CN114460687A - Coupling structure applied to silicon optical chip - Google Patents
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- CN114460687A CN114460687A CN202210059610.3A CN202210059610A CN114460687A CN 114460687 A CN114460687 A CN 114460687A CN 202210059610 A CN202210059610 A CN 202210059610A CN 114460687 A CN114460687 A CN 114460687A
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 164
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 164
- 239000010703 silicon Substances 0.000 title claims abstract description 164
- 230000008878 coupling Effects 0.000 title claims abstract description 72
- 238000010168 coupling process Methods 0.000 title claims abstract description 72
- 238000005859 coupling reaction Methods 0.000 title claims abstract description 72
- 230000003287 optical effect Effects 0.000 title claims abstract description 67
- 239000000758 substrate Substances 0.000 claims abstract description 34
- 125000004430 oxygen atom Chemical group O* 0.000 claims abstract description 14
- 125000004433 nitrogen atom Chemical group N* 0.000 claims abstract description 10
- 238000005253 cladding Methods 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims description 13
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 2
- 239000001301 oxygen Substances 0.000 claims 1
- 229910052760 oxygen Inorganic materials 0.000 claims 1
- 239000000835 fiber Substances 0.000 abstract description 13
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 6
- 230000008859 change Effects 0.000 abstract description 4
- 230000010287 polarization Effects 0.000 abstract description 3
- 239000000377 silicon dioxide Substances 0.000 abstract description 3
- 235000012239 silicon dioxide Nutrition 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 158
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- 230000005540 biological transmission Effects 0.000 description 12
- 238000010586 diagram Methods 0.000 description 7
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- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 4
- 238000004891 communication Methods 0.000 description 3
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- 238000005498 polishing Methods 0.000 description 2
- 239000002210 silicon-based material Substances 0.000 description 2
- 229910020781 SixOy Inorganic materials 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000001808 coupling effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 238000005290 field theory Methods 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
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Classifications
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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
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/14—Mode converters
-
- 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
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
-
- 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
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
-
- 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
-
- 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
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12035—Materials
- G02B2006/12038—Glass (SiO2 based materials)
Abstract
The application provides a coupling structure, including setting up the at least two-layer silicon oxynitride layer on the substrate, the coupling of light is realized in the cooperation of light input end in each layer silicon oxynitride layer. Each of the silicon oxynitride layers is stacked in a direction perpendicular to the plane of the substrate, and the ratio of the number of oxygen atoms to the number of nitrogen atoms in the silicon oxynitride layer closer to the substrate is smaller. The cladding layer is designed to be the outermost structure of the coupling structure, and is matched with the substrate to limit the light beam in at least two silicon oxynitride layers, and in some embodiments, the cladding layer is made of silicon dioxide. The problem of high requirement on the ultra-narrow waveguide etching precision is avoided, the ultra-low coupling loss between the optical waveguide and the single-mode fiber is realized while the original process precision condition is maintained, the etching process precision is not required to be improved, the structure is insensitive to the light energy intensity and temperature change, and the structure can realize quite high coupling efficiency, ultrahigh bandwidth and polarization insensitivity in severe environment.
Description
Technical Field
The application relates to the field of optical fiber communication, in particular to a coupling structure applied to a silicon optical chip.
Background
With the increasing demand of the transmission rate of the optical network further increasing, more and more complex optical transmission systems are applied in the optical network. Silicon materials have the potential to build compact photonic devices due to their high refractive index, and photonic devices based on silicon materials have good compatibility with the current mature and standardized CMOS process platforms, and are increasingly being applied in photonic integrated chips. The interconnection requirement of the optical fiber and the silicon photonic integrated circuit is also gradually increased, and the coupling effect of the optical fiber and the photonic integrated chip is an important factor influencing the system performance. As known to the inventor, the size of a silicon waveguide of a photonic integrated chip (i.e., a silicon optical chip) can be as small as tens of nanometers to hundreds of nanometers, and a typical diameter of a Single Mode Fiber (SMF) coupled thereto is about 125 micrometers, and a core diameter of the single mode fiber is close to 10 micrometers, so that there is a large size mismatch between the single mode fiber and the silicon waveguide, and the size mismatch will cause considerable optical transmission loss.
Couplers are commonly used to address the problem of dimensional mismatch between optical fibers and silicon waveguides, which can guide light to effect mode conversion to address the above-mentioned problems. The coupler is mainly arranged in two modes of vertical coupling and edge coupling. The vertical coupling known to the inventors has mostly used grating couplers, where the fiber is placed vertically above the coupler or slightly tilted to ensure a high coupling efficiency. The grating coupler has compact size, wafer-level testing capability and flexible coupling position, but has relatively low coupling efficiency (generally lower than 3dB), narrow bandwidth and wavelength sensitivity. The edge coupler is placed on the end face of the wafer and is horizontally aligned with the silicon waveguide to realize optical coupling of the optical fiber and the silicon waveguide on the silicon optical chip. Edge couplers can achieve fairly high coupling efficiency, wide bandwidth and are polarization insensitive, but they also have some limitations, such as the need to use an inverted taper structure (invertedvane). The reverse inverted cone structure is commonly used in the industry at present. "inverse" means corresponding to the direction of propagation of light, and inverse taper means a tapered waveguide of increasing width along the direction of mode propagation, i.e. the narrow end of the taper is close to the fiber, while the wide end is connected to the photonic waveguide.
The mode distribution in the optical waveguide is determined by the mode order and the waveguide structure, and once the optical waveguide and the optical fiber are produced and shaped, the optical transmission mode is determined. For a particular mode, only a waveguide with a certain cross-sectional area can match the transmission of the entire mode. Presently, silicon optical waveguide dimensions known to the inventors to support fundamental TE mode propagation with negligible loss are about 200nm high and about 500nm wide. If the cross-sectional area of the silicon waveguide is too small, the entire fundamental mode cannot be supported, and a part of the fundamental mode is distributed in the outer region of the waveguide. Whereas a waveguide with an excessively large cross-sectional area is prone to excite unwanted higher-order modes. The inventor is aware of the fact that in edge couplers where the silicon waveguide is designed as an inverted cone with gradually changing cross-sectional area supporting mode conversion and mode size change, this design is only suitable for mode conversion, the tip area of the inverted cone is smaller than the mode size required for matching the external fiber/laser, a considerable portion of the electromagnetic field is distributed around the cone tip and the transmission of the incident mode in the waveguide cannot be completely constrained. As the taper width becomes larger, it is possible to support the transmission of the entire mode and confine the electric field entirely inside the waveguide.
Disclosure of Invention
The application provides a coupling structure for silicon optical chip, including setting up two at least layers of silicon oxynitride layer on the substrate, the coupling of light is realized in the cooperation of light input end in each layer of silicon oxynitride layer. Each of the silicon oxynitride layers is stacked in a direction perpendicular to the plane of the substrate, and the closer to the substrate, the smaller the ratio of the number of oxygen atoms to the number of nitrogen atoms in the silicon oxynitride layer. In some embodiments, the silicon oxynitride layer bonded to the substrate has zero atomic oxygen content, i.e., is a silicon nitride layer. The cladding layer is designed to be the outermost layer structure of the coupling structure, and is matched with the substrate to limit the light beam in at least two layers of silicon oxynitride layers.
In some embodiments, each of the at least two layers of silicon oxynitride has the same width at the light input end. The length of each silicon oxynitride layer in the light transmission direction is designed to be gradually reduced in some embodiments, and each silicon oxynitride layer is trapezoidal in a top view.
In some embodiments, the at least two silicon oxynitride layers each have a different length along the direction of propagation of the light beam, and the length variation law is such that the closer the silicon oxynitride layer is to the substrate, the greater the length along the direction of propagation of the light beam.
In certain embodiments, the silicon oxynitride layer on the substrate is designed to be two, three, four, five, six, seven, eight, or more layers. In some embodiments, the silicon oxynitride layer on the substrate comprises four layers including a first silicon oxynitride layer, a second silicon oxynitride layer, a third silicon oxynitride layer and a fourth silicon oxynitride layer from top to bottom on the substrate layer, and the length of each silicon oxynitride layer along the propagation direction of the light beam is in a relationship of the first silicon oxynitride layer < the second silicon oxynitride layer < the third silicon oxynitride layer < the fourth silicon oxynitride layer.
In other embodiments, the heights of the first silicon oxynitride layer, the second silicon oxynitride layer, the third silicon oxynitride layer and the fourth silicon oxynitride layer are all the same, and the sum of the heights of the four silicon oxynitride layers ranges from 6 microns to 14 microns. The design of the height is determined according to the calculation of relevant factors such as the wavelength of the transmitted light.
In some embodiments, the first, second, third and fourth silicon oxynitride layers have equal widths at the light input end for coupling light into the silicon optical chip.
Based on design requirements, each layer SixOyNzThe content of the oxygen atoms is calculated and determined according to the formula of 4 x-2 y +3z, and in certain embodiments, the first silicon oxynitride layer is made of Si6O9N2The second layer of silicon oxynitride layer is made of Si3O3N2The third layer of silicon oxynitride layer is made of Si2ON2The fourth layer of silicon oxynitride layer is made of Si3N4。
Drawings
FIG. 1 is a schematic illustration of a silicon optical coupling scheme known to the inventors;
FIG. 2 is a schematic diagram of another silicon optical coupling scheme known to the inventors;
FIG. 3 is a schematic diagram of an inverted taper silicon optical coupling scheme known to the inventors;
FIG. 4 is a schematic diagram of a coupling structure in an embodiment implemented based on the inventive concepts of the present application;
FIG. 5 is a schematic diagram of the optical input end of the coupling structure in one embodiment;
FIG. 6 is a schematic diagram of an optical transmission layer in a coupling structure according to an embodiment;
FIG. 7 is a schematic diagram of a coupling structure in an embodiment implemented based on the inventive concepts of the present application;
fig. 8 is a schematic diagram of a coupling structure in an embodiment implemented based on the inventive concept of the present application.
Detailed Description
The following provides a more detailed description of the present invention, with reference to the accompanying drawings. It should be noted that the filling pattern of each structure in the drawings is only used for identifying the enclosing and easy understanding of each structure, and is not used for indicating the characteristics of the material, the relative size and the like of each structure.
An edge coupler solution known to the inventor is shown in fig. 1, where the diameter of the core 101 of the optical fiber is about 9 μm, the size of the silicon optical chip coupling optical waveguide 102 is several hundred nm, and there is a large size mismatch between the core 101 and the optical waveguide 102, which is accompanied by a mode field mismatch. When a light beam is coupled from the core 101 to the optical waveguide 102, the optical coupling loss is large due to mode field mismatch, and the optical coupling efficiency is low.
In another coupler scheme known to the inventors, the eigenmodes are expanded by reducing the waveguide size, and thus the eigenmodes, at the end of the optical waveguide 202 near the optical input, as shown in fig. 2, to match the mode field of the core 201, to increase coupling efficiency. As the optical input end of the optical waveguide 202 is reduced in size, the geometry of the waveguide edge due to process tolerances becomes a major factor in the coupling efficiency. This requires extremely high etching accuracy of the reduced-size portion of the optical input end of the optical waveguide 202 to avoid optical loss due to the reduced size of the optical input end waveguide.
In one coupler scheme known to the inventors, the size of the optical input end in the optical waveguide 302 is increased, as shown in fig. 3, to expand the eigenmodes and match the mode field of the fiber core 301 in an attempt to improve coupling efficiency. However, the single-layer optical waveguide 302 has a thickness of only a few hundred nanometers and cannot match the mode field of the core 301 in the thickness direction of the optical waveguide 302. In order to reduce the effect of too thin a thickness, a wider optical waveguide is required to be designed to reduce the loss.
In some examples, a multi-level cone-coupled structure 4 based on silicon oxynitride is designed, as shown in fig. 400, four silicon oxynitride layers with different lengths are arranged on a silicon dioxide substrate, and are sequentially Si6O9N2Layer 401, Si3O3N2Layer 402, Si2ON2 Layer 403, Si3N4 Layer 404. As shown in FIG. 4, the cross-section of the four-layer cascade taper coupling structure is trapezoidal, the width of each layer at the optical input port is the same as 10 + -5 μm, and then the width of each layer gradually decreases along the optical transmission direction, and the Si at the bottommost layer3N4The light output end of layer 404 is 1 + -0.5 μm wide. The light input end width of the four-stage coupling structure is matched with the diameter of the fiber core of the optical fiber, and the mode field in the width direction is matched with the fiber core, so that the loss is reduced. Meanwhile, the ratio of the number of oxygen atoms to the number of nitrogen atoms of the four layers of silicon oxynitride layers is gradually reduced from the top layer far away from the substrate to the bottom layer near the substrate, so that the loss of light propagating at the interface of two materials with different refractive indexes is reduced.
Fig. 5 is a schematic cross-sectional view of an optical input end of a coupling structure in some embodiments, which includes a fourth silicon oxynitride layer 504, a third silicon oxynitride layer 503, a second silicon oxynitride layer 502, and a first silicon oxynitride layer 501 in sequence from the substrate to a direction away from the substrate, where the ratio of the number of oxygen atoms to the number of nitrogen atoms in the materials of the four silicon oxynitride layers is that the first silicon oxynitride layer 501 is greater than the second silicon oxynitride layer 502 is greater than the third silicon oxynitride layer 503 is greater than the fourth silicon oxynitride layer 504, and the corresponding refractive index gradually increases from the first silicon oxynitride layer 501 to the fourth silicon oxynitride layer 504. The total thickness of the four silicon oxynitride layers is 12 +/-2 microns, and the thickness of each layer is 3 +/-0.5 microns. The thickness of the optical fiber in the direction vertical to the plane of the substrate is matched with the diameter of the optical fiber core, and the optical fiber core is matched with the mode field of the coupling structure in the thickness direction, so that the optical coupling loss is further reduced. Fig. 6 is a schematic front view of a silicon oxynitride layer in an embodiment, which includes a silicon nitride layer 604, a silicon oxynitride layer 603, a silicon oxynitride layer 602, and a silicon oxynitride layer 601 from a substrate upwards in sequence, where the length of the silicon nitride layer 604 along the light transmission direction is the largest, and the lengths of the silicon oxynitride layer 603, the silicon oxynitride layer 602, and the silicon oxynitride layer 601 decrease in sequence, and this design is applied to the coupling structure 400, that is: in propagating along the beamIn the direction of Si6O9N2Layer 401 has a length of 50 + -10 μm, Si3O3N2The length of the layer 402 is 80 + -10 μm, Si2ON2The length of the layer 403 is 110 + -10 μm, Si3N4The length of layer 404 is 140 + -10 μm.
In practical application, the thickness of the coupling structure, the thickness and the width of each layer are designed according to the overall design of the optical fiber model, the silicon optical chip waveguide material structure and the like. The method comprises the following specific steps:
based on the coupling field theory, the coupling efficiency between the optical fiber and the silicon optical chip is expressed as follows:
wherein eta is12Represents the coupling efficiency between the optical fiber and the silicon optical chip, and eta12∈[0，1]，φ1Shows the electric field intensity distribution phi of the single mode fiber near the section of the silicon optical chip1 *Represents the conjugation thereof; phi is a2Shows the electric field intensity distribution phi of the silicon optical chip waveguide close to the end section of the single-mode fiber2 *Represents the conjugation thereof; s represents the area of the intrinsic mode overlapping region of the end section of the optical fiber close to the silicon optical chip and the end section of the silicon optical chip waveguide close to the optical fiber.
Coupling efficiency eta according to design requirements12The intrinsic mode area of the optical fiber after the type of the optical fiber is determined and the electric field distribution phi of the optical fiber close to the silicon optical chip1And its conjugation phi1 *And deducing the size, mode distribution and the like of the coupling structure according to the formula I. The matching degree of the eigenmodes of the section of the optical fiber close to the optical input end of the coupling structure and the section of the coupling structure close to the tail end of the optical fiber is improved, the coupling loss caused by mode mismatching between the section of the optical input end of the optical fiber and the section of the coupling structure close to the tail end of the optical fiber is reduced, and the loss is reduced to be close to 0.
The implementation of the coupling structure 400 avoids the problem of high requirement on the ultra-narrow waveguide etching precision, realizes the ultra-low coupling loss between the optical waveguide and the single-mode fiber while maintaining the original process precision, does not need to improve the etching process precision, is insensitive to the energy intensity and temperature change of light, and can realize quite high coupling efficiency, ultra-high bandwidth and polarization insensitivity in severe environment. The optical fiber has the advantages of large light spot, small mode mismatch, high alignment tolerance and the like, and is particularly suitable for the field of high-speed optical communication, such as single-wave 100G or even higher communication rate application scenes, which need to use single-mode optical fibers for optical signal transmission.
Based on the extension scheme of the above embodiment concept, in other embodiments, as shown in fig. 7, the coupling structure 700 is configured to design eight silicon oxynitride structures on the substrate, which are, in order from the far side to the near side, a silicon oxynitride layer 701, a silicon oxynitride layer 702, a silicon oxynitride layer 703, a silicon oxynitride layer 704, a silicon oxynitride layer 705, a silicon oxynitride layer 706, a silicon oxynitride layer 707, and a silicon oxynitride layer 708. The height of each layer is 1.5 +/-0.2 mu m, the width of the light input end is 10 +/-2 mu m, and the width of the end face of the silicon oxynitride layer 708 coupled with the functional part of the silicon optical chip is 1 +/-0.1 mu m. The length of the silicon oxynitride layer 701 is 50 +/-2 μm, the length of the silicon oxynitride layer 702 is 65 +/-2 μm, the length of the silicon oxynitride layer 703 is 80 +/-2 μm, the length of the silicon oxynitride layer 704 is 95 +/-2 μm, the length of the silicon oxynitride layer 705 is 110 +/-2 μm, the length of the silicon oxynitride layer 706 is 125 +/-2 μm, the length of the silicon oxynitride layer 707 is 140 +/-2 μm, and the length of the silicon oxynitride layer 708 is 155 +/-2 μm along the direction of light beam transmission. The coupling structure 700 is configured such that the silicon oxynitride layer 701 is Si based on the design of the oxygen atom content of each layer12O21N2The silicon oxynitride layer 702 is Si6O9N2The silicon oxynitride layer 703 is Si4O5N2704Si oxynitride layer3O3N2The silicon oxynitride layer 705 is Si12O9N10The silicon oxynitride layer 706 is Si2ON2 Silicon oxynitride layer 707 is Si12O3N14The silicon oxynitride layer 708 is Si3N4。
In other embodiments, as shown in FIG. 8, the coupling structure 800 has two SiON layers disposed on a substrate, a SiON layer 802, and a second SiON layer 802, in that order from the substrate up to the first,The length of the silicon oxynitride layer 801 in the beam propagation direction is smaller than that of the silicon oxynitride layer 802, and the two silicon oxynitride layers are coated by the substrate and the silicon dioxide cladding layer and used for limiting the beam from propagating in the silicon oxynitride layers. The thickness of the silicon oxynitride layer 801 and the silicon oxynitride layer 802 is 5 + -1 μm, and the sum of the thicknesses is 10 + -2 μm. The silicon oxynitride layer 802 is made of silicon nitride, and the silicon oxynitride layer 801 is made of Si3O3N2。
The cross-sectional dimension of the silicon oxynitride layer at the optical input end of the coupling structure 800 is matched with the dimension of the optical output end of the receiving optical fiber core/light emitting mechanism, so that the mode matching degree of the optical input mechanism and the optical coupling structure is improved, and light can be coupled into the coupling structure with relatively low loss.
In the multi-level taper region, the taper length of the uppermost layer is shortest, and the taper length of the lowermost layer is longest. When light propagates in the cascaded multi-stage cones to reach the tip of the first cone at the end of the top cone, the cross-sectional area of the topmost silicon oxynitride layer is too small, so that the light cannot be well confined to the top layer and continues to be transmitted to the next layer. Likewise, light travels a distance in the second layer taper and then continues to travel downward as it travels to the end of the second taper until it reaches the bottom layer. For the material layer, the uppermost layer is made of SiON material, wherein the proportion of oxygen atoms to the sum of oxygen atoms and nitrogen atoms is the highest, and the proportion of N atoms is the lowest; the material of the second layer is SiON material, the proportion of oxygen atoms is reduced compared with the first layer cone, and the proportion of N atoms is increased compared with the first layer cone; the third layer is made of SiON material, the oxygen atom proportion is lower than that of the second layer, the N atom proportion is higher than that of the second layer, and the rest is done in the same way until the bottom layer is an SiN cone which is cascaded with the upper layer in the same direction, the wide end is close to the optical fiber, and the narrow end is connected with the photonic circuit. In each layer, the light first exists as a fully propagating mode, with the mode transitioning to a evanescent mode as it propagates to the narrow tapered end, and further to the lower layer, which is longer in size. Until the mode can be transferred to the bottom SiN layer and finally propagate into the SiN waveguide. Due to the influence of the manufacturing process, when the silicon oxynitride layer is manufactured, a spiral dislocation is generated between the crystal lattices of the silicon oxynitride layer with different oxygen atom contents, light is transmitted to the spiral dislocation to generate additional scattering and refraction, and the loss of the light is increased. Therefore, in designing, the material defects between the optical waveguide layers should be taken into consideration, and the change of the oxygen atom content of different layer materials should be relatively moderate, so as to minimize the loss of light propagating between different optical waveguide layers.
The number of stages of cascaded multistage edge couplers is not limited, but should be appropriate because too many layers add manufacturing complexity, too many deposition and lithography steps, and too few layers may result in an insufficiently critical silicon layer for mode conversion. The complexity of the manufacturing process depends on the number of stages used, since the preparation of the tapered structures in each layer requires photolithography, etching and polishing. In addition, the sidewall roughness of each layer taper also results in excessive loss of coupling efficiency. In addition, inter-layer tapered tip alignment should be considered and a thick cladding layer needs to be grown on the conventional SOI structure to reduce the mode size mismatch with the core. The multi-stage edge coupler provided by the application needs to use SiON materials compatible with a CMOS process, and other main manufacturing processes including photoetching, etching, deposition, polishing and the like are compatible with the traditional CMOS process, so that the multi-stage edge coupler has feasibility of technical implementation.
The above embodiments only exemplify preferred specific technical solutions and technical means, and do not exclude the scope of the claims of the present invention, and other alternatives to the technical means that can solve the technical problems should be understood as the contents of the claims of the present invention.
Claims (10)
1. A coupling structure applied to a silicon optical chip is characterized in that: the substrate is provided with at least two silicon oxynitride layers and a cladding layer, wherein the at least two silicon oxynitride layers are arranged on the substrate, the ratio of the number of oxygen atoms to the number of nitrogen atoms in each layer of the at least two silicon oxynitride layers is different, and the ratio of the number of oxygen atoms to the number of nitrogen atoms in the material is increased along with the increase of the distance from the substrate; the cladding layer is wrapped outside the coupling structure and used for being matched with the substrate to limit the light beam in the at least two silicon oxynitride layers.
2. The coupling structure of claim 1, wherein: the silicon oxynitride layer directly coupled to the substrate has an atomic weight of zero oxygen.
3. The coupling structure of claim 1, wherein: each of the at least two silicon oxynitride layers has a length along a direction of propagation of the light beam that is longer the closer to the substrate.
4. The coupling structure of claim 1, wherein: the silicon oxynitride layer arranged on the substrate is two to eight layers.
5. The coupling structure of claim 1, wherein: the silicon oxynitride layer is arranged on the substrate and comprises a first silicon oxynitride layer, a second silicon oxynitride layer, a third silicon oxynitride layer and a fourth silicon oxynitride layer which are far away from the substrate, and the length relation of the silicon oxynitride layers along the propagation direction of the light beam is that the length of the first silicon oxynitride layer is less than that of the second silicon oxynitride layer, and the length of the third silicon oxynitride layer is less than that of the fourth silicon oxynitride layer.
6. The coupling structure of claim 5, wherein: the first silicon oxynitride layer, the second silicon oxynitride layer, the third silicon oxynitride layer and the fourth silicon oxynitride layer are all the same in height, and the sum of the heights of the four silicon oxynitride layers ranges from 6 microns to 14 microns.
7. The coupling structure of claim 5, wherein: the widths of the light input ends of the first silicon oxynitride layer, the second silicon oxynitride layer, the third silicon oxynitride layer and the fourth silicon oxynitride layer are equal, and the first silicon oxynitride layer, the second silicon oxynitride layer, the third silicon oxynitride layer and the fourth silicon oxynitride layer are used for coupling light into the silicon optical chip.
8. The coupling structure of claim 1, wherein: the width of each of the at least two silicon oxynitride layers is gradually reduced along the beam direction.
9. The coupling structure of claim 5, wherein: the first layer of silicon oxynitride layer is made of Si6O9N2The second layer of silicon oxynitride layer is made of Si3O3N2The third layer of silicon oxynitride layer is made of Si2ON2The fourth layer of silicon oxynitride layer is made of Si3N4。
10. The coupling structure of claim 8, wherein each of the at least two silicon oxynitride layers has a trapezoidal cross-sectional shape in a plane parallel to the substrate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210059610.3A CN114460687A (en) | 2022-01-19 | 2022-01-19 | Coupling structure applied to silicon optical chip |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114924348A (en) * | 2022-06-06 | 2022-08-19 | 吉林大学 | Three-dimensional edge coupler based on silicon dioxide optical waveguide |
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