All-optical wavelength converter and conversion method

Abstract

The invention belongs to the field of all-optical signal processing, and particularly discloses an all-optical wavelength converter and a conversion method, the converter comprises a straight-through waveguide and a micro-ring resonant cavity, the converter is provided with two coupling areas, and the straight-through waveguide, the two coupling areas and a waveguide section, located between the two coupling areas, on the micro-ring resonant cavity form an MZI; the design of the MZI coupled micro-ring resonant cavity meets the following conditions: the resonance peak of the all-optical wavelength converter is in wide-narrow-wide distribution: the FSR of the MZI is twice of the FSR of the micro-ring resonant cavity; the phase difference generated by the pump light introduced from one end of the straight-through waveguide on the upper and lower arms of the MZI is pi; when pump light and signal light are introduced into one end of the straight-through waveguide, the other end of the straight-through waveguide outputs the pump light, the signal light and idler frequency light so as to achieve all-optical wavelength conversion. The difference between the wavelength of the signal light and the wavelength of the pump light is near the odd number of FSRs of the micro-ring resonant cavity. According to the invention, when all-optical wavelength conversion is carried out, a large conversion bandwidth can be obtained while relatively high conversion efficiency is ensured.

Description

Technical Field

[0001] The present 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 a signal carried at a certain frequency to another frequency in the optical domain. Since it processes the signal directly in the optical domain and does not require traditional optical-electrical-optical conversion, it has a processing bandwidth far superior to that of electronic devices. All-optical wavelength conversion can be accomplished on different material platforms through different structures and nonlinear processes. Among many schemes, if an ordinary straight waveguide structure is used for wavelength conversion, although a large conversion bandwidth can be obtained, in order to ensure the conversion efficiency, the system will be difficult to integrate and the power consumption will be high; if a multi-ring cascade solution is used, although it is convenient for system integration, the conversion bandwidth and conversion efficiency are difficult to be compatible and the system is not easy to tune. The following are two experimental schemes for wavelength conversion through microrings: 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 dual-ring structure is used to regulate the micro-ring so that the system output spectrum presents a wide-narrow-wide line shape, achieving all-optical wavelength conversion with coexistence of conversion efficiency and conversion bandwidth, the thermal tuning of the dual-ring structure is relatively complicated. In addition, the high performance demonstrated by the system depends largely on the excellent performance of the AlGaAs platform, such as high nonlinearity and high power threshold, and is incompatible with the current complementary metal oxide semiconductor (CMOS) process.

[0003] Technical Literature 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 Bragg grating effect caused by the parallel micro-ring structure based on the silicon-based platform realizes a wide-narrow-wide transmission line shape and achieves the all-optical wavelength conversion function with coexistence of conversion efficiency and conversion bandwidth under low power consumption, it has high requirements for inter-ring thermal tuning and strong out-of-band ripple phenomenon.

[0004] Therefore, the current all-optical wavelength conversion solutions have problems such as complex and difficult to tune systems, poor compatibility between conversion efficiency and conversion bandwidth, and relatively small conversion bandwidth. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of the present application is to provide an all-optical wavelength converter and a conversion method, aiming to solve the problems of the existing all-optical wavelength conversion scheme, such as the system is complex and difficult to tune, the conversion efficiency and conversion bandwidth are difficult to be compatible, and the conversion bandwidth is still small.

[0006] To achieve the above objectives, in a first aspect, the present application provides an all-optical wavelength converter, comprising: a straight waveguide and a micro ring resonator (Micro Ring Resonator, MRR); The straight waveguide and the micro-ring resonant cavity have two coupling regions, the straight waveguide and the two coupling regions and the waveguide section located between the two coupling regions on the micro-ring resonant cavity form a Mach-Zehnder Interferometer (MZI), and the MZI is coupled with the micro-ring resonant cavity; The design of the MZI-coupled microring resonant cavity satisfies the following conditions so that the resonance peak of the all-optical wavelength converter presents a wide-narrow-wide distribution: the free spectral range (FSR) of the MZI is twice the FSR of the microring resonant cavity; 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 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 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.

[0007] It should be noted that when the FSR of the MZI is twice the FSR of the microring resonant cavity, and the phase difference generated by the pump light in the upper and lower arms of the MZI is π, a group of adjacent interference phase growth wavelengths and interference destructive wavelengths of the MZI are simultaneously aligned with a group of adjacent resonant wavelengths of the microring resonant cavity, so that the resonant peaks of the all-optical wavelength converter are distributed in a wide-narrow-wide manner.

[0008] In the present application, the wide peak achieved by modulating a single microring resonant cavity using MZI can have a wider working bandwidth than the wide peak achieved by the existing microring regulation microring. On this basis, pump light is injected at a narrow line width to ensure the conversion efficiency of the all-optical wavelength converter, and signal light is injected at a wide line width to ensure that the all-optical wavelength converter has a larger conversion bandwidth.

[0009] In a possible implementation manner, the two coupling regions are both overcoupled.

[0010] Specifically, overcoupling of the two coupling regions can make the broad peak of the all-optical wavelength converter wider, and can achieve a larger conversion bandwidth; further, overcoupling of the two coupling regions, combined with the aforementioned wide-narrow-wide resonance peak distribution, can ensure that the all-optical wavelength converter has a relatively ideal conversion efficiency and a large conversion bandwidth.

[0011] In a possible implementation manner, a cross-sectional area of ​​the waveguide in the coupling region is smaller than or equal to a cross-sectional area of ​​the waveguide in the non-coupling region.

[0012] Specifically, the waveguide in the coupling region refers to 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 waveguide outside the two coupling regions in the all-optical wavelength converter. The cross-sectional area size of the waveguide in the coupling region is the same, and the cross-sectional area size of the waveguide in the non-coupling region is the same. The cross-sectional area 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, so as to further ensure a high conversion efficiency and a wide conversion bandwidth.

[0013] In a possible implementation, the wavelength at the microring resonant cavity that differs from the pump light wavelength by an odd number of FSRs is the central wavelength of the signal light, and the design of the MZI-coupled microring resonant cavity 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 in the corresponding broad resonance peak; and / or taking the central wavelength of the signal light as a reference, the difference between the wavelength of the signal light and the central wavelength of the signal light is within half a 3dB conversion bandwidth of the all-optical wavelength converter; Preferably, the wavelength of the signal light differs from the wavelength of the pump light by approximately one FSR of the microring resonator.

[0014] It can be understood that the bandwidth of the all-optical wavelength converter is usually the 3dB conversion bandwidth, which is the signal light wavelength range from the maximum conversion efficiency to the time when the conversion efficiency 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 in the corresponding wide resonance peak, and the purpose is to make the 3dB conversion bandwidth of the all-optical wavelength converter include the center wavelength of the signal light to ensure that the conversion bandwidth is wide enough. The wavelength of the signal light is the wavelength within half of the 3dB conversion bandwidth on the left and right sides, based on the center wavelength of the signal light.

[0015] It can be understood by those skilled in the art that, when the wavelength of the signal light differs from the wavelength of the pump light by an odd number of FSRs, it corresponds to the broad peak of the all-optical wavelength converter, and a large conversion bandwidth can be achieved accordingly. As the distance between the wavelength of the signal light and the wavelength of the pump light increases, the corresponding conversion efficiency may decrease, so those skilled in the art can select a suitable signal light wavelength and bandwidth to meet the corresponding all-optical wavelength conversion requirements.

[0016] In a possible implementation, 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 straight-line parallelism or curved parallelism.

[0017] It should be noted that the parameter design and shape design of the above coupling regions are all for the purpose of making the two coupling regions overcoupled.

[0018] 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.

[0019] In a possible implementation, the equivalent coupling coefficient of the MZI coupled microring resonator is for:

[0020] in, k 1 , k 2 are the coupling coefficients of the two coupling regions, , i=1, 2; , and is the phase change 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 MZI respectively; 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 overcoupled, by adjusting k 1 , k 2 , the equivalent coupling coefficient of different incident lights in the MZI coupled microring resonator is controlled, so that the pump light works in the critical coupling state in the all-optical wavelength converter, and the signal light and idler light work in the over-coupling state in the all-optical wavelength converter.

[0021] In a possible implementation, the conversion efficiency of the all-optical wavelength converter in converting the signal light and the pump light into the idler light is for:

[0022] in, is the nonlinear coefficient, is the pump light power, is the field enhancement of the pump light in the upper arm of the MZI, The signal light is enhanced in the MZI upper arm. 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, 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, To enhance the field of the pump light in the waveguide section of the microring resonator except the lower arm, The field enhancement of the signal light in the waveguide section of the microring resonator except the lower arm is: is the field enhancement of the idler light in the waveguide section other than the lower arm in the microring resonator, represents conjugation, 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 in the microring resonator except the lower arm, ,i=1,2,3, , are the propagation constants of 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 except the lower arm mentioned above, 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.

[0023] In a second aspect, the present application provides an all-optical wavelength conversion method, comprising: 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; 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; 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.

[0024] 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.

[0025] 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.

[0026] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: The present application provides an all-optical wavelength converter and a conversion method. By using MZI to regulate a microring, the FSR of the MZI is controlled to be twice the FSR of a microring resonant cavity, and the phase difference generated by the pump light in the upper and lower arms of the MZI is π, and a group of adjacent interference phase growth wavelengths and interference destructive wavelengths of the MZI are simultaneously aligned with a group of adjacent resonant wavelengths of the microring resonant cavity, so that the system spectrum line presents a wide-narrow-wide line type; the wide peak achieved by modulating a single microring by MZI in the present application can have a wider working bandwidth than the wide peak achieved by regulating the microring by the existing microring; on this basis, pump light is injected at a narrow line width, and signal light is injected at a wide line width, so that the pump light is controlled to work in a critical coupling state in the all-optical wavelength converter, and the signal light and the idler light work in an over-coupling state in the all-optical wavelength converter, so that a large conversion bandwidth can be achieved while ensuring a high conversion efficiency, and it is expected to promote the realization of high-speed all-optical signal processing.

[0027] The present application provides an all-optical wavelength converter and conversion method, which simplifies the all-optical wavelength conversion system that requires multi-ring coupling tuning by MZI coupling and regulation of microrings. High-speed wavelength conversion function and nonlinear optical signal processing process are realized in a single MZI-coupled microring. Compared with the previous solution of using multi-ring coupling to tune the linewidth to achieve a larger range of wavelength conversion function, this solution is more flexible in linewidth regulation and achieves a larger bandwidth. This makes the entire all-optical signal processing system simpler and easier to integrate on-chip.

[0028] The present application provides an all-optical wavelength converter and conversion method, which uses MZI to control microrings. Compared with the existing microring control microring method, this control method is simpler to control, can achieve a larger conversion bandwidth, and can stably ensure that the system resonance peak presents a wide-narrow-wide line type without the need for electrode adjustment of the coupling state. The present application uses an MZI-coupled microring structure to periodically control the line width of the system, which can achieve a large conversion bandwidth while ensuring a high conversion efficiency, with a simpler structure, a larger process tolerance, and is compatible with CMOS processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a simplified diagram of an all-optical wavelength converter provided in an embodiment of the present application; Figure 2 This is a first structural diagram of the all-optical wavelength converter provided in the embodiment of the present application; Figure 3 This is a second structural diagram of the all-optical wavelength converter provided in an embodiment of the present application; Figure 4 is a transmission spectrum of the all-optical wavelength converter provided in an embodiment of the present application; Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 100 is a straight waveguide, and 200 is a microring resonant cavity. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with 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.

[0031] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0032] The present application belongs to the field of on-chip integrated all-optical signal processing. By using MZI to control the line width of MRR, the problem of not being able to take into account both the conversion bandwidth and the conversion efficiency when using microrings to realize all-optical wavelength conversion is solved. Therefore, the all-optical wavelength converter provided by the present application can also be referred to as MZI-MRR for short. By using MZI to control the microrings to realize a wide-narrow-wide line type of system spectral lines, pump light is injected at the narrow line width, and signal light is injected at the wide line width, so that a large conversion bandwidth can be obtained while ensuring a high conversion efficiency, which 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.

[0033] Figure 1 is a simplified diagram of the all-optical wavelength converter provided in the embodiment of the present application; Figure 1 As shown, the straight waveguide 100 and the microring resonator 200 have two coupling regions, and the coupling coefficients of the two coupling regions are k 1 and k 2 ; Further, the straight waveguide and the two coupling regions and the waveguide section L located between the two coupling regions on the microring resonator 2 The upper and lower arms of MZI are L 1 and L 2 , upper arm L 1 is a part of the straight waveguide 100; Specifically, the design of the MZI and the microring resonator 200 satisfies the following conditions so that the resonance peak of the all-optical wavelength converter presents a wide-narrow-wide distribution: the FSR of the MZI is twice the FSR of the microring resonator; 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 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 introduced into one end of the straight waveguide, the other end will output pump light, signal light and idler light to achieve 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.

[0034] Specifically, the wavelength at the microring resonant cavity that differs from the wavelength of the pump light by an odd number of FSRs is the central wavelength of the signal light, and the design of the MZI-coupled microring resonant cavity 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 in the corresponding wide resonance peak; taking 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 a 3dB conversion bandwidth of the all-optical wavelength converter.

[0035] It can be understood that the bandwidth of the all-optical wavelength converter is usually the 3dB conversion bandwidth, which is the signal light wavelength range from the maximum conversion efficiency to the time when the conversion efficiency 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 in the corresponding wide resonance peak, and the purpose is to make the 3dB conversion bandwidth of the all-optical wavelength converter include the center wavelength of the signal light to ensure that the conversion bandwidth is wide enough. The wavelength of the signal light is the wavelength within half of the 3dB conversion bandwidth on the left and right sides, based on the center wavelength of the signal light.

[0036] It should be noted that when the FSR of the MZI is twice the FSR of the microring resonant cavity, and the phase difference generated by the pump light in the upper and lower arms of the MZI is π, a group of adjacent interference phase growth wavelengths and interference phase destructive wavelengths of the MZI are simultaneously aligned with a group of adjacent resonant wavelengths of the microring resonant cavity, so that the resonant peak of the all-optical wavelength converter is distributed in a wide-narrow-wide manner. The wide peak achieved by modulating a single microring resonant cavity by MZI in this application can have a wider working bandwidth than the wide peak achieved by the existing microring regulation microring; on this basis, the pump light is injected at the narrow line width and the signal light is injected at the wide line width, which can ensure that the all-optical wavelength converter has a higher conversion efficiency and a larger conversion bandwidth.

[0037] Preferably, both coupling regions are overcoupled. Specifically, both coupling regions are overcoupled in order to expand the wide resonance peak to a wider width and achieve a larger conversion bandwidth; further, the two coupling regions are overcoupled, combined with the aforementioned wide-narrow-wide resonance peak distribution, to ensure that the all-optical wavelength converter has a relatively ideal conversion efficiency and a large conversion bandwidth.

[0038] 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.

[0039] Specifically, the waveguide in the coupling region refers to 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 waveguide outside the two coupling regions in the all-optical wavelength converter. The cross-sectional area size of the waveguide in the coupling region is the same, and the cross-sectional area size of the waveguide in the non-coupling region is the same. The cross-sectional area 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, so as to further ensure a high conversion efficiency and a wide conversion bandwidth.

[0040] In one example, to ensure over-coupling of the above-mentioned two coupling regions, the coupling coefficient of each coupling region is within a preset range, and cannot be too small or too large, and is adjusted by adapting the parameters of the device so that the device achieves predetermined performance; further, the two coupled waveguide segments in each coupling region can be controlled to be parallel to each other; the parallelism is straight-line parallelism or curved parallelism.

[0041] In some embodiments, the microring resonant cavity 200 is a ring-shaped microring resonant cavity (circular microring) or a racetrack microring resonant cavity; when it is a ring-shaped microring resonant cavity, such as Figure 2 As shown in the figure, the two coupled waveguide segments in each coupling region are coupled in parallel in a curved manner, i.e., pulley-type coupling. When it is a racetrack-type microring resonator, as shown in the figure, Figure 3 As shown, it includes two straight waveguide sections and two curved waveguide sections. At this time, the two regions on the straight waveguide are respectively coupled with partial regions on the two straight waveguide sections, that is, directional couplers, to form two coupling regions.

[0042] Figure 2 is a first structural diagram of the all-optical wavelength converter provided in the embodiment of the present application; Figure 2 As shown, the coupling region is a pulley type coupling, and the internal micro-ring is a circular ring cavity. In some scenarios, the above-mentioned all-optical wavelength converter is suitable for the case where the coupling coefficient is large.

[0043] Figure 3 is a second structural diagram of the all-optical wavelength converter provided in the embodiment of the present application; Figure 3 As shown, the coupling region is a directional coupler, and the internal micro-ring is a racetrack-type micro-ring. In some scenarios, the above-mentioned all-optical wavelength converter is suitable for situations where the coupling coefficient requirements are more refined and suitable for different coupling coefficient designs. Figure 2 , Figure 3 The resulting device design is easier and the process tolerance is greater.

[0044] Further, Figure 3 For example, this example is based on a CMOS-compatible SOI platform, and the waveguide cross-sectional area is 500nm×220nm. The straight waveguide and the micro-ring have two coupling regions. According to the order of coupling, the coupling coefficients at the two coupling regions are recorded as k 1 , k 2 The structure can be divided into two parts. The first part is composed of L 1 , L 2 The MZI structure consists of two coupling regions and input and output ports. The laser input light passes through the first coupling region and then travels along L 1 , L 2 The light is transmitted through the first segment, 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 of light at the output port. The second part is determined by L2 With L 3 The single-ring structure formed can be regarded as a coupling area.

[0045] In this structure, since both coupling regions require a large coupling coefficient, the coupling region is designed to be runway-shaped, and the total length of a single ring can be in the range of 200 microns to 500 microns. In order to achieve a wide-narrow-wide line type, it is also necessary to ensure that the FSR of the MZI structure is twice the FSR of the single ring structure and the single ring is resonant for the pump light. In addition, according to the derivation, the equivalent coupling coefficient of the MZI-MRR structure is ,in, , the phase difference of the pump light generated in the upper and lower arms of the MZI is controlled by design. The phase difference between the signal light and the idler light in the upper and lower arms of the MZI is About (the wavelength of the signal light differs from the wavelength of the pump light by an odd number of FSRs of the microring), the pump light can be made to work in critical coupling, and the signal light and the idler light can be made to work in over coupling, thus obtaining a large conversion bandwidth while ensuring a high conversion efficiency.

[0046] The above transmission spectrum is as follows Figure 4 As shown. By using MZI to control the microring, the resonance peak of the microring can be periodically tuned to a wide-narrow-wide line type. 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 in the ring. When resonance occurs in the ring, a great power enhancement can be obtained, and the conversion efficiency is related to the power in the ring. Figure 4 As shown, at a wavelength of 1550nm, the transmittance is about -12dB, and with 0dB as the benchmark, the extinction ratio is 12dB. In the experiment, it can be considered that the light of this wavelength is roughly in critical coupling with respect to the microring. Secondly, the wavelength of light at the wide resonance peak is in an over-coupled state relative to the microring, which sacrifices the field enhancement within the ring to a certain extent, but also makes the field enhancement of light in a larger range change slowly, so the conversion efficiency decreases slowly within a certain range, and the 3dB conversion bandwidth is larger. In addition, although part of the 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 (conversion efficiency that meets the requirements) can be guaranteed, and a larger conversion bandwidth is achieved at the same time.

[0047] It should be noted that the phase difference generated by the pump light in the upper and lower arms of the MZI is First, the spectrum lines of MZI and microring can be aligned to obtain wide-narrow-wide resonance peaks, and the pump light can be more easily regulated at the critical coupling. Similarly, the wavelength difference between the signal light and the pump light is controlled to be near an odd number of FSRs of the microring (preferably near 1 FSR of the microring). The phase difference between the natural signal light and the idler light in the upper and lower arms of MZI is By doing so, the spectral lines of the MZI and the microring can be aligned, and the signal light and the idler light can be more easily controlled to be overcoupled.

[0048] The 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) of the required pump narrow peak to the red detuned side (long wavelength) until the optical power drops significantly, and the cold cavity resonant wavelength is measured; in the second step, the signal light input wavelength is set to an odd number of FSRs away from the pump light cold cavity wavelength, and the idler light is generated in the microring and the upper arm of the MZI.

[0049] In Example 1, due to the limitation of two-photon absorption and free carrier effect, the optical power in the silicon waveguide has an upper limit. Figure 2 and Figure 3 The cross-sectional area of ​​the waveguide outside the dotted box is 1000nm×220nm, and the cross-sectional area of ​​the waveguide at the coupling point is 500nm×220nm, which can effectively reduce the loss and increase the power threshold to achieve the effect of reducing power consumption, improving conversion efficiency and further expanding the conversion bandwidth.

[0050] According to the derivation, the conversion efficiency formula of this structure is as follows:

[0051] in, For the field enhancement of the pump light in the L1 segment, is the field enhancement of the signal light in the L1 segment, is the field enhancement of idler light in the L1 segment, V and W represent the L2 and L3 segments respectively. Specifically, is the output idler optical power, is the input signal optical 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, The signal light is enhanced in the MZI upper arm. 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, 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, To enhance the field of the pump light in the waveguide section of the microring resonator except the lower arm, The field enhancement of the signal light in the waveguide section of the microring resonator except the lower arm is: is the field enhancement of the idler light in the waveguide section other than the lower arm in the microring resonator, represents conjugation, 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 in the microring resonator except the lower arm, ,i=1,2,3, , are the propagation constants of 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 except the lower arm mentioned above, 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.

[0052] The present application uses MZI to control the line width of the micro-ring to achieve a stable and easy-to-tune system with a larger conversion bandwidth while taking into account the all-optical wavelength conversion function of high conversion efficiency.

[0053] It should be understood that expressions such as "including" and "may include" that may be used in the present 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 the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0054] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0055] In the description of the embodiments of the present 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 relative position relationship after connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present 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 on the embodiments of the present application.

[0056] In addition, in the embodiments of the present application, the mathematical concepts mentioned are symmetry, equality, parallelism, verticality, etc. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense, and allow a small amount of deviation, approximation to symmetry, approximation to equality, approximation to parallelism, approximation to verticality, etc. are all possible. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0057] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An all-optical wavelength converter, characterized in that: include: Straight-through waveguide and microring resonator; The straight waveguide and the micro-ring resonant cavity have two coupling regions, the straight waveguide and the two coupling regions and the waveguide section located between the two coupling regions on the micro-ring resonant cavity form a Mach-Zehnder interferometer MZI, and the MZI is coupled with the micro-ring resonant cavity; The design of the MZI-coupled microring resonant cavity satisfies the following conditions so that the resonance peak of the all-optical wavelength converter presents a wide-narrow-wide distribution: the free spectral range FSR of the MZI is twice the FSR of the microring resonant cavity; 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 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 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.

2. The all-optical wavelength converter according to claim 1, characterized in that: The two coupling regions are both overcoupled.

3. The all-optical wavelength converter according to claim 1, characterized in that: 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, characterized in that: The wavelength at the microring resonant cavity that differs from the pump light wavelength by an odd number of FSRs is the central wavelength of the signal light, and the design of the MZI-coupled microring resonant cavity meets 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 in the corresponding broad resonance peak; and / or taking the central wavelength of the signal light as a reference, the difference between the wavelength of the signal light and the central wavelength of the signal light is within half a 3dB conversion bandwidth of the all-optical wavelength converter; Preferably, the wavelength of the signal light differs from the wavelength of the pump light by approximately one FSR of the microring resonator.

5. The all-optical wavelength converter according to claim 2, characterized in that: 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 straight-line parallelism or curved parallelism.

6. The all-optical wavelength converter according to claim 1, 2 or 5, characterized in that: 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, 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.

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 for: in, k 1. k 2 are the coupling coefficients of the two coupling regions, , i=1, 2; , and is the phase change 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 MZI respectively; and / or, by adjusting k 1. k 2. Control the equivalent coupling coefficient 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 idler light work in the over-coupling state in the all-optical wavelength converter.

8. An all-optical wavelength conversion method, characterized in that: include: 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 a Mach-Zehnder interferometer MZI, and the MZI is coupled with the microring resonant cavity; The free spectral range (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; 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.

9. The all-optical wavelength conversion method according to claim 8, characterized in that: 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, 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.

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

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