Waveguide cross junction

Abstract

The present application provides a waveguide crossing junction comprising: an input waveguide extending in a direction L1 and having a fixed size in a direction L2, L1 and L2 being perpendicular to each other and both being parallel to a surface of a substrate; the first conical waveguide extends along the L1 and is provided with a first end and a second end on the L1, the first end is connected with the input waveguide, and the size of the first end on the L2 is smaller than that of the second end on the L2; the first straight waveguide extends along the L1 and is connected with the second end, and the size of the first straight waveguide in the L2 is fixed; the second conical waveguide extends along the L1 and is provided with a third end and a fourth end on the L1, the third end is connected with the first straight waveguide, and the size of the third end on the L2 is larger than that of the fourth end on the L2; the output waveguide extends along the L1 and is connected with the fourth end, and the size of the output waveguide in the L2 is fixed; and a first waveguide group connected to the first straight waveguide, located on one side of the first straight waveguide on the L2, and extending along the L2. According to the invention, the loss and crosstalk of the waveguide cross junction can be reduced.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and particularly to a waveguide crossing junction. Background Art

[0002] The silicon-on-insulator (SOI) platform is expected to be used for ultra-large-scale and ultra-high-density integration of photonic devices. The complementary metal-oxide-semiconductor (CMOS) process based on the SOI platform can integrate optical devices or systems with traditional microelectronic devices on a single chip (chip), thus attracting double attention from the academic and industrial communities. Optical devices or systems are, for example, optical switches and the like.

[0003] Most optical switch arrays require the optical path to cross another optical path. Different from the freely routed circuit connections, silicon-based waveguides are planar waveguides. The propagation of the optical path between different planes needs to consider the mode coupling of light and the cost. To implement a large-capacity on-chip optical system, it is inevitable to use a waveguide crossing junction (crossing). Direct waveguide crossing will form severe diffraction in the junction region, resulting in loss and crosstalk. Only about 80% of the light flows to the output end of the waveguide crossing junction. Therefore, it is very important to implement a waveguide crossing junction with low insertion loss and low crosstalk.

[0004] It should be noted that the above introduction to the technical background is only for the convenience of clearly and completely explaining the technical solutions of this application and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well-known to those skilled in the art just because these solutions are described in the background art part of this application. Summary of the Invention

[0005] The traditional waveguide crossing junction based on the multimode interference (MMI) principle consists of two 90° crossed 1*1 multimode interference (MMI) couplers. By reasonably designing the length of the MMI coupler, the optical mode field can be focused in the waveguide crossing junction area, reducing scattering loss and crosstalk.

[0006] However, the loss of the traditional waveguide crossing junction based on the MMI principle can be optimized to at most about 0.1 dB. A large number of waveguide crossing junctions are required for a multi-channel optical switch array, which will still introduce extremely large waveguide losses. Therefore, there is a great need for a waveguide crossing junction with extremely low loss and crosstalk.

[0007] An embodiment of this application provides a waveguide crossing junction, which has a tapered waveguide structure and can achieve low loss and low crosstalk; in addition, using silicon oxynitride material to fabricate this waveguide crossing junction can further reduce the loss.

[0008] According to one aspect of the embodiments of this application, a waveguide crossing junction is provided, which is disposed on a substrate. The waveguide crossing junction includes:

[0009] An input waveguide that extends in a first direction and has a fixed dimension in a second direction, where the first direction and the second direction are perpendicular to each other, and both the first direction and the second direction are parallel to the surface of the substrate;

[0010] A first tapered waveguide that extends in the first direction and has a first end and a second end in the first direction. The first end is connected to the input waveguide, and the dimension of the first end in the second direction is smaller than the dimension of the second end in the second direction;

[0011] A first straight waveguide that extends in the first direction and is connected to the second end. The first straight waveguide has a fixed dimension in the second direction;

[0012] A second tapered waveguide that extends in the first direction and has a third end and a fourth end in the first direction. The third end is connected to the first straight waveguide, and the dimension of the third end in the second direction is larger than the dimension of the fourth end in the second direction;

[0013] An output waveguide that extends in the first direction and is connected to the fourth end. The output waveguide has a fixed dimension in the second direction; and

[0014] A first waveguide group that is connected to the first straight waveguide, is located on one side of the first straight waveguide in the second direction, and extends in the second direction.

[0015] In at least some embodiments, the first waveguide group includes:

[0016] A second straight waveguide that extends in the second direction, is connected to the side wall of the first straight waveguide in the second direction, and has a fixed dimension in the first direction;

[0017] A third tapered waveguide that extends in the second direction and has a fifth end and a sixth end in the second direction. The fifth end is connected to the second straight waveguide, and the dimension of the fifth end in the first direction is larger than the dimension of the sixth end in the first direction; and

[0018] A third straight waveguide that extends in the second direction and is connected to the sixth end and has a fixed dimension in the first direction.

[0019] In at least some embodiments, the waveguide crossing junction further includes:

[0020] A second waveguide group that is connected to the first straight waveguide, is located on the other side of the first straight waveguide in the second direction, and extends in the second direction.

[0021] In at least some embodiments, the second waveguide group includes:

[0022] A fourth straight waveguide, which extends along the second direction, is connected to the other sidewall of the first straight waveguide in the second direction, and has a fixed dimension in the first direction;

[0023] A fourth tapered waveguide, which extends along the second direction, has a seventh end and an eighth end in the second direction, the seventh end is connected to the fourth straight waveguide, and the dimension of the seventh end in the first direction is larger than the dimension of the eighth end in the first direction; and

[0024] A fifth straight waveguide, which extends along the second direction, is connected to the eighth end, and has a fixed dimension in the first direction.

[0025] In at least some embodiments, the sidewall shape of at least one of the first tapered waveguide, the second tapered waveguide, the third tapered waveguide, and the fourth tapered waveguide is an exponential curve.

[0026] In at least some embodiments, the input waveguide and the output waveguide have the same dimension in the first direction; and / or

[0027] The input waveguide and the output waveguide have the same dimension in the second direction; and / or

[0028] The first tapered waveguide and the second tapered waveguide have the same dimension in the first direction; and / or

[0029] The third tapered waveguide and the fourth tapered waveguide have the same dimension in the second direction; and / or

[0030] The dimension of the first tapered waveguide and / or the second tapered waveguide in the first direction is the same as the dimension of the third tapered waveguide and / or the fourth tapered waveguide in the second direction; and / or

[0031] The second straight waveguide and the fourth straight waveguide have the same dimension in the first direction; and / or

[0032] The second straight waveguide and the fourth straight waveguide have the same dimension in the second direction; and / or

[0033] The third straight waveguide and the fifth straight waveguide have the same dimension in the first direction; and / or

[0034] The third straight waveguide and the fifth straight waveguide have the same dimension in the second direction; and / or

[0035] The dimension of the second straight waveguide and / or the fourth straight waveguide in the first direction is equal to the dimension of the first straight waveguide in the second direction; and / or

[0036] The size of the third straight waveguide and / or the fifth straight waveguide in the first direction is equal to the size of the input waveguide and / or the output waveguide in the second direction; and / or

[0037] The size of the third straight waveguide and / or the fifth straight waveguide in the second direction is equal to the size of the input waveguide and / or the output waveguide in the first direction.

[0038] In at least some embodiments, in the first direction, the first waveguide group and / or the second waveguide group are located at the middle position of the first straight waveguide.

[0039] In at least some embodiments, the material of the waveguide crossing junction is silicon oxynitride.

[0040] In at least some embodiments, the waveguide crossing junction is supported by the buried oxide layer of the substrate,

[0041] The top and side walls of the waveguide crossing junction are covered by a silicon oxide layer.

[0042] The beneficial effects of the present application are as follows: The waveguide crossing junction has a tapered waveguide structure, which can achieve low loss and low crosstalk; in addition, using silicon oxynitride material to fabricate the waveguide crossing junction can further reduce the loss.

[0043] Referring to the following description and drawings, specific embodiments of the present application are disclosed in detail, indicating the ways in which the principles of the present application can be adopted. It should be understood that the embodiments of the present application are not limited in scope thereby. Within the spirit and terms of the appended claims, the embodiments of the present application include many changes, modifications and equivalents.

[0044] Features described and / or illustrated for one embodiment can be used in the same or similar way in one or more other embodiments, combined with features in other embodiments, or replace features in other embodiments.

[0045] It should be emphasized that the term "comprising / including" when used herein refers to the presence of features, whole things, steps or components, but does not exclude the presence or addition of one or more other features, whole things, steps or components. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings included are used to provide a further understanding of the embodiments of the present application, which form a part of the specification, are used to illustrate the embodiments of the present application, and are used to explain the principles of the present application together with the written description. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0047] Figure 1 is a top view schematic diagram of the waveguide cross-junction according to an embodiment of the present application;

[0048] Figure 2 is a cross-sectional schematic diagram of the waveguide cross-junction according to an embodiment of the present application;

[0049] Figure 3 is a schematic diagram of the simulation result of the overall structure of the waveguide cross-junction of the present application. Detailed Embodiments

[0050] Referring to the accompanying drawings, through the following description, the foregoing and other features of the present application will become apparent. In the description and drawings, specific embodiments of the present application are disclosed, which show some embodiments in which the principles of the present application can be adopted. It should be understood that the present application is not limited to the described embodiments. On the contrary, the present application includes all modifications, variations, and equivalents falling within the scope of the appended claims.

[0051] In the description of the embodiments of the present application, for convenience of description, the direction parallel to the surface of the substrate is referred to as "lateral", and the direction perpendicular to the surface of the substrate is referred to as "longitudinal".

[0052] Embodiment

[0053] An embodiment of the present application provides a waveguide cross-junction.

[0054] Figure 1 is a top view schematic diagram of the waveguide cross-junction according to an embodiment of the present application. In Figure 1 it, the first direction L1 and the second direction L2 are perpendicular to each other, and both the first direction L1 and the second direction L2 are parallel to the surface of the substrate.

[0055] As Figure 1 shown, the waveguide cross-junction 100 includes: an input waveguide 1, a first tapered waveguide 2, a first straight waveguide 3, a second tapered waveguide 4, an output waveguide 5, and a first waveguide group 6.

[0056] The input waveguide 1 extends along the first direction L1, and its dimension in the second direction L2 is fixed. For example, the input waveguide 1 can be rectangular.

[0057] The first tapered waveguide 2 extends along the first direction L1 and has a first end 21 and a second end 22 in the first direction L1. The first end 21 is connected to the input waveguide 1, and the dimension of the first end 21 in the second direction L2 is smaller than the dimension of the second end 22 in the second direction L2.

[0058] The first straight waveguide 3 extends along the first direction L1 and is connected to the second end 22. The dimension of the first straight waveguide 3 in the second direction L2 is fixed. For example, the first straight waveguide 3 can be rectangular.

[0059] The second tapered waveguide 4 extends along the first direction L1 and has a third end 41 and a fourth end 42 in the first direction L1. The third end 41 is connected to the first straight waveguide 3. The dimension of the third end 41 in the second direction L2 is larger than the dimension of the fourth end 42 in the second direction L2.

[0060] The output waveguide 5 extends along the first direction L1 and is connected to the fourth end 42. The dimension of the output waveguide 5 in the second direction L2 is fixed. For example, the output waveguide 5 can be rectangular.

[0061] The first waveguide group 6 is connected to the first straight waveguide 3 and is located on one side of the first straight waveguide 3 in the second direction L2 (for example, Figure 1 the upper side), and extends along the second direction L2.

[0062] As Figure 1 shown, the first waveguide group 6 includes: a second straight waveguide 61, a third tapered waveguide 62, and a third straight waveguide 63.

[0063] Among them, the second straight waveguide 61 extends along the second direction L2, is connected to the side wall of the first straight waveguide 3 in the second direction L2, and the dimension in the first direction L1 is fixed. For example, the second straight waveguide 61 is rectangular.

[0064] The third tapered waveguide 62 extends along the second direction L2 and has a fifth end 621 and a sixth end 622 in the second direction L2. The fifth end 621 is connected to the second straight waveguide 61, and the dimension of the fifth end 621 in the first direction L1 is larger than the dimension of the sixth end 622 in the first direction L1.

[0065] The third straight waveguide 63 extends along the second direction L2 and is connected to the sixth end 622. The dimension of the third straight waveguide 63 in the first direction L1 is fixed. For example, the third straight waveguide 63 is rectangular.

[0066] As Figure 1 shown, the waveguide cross-junction 100 further includes: a second waveguide group 7. Among them, the second waveguide group 7 is connected to the first straight waveguide 3 and is located on the other side of the first straight waveguide 3 in the second direction L2 (for example, Figure 1 the lower side), and extends along the second direction L2.

[0067] The second waveguide group 7 includes: a fourth straight waveguide 71, a fourth tapered waveguide 72, and a fifth straight waveguide 73.

[0068] The fourth straight waveguide 71 extends along the second direction L2 and is connected to the other side wall (for example, the lower side wall) of the first straight waveguide 3 in the second direction L2. The dimension of the fourth straight waveguide 71 in the first direction L1 is fixed. For example, the fourth straight waveguide 71 is rectangular.

[0069] The fourth tapered waveguide 72 extends along the second direction L2 and has a seventh end 721 and an eighth end 722 in the second direction L2. The seventh end 721 is connected to the fourth straight waveguide 71, and the dimension of the seventh end 721 in the first direction L1 is larger than the dimension of the eighth end 722 in the first direction L1.

[0070] The fifth straight waveguide 73 extends along the second direction L2 and is connected to the eighth end 722. The dimension of the fifth straight waveguide 73 in the first direction L1 is fixed. For example, the fifth straight waveguide 73 is rectangular.

[0071] In the first direction L1, the first waveguide group 6 and / or the second waveguide group 7 is / are located at the middle position of the first straight waveguide 3.

[0072] In this application, when observed along the direction perpendicular to the surface of the substrate, the side wall shape of at least one of the first tapered waveguide 2, the second tapered waveguide 4, the third tapered waveguide 62, and the fourth tapered waveguide 72 is an exponential curve.

[0073] The input waveguide 1 and the output waveguide 5 have the same dimension in the first direction L1; and / or, the input waveguide 1 and the output waveguide 5 have the same dimension in the second direction L2; and / or, the second straight waveguide 61 and the fourth straight waveguide 71 have the same dimension in the first direction L1; the first tapered waveguide 2 and the second tapered waveguide 4 have the same dimension in the first direction L1; and / or, the third tapered waveguide 62 and the fourth tapered waveguide 72 have the same dimension in the second direction L2; and / or, the dimension of the first tapered waveguide 2 and / or the second tapered waveguide 4 in the first direction L1 is the same as the dimension of the third tapered waveguide 62 and / or the fourth tapered waveguide 72 in the second direction L2; and / or, the second straight waveguide 61 and the fourth straight waveguide 71 have the same dimension in the second direction L2; and / or, the third straight waveguide 63 and the fifth straight waveguide 73 have the same dimension in the first direction L1; and / or, the third straight waveguide 63 and the fifth straight waveguide 73 have the same dimension in the second direction L2; and / or, the dimension of the second straight waveguide 61 and / or the fourth straight waveguide 71 in the first direction L1 is equal to the dimension of the first straight waveguide 3 in the second direction L2; and / or, the dimension of the third straight waveguide 63 and / or the fifth straight waveguide 73 in the first direction L1 is equal to the dimension of the input waveguide 1 and / or the output waveguide 5 in the second direction L2; and / or, the dimension of the third straight waveguide 63 and / or the fifth straight waveguide 73 in the second direction L2 is equal to the dimension of the input waveguide 1 and / or the output waveguide 5 in the first direction L1.

[0074] In a specific example: the sizes of the input waveguide 1 and the output waveguide 5 in the second direction L2 are D1, and D1 is, for example, 1.2 μm; the sizes of the first tapered waveguide 2 and the second tapered waveguide 4 in the first direction L1 are D2, and the sizes of the third tapered waveguide 62 and the fourth tapered waveguide 72 in the second direction L2 are also D2, and D2 is, for example, 7.4 μm; the size of the first straight waveguide 3 in the first direction L1 is D3, and in addition, the distance between the fifth end 621 and the seventh end 721 in the second direction L2 is also D3, and D3 is, for example, 25.2 μm; the size of the first straight waveguide 3 in the second direction L2 is D4, and the sizes of the second straight waveguide 61 and the fourth straight waveguide 71 in the first direction L1 are also D4, and D4 is, for example, 3.2 μm.

[0075] In the present application, the material of the waveguide crossing 100 is silicon oxynitride. Compared with silicon, using silicon oxynitride material to manufacture waveguides has a lower refractive index difference, which is beneficial to realizing a crossing with smaller insertion loss and can be compatible with traditional CMOS processes. Therefore, the present application uses silicon oxynitride material to prepare the waveguide crossing 100, which can better solve the problems of excessive loss and crosstalk.

[0076] Figure 2 is a schematic cross-sectional view of a waveguide crossing, showing the cross-section of the waveguide crossing 100 observed along the Figure 1 A-A' direction. As Figure 2 shown, the waveguide crossing 100 is supported by the buried oxide layer 101 of the substrate, and the top and side walls of the waveguide crossing 100 are covered by the silicon oxide layer 102. For example, the thicknesses of the buried oxide layer 101, the waveguide crossing 100, and the silicon oxide layer 102 are 5 μm, 1.2 μm, and 5 μm respectively.

[0077] Compared with the prior art, the waveguide crossing of the present application has tapered waveguides. After the light from the input straight waveguide enters the tapered waveguide, the gradual change of the waveguide width causes the mode of the input waveguide to gradually transform into the mode of the multimode interference region, reducing the loss introduced due to mode mismatch, and finally outputting the transverse electric / transverse magnetic (TE / TM) mode at the output port of the right straight waveguide; in addition, the side wall of the tapered waveguide is an exponential curve, so that part of the light energy of the input waveguide is converted into higher-order modes, and the other part is converted into the fundamental mode of the multimode interference region. Therefore, the length of the multimode interference region is reduced, making the size of the entire waveguide crossing more compact.

[0078] Figure 3 is a schematic diagram of the simulation result of the overall structure of the waveguide crossing of the present application. In Figure 3 it, TM 0 and TE 0 respectively represent the fundamental wave of the TM mode and the fundamental wave of the TE mode. As Figure 3As shown, within the entire 1260 - 1360 nm wavelength band, both TE and TM mode light sources have an insertion loss of less than 0.05 dB. It can be seen that the silicon waveguide crossing structure of this application well solves the problem of large insertion loss in traditional waveguide crossings, can reduce crosstalk, and has a more compact size.

[0079] The above description of the present application is made in combination with specific implementation manners. However, those skilled in the art should clearly understand that these descriptions are exemplary and not a limitation on the protection scope of the present application. Those skilled in the art can make various variations and modifications to the present application according to the spirit and principle of the present application, and these variations and modifications are also within the scope of the present application.

Claims

1. A waveguide cross-junction is disposed on a substrate. Characterized in that, The waveguide cross-junction includes: An input waveguide extending along a first direction with a fixed dimension in a second direction, where the first direction and the second direction are perpendicular to each other, and both the first direction and the second direction are parallel to the surface of the substrate; A first tapered waveguide extending along the first direction, having a first end and a second end in the first direction, the first end being connected to the input waveguide, and the dimension of the first end in the second direction being smaller than the dimension of the second end in the second direction; A first straight waveguide extending along the first direction and connected to the second end, with a fixed dimension of the first straight waveguide in the second direction; A second tapered waveguide extending along the first direction, having a third end and a fourth end in the first direction, the third end being connected to the first straight waveguide, and the dimension of the third end in the second direction being larger than the dimension of the fourth end in the second direction; An output waveguide extending along the first direction and connected to the fourth end, with a fixed dimension of the output waveguide in the second direction; and A first waveguide group connected to the first straight waveguide, located on one side of the first straight waveguide in the second direction, and extending along the second direction.

2. The waveguide cross-junction according to claim 1, Characterized in that, The first waveguide group includes: A second straight waveguide extending along the second direction, connected to the side wall of the first straight waveguide in the second direction, with a fixed dimension in the first direction; A third tapered waveguide extending along the second direction, having a fifth end and a sixth end in the second direction, the fifth end being connected to the second straight waveguide, and the dimension of the fifth end in the first direction being larger than the dimension of the sixth end in the first direction; and A third straight waveguide extending along the second direction and connected to the sixth end, with a fixed dimension in the first direction.

3. The waveguide cross-junction according to claim 2, Characterized in that, The waveguide cross-junction further includes: A second waveguide group connected to the first straight waveguide, located on the other side of the first straight waveguide in the second direction, and extending along the second direction.

4. The waveguide cross-junction according to claim 3, Characterized in that, The second waveguide group includes: A fourth straight waveguide extending along the second direction, connected to the other side wall of the first straight waveguide in the second direction, with a fixed dimension in the first direction; A fourth tapered waveguide extending along the second direction, having a seventh end and an eighth end in the second direction, the seventh end being connected to the fourth straight waveguide, and the dimension of the seventh end in the first direction being larger than the dimension of the eighth end in the first direction; and A fifth straight waveguide extending along the second direction and connected to the eighth end, with a fixed dimension in the first direction.

5. The waveguide cross-junction according to claim 4, Characterized in that, The side wall shape of at least one of the first tapered waveguide, the second tapered waveguide, the third tapered waveguide, and the fourth tapered waveguide is an exponential curve.

6. The waveguide cross-junction according to claim 4, characterized in that, the input waveguide and the output waveguide have the same size in the first direction; and / or the input waveguide and the output waveguide have the same size in the second direction; and / or the first tapered waveguide and the second tapered waveguide have the same size in the first direction; and / or the third tapered waveguide and the fourth tapered waveguide have the same size in the second direction; and / or the size of the first tapered waveguide and / or the second tapered waveguide in the first direction is the same as the size of the third tapered waveguide and / or the fourth tapered waveguide in the second direction; and / or the second straight waveguide and the fourth straight waveguide have the same size in the first direction; and / or the second straight waveguide and the fourth straight waveguide have the same size in the second direction; and / or the third straight waveguide and the fifth straight waveguide have the same size in the first direction; and / or the third straight waveguide and the fifth straight waveguide have the same size in the second direction; and / or the size of the second straight waveguide and / or the fourth straight waveguide in the first direction is equal to the size of the first straight waveguide in the second direction; and / or the size of the third straight waveguide and / or the fifth straight waveguide in the first direction is equal to the size of the input waveguide and / or the output waveguide in the second direction; and / or the size of the third straight waveguide and / or the fifth straight waveguide in the second direction is equal to the size of the input waveguide and / or the output waveguide in the first direction.

7. The waveguide cross-junction according to claim 3, characterized in that, in the first direction, the first waveguide group and / or the second waveguide group are located at the middle position of the first straight waveguide.

8. The waveguide cross-junction according to claim 3, characterized in that, the material of the waveguide cross-junction is silicon oxynitride.

9. The waveguide cross-junction according to claim 8, characterized in that, the waveguide cross-junction is supported by the buried oxide layer of the substrate, the top and side walls of the waveguide cross-junction are covered by a silicon oxide layer.

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