All-optical wavelength converter and conversion method

Abstract

This application belongs to the field of all-optical signal processing, and specifically discloses an all-optical wavelength converter and a conversion method. The converter includes: a through waveguide and a microring resonator, which together have two coupling regions. The through waveguide, the two coupling regions, and the waveguide section on the microring resonator located between the two coupling regions form an MZI. The design of the MZI-coupled microring resonator satisfies the following conditions to make the resonance peaks of the all-optical wavelength converter exhibit a wide-narrow-wide distribution: The FSR of the MZI is twice that of the microring resonator; the phase difference generated by the pump light introduced from one end of the through waveguide in the upper and lower arms of the MZI is π; when the pump light and the signal light are introduced into one end of the through waveguide, the other end will output the pump light, the signal light, and the idler light to achieve all-optical wavelength conversion; the wavelength difference between the signal light and the pump light is near an odd number of FSRs of the microring resonator. Through this application, during all-optical wavelength conversion, a large conversion bandwidth can be obtained while ensuring a high conversion efficiency.

Description

Technical Field

[0001] This application belongs to the field of all-optical signal processing, and more specifically, relates to an all-optical wavelength converter and a conversion method. Background Art

[0002] All-optical wavelength conversion refers to the technology of directly converting the signal carried at a certain frequency to another frequency of light in the optical domain. Since it directly processes the signal in the optical domain without going through the traditional optical-electric-optical conversion, it has a processing bandwidth far superior to that of electronic devices. All-optical wavelength conversion can be completed through different structures and nonlinear processes on different material platforms. Among many solutions, if a common straight waveguide structure is used for wavelength conversion, although a large conversion bandwidth can be obtained, the system is difficult to integrate and has high power consumption to ensure the conversion efficiency; if solutions such as multi-ring cascading are used, although it is convenient for system integration, it is difficult to balance the conversion bandwidth and conversion efficiency, and the system is not easy to tune. The following are two experimental solutions for wavelength conversion using microrings:

[0003] Technical Document 1: 1 Milliwatt Pumped Error-Free 38 GBaud WavelengthConversion with AlGaAs Microresonators of 1 GHz Intrinsic Linewidth’ 2023 Asia Communications and Photonics Conference / 2023 International Photonics and Optoelectronics Meetings (ACP / POEM), Wuhan, China, 2023, pp. 1 Although the all-optical wavelength conversion with coexistence of conversion efficiency and conversion bandwidth is achieved by using a double-ring structure to control the microring to make the output spectrum of the system present a wide-narrow-wide line shape, the thermal tuning of the double-ring structure is relatively complex. In addition, the high performance demonstrated by the system largely depends on the excellent properties such as high nonlinearity and high power threshold of the aluminum gallium arsenide platform, and it is not compatible with the current Complementary Metal-Oxide-Semiconductor (CMOS) process.

[0004] Technical Document 2: "Broadband Wavelength Conversion Based on Parallel-Coupled Micro-Ring Resonators", IEEE Photonics Technology Letters, vol. 30, no. 17, pp. 1559-1562, 1 Sept. 1, 2018. Although the use of a parallel micro-ring structure based on a silicon-based platform results in a Bragg grating effect to achieve a wide-narrow-wide transmission line shape and realizes an all-optical wavelength conversion function with coexistence of low-power conversion efficiency and conversion bandwidth, it has high requirements for inter-ring thermal tuning and strong out-of-band ripple phenomena.

[0005] Therefore, current all-optical wavelength conversion schemes have problems such as being difficult to tune due to complex systems, incompatibility between conversion efficiency and conversion bandwidth, and still relatively small conversion bandwidth. Summary of the Invention

[0006] Aiming at the defects of the prior art, the purpose of this application is to provide an all-optical wavelength converter and a conversion method, aiming to solve the problems of complex systems that are difficult to tune, incompatibility between conversion efficiency and conversion bandwidth, and still relatively small conversion bandwidth existing in existing all-optical wavelength conversion schemes.

[0007] To achieve the above purpose, in the first aspect, this application provides an all-optical wavelength converter, including: a through waveguide and a micro-ring resonator (Micro Ring Resonator, MRR);

[0008] The through waveguide and the micro-ring resonator have two coupling regions, and the through waveguide, the two coupling regions, and the waveguide section on the micro-ring resonator located in the middle of the two coupling regions form a Mach-Zehnder Interferometer (Mach-Zehnder Interferometer, MZI), and the MZI is coupled with the micro-ring resonator;

[0009] The design of the MZI coupling the micro-ring resonator satisfies the following conditions so that the resonance peaks of the all-optical wavelength converter show a wide-narrow-wide distribution: the free spectral range (Free Spectral Range, FSR) of the MZI is twice that of the micro-ring resonator FSR; the phase difference generated by the pump light incident from one end of the through waveguide on the upper and lower arms of the MZI is π; the pump light wavelength is the wavelength at any narrow resonance peak of the all-optical wavelength converter;

[0010] When pump light and signal light are incident on one end of the through waveguide, pump light, signal light, and idler light will be output at the other end to achieve all-optical wavelength conversion; the wavelength difference between the signal light and the pump light is near an odd number of FSRs of the micro-ring resonator.

[0011] It should be noted that when the FSR of the MZI is twice that of the microring resonator FSR, and the phase difference generated by the pump light in the upper and lower arms of the MZI is π, a set of adjacent interference constructive wavelengths and interference destructive wavelengths of the MZI are simultaneously aligned with a set of adjacent resonant wavelengths of the microring resonator, such that the resonant peaks of the all-optical wavelength converter exhibit a wide-narrow-wide distribution.

[0012] In this application, the wide peak achieved by modulating a single microring resonator using an MZI can have a wider operating bandwidth compared to the wide peaks achieved by modulating microrings using existing microring modulation methods. On this basis, injecting the pump light at the narrow linewidth can ensure the conversion efficiency of the all-optical wavelength converter, and injecting the signal light at the wide linewidth can ensure that the all-optical wavelength converter has a larger conversion bandwidth.

[0013] In a possible implementation, both of the two coupling regions are overcoupled.

[0014] Specifically, both of the two coupling regions being overcoupled can broaden the wide peak of the all-optical wavelength converter even wider, enabling a larger conversion bandwidth. Further, with both of the two coupling regions being overcoupled, combined with the aforementioned wide-narrow-wide resonant peak distribution, it can ensure that the all-optical wavelength converter has a relatively ideal conversion efficiency and a large conversion bandwidth.

[0015] In a possible implementation, the cross-sectional area of the waveguide in the coupling region is less than or equal to the cross-sectional area of the waveguide in the non-coupling region.

[0016] Specifically, the waveguide in the coupling region refers to the two waveguides that are coupled to each other in the two coupling regions, and the waveguide in the non-coupling region refers to the waveguide in the all-optical wavelength converter outside the two coupling regions. The cross-sectional area sizes of the waveguides in the coupling region are the same, and the cross-sectional area sizes of the waveguides in the non-coupling region are the same. The cross-sectional areas of the waveguide in the coupling region and the non-coupling waveguide can be the same or different. By increasing the cross-sectional area of the waveguide in the non-coupling region, waveguide loss can be reduced and the power threshold can be increased to further ensure a large conversion efficiency and a wide conversion bandwidth.

[0017] In a possible implementation, the wavelength that is different from the pump light wavelength by an odd number of FSRs of the microring resonator is the central wavelength of the signal light, and the design of the MZI-coupled microring resonator satisfies the following conditions: the wavelength conversion efficiency at the central wavelength of the signal light is not less than half of the maximum wavelength conversion efficiency within the corresponding wide resonant peak;

[0018] and / or with the central wavelength of the signal light as a reference, the difference between the signal light wavelength and the central wavelength of the signal light is within half of the 3dB conversion bandwidth of the all-optical wavelength converter;

[0019] Preferably, the wavelength of the signal light is different from the pump light wavelength by around one FSR of the microring resonator.

[0020] It can be understood that generally, the bandwidth of the above-mentioned all-optical wavelength converter is the 3dB conversion bandwidth, and the above-mentioned 3dB conversion bandwidth is: the signal optical wavelength range from when the conversion efficiency is maximum to when it drops to half. Specifically, the wavelength conversion efficiency at the center wavelength of the signal light is not less than half of the maximum conversion efficiency within the corresponding wide resonance peak. The purpose is to make the 3dB conversion bandwidth of the all-optical wavelength converter include the above-mentioned signal light center wavelength to ensure that the above-mentioned conversion bandwidth is wide enough. Among them, the wavelength of the signal light is the wavelength within half of the 3dB conversion bandwidth on both the left and right sides based on the above-mentioned signal light center wavelength.

[0021] Those skilled in the art can understand that near an odd number of FSRs where the signal optical wavelength differs from the pump optical wavelength, it corresponds to the wide peak of the all-optical wavelength converter, and a large conversion bandwidth can be achieved correspondingly. As the distance between the signal optical wavelength and the pump optical wavelength increases, the corresponding conversion efficiency may decrease. Therefore, those skilled in the art can select appropriate signal optical wavelengths and bandwidths to meet the corresponding all-optical wavelength conversion requirements.

[0022] In a possible implementation manner, the coupling coefficient of each coupling region is within a preset range; and / or the two coupled waveguide segments in each coupling region are parallel to each other; the parallelism is in a straight-line parallel or a curved parallel manner.

[0023] It should be noted that the parameter design and shape design of the above-mentioned coupling regions are all to make the two coupling regions over-coupled.

[0024] In a possible implementation manner, the micro-ring resonator is an annular micro-ring resonator or a racetrack-shaped micro-ring resonator; when it is an annular micro-ring resonator, the two coupled waveguide segments in each coupling region are coupled in a curved parallel manner; when it is a racetrack-shaped micro-ring resonator, it includes two straight waveguide segments and two curved waveguide segments. At this time, the two regions on the through waveguide are respectively coupled to the partial regions on the two straight waveguide segments to form two coupling regions.

[0025] In a possible implementation manner, the equivalent coupling coefficient of the MZI-coupled micro-ring resonator is:

[0026]

[0027] where k 1, k 2 are respectively the coupling coefficients of the two coupling regions, , i = 1, 2; , and are the phase changes of the incident light on the upper and lower arms of the MZI respectively; the incident light is the pump light or the signal light; , , is the waveguide loss of the all-optical wavelength converter, and are the waveguide lengths of the two arms of the MZI respectively;

[0028] And / or, on the basis that the resonance peak of the all-optical wavelength converter presents a wide-narrow-wide distribution and the two coupling regions are over-coupled, by adjusting k 1, k 2, control the equivalent coupling coefficients of different incident lights in the MZI coupled microring resonator, so that the pump light works in the critical coupling state in the all-optical wavelength converter, and the signal light and the idler light work in the over-coupled state in the all-optical wavelength converter.

[0029] In a possible implementation manner, the conversion efficiency of the all-optical wavelength converter for converting the signal light and the pump light into the idler light is:

[0030]

[0031] Wherein, is the nonlinear coefficient, is the optical power of the pump light, is the field enhancement of the pump light in the upper arm of the MZI, is the field enhancement of the signal light in the upper arm of the MZI, is the field enhancement of the idler light in the upper arm of the MZI, is the field enhancement of the pump light in the lower arm of the MZI, is the field enhancement of the signal light in the lower arm of the MZI, is the field enhancement of the idler light in the lower arm of the MZI, is the field enhancement of the pump light in the waveguide section of the microring resonator other than the above-mentioned lower arm, is the field enhancement of the signal light in the waveguide section of the microring resonator other than the above-mentioned lower arm, is the field enhancement of the idler light in the waveguide section of the microring resonator other than the above-mentioned lower arm, and the superscript represents conjugate, is the effective length of the upper arm of the MZI, is the effective length of the lower arm of the MZI, is the effective length of the waveguide section of the microring resonator other than the above-mentioned lower arm, , i = 1, 2, 3, , are the propagation constants of the pump light, the signal light, and the idler light respectively, is the waveguide loss of the all-optical wavelength converter, , is the waveguide section length of the microring resonator other than the above-mentioned lower arm, is the phase change of the idler light in the upper arm of the MZI, is the phase change of the idler light in the lower arm of the MZI, is the phase change of the idler light in the waveguide section of the microring resonator except the lower arm mentioned above.

[0032] In a second aspect, the present application provides an all-optical wavelength conversion method, comprising:

[0033] Controlling the straight waveguide and the microring resonant cavity to have two coupling regions, so that the straight waveguide, the two coupling regions and the waveguide section located between the two coupling regions on the microring resonant cavity form an MZI, and the MZI is coupled to the microring resonant cavity;

[0034] The FSR of the MZI is controlled to be twice the FSR of the microring resonant cavity; and the phase difference generated by the pump light introduced from one end of the straight waveguide in the upper and lower arms of the MZI is controlled to be π, so that the resonance peak of the all-optical wavelength converter presents a wide-narrow-wide distribution; the wavelength of the pump light is the wavelength at any narrow resonance peak of the all-optical wavelength converter;

[0035] When pump light and signal light are introduced into one end of the straight waveguide, the other end thereof outputs pump light, signal light and idler light to realize all-optical wavelength conversion; the wavelength of the signal light differs from that of the pump light by an odd number of FSRs of the microring resonator.

[0036] In a possible implementation, the microring resonant cavity is a ring-shaped microring resonant cavity or a racetrack-shaped microring resonant cavity; when it is a ring-shaped microring resonant cavity, the two coupled waveguide segments in each coupling region are curved and parallel coupled; when it is a racetrack-shaped microring resonant cavity, it includes two straight waveguide segments and two curved waveguide segments, and at this time, the two regions on the straight waveguide are respectively coupled with partial regions on the two straight waveguide segments to form two coupling regions.

[0037] In a possible implementation, on the basis that the resonance peak of the all-optical wavelength converter presents a wide-narrow-wide distribution and the two coupling regions are over-coupled, the equivalent coupling coefficient of different incident lights in the MZI coupled microring resonant cavity is controlled by adjusting the coupling coefficients of the two coupling regions, so that the pump light works in a critical coupling state in the all-optical wavelength converter, and the signal light and the idler light work in an over-coupled state in the all-optical wavelength converter.

[0038] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art:

[0039] The present application provides an all-optical wavelength converter and a conversion method. By using an MZI to control a microring, the FSR of the MZI is controlled to be twice that of the microring resonator, and the phase difference generated by the pump light in the upper and lower arms of the MZI is π. One set of adjacent constructive interference wavelengths and destructive interference wavelengths of the MZI are aligned with one set of adjacent resonant wavelengths of the microring resonator at the same time, so that the system spectral line exhibits a wide-narrow-wide line shape. The wide peak realized by using an MZI to modulate a single microring in the present application can have a wider working bandwidth compared with the wide peak realized by the existing microring control of microrings. On this basis, a pump light is injected at the narrow linewidth, and a signal light is injected at the wide linewidth. By controlling the pump light to operate in a critical coupling state in the all-optical wavelength converter and the signal light and the idler light to operate in an over-coupling state in the all-optical wavelength converter, a large conversion bandwidth can be achieved while ensuring a high conversion efficiency, which is expected to promote the realization of high-speed all-optical signal processing.

[0040] The present application provides an all-optical wavelength converter and a conversion method. By using an MZI to couple and control a microring, the all-optical wavelength conversion system that requires multi-ring coupling tuning is simplified. The functions of high-speed wavelength conversion and non-linear optical signal processing are realized in the MZI coupling of a single microring. Compared with the previous scheme of using multi-ring coupling tuning of the linewidth to achieve a large range of wavelength conversion functions, this scheme is more flexible in controlling the linewidth and has a larger realized bandwidth. This makes the entire all-optical signal processing system simpler and easier to integrate on a chip.

[0041] The present application provides an all-optical wavelength converter and a conversion method. By using an MZI to control a microring, this control method is simpler than the existing method of using a microring to control a microring. It can achieve a larger conversion bandwidth and can stably ensure that the system resonant peak exhibits a wide-narrow-wide line shape without adjusting the coupling state of the electrodes. The present application uses the MZI-coupled microring structure to periodically control the linewidth of the system, which can ensure a high conversion efficiency while obtaining a large conversion bandwidth, has a simpler structure, a larger process tolerance, and is compatible with the CMOS process. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a simplified diagram of the all-optical wavelength converter provided by an embodiment of the present application;

[0043] Figure 2 is the first structural diagram of the all-optical wavelength converter provided by an embodiment of the present application;

[0044] Figure 3 is the second structural diagram of the all-optical wavelength converter provided by an embodiment of the present application;

[0045] Figure 4 is the transmission spectrum diagram of the all-optical wavelength converter provided by an embodiment of the present application;

[0046] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, where:

[0047] 100 is a straight waveguide, and 200 is a microring resonator. Detailed implementation manners

[0048] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0049] The embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

[0050] The present application belongs to the field of on-chip integrated all-optical signal processing. By using an MZI to regulate the linewidth of an MRR, the problem that it is impossible to simultaneously take into account the conversion bandwidth and conversion efficiency when using a microring to achieve all-optical wavelength conversion is solved. Therefore, the all-optical wavelength converter provided by the present application can also be simply referred to as an MZI-MRR. By using an MZI to regulate the microring, the system spectrum line presents a wide-narrow-wide line shape. The pump light is injected at the narrow linewidth, and the signal light is injected at the wide linewidth, which can ensure a high conversion efficiency while obtaining a large conversion bandwidth, and is expected to promote the realization of high-speed all-optical signal processing. The present application simplifies the all-optical wavelength conversion system that requires multi-ring coupling tuning.

[0051] Figure 1 is a simplified diagram of the all-optical wavelength converter provided by the embodiment of the present application; as Figure 1 shown, the straight waveguide 100 and the microring resonator 200 have two coupling regions, and the coupling coefficients of the two coupling regions are k1 and k2 respectively; further, the straight waveguide, the two coupling regions and the waveguide section L2 on the microring resonator located in the middle of the two coupling regions form an MZI. The upper and lower arms of the MZI are L1 and L2 respectively, and the upper arm L1 is a part of the straight waveguide 100;

[0052] Specifically, the design of the MZI and the microring resonator 200 satisfies the following conditions to make the resonance peaks of the all-optical wavelength converter present a wide-narrow-wide distribution: the FSR of the MZI is twice that of the microring resonator FSR; the phase difference generated by the pump light in the upper and lower arms of the MZI when the pump light is injected from one end of the straight waveguide is π; the pump light wavelength is the wavelength at any narrow resonance peak of the all-optical wavelength converter;

[0053] When pump light and signal light are injected into one end of the straight waveguide, pump light, signal light and idler light will be output at the other end to achieve all-optical wavelength conversion; the wavelength difference between the signal light and the pump light is near an odd number of FSRs of the microring resonator.

[0054] Specifically, the wavelength that is an odd number of FSRs away from the pump light wavelength in the microring resonator is the central wavelength of the signal light. The design of the MZI-coupled microring resonator satisfies the following conditions: the wavelength conversion efficiency at the central wavelength of the signal light is not less than half of the maximum wavelength conversion efficiency within the corresponding wide resonance peak; based on the central wavelength of the signal light, the difference between the signal light wavelength and the central wavelength of the signal light is within half of the 3dB conversion bandwidth of the all-optical wavelength converter.

[0055] It can be understood that usually the bandwidth of the above all-optical wavelength converter is the 3dB conversion bandwidth, and the above 3dB conversion bandwidth is: the signal light wavelength range from when the conversion efficiency is maximum to when the conversion efficiency drops to half. Specifically, the wavelength conversion efficiency at the central wavelength of the signal light is not less than half of the maximum conversion efficiency within the corresponding wide resonance peak. The purpose is to make the 3dB conversion bandwidth of the all-optical wavelength converter include the above central wavelength of the signal light to ensure that the above conversion bandwidth is wide enough. Among them, the wavelength of the signal light is the wavelength within half of the 3dB conversion bandwidth on both the left and right sides based on the above central wavelength of the signal light.

[0056] It should be noted that when the FSR of the MZI is twice the FSR of the microring resonator, and the phase difference generated by the pump light in the upper and lower arms of the MZI is π, a set of adjacent constructive interference wavelengths and destructive interference wavelengths of the MZI are simultaneously aligned with a set of adjacent resonant wavelengths of the microring resonator, making the resonance peaks of the all-optical wavelength converter exhibit a wide-narrow-wide distribution. The wide peak realized by using the MZI to modulate a single microring resonator in this application can have a wider working bandwidth compared to the wide peak realized by the existing microring regulating microring. On this basis, injecting the pump light at the narrow linewidth and injecting the signal light at the wide linewidth can ensure that the all-optical wavelength converter has a high conversion efficiency and a large conversion bandwidth.

[0057] Preferably, both coupling regions are overcoupled. Specifically, both coupling regions being overcoupled is to broaden the wide resonance peak wider to achieve a larger conversion bandwidth; further, with both coupling regions overcoupled, combined with the aforementioned wide-narrow-wide resonance peak distribution, it can ensure that the all-optical wavelength converter has a relatively ideal conversion efficiency and a large conversion bandwidth.

[0058] Further preferably, the cross-sectional area of the waveguide in the coupling region is less than or equal to the cross-sectional area of the waveguide in the non-coupling region.

[0059] Specifically, the waveguide in the coupling region refers to the two sections of waveguides that are coupled to each other in the two coupling regions, and the waveguide in the non-coupling region refers to the waveguides outside the two coupling regions in the all-optical wavelength converter. The cross-sectional area sizes of the waveguides in the coupling region are the same, and the cross-sectional area sizes of the waveguides in the non-coupling region are the same. The cross-sectional areas of the waveguide in the coupling region and the non-coupling waveguide can be the same or different. By increasing the cross-sectional area of the waveguide in the non-coupling region, the waveguide loss can be reduced and the power threshold can be increased to further ensure a large conversion efficiency and a wide conversion bandwidth.

[0060] In one example, to ensure that the above two coupling regions are overcoupled, the coupling coefficient of each coupling region is within a preset range, neither too small nor too large, and is adjusted to match the parameters of the device so that the device achieves the predetermined performance; further, the two coupled waveguide segments in each coupling region can be controlled to be parallel to each other; the parallelism can be linear parallelism or curved parallelism.

[0061] In some embodiments, the above micro-ring resonator 200 is an annular micro-ring resonator (circular micro-ring) or a racetrack micro-ring resonator; when it is an annular micro-ring resonator, as Figure 2 shown, the two coupled waveguide segments in each coupling region are coupled in a curved parallel manner, that is, pulley-type coupling; when it is a racetrack micro-ring resonator, as Figure 3 shown, it includes two straight waveguide segments and two curved waveguide segments. At this time, the two regions on the through waveguide are respectively coupled to partial regions on the two straight waveguide segments, that is, a directional coupler, forming two coupling regions.

[0062] Figure 2 is the first structural diagram of the all-optical wavelength converter provided by the embodiment of the present application; as Figure 2 shown, the coupling region is pulley-type coupling, and the internal micro-ring is a circular ring cavity. In some scenarios, the above all-optical wavelength converter is applicable to the case of a relatively large coupling coefficient.

[0063] Figure 3 is the second structural diagram of the all-optical wavelength converter provided by the embodiment of the present application; as Figure 3 shown, the coupling region is a directional coupler, and the internal micro-ring is a racetrack micro-ring. In some scenarios, the above all-optical wavelength converter is applicable to the case where a more precise coupling coefficient is required and is suitable for different coupling coefficient designs. Compared with Figure 2 Figure 3 the device design given is easier and the process tolerance is larger.

[0064] Further, taking Figure 3 as an example, this example is fabricated based on a SOI platform compatible with CMOS technology, and the waveguide cross-sectional area is 500nm×220nm. The through waveguide and the micro-ring have two coupling regions. According to the order before and after coupling, the coupling coefficients at the two coupling regions are denoted as k1 and k2 respectively. This structure can be mainly divided into two parts. The first part is an MZI structure composed of L1, L2, two coupling regions, and input and output ports. The light input by the laser is transmitted along the L1 and L2 segments respectively after passing through the first coupling region, and interference occurs after passing through the second coupling region. The length difference between the upper and lower arms of the MZI determines the transmission situation of the light at the output port; the second part is a single-ring structure composed of L2 and L3. At this time, the MZI structure can be regarded as an equivalent coupling region.

[0065] In this structure, since relatively large coupling coefficients are required for both coupling regions, the coupling regions are designed to be racetrack-shaped. The total length of a single ring can be in the range of 200 to 500 microns. To achieve the wide-narrow-wide line shape, it is also necessary to ensure that the FSR of the MZI structure is twice that of the single-ring structure and the single ring resonates with the pump light. In addition, according to the derivation, the equivalent coupling coefficient of the MZI-MRR structure is , where . By designing and controlling the phase difference generated by the pump light in the upper and lower arms of the MZI to be , and the phase difference generated by the signal light and the idler light in the upper and lower arms of the MZI to be or so (the wavelength difference between the signal light and the pump light is about an odd number of FSRs of the microring), the pump light can be made to operate at critical coupling, and the signal light and the idler light can be made to operate at over-coupling, while ensuring a high conversion efficiency while obtaining a large conversion bandwidth.

[0066] The transmission spectrum described above is as Figure 4 shown. By using the MZI to regulate the microring, the resonant peaks of the microring can be periodically tuned to the wide-narrow-wide line shape. Among them, the larger the extinction ratio, the closer it is to critical coupling, and the greater the field enhancement of the light at the corresponding wavelength inside the ring. When resonance occurs inside the ring, a large power enhancement can be obtained, and the conversion efficiency is related to the power inside the ring. As Figure 4 shown, at a wavelength of 1550 nm, the transmittance is about -12 dB. Taking 0 dB as the reference, the extinction ratio is 12 dB. In the experiment, it can be considered that the light at this wavelength is approximately at critical coupling with respect to the microring. Secondly, the light wavelength at the wide resonant peak is in an over-coupled state with respect to the microring. This sacrifices the field enhancement inside the ring to a certain extent, but also makes the variation trend of the field enhancement received by light in a larger range slow. Therefore, the conversion efficiency decreases slowly within a certain range, and the 3 dB conversion bandwidth is larger. In addition, although some field enhancement is sacrificed at the wide peak, there is still field enhancement that can enhance the signal light, so a relatively ideal conversion efficiency (meeting the required conversion efficiency) can be ensured, and at the same time, a large conversion bandwidth is achieved.

[0067] It should be noted that controlling the phase difference generated by the pump light in the upper and lower arms of the MZI to be can, firstly, align the spectra of the MZI and the microring to obtain wide-narrow-wide resonant peaks, and can also more easily regulate the pump light at critical coupling; similarly, controlling the wavelength difference between the signal light and the pump light to be near an odd number of FSRs of the microring (preferably near 1 FSR of the microring), naturally the phase difference generated by the signal light and the idler light in the upper and lower arms of the MZI is or so, which can align the spectra of the MZI and the microring and can also more easily regulate the signal light and the idler light at over-coupling.

[0068] Wavelength conversion in the above device is completed in two steps. In the first step, the pump light is scanned from the blue-detuned side (short wavelength) to the red-detuned side (long wavelength) of the desired pump narrow peak until the optical power significantly decreases, and the cold cavity resonance wavelength is measured. In the second step, the signal light input wavelength is set near an odd number of FSRs away from the pump light cold cavity wavelength, and the idler light is generated in the micro-ring and the upper arm of the MZI.

[0069] In Example 1, limited by two-photon absorption and free carrier effects, there is an upper limit to the optical power in the silicon waveguide. By designing the cross-sectional area of the waveguide at the uncoupled location (such as the waveguide outside the dashed box in Figure 2 and Figure 3 ) to be 1000nm×220nm and the cross-section of the waveguide at the coupling location to be 500nm×220nm, the loss can be effectively reduced and the power threshold can be increased to achieve the effects of reducing power consumption, improving conversion efficiency, and further expanding the conversion bandwidth.

[0070] According to the derivation, the conversion efficiency formula for this structure is as follows:

[0071] Among them, is the field enhancement of the pump light in the L1 section, is the field enhancement of the signal light in the L1 section, is the field enhancement of the idler light in the L1 section, V and W respectively represent the L2 and L3 sections. Specifically, is the output idler light power, is the input signal light power, is the nonlinear coefficient, is the pump light power, is the field enhancement of the pump light in the upper arm of the MZI, is the field enhancement of the signal light in the upper arm of the MZI, is the field enhancement of the idler light in the upper arm of the MZI, is the field enhancement of the pump light in the lower arm of the MZI, is the field enhancement of the signal light in the lower arm of the MZI, is the field enhancement of the idler light in the lower arm of the MZI, is the field enhancement of the pump light in the waveguide section of the micro-ring resonator other than the above lower arm, is the field enhancement of the signal light in the waveguide section of the micro-ring resonator other than the above lower arm, is the field enhancement of the idler light in the waveguide section of the micro-ring resonator other than the above lower arm, and the superscript represents the conjugate, is the effective length of the upper arm of the MZI, is the effective length of the lower arm of the MZI, is the effective length of the waveguide section of the micro-ring resonator other than the above lower arm, ,i = 1, 2, 3, , are the propagation constants of the pump light, signal light, and idler light respectively. is the waveguide loss of the all-optical wavelength converter. , is the length of the waveguide section in the microring resonator other than the above-mentioned lower arm. is the phase change of the idler light in the upper arm of the MZI. is the phase change of the idler light in the lower arm of the MZI. is the phase change of the idler light in the waveguide section in the microring resonator other than the above-mentioned lower arm.

[0072] In this application, by using the MZI to control the linewidth of the microring, an all-optical wavelength conversion function with stable and easy tunability, a larger conversion bandwidth, and a high conversion efficiency can be achieved.

[0073] It should be understood that expressions such as "including" and "may include" that can be used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "including" and / or "having" can be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or a combination thereof, but cannot be interpreted as excluding the existence or possibility of addition of one or more other characteristics, numbers, operations, constituent elements, components, or a combination thereof.

[0074] In addition, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" can include A, can include B, or can include both A and B.

[0075] In the description of the embodiments of this application, it should be noted that unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the two are connected and the relative positional relationship after connection remains unchanged. "Rotational connection" means that the two are connected and can rotate relative to each other after connection. "Sliding connection" means that the two are connected and can slide relative to each other after connection. The orientation terms mentioned in the embodiments of this application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only references to the direction of the drawings. Therefore, the orientation terms used are for better and clearer description and understanding of the embodiments of this application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the embodiments of this application.

[0076] In addition, in the embodiments of the present application, mathematical concepts such as symmetry, equality, parallelism, and perpendicularity are mentioned. These definitions are all based on the current technological level, rather than the absolutely strict definitions in the mathematical sense. A small deviation is allowed, and being approximately symmetric, approximately equal, approximately parallel, approximately perpendicular, etc. are all acceptable. For example, when it is stated that A is parallel to B, it means that A and B are parallel or approximately parallel, and the included angle between A and B can be between 0 degrees and 10 degrees. When it is stated that A is perpendicular to B, it means that A and B are perpendicular or approximately perpendicular, and the included angle between A and B can be between 80 degrees and 100 degrees.

[0077] As described above, the above are only the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An all-optical wavelength converter, characterized in that, Comprising: A straight waveguide and a microring resonator; The straight waveguide and the microring resonator have two coupling regions. The straight waveguide, the two coupling regions, and the waveguide section of the microring resonator located between the two coupling regions form a Mach-Zehnder interferometer (MZI), and the MZI is coupled to the microring resonator; The design of the MZI coupling the microring resonator satisfies the following conditions so that the resonance peaks of the all-optical wavelength converter exhibit a wide-narrow-wide distribution: The free spectral range (FSR) of the MZI is twice that of the microring resonator FSR; The phase difference generated by the pump light incident from one end of the straight waveguide on the upper and lower arms of the MZI is π; The wavelength of the pump light is the wavelength at any narrow resonance peak of the all-optical wavelength converter; When pump light and signal light are incident on one end of the straight waveguide, pump light, signal light, and idler light will be output at the other end to achieve all-optical wavelength conversion; The wavelength difference between the signal light and the pump light is near an odd number of FSRs of the microring resonator.

2. The all-optical wavelength converter according to claim 1, wherein Both of the two coupling regions are over-coupled.

3. The all-optical wavelength converter according to claim 1, wherein The cross-sectional area of the waveguide in the coupling region is less than or equal to the cross-sectional area of the waveguide in the non-coupling region.

4. The all-optical wavelength converter according to claim 1, wherein The wavelength that differs from the pump light wavelength by an odd number of FSRs of the microring resonator is the central wavelength of the signal light. The design of the MZI coupling the microring resonator satisfies the following conditions: The wavelength conversion efficiency at the central wavelength of the signal light is not less than half of the maximum wavelength conversion efficiency within the corresponding wide resonance peak; And / or with the central wavelength of the signal light as a reference, the wavelength difference between the signal light and the central wavelength of the signal light is within half of the 3dB conversion bandwidth of the all-optical wavelength converter.

5. The all-optical wavelength converter according to claim 2, wherein The coupling coefficient of each coupling region is within a preset range; and / or the two coupled waveguide sections in each coupling region are parallel to each other; The parallelism is in a straight line or a curved shape.

6. The all-optical wavelength converter according to claim 1, 2 or 5, characterized in that The microring resonator is an annular microring resonator or a racetrack-shaped microring resonator; When it is an annular microring resonator, the two coupled waveguide sections in each coupling region are coupled in a curved parallel manner; When it is a racetrack-shaped microring resonator, it includes two straight waveguide sections and two curved waveguide sections. At this time, two regions on the straight waveguide are respectively coupled to partial regions on the two straight waveguide sections to form two coupling regions.

7. The all-optical wavelength converter according to any one of claims 1 to 5, characterized in that The equivalent coupling coefficient of the MZI-coupled microring resonator is as follows: Among them, k 1, k 2 are the coupling coefficients of two coupling regions, , i = 1, 2; , and are the phase changes of the incident light in the upper and lower arms of the MZI respectively; the incident light is pump light or signal light; , , is the waveguide loss of the all-optical wavelength converter, and are the waveguide lengths of the two arms of the MZI respectively; And / or, by adjusting k 1、 k 2, controlling the equivalent coupling coefficients of different incident lights in the MZI coupled microring resonator, so that the pump light works in the critical coupling state in the all-optical wavelength converter, and the signal light and the idler light work in the over-coupling state in the all-optical wavelength converter.

8. A method for all-optical wavelength conversion, characterized in that, Comprising: Controlling the straight waveguide and the microring resonator to have two coupling regions so that the straight waveguide, the two coupling regions, and the waveguide section of the microring resonator located between the two coupling regions form a Mach-Zehnder interferometer (MZI), and the MZI is coupled to the microring resonator; Controlling the free spectral range (FSR) of the MZI to be twice that of the microring resonator FSR; and controlling the phase difference generated by the pump light incident from one end of the straight waveguide on the upper and lower arms of the MZI to be π so that the resonance peaks of the all-optical wavelength converter exhibit a wide-narrow-wide distribution; The wavelength of the pump light is the wavelength at any narrow resonance peak of the all-optical wavelength converter; When pump light and signal light are incident on one end of the straight waveguide, pump light, signal light, and idler light will be output at the other end to achieve all-optical wavelength conversion; The wavelength difference between the signal light and the pump light is near an odd number of FSRs of the microring resonator.

9. The all-optical wavelength conversion method according to claim 8, wherein The micro-ring resonator is a ring-shaped micro-ring resonator or a racetrack-shaped micro-ring resonator; when it is a ring-shaped micro-ring resonator, the two coupled waveguide segments in each coupling region are in curved parallel coupling; when it is a racetrack-shaped micro-ring resonator, it includes two straight waveguide segments and two curved waveguide segments. At this time, two regions on the through waveguide are respectively coupled with partial regions on the two straight waveguide segments to form two coupling regions.

10. The all-optical wavelength conversion method according to claim 8, characterized in that, By adjusting the coupling coefficients of the two coupling regions, the equivalent coupling coefficients of different incident lights in the MZI-coupled micro-ring resonator are controlled, so that the pump light operates in a critical coupling state in the all-optical wavelength converter, and the signal light and the idler light operate in an over-coupling state in the all-optical wavelength converter.

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