A double-injection micro-ring type reconfigurable multi-spectrum response unit prepared based on SOI material

Abstract

This invention relates to a dual-injection microring reconfigurable multi-spectral response unit based on SOI material, comprising three symmetrical Mach-Zehnder interferometers (MZIs) and two sets of equal-length connecting waveguides. Each MZI includes two 2×2 multimode interferometers and their connecting waveguides, as well as multiple thermoelectrodes directly above the waveguides. First, the input optical signal is split into two beams by a tunable MZI beam splitter according to the desired power ratio. Then, after passing through a set of equal-length waveguides, it enters a tunable microring resonator composed of two tunable MZIs. During this process, the phase relationship between the two beams is controlled by a thermal tuner. The two beams enter opposite ports of the tunable microring resonator, and the coupling coefficients of the two beams entering the microring are controlled by the tunable MZIs. By controlling the optical power ratio, phase relationship, and coupling coefficient, this unit device can achieve multiple spectral responses and spectral reconfigurability.

Description

Technical Field

[0001] This invention relates to a response unit, specifically to a dual-injection micro-ring reconfigurable multi-spectral response unit based on SOI material, belonging to the field of optical communication technology. Background Technology

[0002] With the rapid development of communication technology, the requirements for information transmission and processing are becoming increasingly stringent. Optical communication, with its advantages such as low loss, high bandwidth, and strong anti-interference capabilities, has attracted much attention and greatly promoted the development of integrated optics. For integrated optics, the choice of materials for designing highly integrated, low-loss waveguide devices not only affects the device's performance parameters but also its manufacturing cost, fabrication feasibility, and compatibility with existing systems.

[0003] The large refractive index difference between silicon and silicon dioxide in the SOI material system allows optical signals to be effectively confined within silicon. Furthermore, silicon has a thermo-optic coefficient on par with polymers, making it well-suited for waveguide materials. SOI also offers advantages such as low bending loss, mature fabrication processes, low manufacturing costs, and compatibility with CMOS processes, facilitating the miniaturization of waveguide devices and their application in large-scale integration.

[0004] Compared to the advantages of integrated circuits in digital computing, integrated optical circuits have more prominent advantages in transmission and analog signal processing. Currently, the mainstream integrated optical circuit design approach is ASPIC (Application Specific Photonic Integrated Circuit), but it suffers from long research and iteration cycles. Therefore, a general-purpose optical processor architecture is needed to reduce development time. This architecture is called "optical FPGA," or FPPGA (Field Programmable Photonic Gate Array).

[0005] The unit devices used in the proposed FPPGA architecture include MZI units and MDR (Micro Disk Resonator) units. Each has its own advantages and disadvantages, and their functions are complementary. However, each has a specific spectral morphology. To achieve complex spectra, multiple tuning units need to be called, which will lead to a decrease in device stability.

[0006] The dual-injection microring structure injects two coherent beams of light into a predetermined location on a resonator. The output at the final port can be considered as the superposition of the outputs from the through and drain ends of two nearly identical add-drop ring resonators. To ensure coherence, one beam is split into E beams using a beam splitter at a specific power ratio. i1 E i2Two beams are injected into the microring through different optical path lengths, maintaining the same direction of rotation within the ring. By adjusting the power ratio and phase difference of the two beams injected into the microring, as well as the coupling coefficient of the microring, different frequency response results can be achieved. However, current structures are designed with fixed beam splitting ratios, phase differences, and coupling coefficients to achieve a specific spectral morphology, failing to realize the theoretically rich spectral response forms. Therefore, a new solution is urgently needed to address the aforementioned technical problems. Summary of the Invention

[0007] This invention addresses the problems existing in the prior art by providing a dual-injection microring reconfigurable multi-spectral response unit based on SOI material. This technical solution aims to provide a reconfigurable optical unit with multi-spectral response through simple tuning methods. Based on the dual-injection microring structure, and leveraging the advantages of high integration and mature fabrication processes of SOI material, this invention discloses a dual-injection microring reconfigurable multi-spectral response unit based on SOI material, providing a simple and effective unit device for FPPGA requirements. Compared to existing FPPGA unit devices, it can achieve richer spectral configurations with less modulation, thereby meeting the needs of more diverse optical processing environments.

[0008] To achieve the above objectives, the technical solution of this invention is as follows: a dual-injection microring reconfigurable multi-spectral response unit based on SOI material, comprising a SiO2 cladding, with a horizontally arranged waveguide layer inside the cladding. The waveguide layer is made of Si material. A thermoelectric electrode is provided on the upper plane of the SiO2 cladding. The waveguide layer includes three microrings (MZIs) and two sets of connecting waveguides, each set consisting of two waveguides of equal length; each MZI consists of two microrings (MMIs) with equal power ratios and two waveguides of equal length. The morphology of the thermoelectric electrode is consistent with the morphology of the corresponding waveguide, located directly above the straight waveguide in the MZI structure, and on one of the waveguides at the output end of the first MZI. A SiO2 buffer layer is provided between the thermoelectric electrode and the waveguide. The required bias voltage is applied to both ends of the thermoelectric electrode to achieve different coupling coefficients, power ratios, or phase differences, ultimately achieving different spectral responses.

[0009] As a preferred technical solution of the present invention: the MZI splits the input optical signal, and the splitting ratio is determined by the voltage of the thermoelectric electrode directly above the waveguide connecting the MMIs, which can realize a continuous change in the splitting ratio from 0 to 1, and obtain two coherent beams with the required power ratio.

[0010] As a preferred technical solution of the present invention: the two MZIs are connected by a set of ring waveguides to form a tunable micro-ring resonator. Each MZI is a tunable coupler, and its coupling coefficient is determined by the voltage of the hot electrode directly above the connecting waveguide between the MMIs. The coupling coefficient can be continuously varied from 0 to 1 to meet the flexible control requirements.

[0011] As a preferred technical solution of the present invention: the set of equal-length waveguides connects the beam splitting MZI and the two MZIs that constitute the tunable microring resonator. Their equal length ensures that the two beams after beam splitting do not generate additional phase difference due to different optical paths. The phase difference between the two is entirely determined by the voltage of the thermoelectric electrode directly above the set of waveguides, which can realize a continuous change in phase difference from 0 to 2π.

[0012] As a preferred technical solution of the present invention: the two ports of the tunable microring resonator are selected to be on opposite sides, so as to ensure that the optical signals input from the two ports propagate in the same direction in the ring, thereby achieving better coherence of the two optical paths in the ring.

[0013] As a preferred technical solution of the present invention: the waveguide layer includes three MZI and two sets of waveguides of equal length, all of which are made of SOI material system, all of which are rectangular waveguides, and the cross-sectional dimensions of the connecting waveguides are all 500nm×220nm.

[0014] As a preferred embodiment of the present invention, the MMI structure in the MZI requires a Taper-type graded waveguide to assist in the connection between the multimode waveguide region and the single-mode waveguide, in order to reduce optical loss caused by mode mismatch.

[0015] As a preferred embodiment of the present invention: the waveguide used in the unit device is relatively long, and a 90-degree curved waveguide can be implemented by introducing, for example, an Euler curve, to reduce light propagation loss. The thermoelectrode is made of TiN material, and its temperature can be changed by applying a voltage to both ends of the thermoelectrode; its cross-sectional width is 5 μm.

[0016] Compared to existing technologies, this invention offers the following advantages: It proposes a dual-injection microring reconfigurable multi-spectral response unit based on SOI material. The input light is flexibly split using a thermo-optical MZI-type tunable coupler. The two beams then pass through a set of equal-length waveguides, with the phase relationship modulated by thermoelectrodes on the waveguides, before entering a tunable microring resonator composed of two MZIs. The two beams enter the two opposite ports of this add-drop microring resonator to ensure consistent directionality during their circumduction within the ring. By adjusting the coupling coefficients at two points forming the ring, the coherence results of the two beams within the ring differ, resulting in diverse spectral configurations. Compared to existing reconfigurable optical processors based on MZI or MDR units, this invention achieves rich spectral profiles without requiring large-scale cascading and numerous modulation devices, improving the reconfigurability of the unit device itself and avoiding the stability degradation caused by excessive cascading in the future, thus offering broader application scenarios. Furthermore, the fabrication process of this invention is compatible with CMOS technology, is mature, and easy to implement in actual production. Overall, this invention has the potential characteristics and advantages of strong unit device functionality, capable of forming various morphological spectra to meet different signal processing needs; simple design of the modulation method and device based on thermo-optic effect, low production cost and low power consumption; fewer modulation units used, convenient operation, and higher device robustness. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0018] Figure 2 is a top view of the waveguide structure of the present invention.

[0019] (a) Overall waveguide model diagram; (b) MZI section; (c) Connecting waveguide section; (d) Tunable microring resonator section.

[0020] Figure 3 This is a schematic diagram of the interface of the thermoelectrode part of the present invention.

[0021] Figure 4 The curves showing the relationship between the power and phase of the Mach-Zehnder interferometer in this invention, with an incident optical signal at a wavelength of 1550nm from IN 1 and the output power and phase at tempOUT 1-2, are as a function of the applied power.

[0022] Figure 5 shows the output spectrum of the port of the present invention under a specific external power (taking IN 1 as an example): (a) the concave spectrum of the micro-ring resonator; (b) the concave spectrum of the micro-ring resonator (twice the free spectral range); (c) the square spectrum.

[0023] Figure 6 This is a graph showing the relationship between the applied power and the waveguide temperature of this invention. Detailed Implementation

[0024] To enhance understanding of the present invention, the embodiments will be described in detail below with reference to the accompanying drawings.

[0025] Example 1: As Figure 1 As shown in Figure 2(a), this invention designs a dual-injection micro-ring reconfigurable multi-spectral response unit based on SOI material. Its waveguide layer is a Si waveguide embedded in SiO2. The main structure includes three Mach-Zehnder interferometers and two sets of connecting waveguides, each set consisting of two waveguides of equal length. As shown in Figure 2(b), the MZI structure uses a rectangular waveguide fabrication process, including two multimode interferometers 1-1 and two connecting waveguides 1-2. Each multimode interferometer includes four transition waveguides 1-1-2 and a multimode waveguide region 1-1-1. Taper-type waveguides can be used for the transition waveguides to reduce mode mismatch loss. The input ports of the MZI are IN1 and IN2, which are also the input ports of this unit device. As shown in Figure 2(c), the connecting waveguides use a rectangular waveguide fabrication process, including waveguide 2-1 and waveguide 2-2. The two waveguides are not symmetrical, but their total lengths are equal. The thermoelectrode is installed only directly above one of the waveguides. As shown in Figure 2(d), the tunable microring resonator is fabricated using a rectangular waveguide process, including: two Mach-Zehnder interferometers 3-1 as tunable couplers, whose specific structural components are shown in Figure 2(b), and two ring waveguides 3-2 for interconnection of the MZI. Figure 1 As shown, rectangular TiN thermoelectric electrodes 4 are placed above one of the three MZI waveguides and above one of the waveguides in the long connecting waveguide group. Ohmic heat is generated by applying a voltage across the thermoelectric electrodes, thereby changing the temperature of the waveguide in the electrode-covered area. A cross-sectional view of the electrode is shown below. Figure 3 As shown. Figure 1 and Figure 3 In the middle, the upper cladding layer 5-1 is used to protect the electrode; the lower cladding layer 5-2 is a buffer layer between the waveguide layer and the hot electrode 4; the bottom layer is the Si substrate layer 6.

[0026] The principle of the unit device of the present invention is as follows: the dual-injection micro-ring structure injects two coherent beams of light into a predetermined position of a resonator, and the output at the final port can be considered as the superposition of the outputs of the through end and the drain end of two almost identical add-drop type ring resonators. In this invention, the input optical signal with a center wavelength at the operating wavelength of the unit device enters the straight waveguide through IN 1 (or IN 2), and is split into beams with a 1:1 ratio by the multimode interferometer 1-1. Under the modulation of the thermoelectric electrode 4-1, the phase relationship of the optical signals in the upper and lower waveguides 1-2 changes, and they enter the multimode waveguide region 1-1-1 of the second multimode interferometer 1-1 to interfere, forming beams with different power ratios, which are output from ports tempOUT 1-1 and tempOUT 1-2 respectively. tempOUT 1-1 and tempOUT 1-2 are respectively connected to tempIN 2-1 and tempIN 2-2, so that the two coherent beams pass through waveguides 2-1 and 2-2 respectively, and their phase relationship is modulated by the thermoelectric electrode 4-2. The coherent light in waveguide 2-1 enters tempIN 3-1 through tempOUT 2-1, and thus enters the tunable micro-ring. The coupling coefficient of the coherent light entering the ring is controlled by the thermoelectric electrode 4-3. Similarly, the coherent light in waveguide 2-2 enters tempIN 3-1 through tempOUT 2-1. 2-2 enters tempIN 3-2, thus entering the tunable micro-ring, and the coupling coefficient of the coherent light entering the ring is controlled by the thermoelectrode 4-4. By adjusting the thermoelectrode group 4, the output spectrum can ultimately be changed.

[0027] To verify that the present invention can achieve this function, a verification example is provided for illustration.

[0028] This verification example uses a combination of the finite-difference time-domain method and the transfer matrix method for computational analysis. The main parameters used in the simulation are: a rectangular waveguide cross-section with a width of 500 nm and a height of 220 nm; and thermo-optical coefficients of silicon and silicon dioxide of 1.84 × 10⁻⁶. -4 1×10 -5 For the multimode interferometer 1-1 in the Mach-Zehnder interferometer 1, its multimode waveguide region 1-1-1 has a width of 6 μm and a length of 41.8 μm. The transition waveguide 1-1-2 is a linear Taper waveguide with a long side width of 1.6 μm and a length of 10 μm. The middle waveguide 1-2 has a length of 200 μm. The connecting waveguide group 2 is a combination of multiple waveguide segments. The total length of the waveguides is ensured to be equal through topology design. Among them, the radius of the ring waveguide is 50 μm and the total length is π×2×50 μm. The total length of the straight waveguide is 332 μm. The parameters of the Mach-Zehnder interferometer 3-1 in the tunable microring resonator 3 are the same as those of the Mach-Zehnder interferometer 1. The two are connected by a 150 μm semicircular ring waveguide 3-2.

[0029] Taking light input from IN1 as an example, the curves showing the output power and phase relationship of the MZI from IN1 input to tempOUT1-2 as a function of applied power in the case of a 1550nm optical signal input are as follows: Figure 4 As shown.

[0030] By jointly modulating the thermoelectrode group 4, a variety of spectral morphologies can be obtained. Figure 5 shows three representative spectra. Figure 5(a) is the spectrum of the direct end of the microring resonator, Figure 5(b) is the spectrum of the direct end of the microring resonator with the free spectral range expanded, and Figure 5(c) is the spectrum of an approximately square shape.

[0031] Figure 6 The waveguide temperature change corresponds to different power consumptions. It can be seen that the waveguide temperature change corresponding to the power consumption is approximately proportional, with a proportionality coefficient of about 3.05 K / mW. The resonant peak shift is approximately linear, which can be better used for MZI control.

[0032] In summary, the dual-injection micro-ring reconfigurable multi-spectral response unit based on SOI material provided by this invention can directly perform various frequency domain processing on optical signals, with relatively simple modulation methods, better functionality, and can be better integrated into the design of optical processors. It also possesses the potential advantages of simple fabrication, CMOS compatibility, and low power consumption.

[0033] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

Claims

1. A dual-injection microring reconfigurable multi-spectral response unit based on SOI material, characterized in that, It includes a SiO2 cladding, and a horizontally arranged waveguide layer is provided inside the cladding. The waveguide layer is made of Si material, and a thermoelectric electrode is provided on the upper plane of the SiO2 cladding. The waveguide layer includes three Mach-Zehnder interferometers (MZIs) and two sets of connecting waveguides, each set consisting of two waveguides of equal length. Each MZI consists of two multi-mode interferometers (MMIs) with equal power ratios and two straight waveguides of equal length. The thermoelectrode morphology is consistent with the corresponding waveguide morphology and is located directly above the straight waveguide in the MZI structure, and on one of the waveguides in the waveguide group connected to the output end of the beam splitter MZI. The input signal is split by an MZI, and the splitting ratio is determined by the voltage of the thermoelectric electrode directly above the straight waveguide between the MMIs, achieving a continuous change in the splitting ratio from 0 to 1. The other two MZIs are connected by a set of ring waveguides of equal length to form a tunable micro-ring resonator. The coupling coefficient of the tunable coupler formed by each MZI is determined by the voltage of the hot electrode directly above the straight waveguide between the MMIs, so as to achieve a continuous change of coupling coefficient from 0 to 1. The beam splitting ratio and phase difference of the two ports on the output side of the MZI exhibit periodic changes with respect to the heating power of the thermoelectric electrode directly above the straight waveguide, and the phase difference between the two ports is 0 or π. The input signal is split into two beams as required by an MZI and then fed into the two ports of a tunable microring resonator via a set of connecting waveguides. The two ports of the tunable microring resonator are on opposite sides to ensure that the optical signals input from the two ports propagate in the same direction. The total length of the connecting waveguides must be kept constant to ensure that no additional phase difference is generated. The phase difference between the two beams of light entering the tunable microring resonator is determined by the voltage of the thermoelectric electrode directly above the connecting waveguides, so as to achieve a continuous change in phase difference from 0 to 2π.

2. The dual-injection microring reconfigurable multi-spectral response unit based on SOI material according to claim 1, characterized in that: The silicon waveguide layer of the SOI material system has a thickness of 220 nm, and the cross-sectional dimensions of the connecting waveguide are 500 nm × 220 nm.

3. The dual-injection microring reconfigurable multi-spectral response unit based on SOI material according to claim 1, characterized in that: In the MZI structure, the multimode waveguide region and the single-mode waveguide need to be connected by a tapered waveguide.

4. The dual-injection microring reconfigurable multi-spectral response unit based on SOI material according to claim 1, characterized in that: The thermoelectrode is made of TiN material, and its temperature can be changed by applying a voltage across its two ends. Its cross-sectional width is 5 μm.

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