or is not equal to either the fourth width W4 or the fifth width W5. The phase of the second waveguide arm (52) changes with temperature as a sum of the following three factors: the product of the fourth total length L4 and the equivalent thermo-optic coefficient of the fourth waveguide segment (521), the product of the fifth total length L5 and the equivalent thermo-optic coefficient of the fifth waveguide segment (522), and the product of the sixth total length L6 and the equivalent thermo-optic coefficient of the second coupling segment (523).

11. The micro-ring assisted MZ I wavelength division multiplexer according to claim 9 or 10, characterized in that, Waveguide segments of different widths are connected by tapered waveguides.

12. A chip, characterized in that, Includes the micro-ring assisted MZI wavelength division multiplexer as described in any one of claims 1-11.

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