CN115113329B - Optical waveguide mode spot conversion device and manufacturing method thereof - Google Patents
Optical waveguide mode spot conversion device and manufacturing method thereof Download PDFInfo
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- CN115113329B CN115113329B CN202211038179.0A CN202211038179A CN115113329B CN 115113329 B CN115113329 B CN 115113329B CN 202211038179 A CN202211038179 A CN 202211038179A CN 115113329 B CN115113329 B CN 115113329B
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Abstract
The application relates to the technical field of integrated optical chips, in particular to an optical waveguide mode spot conversion device and a manufacturing method thereof, wherein the device comprises a silicon substrate, a silicon oxide buried layer, an insulator layer, a wedge-shaped waveguide, a dielectric layer and an auxiliary waveguide; the wedge waveguide is arranged on the insulator layer; the insulator layer is arranged on the silicon oxide buried layer; the silicon oxide buried layer is arranged on the substrate; the big end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide; the dielectric layer is arranged on the insulator layer and surrounds the wedge-shaped waveguide; the auxiliary waveguide is arranged on the dielectric layer; the auxiliary waveguide is used for coupling with the optical fiber at the small end of the wedge-shaped waveguide; the big end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide; the first refractive index of the auxiliary waveguide is less than the second refractive index of the wedge waveguide and greater than the third refractive index of the dielectric layer. The sensitivity to the small end size of the wedge-shaped waveguide during the size conversion of the mode spot can be reduced; reducing light polarization dependent loss; and the mismatch loss of the mode spot conversion between the silicon optical waveguide and the optical fiber is reduced.
Description
Technical Field
The present disclosure relates to the field of integrated optical chip technologies, and in particular, to an optical waveguide speckle conversion device and a method for manufacturing the same.
Background
Silicon optical waveguides have been developed and applied gradually because of their small spot size and high integration, which can provide a low-loss, high-performance solution for optical interconnects.
The end face size difference between the silicon optical waveguide and the common single-mode fiber is large, so that the problem of high mismatch loss exists when the end face coupling is carried out between the silicon optical waveguide and the common fiber.
A mode-spot conversion device is typically used to convert the silicon waveguide mode spot to the fiber mode spot, thereby reducing mismatch losses. The mode spot conversion device mainly adopts an inverted wedge waveguide (inverted taper). The width of the reverse wedge-shaped waveguide is gradually narrowed from a large head end (a silicon optical waveguide connecting end) to a small head end (an optical fiber coupling end); the width of the small tip of the inverted wedge waveguide is small (about 100 nm). The width of the reverse wedge-shaped waveguide gradually narrows from the large head end to the small head end, so that the mode spot of the silicon optical waveguide can be enlarged, and the matching of the silicon optical waveguide mode spot and the optical fiber mode spot is realized.
However, since the spot size is sensitive to the width and thickness of the waveguide (e.g., inverted wedge waveguide) of the spot-converting device, the process tolerance is small and the uniformity of the spot-converting device is poor. The size of the mode spot of the tail end of the waveguide (i.e. the optical fiber coupling end, such as the small end of the reverse wedge waveguide) in the mode spot conversion device is related to the polarization direction of the input light at the starting end of the waveguide (i.e. the silicon optical waveguide connecting end), which is easy to generate larger polarization dependent loss, and has a larger influence on the performance of the optical integrated chip (especially the performance of the optical receiver).
Therefore, it is desirable to provide an optical waveguide speckle conversion device and a method for manufacturing the same, which can reduce the sensitivity of the speckle size (the speckle size amplified at the fiber coupling end) to the size of the end (i.e., the fiber coupling end) of the waveguide in the speckle conversion device; reducing light polarization dependent loss; and the mismatch loss of the mode spot conversion between the silicon optical waveguide and the optical fiber is reduced.
Disclosure of Invention
The embodiment of the application provides an optical waveguide spot size conversion device and a manufacturing method thereof, and specifically, the device comprises: the waveguide comprises a substrate, a buried silicon oxide layer, an insulator layer, a wedge-shaped waveguide, a dielectric layer and an auxiliary waveguide; the wedge waveguide is disposed on the insulator layer; the insulator layer is arranged on the silicon oxide buried layer; the silicon oxide buried layer is arranged on the silicon substrate; the large end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide; the dielectric layer is arranged on the insulator layer and surrounds the wedge-shaped waveguide; the auxiliary waveguide is arranged on the dielectric layer and extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for being coupled with an optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide is less than the second refractive index of the wedge waveguide and greater than the third refractive index of the dielectric layer. The sensitivity of the size of the mode spot (the size of the mode spot amplified at the optical fiber coupling end) to the size of the tail end (namely the optical fiber coupling end) of the waveguide in the mode spot conversion device can be reduced; reducing light polarization dependent loss; and the mismatch loss of the mode spot conversion between the silicon optical waveguide and the optical fiber is reduced.
In one aspect, an embodiment of the present application provides an optical waveguide spot size conversion device, including:
the waveguide comprises a substrate, a buried silicon oxide layer, an insulator layer, a wedge-shaped waveguide, a dielectric layer and an auxiliary waveguide;
the wedge waveguide is disposed on the insulator layer; the insulator layer is disposed on the substrate;
the dielectric layer is arranged on the insulator layer and surrounds the wedge-shaped waveguide;
the auxiliary waveguide is arranged on the dielectric layer and extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for being coupled with an optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide is less than the second refractive index of the wedge waveguide and greater than the third refractive index of the dielectric layer.
In some alternative embodiments, the first refractive index of the auxiliary waveguide ranges between 1.45-1.6.
In some alternative embodiments, the width of the auxiliary waveguide ranges from 4 μm to 8 μm; the height of the auxiliary waveguide ranges from 4 μm to 8 μm.
In some alternative embodiments, the auxiliary waveguide comprises silicon-rich silicon dioxide.
In some alternative embodiments, the distance between the top of the wedge waveguide and the bottom of the auxiliary waveguide is in the range of 0 μm to 2 μm.
In some alternative embodiments, the second refractive index of the wedge waveguide is greater than 1.45.
In some alternative embodiments, the tapered waveguide comprises a silicon nitride waveguide or a silicon waveguide.
In some optional embodiments, two end faces of the wedge waveguide are rectangular, and the thickness of the wedge waveguide is uniform.
In some alternative embodiments, the end face side of the small end of the wedge waveguide is less than 130nm.
In some alternative embodiments, the auxiliary waveguide is a wedge-shaped structure with a uniform thickness.
In another aspect, the present application provides a method for manufacturing an optical waveguide speckle conversion device, including:
forming a wedge-shaped waveguide on the insulating layer by adopting a microelectronic process;
depositing a dielectric layer on the insulating layer, the dielectric layer covering the wedge waveguide; the large end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide;
forming an auxiliary waveguide layer on the dielectric layer by using a microelectronic process;
etching the auxiliary waveguide layer and the dielectric layer to form an auxiliary waveguide and a groove; the auxiliary waveguide extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for being coupled with an optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide is smaller than the second refractive index of the wedge-shaped waveguide and larger than the third refractive index of the dielectric layer.
The embodiment of the application provides an optical waveguide mode spot conversion device, which comprises a substrate, a silicon oxide buried layer, an insulator layer, a wedge-shaped waveguide, a dielectric layer and an auxiliary waveguide; the wedge waveguide is disposed on the insulator layer; the insulator layer is arranged on the silicon oxide buried layer; the silicon oxide buried layer is arranged on the silicon substrate; the large end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide; the dielectric layer is arranged on the insulator layer and surrounds the wedge-shaped waveguide; the auxiliary waveguide is arranged on the dielectric layer and extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for being coupled with an optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide is less than the second refractive index of the wedge waveguide and greater than the third refractive index of the dielectric layer. The sensitivity of the size of the mode spot (the size of the mode spot amplified at the optical fiber coupling end) to the size of the tail end (namely the optical fiber coupling end) of the waveguide in the mode spot conversion device can be reduced; reducing light polarization dependent loss; and the mismatch loss of mode spot conversion between the silicon optical waveguide and the optical fiber is reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is an application scenario diagram of a spot size conversion apparatus according to an embodiment of the present application;
FIG. 2A is a schematic end view of a spot-size conversion apparatus according to some embodiments;
FIG. 2B is a schematic cross-sectional view of the spot-size conversion device of FIG. 2A taken along M-M;
FIG. 2C is a schematic cross-sectional view of the spot-size conversion device of FIG. 2A taken along N-N;
fig. 3A is a schematic end-face structure diagram of an optical waveguide mode-spot conversion device according to an embodiment of the present disclosure;
FIG. 3B is a schematic cross-sectional view of the optical waveguide mode spot conversion device of FIG. 3A taken along O-O;
FIG. 4 is a manufacturing method of an optical waveguide mode spot converting device provided by an embodiment of the present application;
fig. 5 is a schematic end face structure diagram of another optical wave mode spot conversion device provided in the embodiments of the present application.
The reference numbers in the figures have the meaning:
1-an optical fiber; 2-silicon optical waveguides; 3-a spot size conversion device; 31-a wedge waveguide; a 32-silicon substrate; 33-an insulator layer; 34-a dielectric layer; 35-an auxiliary waveguide; 36-a silicon layer; 37-a silicon waveguide; 38-buried layer of silicon oxide.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic may be included in at least one implementation of the invention. In the description of the present invention, it is to be understood that the terms "upper", "top", "bottom", and the like, as used herein, refer to an orientation or positional relationship based on that shown in the drawings, which is for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be taken as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in other sequences than those illustrated or described herein.
First, an application scenario of the speckle conversion apparatus will be described by way of example.
Referring to fig. 1, fig. 1 is an application scenario of a speckle conversion apparatus according to an embodiment of the present disclosure.
As shown in fig. 1, the end face sizes of the silicon optical waveguide 1 and the optical fiber 2 are greatly different, which results in a large difference between the end face spot sizes of the optical fiber 2 and the silicon optical waveguide 1. Therefore, when the silicon optical waveguide 1 is end-coupled to the optical fiber 2, there is a problem that the optical loss is high due to the mismatch of the mode spots. Converting the size of the spot of the silicon optical waveguide 1 into the size of the spot of the optical fiber 2 by the spot conversion device 3, or converting the size of the spot of the optical fiber 2 into the size of the spot of the silicon optical waveguide 1; to reduce optical loss due to speckle mismatch.
FIG. 2A is a schematic diagram of an end face configuration of a spot conversion device in some embodiments; FIG. 2B is a schematic cross-sectional view of the spot-size conversion device of FIG. 2A taken along M-M; fig. 2C is a schematic cross-sectional view of the spot-size converting apparatus of fig. 2A taken along N-N. As shown in fig. 2A, 2B and 2C, the mode spot converting device 3 includes a reverse wedge waveguide 31, and the reverse wedge waveguide 31 is used for enlarging the mode spot along the extending direction of the reverse wedge waveguide 31 (i.e., gradually enlarging the mode spot from a large end to a small end).
As shown in fig. 2B, the inverted wedge waveguide 31 is uniform in thickness; as shown in fig. 2C, the transverse width of the inverted wedge waveguide 31 gradually decreases along the extending direction, and the end of the inverted wedge waveguide 31 in the extending direction is a small end. The end face of the small end of the inverted wedge waveguide 31 matches and aligns with the end face of the optical fiber 2 shown in fig. 1; the end face of the large end of the inverted wedge waveguide 31 is connected to the end face of the silicon optical waveguide 1 shown in fig. 1.
As mentioned previously, the size of the mode spot of the inverted wedge waveguide 31 at the small end is sensitive to the size of the end face of the small end of the inverted wedge waveguide 31; resulting in small process tolerances and poor uniformity of the inverted wedge waveguide 31. The size of the mode spot at the small end of the reverse wedge waveguide 31 in the mode spot conversion device 3 is related to the polarization direction of the output light of the silicon optical waveguide 1, and a large polarization-dependent insertion loss is easily generated at the small end of the reverse wedge waveguide 31, which has a large influence on the performance of the optical integrated chip (especially the performance of the optical receiver).
In view of the above problems, an embodiment of the present application provides an optical waveguide mode-spot conversion device, which includes a silicon substrate, a buried silicon oxide layer, an insulator layer, a wedge waveguide, a dielectric layer, and an auxiliary waveguide; the wedge waveguide is disposed on the insulator layer; the insulator layer is arranged on the silicon oxide buried layer; the silicon oxide buried layer is arranged on the silicon substrate; the large end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide; the dielectric layer is arranged on the insulator layer and surrounds the wedge-shaped waveguide; the auxiliary waveguide is arranged on the dielectric layer and extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for being coupled with an optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide is smaller than the second refractive index of the wedge-shaped waveguide and larger than the third refractive index of the dielectric layer. The sensitivity of the size of the mode spot (the size of the mode spot amplified at the optical fiber coupling end) to the size of the tail end (namely the optical fiber coupling end) of the waveguide in the mode spot conversion device can be reduced by coupling the auxiliary waveguide with the optical fiber at the small end of the wedge-shaped waveguide; reducing light polarization damage; and the mismatch loss of the mode spot conversion between the silicon optical waveguide and the optical fiber is reduced.
A specific embodiment of an optical waveguide speckle conversion device according to the present application is described below, and fig. 3A is a schematic end-face structure diagram of a small end of an optical waveguide speckle conversion device according to the present application; FIG. 3B is a schematic cross-sectional view of the optical waveguide mode spot conversion device along O-O in FIG. 3A. Specifically, as shown in fig. 3A, the optical waveguide spot size conversion device 3 (i.e., corresponding to the spot size conversion device 3) includes:
a wedge waveguide 31, a silicon substrate 32, a buried silicon oxide layer 38, an insulator layer 33, a dielectric layer 34, and an auxiliary waveguide 35;
the wedge waveguide 31 is disposed on the insulator layer 33; the insulator layer 33 is disposed on the silicon substrate 32; the insulator layer 33 is arranged on the silicon oxide buried layer 38; the buried silicon oxide layer 38 is disposed on the silicon substrate 32; the big end of the wedge-shaped waveguide 31 is used for connecting with the silicon optical waveguide 1;
the dielectric layer 34 is disposed on the insulator layer 33 and surrounds the wedge waveguide 31;
the auxiliary waveguide 35 is arranged on the dielectric layer 34 and extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide 35 is used for coupling with the optical fiber 2 shown in FIG. 1 at the small end of the wedge waveguide 31; the first refractive index of the auxiliary waveguide 35 is smaller than the second refractive index of the wedge waveguide 31 and larger than the third refractive index of the dielectric layer 34.
In some alternative embodiments, a thin film layer having a refractive index higher than that of silicon dioxide is produced as the auxiliary waveguide 35 using a PECVD (Plasma Enhanced Chemical Vapor Deposition) technique. The end face of the auxiliary waveguide 35 is adapted to match and couple with the end face of the optical fiber 2.
For example, as shown in fig. 3B, since the first refractive index of the auxiliary waveguide 35 is smaller than the second refractive index of the wedge waveguide 31, the input light P is transmitted in the wedge waveguide 31; since the width of the wedge waveguide 31 is gradually reduced along the light transmission direction, light is gradually transmitted into the auxiliary waveguide 35 through the dielectric layer 34; the final light is output from the auxiliary waveguide 35 (the small end of the wedge waveguide) into the optical fiber 2.
In the above embodiment, by arranging the auxiliary waveguide 35 with a larger end face to match and couple with the end face of the optical fiber, the sensitivity of the size of the mode spot of the optical fiber to the size of the waveguide tail end (i.e., the small end of the wedge waveguide 31) of the mode spot conversion device can be reduced; reducing light polarization dependent loss; the mismatch loss of the mode spot conversion between the silicon optical waveguide 1 and the optical fiber 2 can be reduced, and the performance of the optical chip based on the mode spot conversion device is improved. Moreover, the end face of the auxiliary waveguide 35 may be set to be much larger than the end face size of the small end of the wedge waveguide 31, so that when the auxiliary waveguide 35 is matched and coupled with the end face of the optical fiber 2, the alignment accuracy may be reduced, and the alignment efficiency may be improved.
In some alternative embodiments, the auxiliary waveguide 35 comprises silicon-rich silicon dioxide. As shown in fig. 3A, the auxiliary waveguide 35 is a silicon rich silicon dioxide (SRO) film. Specifically, the silicon-rich silicon dioxide film can be realized by adjusting the flow rate of silane in the process on the basis of the process for growing silicon dioxide. Wherein the refractive index of silicon is greater than that of silicon-rich silicon dioxide, and the refractive index of silicon-rich silicon dioxide is greater than that of silicon dioxide.
By controlling the content of silicon and thus the first refractive index of the silicon-rich silica film, the light transmitted in the wedge waveguide 31 is gradually transmitted into the auxiliary waveguide 35 as the width of the wedge waveguide 31 is gradually reduced along the light transmission direction. Similarly, the light of the auxiliary waveguide 35 is gradually input into the wedge waveguide 31 along the reverse light transmission direction while the light is reversely transmitted in the wedge waveguide 31.
In some alternative embodiments, silica (i.e., insulator layer 33 in FIG. 3A) and epoxy (not numbered in FIG. 3A) having an index of refraction less than 1.45 are used as the cladding material for wedge waveguide 31, which is less than the first index of refraction of auxiliary waveguide 35.
When a waveguide (such as the tapered waveguide 31 described above) in the spot size converting device is close to the silicon substrate 32 having a high refractive index in fig. 3A, leakage of transmission light of the waveguide in the spot size converting device to the silicon substrate is easily caused, thereby causing optical loss. In the prior art, a method for locally removing a silicon substrate is generally adopted to reduce loss, but the method has the problems of high process difficulty, easy damage to a spot-size conversion device, weak mechanical strength and the like.
In the above embodiment, the auxiliary waveguide 35 and the silicon substrate 32 are further provided with the insulator layer 33 and the dielectric layer 34 therebetween. By modulating the thickness of the insulator layer 33 such that the mode field (i.e., mode spot) of the auxiliary waveguide 35 is further away from the silicon substrate 32, mode field leakage of the auxiliary waveguide 35 is avoided or reduced. Therefore, the process is simplified, and the reliability of the device is improved.
For example, the insulator layer 33 is obtained by using a trench isolation (STI) technique; dielectric layer 34 comprises an inter-metal dielectric (IMD).
For example, the wedge waveguide 31 is a silicon nitride waveguide, and light is gradually converted from the silicon nitride waveguide (the wedge waveguide 31) into the silicon-rich silica thin film waveguide (the auxiliary waveguide 35) while being transmitted through the spot size conversion device 3.
In some optional embodiments, the structure of the wedge waveguide 31 that gradually narrows from the large end to the small end may adopt linear transformation, or may adopt a nonlinear structure to reduce the length of the optical waveguide spot size conversion device 3, reduce the volume of the optical waveguide spot size conversion device 3, and save cost.
In some alternative embodiments, the first refractive index of the auxiliary waveguide 35 ranges between 1.45-1.6, such as a first refractive index of 1.453. The third refractive index of dielectric layer 34 may be 1.448. Specifically, the light is slowly converted from the silicon nitride waveguide into the silicon-rich silica thin film waveguide according to the second refractive index (for example, the second refractive index is 2.0) of the wedge-shaped waveguide 31 and the distance between the bottom of the auxiliary waveguide 35 and the bottom of the wedge-shaped waveguide 31, and the mode spot conversion efficiency is ensured.
In some alternative embodiments, the auxiliary waveguide 35 is a wedge-shaped structure with a uniform thickness. Thus, the process difficulty can be reduced.
In some alternative embodiments, the width of the auxiliary waveguide 35 ranges from 4 μm to 8 μm; the height of the auxiliary waveguide 35 ranges from 4 μm to 8 μm.
In this embodiment, since the width and the height of the auxiliary waveguide 35 are both relatively large, when the mode spot of the auxiliary waveguide 35 at the end of the optical waveguide mode spot conversion device 3 is matched with the mode spot of the optical fiber 2, the optical coupling loss is small. And the mode spot of the auxiliary waveguide 35 at the small end of the wedge waveguide 31 is insensitive to the size of the small end of the wedge waveguide 31, and the process tolerance is large.
The distance between the top of the wedge waveguide 31 and the bottom of the auxiliary waveguide 35 is too large, which increases the difficulty of converting light from the auxiliary waveguide 35 to the wedge waveguide 31, and thus the length of the optical waveguide mode spot conversion device 3 is increased. In some alternative embodiments, the distance between the top of the wedge waveguide 31 and the bottom of the auxiliary waveguide 35 is in the range of 0 μm to 2 μm. Thus, the length of the optical waveguide spot conversion device 3 can be effectively reduced within this distance range.
Since light will travel along materials with large refractive indices, in some alternative embodiments, the second refractive index of the wedge waveguide 31 is greater than 1.45. For example, the wedge waveguide 31 may be a silicon waveguide or other high index (e.g., index greater than 1.45) material waveguide. In this manner, a rapid transition of light from the wedge waveguide 31 to the subsidiary waveguide 35 is ensured.
In alternative embodiments, the tapered waveguide 31 comprises a silicon nitride waveguide or a silicon waveguide.
In some alternative embodiments, two end faces of the wedge waveguide 31 are rectangular, and the thickness of the wedge waveguide 31 is uniform.
In some alternative embodiments, the end face side of the small end of the wedge waveguide 31 is less than 130nm. Specifically, since the small end of the wedge waveguide 31 is no longer used for coupling with an optical fiber, the influence of the size of the small end of the wedge waveguide 31 on optical loss is greatly reduced, and the size of the end face of the small end of the wedge waveguide 31 can be controlled to be smaller than 130nm, thereby reducing the process difficulty of the wedge waveguide 31. The existing scheme usually needs to control the dimensional accuracy of the end face of the wedge waveguide 31 within 10nm, and is difficult in process.
The embodiment of the application provides an optical waveguide mode spot conversion device, which comprises a silicon substrate, a silicon oxide buried layer, an insulator layer, a wedge-shaped waveguide, a dielectric layer and an auxiliary waveguide; the wedge waveguide is disposed on the insulator layer; the insulator layer is arranged on the silicon oxide buried layer; the silicon oxide buried layer is arranged on the silicon substrate; the large end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide; the dielectric layer is arranged on the insulator layer and surrounds the wedge-shaped waveguide; the auxiliary waveguide is arranged on the dielectric layer and extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for being coupled with an optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide is smaller than the second refractive index of the wedge-shaped waveguide and larger than the third refractive index of the dielectric layer. The sensitivity of the size of the mode spot (the size of the mode spot amplified at the optical fiber coupling end) to the size of the tail end (namely the optical fiber coupling end) of the waveguide in the mode spot conversion device can be reduced; reducing light polarization dependent loss; and the mismatch loss of the mode spot conversion between the silicon optical waveguide and the optical fiber is reduced.
Fig. 4 is a manufacturing method of an optical waveguide mode spot conversion device according to an embodiment of the present disclosure. The specification provides the method steps as in the examples or flowcharts, but may include more or fewer steps based on conventional or non-inventive labor. The order of steps recited in the embodiments is merely one manner of performing the steps in a multitude of orders and does not represent the only order of execution. In actual system or server product execution, sequential execution or parallel execution (e.g., parallel processor or multithreaded processing environments) may occur according to the embodiments or methods shown in the figures. Specifically, as shown in fig. 4, the method includes:
s402: and forming a wedge-shaped waveguide on the insulating layer by adopting a microelectronic process.
For example, a wedge waveguide 31 is formed on the insulator layer 33 shown in fig. 3A using a microelectronic process. Specifically, the insulator layer 33 is formed by depositing a filling silicon oxide. A silicon nitride protective layer is formed on the insulator layer 33 by using a plasma chemical vapor deposition (LPCVD) technique and a Low Pressure Chemical Vapor Deposition (LPCVD) technique.
S404: depositing a dielectric layer on the insulating layer, the dielectric layer covering the wedge waveguide. The big end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide.
For example, an inter-metal dielectric (IMD) dielectric layer is deposited on insulator layer 33 as shown in fig. 3A and planarized, resulting in dielectric layer 34. The dielectric layer 34 serves as a middle protective layer of the optical waveguide spot size conversion device 3.
S406: and forming an auxiliary waveguide layer on the dielectric layer by adopting a microelectronic process.
For example, a silicon-rich silicon dioxide thin film layer is deposited by using a plasma chemical vapor deposition technique to obtain an auxiliary waveguide layer, and the auxiliary waveguide layer is polished flat.
S408: etching the auxiliary waveguide layer and the dielectric layer to form an auxiliary waveguide and a groove; the auxiliary waveguide extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for coupling with the optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide layer is less than the second refractive index of the wedge waveguide and greater than the third refractive index of the dielectric layer.
For example, the auxiliary waveguide layer and the dielectric layer 34 are etched by photolithography and etching techniques to form an auxiliary waveguide 35 (e.g., a silicon nitride waveguide) and a trench; then, the groove is filled with epoxy resin, the silicon nitride waveguide is used as a core, and the dielectric layer is a protective layer of the silicon nitride waveguide.
In some alternative embodiments, the metal (not numbered in fig. 5) and dielectric layer (not numbered in fig. 5) required for the spot changing device are formed on the auxiliary waveguide layer.
Fig. 5 is a schematic end view of another optical mode spot conversion device according to an embodiment of the present invention, and in some alternative embodiments, the buried oxide layer 38 shown in fig. 5 may be a silicon dioxide layer.
In some alternative embodiments, silicon layer 36 is deposited over buried oxide layer 38 and silicon waveguide 37 is formed by etching silicon layer 36 before using microelectronics processes to form wedge waveguide 31 on insulator layer 33 as shown in fig. 3A; silicon dioxide is then deposited as insulator layer 33 on the silicon waveguide 37 and lapped flat.
In the present embodiment, the optical mode spot conversion device 3 uses the silicon waveguide 37 shown in fig. 5 to couple light from the waveguide 31 into the silicon waveguide 37. Thus, other silicon optical devices, such as modulators, detectors, etc., may also be integrated into the silicon waveguide 37.
The optical waveguide spot size conversion device is obtained by the manufacturing method of the optical waveguide spot size conversion device, and the optical waveguide spot size conversion device can reduce the sensitivity of the spot size (the spot size amplified at the optical fiber coupling end) to the size of the tail end (namely the optical fiber coupling end) of the waveguide in the spot size conversion device; reducing light polarization dependent loss; and the mismatch loss of the mode spot conversion between the silicon optical waveguide and the optical fiber is reduced.
In summary, the embodiment of the present application provides an optical waveguide speckle conversion device and a manufacturing method thereof, the optical waveguide speckle conversion device includes a silicon substrate, a buried silicon oxide layer, an insulator layer, a wedge waveguide, a dielectric layer, and an auxiliary waveguide; the wedge waveguide is disposed on the insulator layer; the insulator layer is arranged on the silicon oxide buried layer; the silicon oxide buried layer is arranged on the substrate; the large end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide; the dielectric layer is arranged on the insulator layer and surrounds the wedge-shaped waveguide; the auxiliary waveguide is arranged on the dielectric layer and extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for being coupled with an optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide is smaller than the second refractive index of the wedge-shaped waveguide and larger than the third refractive index of the dielectric layer. The sensitivity of the size of the mode spot (the size of the mode spot amplified at the optical fiber coupling end) to the size of the tail end (namely the optical fiber coupling end) of the waveguide in the mode spot conversion device can be reduced; reducing light polarization dependent loss; and the mismatch loss of mode spot conversion between the silicon optical waveguide and the optical fiber is reduced.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Moreover, those of skill in the art will understand that although some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the application and form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.
Claims (11)
1. An optical waveguide speckle conversion apparatus, comprising:
the waveguide comprises a silicon substrate, a buried silicon oxide layer, an insulator layer, a wedge-shaped waveguide, a dielectric layer and an auxiliary waveguide;
the wedge waveguide is disposed on the insulator layer; the insulator layer is arranged on the silicon oxide buried layer; the silicon oxide buried layer is arranged on the silicon substrate; the large end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide;
the dielectric layer is arranged on the insulator layer and surrounds the wedge-shaped waveguide;
the auxiliary waveguide is arranged on the dielectric layer and extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for being coupled with an optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide is smaller than the second refractive index of the wedge-shaped waveguide and larger than the third refractive index of the dielectric layer.
2. The apparatus of claim 1, wherein the first refractive index of the auxiliary waveguide ranges between 1.45-1.6.
3. The apparatus according to claim 1 or 2, wherein the auxiliary waveguide has a width in the range of 4 μ ι η -8 μ ι η; the height of the auxiliary waveguide ranges from 4 μm to 8 μm.
4. The apparatus of claim 1 or 2, wherein the auxiliary waveguide comprises silicon-rich silicon dioxide.
5. The apparatus of claim 1 or 2, wherein the distance between the top of the wedge waveguide and the bottom of the auxiliary waveguide is in the range of 0 μ ι η -2 μ ι η.
6. The device of claim 1 or 2, wherein the second refractive index of the wedge waveguide is greater than 1.45.
7. The apparatus of claim 1 or 2, wherein the wedge waveguide comprises a silicon nitride waveguide or a silicon waveguide.
8. The apparatus of claim 1 or 2, wherein the two end faces of the wedge-shaped waveguide are rectangular, and the thickness of the wedge-shaped waveguide is uniform.
9. The apparatus of claim 1 or 2, wherein the minor end of the wedge waveguide has an end face side length of less than 130nm.
10. The apparatus of claim 1 or 2, wherein the auxiliary waveguide is a wedge-shaped structure of uniform thickness.
11. A method of fabricating an optical waveguide speckle conversion device, the method comprising:
forming a wedge-shaped waveguide on the insulating layer by adopting a microelectronic process; the large end of the wedge-shaped waveguide is used for being connected with the silicon optical waveguide;
depositing a dielectric layer on the insulating layer, the dielectric layer covering the wedge waveguide;
forming an auxiliary waveguide layer on the dielectric layer by using a microelectronic process;
etching the auxiliary waveguide layer and the dielectric layer to form an auxiliary waveguide and a groove; the auxiliary waveguide extends along the extension direction of the wedge-shaped waveguide; the auxiliary waveguide is used for being coupled with an optical fiber at the small end of the wedge-shaped waveguide; the first refractive index of the auxiliary waveguide is less than the second refractive index of the wedge waveguide and greater than the third refractive index of the dielectric layer.
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