CN110941048A - High extinction ratio coarse wavelength division multiplexer/demultiplexer based on multi-mode interference principle - Google Patents
High extinction ratio coarse wavelength division multiplexer/demultiplexer based on multi-mode interference principle Download PDFInfo
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
- G02B6/2808—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using a mixing element which evenly distributes an input signal over a number of outputs
- G02B6/2813—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using a mixing element which evenly distributes an input signal over a number of outputs based on multimode interference effect, i.e. self-imaging
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29344—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by modal interference or beating, i.e. of transverse modes, e.g. zero-gap directional coupler, MMI
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/2938—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0201—Add-and-drop multiplexing
- H04J14/0202—Arrangements therefor
Abstract
A coarse wavelength division multiplexer/demultiplexer comprising: a substrate; a silicon dioxide oxide layer on the substrate; a bulk silicon lower waveguide layer located on the silicon dioxide oxide layer; the silicon nitride waveguide layer is positioned on the bulk silicon lower waveguide layer; a bulk silicon upper waveguide layer located on the silicon nitride waveguide layer; the multi-mode interference coupler comprises a multiplexing/demultiplexing unit, a collecting unit and a filtering unit, wherein the multiplexing/demultiplexing unit is used for 1.31 micron/1.55 micron light waves, the input end of the collecting unit is connected with the multiplexing/demultiplexing unit, and the input end of the filtering unit is connected with the output end of the multiplexing/demultiplexing unit. The multiplexer/demultiplexer can form a reconvergence mirror image point at different positions, so that two light waves can be separated and collected at different positions, and therefore optical signal crosstalk of the multiplexer/demultiplexer is small, and the extinction ratio is high.
Description
Technical Field
The invention relates to the technical field of semiconductor photoelectron, in particular to a high extinction ratio coarse wavelength division multiplexer/demultiplexer based on a multimode interference principle.
Background
In high-speed optical communication systems, wavelength division multiplexing is widely used and provides a large number of communication channels and enormous communication capacity for people. A technique of simultaneously transmitting a plurality of wavelengths at a certain interval and performing communication by multiplexing and demultiplexing is called wavelength division multiplexing. The wavelength division multiplexing technology is one of the indispensable key technologies in modern communication systems, can greatly improve the communication capacity of a single communication line, and is used for transmitting signals with various wavelengths in wired communication and wireless communication systems so as to meet the requirements of the modern society on high-speed and large-capacity communication. In the wavelength division multiplexing system, multiplexers/demultiplexers and multiplexers are the subject of intensive research, and in recent years, multiplexers and multiplexers/demultiplexers of different materials and different structures have been proposed in succession by researchers, wherein the multiplexers and multiplexers/demultiplexers based on the principle of multi-mode interference are widely concerned by the researchers by virtue of their unique advantages, such as low loss, large process tolerance, compact structure and the like. Among these developments, multimode interference couplers of silicon-based silicon nitride structure have some outstanding advantages, such as simple fabrication and compatibility with integrated circuit processes, as well as large refractive index difference between silicon nitride and silicon dioxide, small device size, and low crosstalk. This makes the structure widely used in silicon photonic integration, which is the development trend of wavelength division multiplexing in photonic integration in the future.
First, the wavelength division multiplexer needs to be designed to consider the difference between TE and TM modes of the same wavelength light wave. The light emitted by a laser source in a communication system is generally TE mode light waves, but in the process of transmitting an optical signal in an optical fiber, the TE mode light waves of original signal light are gradually changed into two components of TE and TM modes under the influence of polarization change, and as the TE and TM modes have different refractive indexes and different mirror lengths in a multiplexer/demultiplexer, the multiplexer/demultiplexer needs to select a suitable layer material as much as possible to obtain smaller refractive index difference between the TE mode and the TM mode so as to ensure that the two kinds of TE/TM mode light waves can be simultaneously separated by the multiplexer/demultiplexer without loss, namely polarization insensitivity, and thus a low-loss wave splitting function is realized, the traditional three-five group materials are difficult to realize smaller refractive index difference between the TE and the TM, so the multiplexer/demultiplexer based on the three-five group materials is basically insensitive to polarization, however, the multiplexer/demultiplexer based on the silicon-based silicon nitride structure can change the refractive index by adjusting the composition of the silicon nitride, so that the TE and TM modes have the same refractive index, and realize the polarization-insensitive demultiplexing function.
Secondly, the multiplexer/demultiplexer and the multiplexer designed at present are widely implemented by using a multimode interference method, although these technical schemes can obtain lower loss, the extinction ratio is often limited and cannot be made very high, and a large part of these schemes do not consider the two modes of TE/TM, but only pay attention to the multiplexing and demultiplexing of the 1.3 micron and 1.5 micron optical waves of the TE mode, which will certainly cause the attenuation and deformation of the transmission signal due to the loss of the TM mode in practical application, so that a polarization insensitive multiplexer/demultiplexer having a high extinction ratio and capable of supporting the two modes of TE/TM must be developed. In a high-speed optical communication system, a polarization insensitive coarse wavelength division multiplexer based on multimode interference is not only an effective method for realizing the application of a wavelength division multiplexing technology in photonic integration, but also an important basic technology for realizing a future higher-speed optical network.
At present, there are many reports on the schemes of multiplexers applied to the wavelength division multiplexing technology, including schemes such as a multimode interference waveguide structure, a photonic crystal structure, a directional coupler structure, and a mach-zehnder interferometer structure. However, there is no report on devices that satisfy both high extinction ratios and polarization insensitivity, while most designs do not consider simultaneous splitting of TE and TM modes. That is, there is no device in the prior art that can satisfy both high extinction ratio and polarization insensitivity.
Disclosure of Invention
In view of the above, the main object of the present invention is to provide a coarse wavelength division multiplexer/demultiplexer with high extinction ratio based on the principle of multi-mode interference, so as to partially solve at least one of the above technical problems.
To achieve the above object, as an aspect of the present invention, there is provided a high extinction ratio coarse wavelength division multiplexer/demultiplexer based on a principle of multimode interference, including:
a substrate;
a silicon dioxide oxide layer on the substrate;
a bulk silicon lower waveguide layer located on the silicon dioxide oxide layer;
the silicon nitride waveguide layer is positioned on the bulk silicon lower waveguide layer;
a bulk silicon upper waveguide layer located on the silicon nitride waveguide layer;
the multi-mode interference coupler comprises a multiplexing/demultiplexing unit, a collecting unit and a filtering unit, wherein the multiplexing/demultiplexing unit is used for 1.31 micron/1.55 micron light waves, the input end of the collecting unit is connected with the multiplexing/demultiplexing unit, and the input end of the filtering unit is connected with the output end of the multiplexing/demultiplexing unit.
The coarse wavelength division multiplexing/demultiplexing device further comprises an input waveguide and an output waveguide, and the widths of the input waveguide and the output waveguide are 1 micrometer, so that single-mode transmission of light waves in the coarse wavelength division multiplexing/demultiplexing device is achieved, and the direct connection with a light source is realized without an additional spot size converter.
The bulk silicon lower waveguide layer, the silicon nitride waveguide layer and the bulk silicon upper waveguide layer are all multi-mode interference waveguides, incident light waves are converged again to form mirror image points of the incident light waves after being transmitted for a certain distance, namely the mirror image points converged again can be formed at different positions, and therefore two beams of light waves are separated and collected at different positions.
The silicon nitride waveguide layer changes the refractive index of the material by changing the proportion of nitrogen elements, and obtains the minimum image distance difference of two polarization modes of TE/TM of the same wavelength light wave at a specific refractive index, thereby realizing that the two polarization modes of TE/TM of the same wavelength light wave are emitted from the same outlet at the same time.
The filtering unit is a 1.3 micron light wave filtering unit and is formed by connecting a plurality of multimode interference waveguides in series, and the filtering unit filters redundant 1.5 micron light wave components, so that a high extinction ratio is obtained.
The collecting unit is a 1.5 micron light wave collecting unit and comprises a multimode interference waveguide, collected light waves with the wavelength of 1.5 microns are converged again in the collecting unit and emitted at a mirror image point, and meanwhile, 1.3 micron light wave components are filtered out.
The refractive index of the silicon dioxide oxidation layer is less than or equal to 2 compared with that of bulk silicon, and the silicon dioxide oxidation layer is a cladding layer for isolating an optical field and is used for limiting the optical field in a bulk silicon lower waveguide layer, a silicon nitride waveguide layer and a bulk silicon upper waveguide layer which are positioned on the silicon dioxide oxidation layer without leaking into the substrate.
The silicon nitride waveguide layer is controlled to have a refractive index within a range of 1.7-3.4, preferably within a range of 2.9-3.0, by ion-assisted deposition of silicon nitride.
When the light waves enter from the port of the multiplexing/demultiplexing unit and exit from the filtering unit and the collecting unit, the demultiplexing function is realized; when the light waves enter from the ports of the filtering unit and the collecting unit and exit from the ports of the multiplexing/demultiplexing unit, the multiplexing function is realized.
As another aspect of the present invention, there is also provided an optical communication apparatus for wavelength division multiplexing/demultiplexing using the coarse wavelength division multiplexer/demultiplexer as described above.
Based on the above technical solution, the high extinction ratio coarse wavelength division multiplexer/demultiplexer based on the multi-mode interference principle of the present invention has at least one or some of the following advantages compared with the prior art:
1. the multiplexer/demultiplexer can form a reconvergence mirror image point at different positions, so that two light waves can be separated and collected at different positions, and therefore optical signal crosstalk of the multiplexer/demultiplexer is small, and the extinction ratio is high.
2. The silicon nitride waveguide layer used by the invention changes the material refractive index by changing the proportion of nitrogen elements, so the invention can meet the requirement of polarization insensitivity of modern high-speed communication lines.
3. The invention also adds 1.3 micron filter unit and 1.5 micron collecting unit behind the first multi-mode interference multiplexer/demultiplexer, the filter unit is formed by connecting multiple multi-mode interference waveguides in series, the filter unit filters out the redundant 1.5 micron light wave component to obtain high extinction ratio; the collecting unit is also composed of a multimode interference waveguide, the collected light wave with the wavelength of 1.5 microns is converged in the waveguide again to be emitted at the mirror image point, and simultaneously, the mirror image lengths of the light waves with the wavelength of 1.3 microns and the light waves with the wavelength of 1.5 microns in the collecting unit are different, so that the effect of filtering the light wave component with the wavelength of 1.3 microns is achieved, and the design can achieve a high extinction ratio while keeping a short device length.
Drawings
FIG. 1 is a longitudinal sectional view of a coarse wavelength division multiplexer/demultiplexer with a high extinction ratio according to an embodiment of the present invention;
FIG. 2 is a top view of a high extinction ratio coarse wavelength division multiplexer/demultiplexer of an embodiment of the present invention;
FIG. 3 is a schematic diagram of a triangular region of a high extinction ratio coarse wavelength division multiplexer/demultiplexer after reflection of a wavelength signal of 1.5 μm wavelength in a multimode interference waveguide according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of the transmission of 1.3 micron wavelength lightwaves for a high extinction ratio coarse wavelength division multiplexer/demultiplexer according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of the transmission of 1.5 micron wavelength lightwaves for a high extinction ratio coarse wavelength division multiplexer/demultiplexer according to an embodiment of the present invention;
fig. 6 is a schematic diagram of the size parameters of the coarse wdm/demux with high extinction ratio according to the embodiment of the present invention.
In the above drawings, the reference numerals have the following meanings:
1. a substrate; 2. A silicon dioxide oxide layer;
3. a bulk silicon lower waveguide layer; 4. A silicon nitride waveguide layer;
5. a bulk silicon upper waveguide layer; 6. 1.31 micron/1.55 micron multiplexing/demultiplexing unit;
7. a 1.5 micron collection unit; 8. 1.3 micron filter unit.
Detailed Description
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
According to the multimode interference waveguide adopted by the invention, according to a multimode interference theory, an incident optical signal can form an image with the same intensity as an incident point after being transmitted for a certain distance, the image is called as a mirror image point of the optical signal, the transmitted distance is the mirror image length of the wavelength, the refractive index of materials can be continuously changed for different wavelengths and different polarization modes, and the mirror image lengths are different under the influence of the change.
Because the effective refractive index is determined by the length of the signal mirror image in the waveguide and is determined by all layers of materials, a layer of silicon nitride material with adjustable refractive index is added on the bulk silicon material, so that the refractive index of the silicon nitride is changed, and the effective refractive index of the whole material is changed, thereby changing the mirror image lengths of light waves with different wavelengths.
Through simulation design, when the refractive index of the silicon nitride waveguide layer is 2.985, the TE and TM modes of the light wave with the wavelength of 1.55 microns have the same refractive index, and when the refractive index of the silicon nitride waveguide layer is 2.94, the TE and TM modes of the light wave with the wavelength of 1.3 microns have the same effective refractive index, so that the embodiment selects the refractive index of silicon nitride to be 2.9665, the effective refractive indexes of the TE and TM modes of the light waves with the wavelengths of 1.3 microns and 1.5 microns are both the closest, and the difference of the mirror lengths of the two modes is not more than 1 micron, so that multiplexing and demultiplexing of TM/TE modes with different wavelengths can be simultaneously supported, and polarization insensitivity is realized.
Specifically, the invention discloses a high extinction ratio coarse wavelength division multiplexer/demultiplexer based on the multi-mode interference principle, which comprises:
a substrate;
a silicon dioxide oxide layer on the substrate;
a bulk silicon lower waveguide layer located on the silicon dioxide oxide layer;
the silicon nitride waveguide layer is positioned on the bulk silicon lower waveguide layer;
a bulk silicon upper waveguide layer located on the silicon nitride waveguide layer;
the multi-mode interference coupler comprises a multiplexing/demultiplexing unit, a collecting unit and a filtering unit, wherein the multiplexing/demultiplexing unit is used for 1.31 micron/1.55 micron light waves, the input end of the collecting unit is connected with the multiplexing/demultiplexing unit, and the input end of the filtering unit is connected with the output end of the multiplexing/demultiplexing unit.
The coarse wavelength division multiplexing/demultiplexing device further comprises an input waveguide and an output waveguide, and the widths of the input waveguide and the output waveguide are 1 micrometer, so that single-mode transmission of light waves in the coarse wavelength division multiplexing/demultiplexing device is achieved, and the direct connection with a light source is realized without an additional spot size converter.
The bulk silicon lower waveguide layer, the silicon nitride waveguide layer and the bulk silicon upper waveguide layer are all multi-mode interference waveguides, incident light waves are converged again to form mirror image points of the incident light waves after being transmitted for a certain distance, namely the mirror image points converged again can be formed at different positions, and therefore two beams of light waves are separated and collected at different positions.
The silicon nitride waveguide layer changes the refractive index of the material by changing the proportion of nitrogen elements, and obtains the minimum image distance difference of two polarization modes of TE/TM of the same wavelength light wave at a specific refractive index, thereby realizing that the two polarization modes of TE/TM of the same wavelength light wave are emitted from the same outlet at the same time.
The filtering unit is a 1.3 micron light wave filtering unit and is formed by connecting a plurality of multimode interference waveguides in series, and the filtering unit filters redundant 1.5 micron light wave components, so that a high extinction ratio is obtained.
The collecting unit is a 1.5 micron light wave collecting unit and comprises a multimode interference waveguide, collected light waves with the wavelength of 1.5 microns are converged again in the collecting unit and emitted at a mirror image point, and meanwhile, 1.3 micron light wave components are filtered out.
The refractive index of the silicon dioxide oxidation layer is less than or equal to 2 compared with that of bulk silicon, and the silicon dioxide oxidation layer is a cladding layer for isolating an optical field and is used for limiting the optical field in a bulk silicon lower waveguide layer, a silicon nitride waveguide layer and a bulk silicon upper waveguide layer which are positioned on the silicon dioxide oxidation layer without leaking into the substrate.
The silicon nitride waveguide layer is controlled to have a refractive index within a range of 1.7-3.4, preferably within a range of 2.9-3.0, by ion-assisted deposition of silicon nitride.
When the light waves enter from the port of the multiplexing/demultiplexing unit and exit from the filtering unit and the collecting unit, the demultiplexing function is realized; when the light waves enter from the ports of the filtering unit and the collecting unit and exit from the ports of the multiplexing/demultiplexing unit, the multiplexing function is realized.
Examples
Referring to fig. 1 and fig. 2, in a polarization insensitive coarse wavelength division multiplexer/demultiplexer with a high extinction ratio based on the principle of multimode interference according to an embodiment of the present invention, the input/output waveguides of the device and the straight waveguides connecting each portion have a width of 1 μm, and based on the principle of multimode interference, the device is composed of five multimode interference couplers, which form three parts, namely, a multiplexing/demultiplexing unit, a 1.5 μm collection unit, and a 1.3 μm filtering unit, and the device specifically includes:
a substrate 1 which is an n-type Si substrate;
a silicon oxide layer 2, the two-like silicon oxide layer 2 being formed on the substrate 1;
the refractive index of the silicon dioxide oxide layer 2 corresponding to the light waves of 1.3 microns and 1.5 microns is 1.44, and the difference between the refractive index of the silicon dioxide oxide layer and the refractive index of bulk silicon is large, so that the silicon dioxide oxide layer is a cladding layer for isolating an optical field, and the optical field is completely limited in the waveguide layer above the silicon dioxide oxide layer and cannot be leaked into the Si substrate.
A bulk silicon lower waveguide layer 3, wherein the bulk silicon lower waveguide layer 3 is manufactured on the silicon dioxide oxide layer 2;
wherein the thickness of the bulk silicon waveguide layer is 0.1 micron, the refractive index is 3.43, which is larger than the refractive index of the silicon dioxide oxide layer 2, so that the optical signal will be transmitted in the layer, and the waveguide layer functions as an optical signal waveguide.
A silicon nitride waveguide layer 4, wherein the silicon nitride waveguide layer 4 is manufactured on the bulk silicon lower waveguide layer 3;
the thickness of the silicon nitride waveguide layer 4 is 0.25 microns, and the refractive index of the silicon nitride can be randomly adjusted within the range of 1.7-3.4 through ion-assisted deposition.
A bulk silicon upper waveguide layer 5, wherein the bulk silicon upper waveguide layer 5 is manufactured on the silicon nitride waveguide layer 4;
wherein the bulk silicon upper waveguide layer has a thickness of about 0.1 microns and a refractive index of about 3.43. since the refractive index of bulk silicon is greater than that of silicon nitride and silicon dioxide, the optical signal in the present invention will propagate primarily in both the bulk silicon lower waveguide layer 3 and the bulk silicon upper waveguide layer 5.
The 1.31 micron/1.55 micron multiplexer/demultiplexer 6 is designed by optimization, and uses a multimode interference coupler with a width of 8 microns and a length of 622 microns, and its length is just the mirror length of the 1.3 micron optical wave, so that the 1.3 micron optical wave will exit at the outlet of the coupler and directly enter the next 1.3 micron filter unit part, and there is substantially no loss, and the mirror length of the 1.5 micron optical wave is around 580 microns, so that it will be reflected before the 1.3 micron output port, and there is a triangular region between the reflected 1.5 micron signal and the 1.3 micron output port, and the 1.3 micron output port in the triangular region will not collect any 1.5 micron signal light, so most of the signal enters the next 1.5 micron collection waveguide, and the schematic diagram of the triangular region in the 1.5 micron multimode interference waveguide is shown in fig. 3.
A 1.5 micron collection unit 7, which is composed of a section of multimode interference waveguide, the reflected incoming light wave will interfere again in the waveguide to form a mirror point and exit from the output waveguide, according to the simulation design and structure optimization, the waveguide width is 6.5 microns, the length is 261 microns, the loss of the 1.5 micron output is 1.3dB, the extinction ratio is 35dB, and the transmission diagram of the 1.5 micron wavelength signal in the structure of this embodiment is shown in fig. 4.
A 1.3 micron filter unit 8 comprising three identical sections of multimode interference waveguides having a width of 4 microns and a length of 52 microns, equal to the mirror length of the 1.3 micron wavelength. After three-stage filtering, the extinction ratio of 1.3 micrometers is improved to about 38dB, the loss is about 0.7dB, and the length of the 1.3-micrometer filtering unit is consistent with that of the 1.5-micrometer collecting unit, so that the extinction ratio is improved under the condition of not increasing the length of a device. The transmission diagram of signals with 1.3 micron wavelength in the structure of the design is shown in fig. 5.
According to the reversibility of the optical path, two wavelengths of 1.3 microns and 1.5 microns of a single channel on the left side in the graph 2 are input at the same time, and the multichannel output on the right side realizes the demultiplexing process; otherwise, the two channels are input from the right side, and the single-channel wave-combining output from the left side realizes the multiplexing process of the double wavelengths.
The extinction ratio of 1.5 microns of the final device design can reach 35dB, the loss is as low as 1.3dB, the extinction ratio of 1.3 microns can reach 38dB, the loss is as low as 0.7dB, and the TE/TM mode simultaneous multiplexing/demultiplexing can be realized, the extinction ratios of other designs proposed previously, whether based on silicon and silicon nitride waveguides or three-five material waveguides, are below 25dB, therefore, the design realizes the multiplexing/demultiplexing function of high extinction ratio while the polarization is insensitive, and the schematic diagram of the dimensional parameters of each part of the device structure is shown in FIG. 6.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A coarse wavelength division multiplexer/demultiplexer comprising:
a substrate;
a silicon dioxide oxide layer on the substrate;
a bulk silicon lower waveguide layer located on the silicon dioxide oxide layer;
the silicon nitride waveguide layer is positioned on the bulk silicon lower waveguide layer;
a bulk silicon upper waveguide layer located on the silicon nitride waveguide layer;
the multi-mode interference coupler comprises a multiplexing/demultiplexing unit, a collecting unit and a filtering unit, wherein the multiplexing/demultiplexing unit is used for 1.31 micron/1.55 micron light waves, the input end of the collecting unit is connected with the multiplexing/demultiplexing unit, and the input end of the filtering unit is connected with the output end of the multiplexing/demultiplexing unit.
2. The coarse wavelength division multiplexer/demultiplexer of claim 1, further comprising an input waveguide and an output waveguide each having a width of 1 μm, thereby achieving single-mode transmission of light waves in the coarse wavelength division multiplexer/demultiplexer, enabling direct connection to a light source without an additional spot size converter.
3. The coarse wavelength division multiplexer/demultiplexer of claim 1, wherein the bulk silicon lower waveguide layer, the silicon nitride waveguide layer, and the bulk silicon upper waveguide layer all employ multimode interference waveguides, and incident light waves are converged again after propagating for a certain distance to form mirror points of the incident light waves, that is, the mirror points converged again can be formed at different positions, thereby realizing that two light waves are separated and collected at different positions.
4. The coarse wavelength division multiplexer/demultiplexer of claim 1, wherein the silicon nitride waveguide layer is formed by changing the refractive index of the material by changing the ratio of nitrogen elements, so as to obtain the smallest difference of image distances of the two polarization modes of TE/TM for the same wavelength of light at a specific refractive index, thereby realizing that the two polarization modes of TE/TM for the same wavelength of light exit from the same exit simultaneously.
5. The coarse wavelength division multiplexer/demultiplexer of claim 1, wherein the filtering unit is a 1.3 micron optical wave filtering unit, and is formed by connecting a plurality of multimode interference waveguides in series, and the filtering unit filters out unwanted 1.5 micron optical wave components, so as to obtain a higher extinction ratio.
6. The coarse wavelength division multiplexer/demultiplexer of claim 1, wherein the collection unit is a 1.5 micron optical wave collection unit, comprising a multi-mode interference waveguide, and the collected 1.5 micron wavelength optical waves are re-converged in the collection unit to exit at the mirror point while filtering out 1.3 micron optical wave components.
7. The coarse wavelength division multiplexer/demultiplexer of claim 1, wherein the silica oxide layer has a refractive index of 2 or less than bulk silicon, and is a cladding layer isolating the optical field for confining the optical field to the bulk silicon lower waveguide layer, the silicon nitride waveguide layer and the bulk silicon upper waveguide layer located on the silica oxide layer without leakage into the substrate.
8. The coarse wavelength division multiplexer/demultiplexer of claim 1, wherein the silicon nitride waveguide layer has a refractive index controlled in the range of 1.7 to 3.4, preferably in the range of 2.9 to 3.0, by ion assisted deposition of silicon nitride.
9. The coarse wavelength division multiplexer/demultiplexer of claim 1, wherein a demultiplexing function is implemented when light waves are incident from ports of the multiplexing/demultiplexing unit, and exit from the filtering unit and the collecting unit; when the light waves enter from the ports of the filtering unit and the collecting unit and exit from the ports of the multiplexing/demultiplexing unit, the multiplexing function is realized.
10. An optical communication apparatus for wavelength division multiplexing/demultiplexing using the coarse wavelength division multiplexing/demultiplexing device according to any one of claims 1 to 9.
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