CN219609274U - Mode spot converter based on silicon waveguide - Google Patents
Mode spot converter based on silicon waveguide Download PDFInfo
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- CN219609274U CN219609274U CN202320525679.0U CN202320525679U CN219609274U CN 219609274 U CN219609274 U CN 219609274U CN 202320525679 U CN202320525679 U CN 202320525679U CN 219609274 U CN219609274 U CN 219609274U
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Abstract
The utility model discloses a mode spot converter based on a silicon waveguide, and belongs to the technical field of silicon-based photon chips; the semiconductor device comprises an oxide cladding layer, a substrate and a silicon waveguide structure, wherein the silicon waveguide structure is arranged in a silicon dioxide cladding layer and adopts a trident structure. The input end of the trifurcate-structure silicon waveguide is a single waveguide, the input end of the trifurcate-structure silicon waveguide is connected with the input optical waveguide, the output end of the trifurcate-structure silicon waveguide is double waveguide and is in butt joint with the optical fiber, and the output end of the mode spot converter can improve the coupling efficiency between the waveguide and the optical fiber by adopting the trifurcate-structure. The transmission part of the trifurcate-based silicon waveguide adopts a conical structure, the limiting effect of the waveguide on light is weakened through the gradual reduction of the width of the silicon waveguide, when the width of the waveguide is reduced to a certain degree, the light cannot be limited in the waveguide, and overflows from the waveguide, the light spot size is increased, and the efficient coupling of two mode spots between the waveguide and the optical fiber is realized.
Description
Technical Field
The utility model relates to the technical field of silicon-based photonic chips, in particular to a mode spot converter based on a silicon waveguide.
Background
With the current increasing demands for speed and capacity of optical communication technology, the development of photonic integrated devices has received extensive attention from society. The materials of the photon devices are many at present, and the application of the photon devices is relatively wide and mainly comprises silicon on insulator, inP, lithium niobate and compound semiconductors. Among them, silicon has a large refractive index, and silicon-on-insulator (SOI) technology has a high refractive index contrast between silicon and silicon dioxide layers, which can make the size of nanophotonic devices as small as several hundred nanometers. Since silicon is transparent in the communication band, the optical transmission loss of a waveguide device using silicon as a core layer can reach a relatively small value. In addition, the process of the nano-photonic device based on the silicon waveguide is compatible with the Complementary Metal Oxide Semiconductor (CMOS) process, so that the silicon photonic integrated device is getting more and more attention.
One key technology affecting the integration of silicon photonics devices is to achieve efficient coupling of optical waveguides and optical fibers. The size of the optical waveguide device taking silicon as a core layer is hundred nanometers, the size of a Single Mode Fiber (SMF) is micrometers, the two orders of magnitude differ, and large coupling loss can be generated when the single mode fiber is directly connected with the optical waveguide in a butt joint mode. The mode spot converter based on the silicon waveguide can be used for connecting the optical waveguide in the silicon optical integrated device with external optical fibers to realize larger coupling loss and lower related loss, so that the mode spot converter based on the silicon waveguide is widely studied. At present, many researches on silicon-based photon spot-size converters at home and abroad are carried out, and the researches comprise various structural types such as taper waveguides, cantilever waveguides, grating couplers and the like. The tapered waveguide has the advantages of simple design, large bandwidth, high coupling efficiency and the like. However, most of the current tapered waveguide mode spot converters adopt a single waveguide structure, and in order to achieve high coupling efficiency with the optical fiber, the end face of the joint of the mode spot converter and the optical fiber is required to be small in size, so that the processing difficulty is increased.
Disclosure of Invention
Accordingly, the main object of the present utility model is to provide a mode spot converter based on a silicon waveguide, which comprises an oxide cladding, a substrate and a silicon waveguide structure, wherein the silicon waveguide structure is in the silicon dioxide cladding and adopts a trigeminal cone structure, the limiting effect of the waveguide on light is weakened by gradually reducing the width of the silicon waveguide, when the width of the waveguide is reduced to a certain extent, the light cannot be limited in the waveguide, and overflows from the waveguide, the light spot size is increased accordingly, and the efficient coupling of two modes spots between the waveguide and the optical fiber is realized.
In order to achieve the above object, the present utility model provides a mode spot-size converter based on a silicon waveguide, comprising an oxide cladding layer, a substrate and a silicon waveguide structure, wherein the substrate is at the lowest, the oxide cladding layer is located above the substrate, and the silicon waveguide structure is located in the oxide cladding layer.
Preferably, the silicon waveguide structure is a trifurcate structure formed by sequentially arranging three waveguide bodies at certain intervals, and the trifurcate structure comprises a middle waveguide body and two side waveguide bodies.
Preferably, the structures of the two side waveguides are the same, and the distances from the two side waveguides to the middle waveguide are the same.
Preferably, the two side waveguides and the middle waveguide body each comprise two sections of waveguides which are sequentially arranged, and the first section of waveguide is tightly connected with the second section of waveguide.
Preferably, the top surfaces of the first section waveguide and the second section waveguide of the two side waveguide bodies and the middle waveguide body are planes, the heights of the first section waveguide and the second section waveguide are the same, the width of the first section waveguide is gradually and continuously changed, the width of the output end of the first section waveguide is minimum, the output end is connected with an optical fiber or a laser, the width of the input end of the first section waveguide is maximum, the second section waveguide is a straight waveguide, and the width of the second section waveguide is the same as the width of the connection part of the first section waveguide.
Preferably, the input end faces of the two side waveguides and the connection face of the first section waveguide and the second section waveguide of the intermediate waveguide are on the same plane.
Preferably, the two-sided waveguide body has the same height as the intermediate waveguide body.
The utility model discloses a mode spot converter based on a silicon waveguide, which adopts a three-fork-shaped silicon waveguide structure, three waveguide bodies used by the three-fork-shaped waveguide structure all adopt a conical structure, so that on one hand, the coupling efficiency between an optical fiber and the optical waveguide is improved, on the other hand, the difficulty of a processing technology is reduced under the condition of ensuring the coupling efficiency, and a foundation is laid for the development of a photonic integrated device.
Drawings
Fig. 1 is a side view of a silicon waveguide-based mode spot-size converter according to the utility model.
Fig. 2 is a top view of a silicon waveguide structure of a silicon waveguide-based mode spot-size converter of the present utility model.
FIG. 3 shows the width W of a silicon waveguide at the end face of a mode spot-size converter connected with an optical fiber 1 Profile of the coupling efficiency of a spot-size converter to a fiber end face of 3 μm diameter and W 1 -a change in transmittance.
FIG. 4 shows a narrow end width W of an intermediate waveguide cone structure of a silica waveguide-based spot-size converter according to the present utility model 2 -a change in transmittance.
FIG. 5 shows the width W of a straight waveguide of two side waveguides of a mode spot-size converter based on a silicon waveguide according to the present utility model 3 -a change in transmittance.
Fig. 6 is a graph showing the length change and transmittance change of a two-segment tapered waveguide structure of a silica waveguide-based spot-size converter according to the present utility model.
Detailed Description
The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
As shown in fig. 1, the present example provides a mode spot-size converter based on a silicon waveguide, which includes a substrate 1, an oxide cladding layer 2, and a silicon waveguide structure 30, wherein the oxide cladding layer 2 is located above the substrate 1, and the silicon waveguide structure 30 is located in the oxide cladding layer 2. As shown in fig. 2, the silicon waveguide structure 30 is a trigeminal structure, and is formed by sequentially arranging two side waveguides and an intermediate waveguide at a certain distance, wherein the two side waveguides are composed of a tapered waveguide 301, a straight waveguide 302, a tapered waveguide 303 and a straight waveguide 304, and the intermediate waveguide is composed of a tapered waveguide 305 and a straight waveguide 306. The structures and the dimensions of the tapered waveguide 301 and the tapered waveguide 303 are the same, the structures and the dimensions of the straight waveguide 302 and the straight waveguide 304 are the same, the distances from the waveguide bodies at two sides to the intermediate waveguide body are the same, and the height of the whole silicon waveguide structure 30 from the input end to the output end is a fixed value. The part connected with the optical waveguide is the input end of the mode spot converter, and the part connected with the optical fiber is the output end. The input end surfaces of the straight waveguides 302, 304 and the output end surfaces of the tapered waveguide 305 are on the same plane, and the waveguide widths of the straight waveguides 302, 304 and 306 remain unchanged. The tapered waveguide 301, the tapered waveguide 303, and the tapered waveguide 305 have waveguide widths that are greatest at the input end and gradually decrease from the input end to the output end.
In this embodiment, the substrate 1 and the waveguide structure 30 of the mode spot-size converter are made of silicon material, the oxide cladding 2 is made of silicon dioxide material, the thickness h=220 nm of the silicon waveguide structure 30, and the oxide above the silicon waveguide structure 30Cladding thickness H 1 =2μm, cladding thickness H under silicon waveguide structure 30 2 =3 μm, and the distance l=1 μm of the central axis of the two-sided waveguide body in the light transmission direction. By optimizing the width and length of the waveguide, a higher coupling efficiency is obtained.
The following describes the parameter design process:
first, the minimum width end face width W of the tapered waveguide 301 and the tapered waveguide 303 was studied 1 Width W for influence of coupling efficiency 1 The effect on coupling efficiency mainly includes two aspects, one that affects the transmittance of the transmission process and the other that is the width W due to the connection of the narrow width end faces of the tapered waveguide 301 and the tapered waveguide 303 to light or a laser 1 But also the coupling efficiency with the optical fiber. FIG. 3 is width W 1 -variation curve of coupling efficiency of mode spot converter and optical fiber end face with diameter of 3 μm and width W 1 -a change curve of transmittance. According to width W 1 As can be seen from the transmittance change curve, the transmittance change curve is changed along with W 1 Is higher and higher in transmittance but is wider than W 1 -the mode spot converter and the optical fiber end face coupling efficiency change curve with the diameter of 3 μm reflect W 1 >At 0.15 μm, the coupling efficiency decreases with increasing width, and the width W is selected by combining two factors 1 The mode spot-size converter was coupled to the fiber with a coupling efficiency of 88% and a transmittance of 0.984 =0.16 μm. According to width W 1 As can be seen from the field diagram of the output end face of the optical fiber connection of the spot-size converter when the spot-size converter is=0.16 μm, the spot-size can be increased to a certain extent and the difficulty of the processing process can be reduced compared with the single waveguide structure by using the structure of the double-sided waveguide, so that the coupling efficiency can be improved.
Then, the end face widths W of the tapered waveguide 301 and the tapered waveguide 303 having the largest width are studied 2 For the effect of coupling efficiency, a fixed width W 1 Changing width W 2 The change in the width of the tapered waveguide is substantially changed when the width W of the waveguide 2 The taper waveguide gradually increases in width change rate as the width of the taper waveguide gradually increases, and FIG. 4 shows width W 2 Transmission of the spot-size converterChange curve, W 2 In the range of 0.2 μm to 0.3 μm, the transmittance increases slowly, when the width W 2 At > 0.3 μm, the transmittance of the device is drastically reduced, when W 2 When=0.4 μm, the transmittance decreases to 0.8. When the width W 2 When=0.28 μm, the transmittance is 0.984 at the maximum.
Minimum width end face width W of tapered waveguide 305 3 The change in dimension also affects the coupling efficiency, FIG. 5 being width W 3 -a plot of the transmittance change of the spot-size converter. As can be seen from fig. 5, the width W of the tapered waveguide 305 2 The change in (2) affects the transmittance, but W 3 In the range of 0.05 μm to 0.15 μm, the transmittance was varied to a degree of 0.01, and the transmittance was varied to a small degree. In consideration of the problem of the process, when the width is smaller, the processing difficulty in photoetching, etching and the like is larger, so the width W is selected 3 The transmittance of the spot-size converter at this time was 0.984, =0.15 μm.
After determining the width of the tapered waveguide, the influence of the change in the structural length of the tapered waveguide on the coupling efficiency of the device is studied, and the lengths L of the tapered waveguide 301 and the tapered waveguide 303 are scanned respectively 1 And length L of tapered waveguide 305 2 The obtained curves of L1 and L2 with respect to transmittance are shown in fig. 6. From the curve of the waveguide length versus transmittance of the tapered waveguide, it can be found that the transmittance increases as the waveguide length increases, and the coupling efficiency increases.
According to the waveguide length L 1 A relation curve between transmittance and L in a scanning length range of 0 to 60 μm 1 When the transmittance of the device is less than 30 mu m, the transmittance is changed from 0.75 to about 0.98, and the change of the transmittance is obvious; when the waveguide length L 2 When the transmittance gradually increases within the range of more than 30 mu m, the increase rate of the transmittance is slower according to the change curve, the change amplitude of the transmittance in the process of changing the length by 30 mu m is not more than 0.02, the requirement on the subsequent integration of the device is considered, the shorter waveguide length is selected as much as possible under the condition of not affecting the coupling efficiency, and the waveguide lengths L of the tapered waveguide 301 and the tapered waveguide 303 are selected 1 At 42 μm, the transmittance of the device at this time was 0.99.
According to the waveguide length L 2 A relation curve between transmittance and L in a scanning length range of 0 to 60 μm 1 When the transmittance of the device is less than 15 mu m, the transmittance of the device is fluctuated from 0.2 to 0.99, the change range of the transmittance is large, and the transmittance is unstable; when the waveguide length L 2 In the range of more than 15 μm, according to L 2 As can be seen from the transmittance change curve, the transmittance is basically stabilized, the transmittance floats up and down at 0.99 in the process of changing the length by 45 μm, the amplitude change is not more than 0.01, and the waveguide length L of the tapered waveguide 305 is selected in consideration of the factor of device integration 2 The transmittance of the spot-size converter was 0.99 at 30. Mu.m.
The mode spot converter is in the field diagram of TE mode in horizontal direction at the above selected dimensions (w1=0.16 μm, w2=0.15 μm, w3=0.28 μm, l1=42 μm, l2=30 μm), so that the transmission process of TE mode in the device can be observed, and according to the field diagram, a more obvious three-fork-shaped form can be seen, the TE mode enters the mode spot converter from the input end of the straight waveguide 306 of the intermediate waveguide, when transmitting to the input end positions of the straight waveguides 302 and 304 of the two-side waveguides, light is gradually coupled into the two-side waveguides and transmitted, and in the process of decreasing the width of the tapered waveguides of the two-side waveguides, light cannot be confined in the waveguides, and the mode spot size is also increased, so that efficient coupling with the output end connecting optical fibers is realized.
Claims (6)
1. A silicon waveguide-based mode spot-size converter comprising an oxide cladding layer, a substrate and a silicon waveguide structure, wherein the substrate is at the lowest position, the oxide cladding layer is positioned above the substrate, and the silicon waveguide structure is positioned in the oxide cladding layer; the silicon waveguide structure is formed by arranging three waveguide bodies in sequence at certain intervals, and comprises a middle waveguide body and waveguide bodies on two sides.
2. A silicon waveguide-based spot-size converter according to claim 1, wherein the waveguides on both sides are vertically symmetrical and the distance from the waveguides on both sides to the intermediate waveguide is the same.
3. The silica waveguide-based spot-size converter according to claim 1, wherein the waveguide bodies on both sides and the intermediate waveguide body each comprise two waveguides arranged in sequence, and the first waveguide is closely connected to the second waveguide.
4. A silica waveguide-based spot-size converter according to claim 3 wherein the top surfaces of the first and second waveguides are planar, the first waveguide is the same as the second waveguide in height, the width of the first waveguide is gradually and continuously variable, the width of the output end of the first waveguide is the smallest, the output end is connected to an optical fiber or a laser, the width of the input end of the first waveguide is the largest, the second waveguide is a straight waveguide, and the width of the second waveguide is the same as the width of the junction of the first waveguide.
5. The silica waveguide-based spot-size converter according to claim 4, wherein the input end surfaces of the waveguides on both sides are on the same plane as the connection surface of the first section waveguide and the second section waveguide of the intermediate waveguide.
6. A silicon waveguide based spot-size converter according to claim 1 wherein the waveguides on both sides are at the same height as the intermediate waveguide.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320525679.0U CN219609274U (en) | 2023-03-17 | 2023-03-17 | Mode spot converter based on silicon waveguide |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320525679.0U CN219609274U (en) | 2023-03-17 | 2023-03-17 | Mode spot converter based on silicon waveguide |
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| CN219609274U true CN219609274U (en) | 2023-08-29 |
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| CN202320525679.0U Active CN219609274U (en) | 2023-03-17 | 2023-03-17 | Mode spot converter based on silicon waveguide |
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