CN115437062A - Edge coupler based on gradient refractive index inverted ridge waveguide - Google Patents
Edge coupler based on gradient refractive index inverted ridge waveguide Download PDFInfo
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- G—PHYSICS
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- 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
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- G—PHYSICS
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- 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
- G02B6/1223—Basic optical elements, e.g. light-guiding paths high refractive index type, i.e. high-contrast waveguides
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- 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
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- G02B6/1228—Tapered waveguides, e.g. integrated spot-size transformers
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- 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
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- G—PHYSICS
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- 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
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Abstract
An edge coupler based on a gradient refractive index inverted ridge waveguide belongs to the technical field of silica waveguide integrated optics. From supreme substrate, the low refracting index silica under cladding, the low refracting index silica intermediate cladding and the low refracting index silica overclad of compriseing in proper order down, the cladding has high refracting index silica first waveguide core layer among the low refracting index silica intermediate cladding, the cladding has high refracting index silica second waveguide core layer among the low refracting index silica overclad, second waveguide core layer is located on first waveguide core layer and the silica intermediate cladding. The first waveguide Core layer is a tapered waveguide, the second waveguide Core layer is composed of a tapered waveguide Core1 and a straight waveguide Core2, and the first waveguide Core layer and the tapered waveguide Core1 jointly form a gradient-refractive-index inverted-ridge-shaped waveguide edge coupler. The optical signal from the optical fiber is first coupled into the ridge structure waveguide and then transmitted by the straight waveguide Core2 to other devices such as an optical chip.
Description
Technical Field
The invention belongs to the technical field of silica waveguide integrated optics, and particularly relates to an edge coupler based on a gradient refractive index inverted ridge waveguide.
Background
With the rapid development of integrated optics, miniaturized optical devices for optical computing, storage, information processing and other applications are gaining wide attention, and are particularly widely applied to the aspects of network communication and the like. The mature CMOS process provides a good processing platform for the development of integrated optics, and powerfully promotes the miniaturization and integration of a photonic chip. However, integrated optical devices with different functions, such as semiconductor lasers, optical filters, wavelength converters, optical logic gates, optical time delays, optical modulators/optical switches, optical sensors, etc., still face the need of low-loss optical information exchange with the outside world.
For waveguide type photonic integrated chips, it is necessary to receive signals from optical fibers or transmit optical signals to the outside through optical fibers. Therefore, the low-loss coupling of the optical fiber and the waveguide plays an important role in ensuring the performance of the optical integrated chip. However, compared with the on-chip optical waveguide, the core diameter of the SMF-28 single-mode optical fiber of the current commercial optical fiber is about 8 μm, which is much larger than the mode spot size of the on-chip silica waveguide or silicon waveguide, thereby causing the coupling loss caused by the mode field mismatch between the optical fiber and the waveguide. Therefore, by matching the mode spot size between the fiber and the waveguide, additional optical coupling losses due to fiber-waveguide coupling are reduced, enhancing optical device performance.
At present, the coupling method between the optical fiber and the waveguide mainly includes grating coupling and horizontal end face coupling. The grating coupling has good flexibility, and can be coupled at any position on the chip, but the grating coupling mode is sensitive to wavelength and has strong polarization correlation. End-coupling can increase the mode field in the waveguide or decrease the mode field in the fiber, thereby achieving matching of the mode field size of the fiber to the waveguide. The end face coupling is insensitive to wavelength, has small polarization dependence, high coupling efficiency and is easy to package. Therefore, the end face coupling plays an important role in the coupling of the optical fiber and the integrated photonic chip, and the research on the end face coupler has important significance for developing the photonic chip.
Disclosure of Invention
The invention aims to provide an edge coupler based on a gradient-index inverted ridge waveguide, which is used for realizing low-loss interconnection between an optical fiber and the waveguide. Because the mode field size of ridge structure waveguide is bigger than the ordinary structure waveguide, utilize this characteristic of ridge structure, can design an edge coupler, realize the mode field matching of single mode fiber and waveguide, reduce the coupling loss.
The edge coupler based on the gradient-refractive-index inverted-ridge waveguide is composed of a substrate (1), a low-refractive-index silica lower cladding layer (2), a low-refractive-index silica middle cladding layer (3) and a low-refractive-index silica upper cladding layer (4) from bottom to top in sequence as shown in figures 1 and 2, a high-refractive-index silica first waveguide core layer (5) is wrapped in the low-refractive-index silica middle cladding layer (3), and the high-refractive-index silica first waveguide core layer (5) and the low-refractive-index silica middle cladding layer (3) have the same thickness; a high-refractive-index silica second waveguide core layer (6) is coated in the low-refractive-index silica upper cladding layer (4), the high-refractive-index silica second waveguide core layer (6) is positioned on the high-refractive-index silica first waveguide core layer (5) and the low-refractive-index silica middle cladding layer (3), and the thickness of the high-refractive-index silica second waveguide core layer is smaller than that of the low-refractive-index silica upper cladding layer (4); the low-refractive-index silica upper cladding layer (4), the low-refractive-index silica middle cladding layer (3) and the low-refractive-index silica lower cladding layer (2) have the same refractive index, the refractive index of the high-refractive-index silica second waveguide core layer (6) is larger than that of the high-refractive-index silica first waveguide core layer (5), and the refractive index of the high-refractive-index silica first waveguide core layer (5) is larger than that of the low-refractive-index silica lower cladding layer (2).
Furthermore, the substrate (1) adopts a silicon material, the low-refractive-index silicon dioxide upper cladding (4), the low-refractive-index silicon dioxide middle cladding (3) and the low-refractive-index silicon dioxide lower cladding (2) adopt silicon dioxide materials with the same refractive index, and the refractive index is 1.4470; the first waveguide core layer (5) of high-refractive-index silicon dioxide is made of germanium-doped high-refractive-index silicon dioxide, and the refractive index of the first waveguide core layer is 1.4687; the second waveguide core layer (6) of high refractive silica is made of high refractive index silica doped with germanium, and the refractive index of the second waveguide core layer is 1.4832.
As shown in fig. 3 and 4, the silica first waveguide core layer (5) is a tapered waveguide, and the width of the silica first waveguide core layer (5) gradually narrows along the light transmission direction (+ x direction), and the width at the widest point is W 1 Its narrowest width is W 4 (ii) a The silica second waveguide Core layer (6) consists of a tapered waveguide Core1 and a straight waveguide Core2, the width of the silica first waveguide Core layer (6) is gradually narrowed along the transmission direction of light, and the width of the widest part of the silica first waveguide Core layer is W 2 Its narrowest width is W 3 (ii) a The lengths of the tapered waveguide Core1 and the high-refractive-index silica first waveguide Core layer (5) are the same, the tapered waveguide Core1 is arranged on the upper surface of the high-refractive-index silica first waveguide Core layer (5) in the middle, and the tapered waveguide Core1 and the high-refractive-index silica first waveguide Core layer form a gradient refractive index inverted ridge waveguide edge coupler; the width of the straight waveguide Core2 is W 3 . In the + x direction, an optical signal from the optical fiber is first coupled into the ridge structure waveguide, and then the signal light coupled into the ridge structure waveguide is transmitted to an optical chip or other devices by the straight waveguide Core 2.
Furthermore, in the ridge structure, the heights of the first silicon dioxide waveguide core layer (5) and the second silicon dioxide waveguide core layer (6) are respectively H 1 And H 2 And H is 1 +H 2 =6.5 μm; starting width W of tapered waveguide Core1 2 8 μm, starting width W of the silica first waveguide core layer (5) 1 Is 12 μm, thereby increasing the size of the mode field, realizing the mode field matching with the single-mode fiber and enhancing the coupling efficiency between the fiber and the waveguide. Height H of silica first waveguide core layer (5) 1 3 μm, in the + x direction, the width of the silica first waveguide core layer (5) is defined by W 1 Reduction of =12 μm gradually to W 4 =6 μm; height H of silica second waveguide core layer (6) 2 3.5 μm, the width of the tapered waveguide Core1 of the silica second waveguide Core layer (6) is set to W 2 =8 μm decreasing gradually to W 3 =3.5 μm. The waveguide length L of the ridge structure is composed of a first waveguide Core layer (5) of silicon dioxide and a tapered waveguide Core1 1 =70 μm, output end straight waveguide Core2 width W 3 =3.5 μm, height H 2 =3.5 μm, so that the mode field becomes gradually smaller in the + x direction; total length of device L 3 ＝0.1mm，L 1 +L 2 ＝L 3 . The height of the low-refractive-index silica lower cladding layer (2) and the height of the low-refractive-index silica upper cladding layer (4) are both 15 mu m, and the height of the low-refractive-index silica middle cladding layer (3) is H 1 ＝3μm。
Fig. 5 is an overall mode field profile of an edge coupler, and it can be clearly seen from the figure that, in the + x transmission direction, an input optical signal from a single-mode optical fiber is coupled into a gradient index inverted ridge waveguide edge coupler which is formed by a tapered waveguide Core1 of a high refractive index silica first waveguide Core layer (5) and a high refractive index silica second waveguide Core layer (6) together at x =0, and a light spot area is compressed and gradually reduced through a ridge waveguide coupler with gradually reduced width and is coupled into a straight waveguide Core2 at x =70 μm. Fig. 6 shows the cross-sectional mode field distribution of the straight waveguide Core2 of the second waveguide Core layer (6) of high refractive index silica, and it can be seen that the signal light in the single mode fiber is successfully coupled to the straight waveguide Core2 with height and width of 3.5 μm by the edge coupler of the gradient index inverted ridge waveguide.
The refractive indices of the high refractive index silica second waveguide core layer (6) and the high refractive index silica first waveguide core layer (5) are different, firstly because the width of the silica first waveguide core layer (5) is L in length 1 The width of the second waveguide core layer (6) is larger than that of the silicon dioxide in the conical structure area, if the refractive indexes of the second waveguide core layer (6) and the first waveguide core layer (5) are the same, the effective refractive index of the first waveguide core layer (5) is larger than that of the second waveguide core layer (6), and the optical mode field is not facilitated to be formed by the first waveguide core layer (6)The waveguide Core layer (5) is coupled to the second waveguide Core layer (6) so as to be output by the straight waveguide Core 2. By reducing the refractive index of the first waveguide Core layer (5), the effective refractive index of the first waveguide Core layer can be reduced, so that an optical mode field in the first waveguide Core layer (5) can be coupled into the conical waveguide Core1 of the second waveguide Core layer (6) and output by the straight waveguide Core2, and the optical loss in the transmission process is reduced. And secondly, the refractive index of the first waveguide core layer (5) is reduced, and the overall effective refractive index of the edge coupler with the inverted ridge structure can be reduced, so that the refractive index difference between the optical fiber and the edge coupler is reduced, the mode field matching is enhanced, and the optical coupling efficiency is improved.
Drawings
FIG. 1 is a schematic diagram of a three-dimensional structure of an edge coupler of a gradient index inverted ridge waveguide according to the present invention;
FIG. 2 is a schematic cross-sectional view of an edge coupler of a gradient index inverted ridge waveguide according to the present invention along the light transmission direction;
FIG. 3 is a top view of a gradient index inverted ridge waveguide edge coupler waveguide core layer according to the present invention, taken along the direction of light transmission;
FIG. 4 is a side view of a gradient index inverted ridge waveguide edge coupler waveguide core layer of the present invention in the direction of light transmission;
FIG. 5 is a diagram of mode field transmission in the second waveguide core (6) of the gradient index inverted ridge waveguide edge coupler of the present invention;
fig. 6 is a graph of the Core2 cross-section output optical mode field of a straight waveguide of the second waveguide Core layer (6) of the gradient index inverted ridge waveguide edge coupler of the present invention;
FIG. 7 is a graph of the coupling loss with wavelength for an edge coupler for a gradient index inverted ridge waveguide in accordance with the present invention;
FIG. 8 is a process flow for fabricating an edge coupler for a gradient index inverted ridge waveguide according to the present invention.
Detailed Description
Example 1
1. Determining the width W of a silica first waveguide core waveguide (5) 1 And height H 1 And silica second waveguide Core layer waveguide (6) Core 1 Width W of 2 Heyu (Chinese character) transfusion systemCore with straight waveguide at output end 2 Width W of 3 And height H 2 . In the examples, a single mode optical fiber having a core diameter of 8 μm was selected. In order to match the mode field distribution of the single-mode fiber, the width W of the silica first waveguide core layer waveguide (5) is designed 1 ＝12μm，H 1 =3 μm, silica second waveguide core waveguide width W 2 =8 μm. The refractive index of the selected high-refractive-index silica waveguide Core layer (6) is 1.4832, which meets the requirement of silica second waveguide Core layer waveguide Core 2 Under single mode conditions of (1), selecting W 3 ＝3.5μm，H 2 ＝3.5μm。
2. Determining the length of the Core1 of the silica second waveguide and the length L of the silica first waveguide 1 And width W 4 . In order to ensure that the optical field in the optical fiber is stably transmitted in the silica first waveguide Core layer and the silica second waveguide Core layer Core1 and is efficiently coupled into the straight waveguide of the silica second waveguide Core layer Core2, the waveguide length L of the silica second waveguide Core layer Core1 is determined by calculating and optimizing a Finite-Difference Time-Domain (FDTD) method 1 =70 μm, width W of silica first waveguide core layer 4 =5 μm and a length L 1 With =70 μm, the optical mode field in the silica first and second waveguide Core layers Core1 can be coupled into the Core2 straight waveguide with maximum efficiency.
3. In the structure, the core layer waveguide is made of germanium-doped silica, the refractive index of the silica first waveguide core layer is 1.4687, the refractive index difference between the silica first waveguide core layer and the silica cladding is 1.5%, the refractive index of the silica second waveguide core layer is 1.4832, and the refractive index difference between the silica second waveguide core layer and the silica cladding is 2.5%. Straight waveguide Core with light along a tapered structure to a second waveguide Core layer 2 And the waveguide width becomes gradually smaller along the light transmission direction. The silica second waveguide Core layer Core1 waveguide and the silica first waveguide Core layer waveguide are combined to form a ridge structure waveguide, so that mode field matching in the optical fiber can be realized, and the coupling efficiency of the optical fiber and the optical waveguide can be improved. Coupling the refractive index difference existing between the first waveguide core layer of silica and the second waveguide core layer of silica into the first waveguide core layer of silica by the optical fiberThe optical signals of the Core layer are more easily coupled into the high-refractive-index silica second waveguide Core layer from the low-refractive-index silica first waveguide Core layer, so that the optical field energy coupled into the Core2 straight waveguide is enhanced.
4. Fig. 7 shows the coupling efficiency of the fiber to the edge coupler of the gradient index inverted ridge waveguide as a function of the signal light wavelength. The result shows that the coupling loss variation range is 0.33-0.37 dB within the wavelength range of 1520 nm-1620 nm; at the 1550nm wavelength of the signal light, the coupling loss is 0.357dB, and the wavelength insensitivity requirement can be met.
Example 2: as shown in fig. 8, the specific steps of the device of the present invention are as follows:
1) Cleaning the silicon substrate: selecting a silicon wafer as a substrate, and ultrasonically cleaning various impurities, oil stains and other substances on the silicon substrate by using acetone, ethanol and deionized water in sequence;
2) Thermal oxidation growth of SiO 2 Lower cladding: under the condition of 1000 ℃, a layer of silicon dioxide film with the refractive index of 1.4470 is grown on a cleaned silicon substrate by utilizing a wet thermal oxidation process to be used as a low-refractive-index silicon dioxide lower cladding layer (2), and the thickness H of the silicon dioxide lower cladding layer is controlled by controlling the flow rate of water vapor, the temperature of the substrate and the reaction time 3 Is 15 μm;
3) Deposition of high refractive index SiO 2 First waveguide core layer film: depositing germanium (Ge) -doped high-refractive-index silicon dioxide on the low-refractive-index silicon dioxide lower cladding layer (2) by utilizing a Plasma Enhanced Chemical Vapor Deposition (PECVD) method, and controlling reaction gas GeCl under the conditions that the radio frequency power is 50W and the substrate temperature is 200 DEG C 4 、SiH 4 And N 2 The flow rates of O are 32sccm, 20sccm and 40sccm, respectively, so that SiO with high refractive index 2 The refractive index of the first waveguide core layer is 1.4687, and the reaction time is controlled to ensure that the high refractive index SiO is 2 Thickness H of first waveguide core layer 1 ＝3μm；
4) Growing a polysilicon mask layer: with SiH 4 And H 2 As a reaction gas, a hot filament CVD method was used, and a dilution ratio V (H) was set at a growth pressure of 1Pa, a substrate temperature of 200 ℃ and a dilution ratio of 2 )/(V(SiH 4 )+V(H 2 ) ) 98.4% under the condition of high refractive index SiO by controlling the reaction time 2 A polysilicon layer with the thickness of 1 mu m is grown on the surface of the first waveguide core layer and is used as SiO with high refractive index 2 Etching mask layer of the first waveguide core layer;
5) Photoetching and polysilicon etching to form a waveguide mask pattern: spin-coating a photoresist AZ1500 on the surface of the polycrystalline silicon layer formed in the step 4), and after i-line (365 nm) ultraviolet lithography and development, carrying out on the mask plate and the SiO with high refractive index to be prepared 2 Transferring the waveguide pattern with the same structure as the first waveguide core layer to the surface of the photoresist, and controlling SF by using a Reactive Ion Etching (RIE) method under the condition of radio frequency power of 100W 6 、CHF 3 And O 2 The gas flow is 25sccm, 50sccm and 35sccm, the polysilicon layer without photoresist protection is removed by chemical corrosion and physical bombardment of fluoride ions, and the high refractive index SiO required to be prepared is obtained after the photoresist is removed by exposure and development 2 A polysilicon mask layer with the same structure as the first waveguide core layer;
6) Etching to form SiO 2 A first waveguide core layer: controlling SF by using the Reactive Ion Etching (RIE) method in the step 5) under the condition of 100W of radio frequency power 6 、CHF 3 And O 2 The gas flow is 25sccm, 50sccm and 35sccm, and the high refractive index SiO without the protection of the polysilicon mask is removed by the chemical corrosion and physical bombardment of fluorine ions 2 A waveguide core layer film;
7) Removing the polysilicon mask layer: removing the polysilicon mask layer by using KOH aqueous solution with the mass fraction of 15 percent, thereby preparing SiO with high refractive index on the silicon dioxide lower cladding (2) with low refractive index 2 A first waveguide core layer (5);
8) Deposition of low refractive index SiO 2 Intermediate cladding: by using a PECVD method and controlling the reaction time, the low-refractive-index silicon dioxide lower cladding layer (2) and the high-refractive-index SiO 2 Depositing a layer of silicon dioxide film with the refractive index of 1.4470 on the surface of the first waveguide core layer (5), and controlling SiO by a chemical mechanical polishing method 2 The surface of the intermediate coating has flatness and the thickness of the intermediate coating is 3 mu m, namely the intermediate coating is matched with SiO with high refractive index 2 Thickness of the first waveguide core layer (5)H 1 Uniformly, obtaining SiO with low refractive index 2 An intermediate cladding (3);
9) Deposition of high refractive index SiO 2 Second waveguide core layer film: in the same manner as in step 3), in the presence of GeCl as a reaction gas 4 、SiH 4 And N 2 The flow of O is 35sccm, 22sccm and 40sccm respectively, the radio frequency power is 50W, and a high-refraction silicon dioxide film with the refractive index of 1.4832 is deposited on the upper surfaces of the silicon dioxide intermediate cladding layer (3) and the first waveguide core layer (5) under the condition that the substrate temperature is 200 ℃, and the reaction time is controlled to ensure that the thickness of the high-refraction silicon dioxide film is 3.5 mu m;
10 Growth of polysilicon mask layer: using the method described in step 4) on SiO with a high refractive index 2 A layer of polysilicon layer with the thickness of 1 mu m is grown on the surface of the film and is used as SiO with high refractive index 2 Etching the mask layer;
11 Lithography, polysilicon etching to form waveguide mask pattern: spin-coating photoresist AZ1500 on the surface of the polysilicon layer formed in the step 10), performing i-line (365 nm) ultraviolet lithography, and developing, and then performing high-refractive-index SiO on the mask plate and needing to be prepared 2 Transferring the waveguide pattern with the same structure as the second waveguide core layer to the surface of the photoresist, removing the polysilicon layer without the photoresist protection part by using a Reactive Ion Etching (RIE) method, exposing, developing to remove the photoresist, and obtaining SiO with high refractive index 2 A polysilicon mask layer with the same pattern as the second waveguide core layer;
12 ) etching to form high refractive index SiO 2 A second waveguide core layer: controlling SF using the Reactive Ion Etching (RIE) method described in step 11) 6 、CHF 3 And O 2 The gas flow ratio is utilized to remove the high-refractive-index SiO without the protection of the polysilicon mask by utilizing the chemical corrosion and physical bombardment action of fluorine ions 2 A waveguide core layer;
13 Removing the polysilicon mask layer: removing the polysilicon mask layer by using 15% of KOH aqueous solution by mass fraction so as to obtain SiO with high refractive index 2 A first waveguide core layer (5) and low refractive index SiO 2 Obtaining SiO with high refractive index on the intermediate cladding (3) 2 A second waveguide core layer (6);
14 Deposition of low refractive index SiO 2 And (3) upper cladding: by usingA PECVD method, a layer of silicon dioxide upper cladding with the refractive index of 1.4470 is generated on the surface of the structure obtained in the step 13) through the deposition of the reaction time, the surface flatness of the silicon dioxide upper cladding is controlled through a chemical mechanical polishing method, and the silicon dioxide upper cladding is positioned on SiO with low refractive index 2 The thickness above the intermediate cladding (3) was 15 μm, resulting in a low refractive index SiO 2 And (4) an upper cladding layer, thereby preparing the edge coupler based on the gradient refractive index inverted ridge waveguide.
Claims (4)
1. An edge coupler based on a gradient-index inverted ridge waveguide, characterized in that: the silicon dioxide waveguide structure is characterized by sequentially consisting of a substrate (1), a low-refractive-index silicon dioxide lower cladding layer (2), a low-refractive-index silicon dioxide middle cladding layer (3) and a low-refractive-index silicon dioxide upper cladding layer (4) from bottom to top, wherein a high-refractive-index silicon dioxide first waveguide core layer (5) is coated in the low-refractive-index silicon dioxide middle cladding layer (3), and the high-refractive-index silicon dioxide first waveguide core layer (5) and the low-refractive-index silicon dioxide middle cladding layer (3) have the same thickness; a high-refractive-index silica second waveguide core layer (6) is coated in the low-refractive-index silica upper cladding layer (4), the high-refractive-index silica second waveguide core layer (6) is positioned on the high-refractive-index silica first waveguide core layer (5) and the low-refractive-index silica middle cladding layer (3), and the thickness of the high-refractive-index silica second waveguide core layer is smaller than that of the low-refractive-index silica upper cladding layer (4); the low-refractive-index silica upper cladding (4), the low-refractive-index silica middle cladding (3) and the low-refractive-index silica lower cladding (2) have the same refractive index, the refractive index of the high-refractive-index silica second waveguide core layer (6) is larger than that of the high-refractive-index silica first waveguide core layer (5), and the refractive index of the high-refractive-index silica first waveguide core layer (5) is larger than that of the low-refractive-index silica lower cladding (2); the silica first waveguide core layer (5) is a tapered waveguide, and the width of the silica first waveguide core layer (5) is gradually narrowed along the transmission direction of light; the silica second waveguide Core layer (6) consists of a conical waveguide Core1 and a straight waveguide Core2, and the width of the silica first waveguide Core layer (6) is gradually narrowed along the transmission direction of light; the lengths of the tapered waveguide Core1 and the high-refractive-index silica first waveguide Core layer (5) are the same, the tapered waveguide Core1 is arranged on the upper surface of the high-refractive-index silica first waveguide Core layer (5) in the middle, and the tapered waveguide Core1 and the high-refractive-index silica first waveguide Core layer form a gradient refractive index inverted ridge waveguide edge coupler; in the transmission direction of light, an optical signal from the optical fiber is first coupled into the ridge structure waveguide, and then the signal light coupled into the ridge structure waveguide is transmitted to other devices such as an optical chip by the straight waveguide Core 2.
2. The edge coupler based on the gradient index inverted ridge waveguide of claim 1, wherein: the substrate (1) is made of silicon materials, the low-refractive-index silicon dioxide upper cladding (4), the low-refractive-index silicon dioxide middle cladding (3) and the low-refractive-index silicon dioxide lower cladding (2) are made of silicon materials with the same refractive index, and the refractive index is 1.4470; the first waveguide core layer (5) of high-refractive-index silica is made of germanium-doped high-refractive-index silica, and the refractive index of the first waveguide core layer is 1.4687; the second waveguide core layer (6) of high refractive silica is made of germanium-doped high refractive index silica, and the refractive index of the second waveguide core layer is 1.4832.
3. The edge coupler based on the gradient index inverted ridge waveguide of claim 1, wherein: height H of silica first waveguide core layer (5) 1 3 μm, height H of the silica second waveguide core layer (6) 2 3.5 μm; the starting width W of the silica first waveguide core layer (5) 1 12 μm, starting width W of the tapered waveguide Core1 2 Is 8 μm; the width of the silica first waveguide core layer (5) along the transmission direction of light is W 1 Reduction of =12 μm gradually to W 4 =6 μm, the width of the tapered waveguide Core1 of the silica second waveguide Core layer (6) is set by W 2 =8 μm decreasing gradually to W 3 =3.5 μm; the waveguide length L of the ridge structure is composed of a first waveguide Core layer (5) of silicon dioxide and a tapered waveguide Core1 1 =70 μm; width W of output end straight waveguide Core2 3 =3.5 μm, height H 2 ＝3.5μm。
4. The edge coupler based on the gradient index inverted ridge waveguide of claim 1, wherein: the height of the low-refractive-index silica lower cladding layer (2) and the height of the low-refractive-index silica upper cladding layer (4) are both 15 mu m.
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| CN118625449A (en) * | 2024-08-13 | 2024-09-10 | 江苏南里台科技有限公司 | End face coupler suitable for large-size single-mode fiber and preparation method thereof |
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2022
- 2022-10-11 CN CN202211238246.3A patent/CN115437062A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118625449A (en) * | 2024-08-13 | 2024-09-10 | 江苏南里台科技有限公司 | End face coupler suitable for large-size single-mode fiber and preparation method thereof |
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