CN115128880B - Double-injection micro-ring type reconfigurable multi-frequency response unit prepared based on SOI material - Google Patents

Abstract

The invention relates to a double-injection micro-ring type reconfigurable multi-frequency response unit prepared based on an SOI material, which comprises three symmetrical Mach-Zehnder interferometers prepared based on the SOI material, two groups of connecting waveguides with equal lengths, wherein each Mach-Zehnder interferometer comprises two 2X 2 multimode interferometers and connecting waveguides thereof, and a hot electrode right above a plurality of waveguides. The input optical signal is divided into two beams of light according to the required power ratio by a tunable MZI beam splitter, then enters a tunable micro-ring resonator consisting of two tunable MZIs after passing through a group of equal-length waveguides, in the process, the phase relation of the two beams of light is controlled by a thermal tuner, the two beams of light respectively enter opposite side ports of the tunable micro-ring resonator, and the coupling coefficients of the two beams of light entering a micro-ring are respectively controlled by the tunable MZIs. By controlling the optical power ratio, the phase relation and the coupling coefficient, various frequency spectrum responses and frequency spectrum reconfigurability of the unit device can be realized.

Description

Double-injection micro-ring type reconfigurable multi-frequency response unit prepared based on SOI material

Technical Field

The invention relates to a response unit, in particular to a double-injection micro-ring type reconfigurable multi-frequency response unit prepared based on an SOI material, and belongs to the technical field of optical communication.

Background

With the rapid development of communication technology, the requirements for information transmission and processing are also increasing. Optical communication is paid attention to with the advantages of low loss, large bandwidth, interference resistance and the like, and the development of integrated optics is greatly promoted. For integrated optics, what materials are chosen to design a high-integration low-loss waveguide device is related to the performance parameters of the device, and the problems of manufacturing cost, processing feasibility, compatibility with the existing system and the like are also concerned.

The SOI material system allows the optical signal to be well confined in silicon due to the large refractive index difference between silicon and silicon dioxide. In addition, silicon has the thermo-optical coefficient of the same magnitude as that of polymer, and is suitable for being used as a waveguide material. The SOI also has the advantages of small bending loss, mature manufacturing process, low manufacturing cost, compatibility with CMOS (complementary metal oxide semiconductor) process and the like, and is favorable for miniaturizing waveguide devices and being used for large-scale integration.

Integrated circuits have a significant advantage in transmission and analog signal processing over integrated circuits in digital computing. The current mainstream design method of the integrated optical circuit is ASPIC (Application Specific Photonic Integrated Circuit), but the current design method has the problems of long research and iteration period, and the like, so that a general optical processor architecture is required to reduce development time. This architecture is known as an "optical FPGA", FPPGA (Field Programmable Photonic GATE ARRAY).

The unit device used by the FPPGA architecture currently proposed comprises an MZI unit and a MDR (Micro Disk Resonator) unit, the MZI unit and the MDR (Micro Disk Resonator) unit have advantages and disadvantages, the functions of the MZI unit and the MDR (Micro Disk Resonator) unit are complementary, but the MZI unit and the MDR (Micro Disk Resonator) unit have specific spectrum forms, and a plurality of tuning units are required to be called for realizing the complex spectrum, so that the stability of the device is reduced.

The dual injection micro-ring structure injects two beams of coherent light into a predetermined location of one resonator, and the output at the final port can be considered as a superposition of the outputs from the through and drain ends of two nearly identical add-drop type ring resonators. To ensure coherence, a beam of light is split into two beams of E _i1、E_i2 by a beam splitter according to a certain power ratio, and enters the micro-ring through different optical paths, and the bypassing directions in the ring are kept the same. Different frequency response results can be realized by adjusting the power ratio and the phase difference of the two beams of light injected into the micro-ring and the coupling coefficient of the micro-ring. However, the structure is designed with a fixed beam splitting ratio, phase difference and coupling coefficient in advance to realize a certain specific spectrum form, and cannot develop a theoretically rich spectrum response form, so a new scheme is urgently needed to solve the technical problems.

Disclosure of Invention

The invention provides a double-injection micro-ring type reconfigurable multi-frequency response unit prepared based on an SOI material, which aims at solving the problems existing in the prior art, has a simple tuning means multi-frequency spectrum response reconfigurable optical unit, is based on a double-injection micro-ring type structure, utilizes the advantages of high integration level and mature process of an SOI material system, and provides a simple and effective FPPGA required unit device. Compared with the prior FPPGA unit device, the device can realize richer spectrum morphology with less modulation, thereby meeting the requirements of diversified optical processing environments.

In order to achieve the above purpose, the technical scheme of the invention is as follows, and the double-injection micro-ring type reconfigurable multi-frequency response unit prepared based on SOI material comprises an SiO ₂ cladding layer, wherein a waveguide layer which is horizontally arranged is arranged inside the cladding layer. The waveguide layer is made of Si material. The upper plane of the SiO ₂ cladding is provided with a hot electrode. The waveguide layer comprises three MZIs and two groups of connecting waveguides, each group is two equal-length waveguides, and the MZIs consist of two MMIs with equal power ratio and two equal-length waveguides. The thermode morphology is consistent with the morphology of the corresponding waveguide, and is positioned right above the straight waveguide in the MZI structure and on one waveguide of the first MZI output end. SiO ₂ is arranged between the hot electrode and the waveguide as a buffer layer, and the two ends of the hot electrode are applied with needed bias voltages to realize the functions of different coupling coefficients, power ratios or phase differences, and finally realize different frequency spectrum responses.

As a preferable technical scheme of the invention, the MZI splits an input optical signal, the splitting ratio is determined by the voltage of a hot electrode right above the MMI connecting waveguide, and the continuous change of the splitting ratio of 0-1 can be realized to obtain two beams of coherent light with required power ratio.

As a preferable technical scheme of the invention, the two MZIs are connected by a group of ring waveguides to form the tunable micro-ring resonator, each MZI is used as a tunable coupler, the coupling coefficient is determined by the voltage of a hot electrode right above the connecting waveguide between MMIs, and the continuous change of the coupling coefficient of 0-1 can be realized so as to meet the flexible regulation and control requirements.

As a preferable technical scheme of the invention, the group of equal-length waveguides are connected with the MZI with the beam splitting function and the two MZIs forming the tunable micro-ring resonator, the equal length of the group of equal-length waveguides ensures that two paths of light after beam splitting do not generate extra phase differences due to different optical paths, and the phase differences of the two paths of light are all determined by the voltage of a hot electrode right above the group of waveguides, so that the continuous change of 0-2 pi of phase difference can be realized.

As a preferable technical scheme of the tunable micro-ring resonator, the two ports selected by the tunable micro-ring resonator are different sides, so that the propagation directions of optical signals input from the two ports in the ring are ensured to be the same, and better coherence of two paths of light in the ring is realized.

As a preferable technical scheme, the waveguide layer comprises three MZIs and two groups of equal-length waveguide groups, each waveguide is prepared from an SOI material system, all waveguides are rectangular waveguides, and the cross section size of each connecting waveguide is 500nm multiplied by 220nm.

As a preferable technical scheme of the invention, the MMI structure in the MZI needs to be connected with the single-mode waveguide in an auxiliary way by adopting Taper type graded waveguides. To reduce optical loss due to mode mismatch.

As a preferred embodiment of the invention, the waveguides used for the unit devices are longer, and for example, a 90-degree curved waveguide in an embodiment can be introduced, such as euler curves, to reduce the propagation loss of light. The thermode is made of TiN material, the temperature of which can be changed by applying a voltage across the thermode, the cross-sectional width of which is 5 μm.

Compared with the prior art, the invention has the advantages that the invention provides the double-injection micro-ring type reconfigurable multi-frequency response unit prepared based on the SOI material, which flexibly splits the power of input light through the MZI type tunable coupler based on the thermo-optic effect, then the input light enters the tunable micro-ring resonator consisting of two MZIs through a group of equal-length waveguides and through the thermoelectric pole modulation phase relation of the two light beams on the waveguides, the two light beams enter the two opposite side ports of the add-drop type micro-ring resonator so as to ensure the consistent direction when the two light beams circulate in the ring, and the coherent results of the two light beams in the ring are different by adjusting the two coupling coefficients of the two light beams, so that various frequency spectrum forms are formed. Compared with the existing reconfigurable optical processor based on the MZI or MDR unit, the reconfigurable optical processor provided by the invention can realize rich spectrum morphology without large-scale cascading and more modulation equipment, improves the reconfigurability of unit devices, avoids the problem of device stability reduction caused by excessive cascading use in the future, and has wider application scenes. Moreover, the manufacturing process of the invention can be compatible with the CMOS process, has mature process and is easy for practical production. In general, the invention has the potential characteristics and advantages of strong functionality of unit devices, capability of forming various morphology spectrums to meet different signal processing requirements, simple modulating means and device design scheme based on thermo-optical effect, low production cost, low power consumption, fewer used modulating units, convenient operation, higher device robustness and the like.

Drawings

Fig. 1 is a schematic three-dimensional structure of the present invention.

Fig. 2 is a top view block diagram of a waveguide of the present invention.

The tunable micro-ring resonator comprises a tunable micro-ring resonator, a waveguide section, a MZI section, a waveguide section, a tunable micro-ring resonator section, a waveguide section and a waveguide section.

FIG. 3 is a schematic view of a portion of an interface between thermodes according to the present invention.

FIG. 4 is a graph showing the output power and phase relationship of the Inlet of 1550nm wavelength optical signal from IN 1 and tempOUT 1-2 with the applied power of Mach-Zehnder interferometer according to the present invention.

Fig. 5 shows the output spectrum of the port (taking IN 1 as an example) at a specific applied power, (a) the micro-ring resonator notch spectrum, (b) the micro-ring resonator notch spectrum (twice the free spectral range), and (c) the square spectrum.

FIG. 6 is a graph showing the relationship between applied power and waveguide temperature.

Detailed Description

In order to enhance the understanding of the present invention, the present embodiment will be described in detail with reference to the accompanying drawings.

Embodiment 1 As shown in fig. 1 and2 (a), the invention designs a double-injection micro-ring type reconfigurable multi-frequency response unit prepared based on SOI materials, wherein a waveguide layer is an Si waveguide embedded in SiO ₂, and the main structure comprises three Mach-Zehnder interferometers and two groups of connecting waveguides, wherein each group is two waveguides with equal length. As shown in FIG. 2 (b), the MZI structure is a rectangular waveguide process comprising two multimode interferometers 1-1 and two connecting waveguides 1-2. For each multimode interferometer, four transition waveguides 1-1-2 are included, as well as multimode waveguide regions 1-1-1. The transition waveguide may use Taper-type waveguides to reduce mode mismatch losses. The input ports of the MZI are IN 1 and IN 2, and are also input ports of the unit device. As shown in FIG. 2 (c), the connecting waveguide is a rectangular waveguide process, and includes a waveguide 2-1 and a waveguide 2-2. The two waveguides are asymmetric but have equal total lengths, and the thermode is only mounted directly above one of the waveguides. As shown in FIG. 2 (d), the tunable micro-ring resonator is a rectangular waveguide process, comprising two Mach-Zehnder interferometers 3-1 as tunable couplers, the specific structural components of which are as shown in FIG. 2 (b), and two ring waveguides 3-2 for the interconnection of MZIs. As shown in fig. 1, a rectangular TiN thermode 4 is provided over one of the three MZI connection waveguides and over one of the long connection waveguides of the group, ohmic heat being generated by applying a voltage across the thermode, thereby changing the temperature of the waveguides in the electrode coverage area. A partial cross-sectional view of the electrode is shown in fig. 3. In fig. 1 and3, the upper cladding layer 5-1 protects the electrode, the lower cladding layer 5-2 is a buffer layer between the waveguide layer and the thermode 4, and the lower most is an Si base layer 6.

The principle of the unit device of the invention is that the dual injection micro-ring structure injects two beams of coherent light into a predetermined position of one resonator, and the output at the final port can be regarded as the superposition of the outputs of the through end and the drain end of two nearly identical add-drop ring resonators. Under the structure of the invention, an input optical signal with the center wavelength at the working wavelength of a unit device enters a straight waveguide through IN 1 (or IN 2), a 1:1 beam splitting is formed through a multimode interferometer 1-1, under the modulation of a thermode 4-1, the phase relation of optical signals of an upper waveguide 1-2 and a lower waveguide 1-2 is changed, the optical signals enter a multimode waveguide area 1-1-1 of a second multimode interferometer 1-1 to interfere to form beam splitting with different power ratios, the beam splitting is respectively output from ports tempOUT 1-1 and tempOUT 1-2, tempOUT-1 and tempOUT-2 are respectively IN butt joint with tempIN 2-1 and tempIN-2, two beams of coherent light are respectively modulated through waveguides 2-1 and 2-2, the phase relation of the two beams of coherent light is modulated by a thermode 4-2, the coherent light IN the waveguide 2-1 enters a tempIN-1 through tempOUT-1, the coupling coefficient of the coherent light entering an adjustable micro-ring is controlled through the thermode 4-3, and the coherent light IN the waveguide 2-2 enters the micro-4 through the thermode 35-4. By adjusting the thermode group 4, a variation of the output spectrum can finally be achieved.

In order to verify that the present invention can realize this function, a verification example is specifically described.

The verification example adopts a time domain finite difference method and a transmission matrix method to jointly perform calculation and analysis. The main parameters used in the simulation calculation are that the width of the rectangular waveguide section is 500nm, the height is 220nm, the thermo-optical coefficients of silicon and silicon dioxide are respectively 1.84 multiplied by 10 ^-4、 1×10^-5, the width of a multimode waveguide area 1-1-1 of the multimode interferometer 1-1 in the Mach-Zehnder interferometer 1 is 6 mu m, the length is 41.8 mu m, the transition waveguide 1-1-2 is selected to be a linear Taper waveguide, the length of a long side is 1.6 mu m, the length is 10 mu m, the length of the intermediate waveguide 1-2 is 200 mu m, the connecting waveguide group 2 is a combination of a plurality of sections of waveguides, the total lengths of the waveguides are equal through topological design, the radius of a ring waveguide is 50 mu m, the total length is pi multiplied by 2 multiplied by 50 mu m, the total length of a straight waveguide is 332 mu m, the parameters of the multimode waveguide area 1-1-1 in the tunable micro-ring resonator 3 are consistent with the Mach-Zehnder interferometer 1, and the half-ring waveguide 3-2 of 150 mu m is connected.

Taking the light input from IN 1 as an example, the output power and phase relationship of the MZI input from IN 1 to tempOUT-2 with the applied power IN 1550nm optical signal input are shown IN FIG. 4.

By the joint modulation of the thermode group 4, various spectrum morphologies can be obtained, three kinds of spectrum having a certain representativeness are shown in fig. 5 (a) being the spectrum of the through end of the micro-ring resonator, fig. 5 (b) being the spectrum of the through end of the micro-ring resonator expanding the free spectrum range, and fig. 5 (c) being the spectrum of an approximate square.

Fig. 6 shows the corresponding waveguide temperature change amounts under different power consumption, and it can be seen that the waveguide temperature change amounts corresponding to the consumed electric power are approximately in a proportional relationship, the proportionality coefficient is about 3.05K/mW, and the approximately linear formant shift can be better used for controlling the MZI.

In conclusion, the double-injection micro-ring type reconfigurable multi-frequency response unit prepared based on the SOI material can directly realize various frequency domain processing on an optical signal, has a relatively simple modulation mode, has better functionality, and can be better added into the design of an optical processor. And meanwhile, the semiconductor device has the potential characteristics and advantages of simplicity in manufacturing, compatibility with CMOS and low power consumption.

It should be noted that the above-mentioned embodiments are not intended to limit the scope of the present invention, and equivalent changes or substitutions made on the basis of the above-mentioned technical solutions fall within the scope of the present invention as defined in the claims.

Claims (4)

1. A dual-injection microring reconfigurable multi-spectral response unit based on SOI material, characterized in that it includes a _SiO2 cladding, a horizontally arranged waveguide layer inside the cladding, the waveguide layer being made of Si material, and a thermal electrode being 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 micro-ring 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 size of the connecting waveguide is 500 nm × 220 nm. 3. The dual-injection micro-ring reconfigurable multi-spectral response unit based on SOI material according to claim 1, characterized in that: the MMI structure in the MZI requires a Taper-type tapered waveguide to assist in the connection between its multimode waveguide region and single-mode waveguide. 4. The dual-injection microring reconfigurable multi-spectral response unit based on SOI material according to claim 1, characterized in that: the hot electrode is made of TiN material, and its temperature can be changed by applying voltage to both ends of the hot electrode, and its cross-sectional width is 5μm.