A waveguide intersection device made of different materials for silicon photonic chips

Abstract

The present invention discloses a waveguide crossing device made of different materials for silicon photonic chips. The device comprises an upper waveguide and a lower waveguide that intersect each other. The lower waveguide comprises, in sequence, a first fixed-width section, a first gradually changing width section, a second fixed-width section, a second gradually changing width section, and a third fixed-width section. The first and second gradually changing width sections form a linearly tapered trapezoidal structure. The width of the first gradually changing width section gradually decreases from the second fixed-width section until it becomes the same as the width of the second fixed-width section. The width of the second gradually changing width section gradually increases from the second fixed-width section until it becomes the same as the width of the third fixed-width section. The waveguide crossing structure design of the present invention achieves low transmission loss and low reflection in the silicon-based waveguide, as well as low crosstalk between the silicon nitride waveguide and the silicon nitride waveguide.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon photonic chips, in particular to a method for using different materials for silicon photonic chips.

[0002] waveguide crossover device. Background Art

[0003] With technological advancements, the device density of silicon photonic chips continues to increase. Functionality and performance requirements necessitate the use of different materials within these devices. Therefore, a crisscross structure between waveguides is unavoidable on silicon photonic chips. In chip design, silicon-based waveguides, as key components, must transmit light waves with minimal loss (approximately 0.01dB) and minimal reflection (<-26dB) when passing through this crossover structure. This ensures minimal device degradation and increases in overall insertion loss within the silicon photonic chip.

[0004] Figure 1 (a)-1(b) show typical waveguide crossing structures on existing mass-produced silicon photonic chips. Because the vertical distance between waveguides is very close, typically only around 80-90nm, crosstalk occurs between the waveguides. This crosstalk inevitably affects the waveguide performance on the silicon photonic chip, causing high loss and high reflection when the main light waves pass through the waveguide crossing structure. If the device structure requires it and this cannot be avoided, and a large number of waveguide crossings are required, the high loss and high reflection will render the silicon-based chip essentially unusable. Furthermore, due to the waveguide manufacturing process on silicon-based chips, the waveguide loss is several times higher than that of silicon nitride-based waveguides. Therefore, silicon-based waveguides have a lower tolerance for loss.

[0005] It is necessary to design a waveguide structure with lower loss to meet the needs of the device. Summary of the Invention

[0006] In response to the above problems, the present invention proposes a waveguide crossing device made of different materials for silicon photonic chips, which includes an upper waveguide and a lower waveguide that cross each other, and the lower waveguide includes a first fixed-width section, a first width gradient section, a second fixed-width section, a second width gradient section, and a third fixed-width section in sequence; the first width gradient section and the second width gradient section are linearly gradient trapezoidal structures, and the width of the first width gradient section gradually decreases from the second fixed-width section until its width is the same as that of the second fixed-width section; the width of the second width gradient section gradually increases from the second fixed-width section until its width is the same as that of the third fixed-width section.

[0007] Preferably, the first fixed-width section and the third fixed-width section have the same width.

[0008] Preferably, the width of the widest part of the first width-changing section is the same as the width of the first fixed-width section; the width of the widest part of the second width-changing section is the same as the width of the third fixed-width section.

[0009] Preferably, the first width gradient section and the second width gradient section have the same length.

[0010] Preferably, the lengths of the first width gradient section and the second width gradient section are 50 μm-500 μm.

[0011] Preferably, the second fixed-width section is located below the upper waveguide, and its length is the same as the width of the upper waveguide.

[0012] Preferably, the width of the second fixed-width segment is 300 nm.

[0013] Preferably, the width of the upper waveguide is 700 nm-800 nm.

[0014] Preferably, the width of the first fixed-width segment and the second fixed-width segment is 400 nm-500 nm.

[0015] Preferably, the upper waveguide is a silicon nitride waveguide, and the lower waveguide is a silicon-based waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0017] Figure 1 (a)-1(b) is a structural diagram of a double-layer waveguide cross device in the prior art, where Figure 1 (a) shows the structural relationship of the double-layer waveguide, Figure 1 (b) shows the distance between the upper and lower layers of the double-layer waveguide;

[0018] Figures 2(a)-2(b) are schematic structural diagrams of a double-layer waveguide intersection device of the present invention, wherein Figure 2(a) is a diagram of its overall structure, and Figure 2(b) is a diagram of the structure of the lower waveguide;

[0019] Figure 3 (a)-3(d) is Figure 1 The loss results of the double-layer waveguide crossover device simulation are shown, where Figure 3 (a) is the light wave transmission path of the waveguide device. Figure 3 (b) is the loss of the device light wave from port 1 to port 2, Figure 3 (c) is the reflection of the light wave from port 1 to port 1, Figure 3(d) is the crosstalk of the device light wave from port 1 to port 3 or 4;

[0020] Figure 4 (a)-4(c) are the loss results of the simulation calculation of the exemplary structure of the double-layer waveguide intersection device of the present invention shown in FIG2; Figure 4 (a) is the loss of the device light wave from port 1 to port 2, Figure 4 (b) is the reflection of the light wave from port 1 to port 1, Figure 4 (c) is the crosstalk of the device light wave from port 1 to port 3 or 4;

[0021] Figure 5 (a)-5(b) are the loss results of two other exemplary structures of the double-layer waveguide intersection device of the present invention, where Figure 5 (a) is the loss of the second fixed width segment 1-3 with a width of 200nm, Figure 5 (b) shows the loss of the second fixed-width segment 1-3 with a width of 400 nm. DETAILED DESCRIPTION

[0022] To further illustrate the technical means and effectiveness of the present invention in achieving its intended objectives, the following detailed description of a waveguide intersection structure made of different materials according to the present invention is provided with reference to the accompanying drawings and preferred embodiments. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0023] The term "and / or" in this article is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B, specifically understood as: A and B may be included at the same time, A may exist alone, or B may exist alone, and any of the above three situations may exist.

[0024] As shown in Figures 2(a) and 2(b), a waveguide crossing device of different materials applied to silicon photonic chips proposed by the present invention comprises an upper waveguide 1 and a lower waveguide 2 that cross each other. The vertical distance between the upper waveguide 1 and the lower waveguide 2 is preferably 80nm-90nm. The material of the upper waveguide is preferably silicon nitride, and the material of the lower waveguide is preferably a silicon-based material. Figure 1 As shown in (a)-1(b), the loss of the two-layer cross-waveguide structure device in the prior art is relatively large, and the upper and lower waveguides are designed with the same width. The present invention creatively designs the cross-structure waveguide and designs the lower waveguide 1 into a gradient structure.

[0025] As shown in Figures 2(a)-2(b), the upper waveguide 1 and the lower waveguide 2 are separated by a certain distance. The lower waveguide 1 comprises, in order, a first fixed-width section 1-1, a first gradually varying width section 1-2, a second fixed-width section 1-3, a second gradually varying width section 1-4, and a third fixed-width section 1-5. The widths of the first fixed-width section 1-1 and the third fixed-width section 1-5 are designed to be the same. The widths of the first and second gradually varying width sections 1-2, 1-4 at their widest points are the same as those of the first and third fixed-width sections 1-1 and 1-5, respectively, and are preferably between 400 nm and 500 nm. The first and second gradually varying width sections 1-2, 1-4 have a linearly tapered trapezoidal structure, and are preferably of equal length, preferably between 50 µm and 500 µm. The width of the first gradually changing width section 1-2 gradually decreases from the second fixed-width section 1-1 until its width becomes the same as the width of the second fixed-width section 1-3. The width of the second gradually changing width section 1-4 gradually increases from the second fixed-width section 1-3 until its width becomes the same as the width of the third fixed-width section 1-5. The second fixed-width section 1-3 is located below the upper waveguide 2 and its length is the same as the width of the upper waveguide 2. The width of the upper waveguide 2 is 700nm-800nm. The width of the second fixed-width section 1-3 is not necessarily narrower, and is preferably 300nm. If the width of this section is designed to be narrower or wider, it will lead to increased loss, which is contrary to the design of the present invention.

[0026] The thickness of the lower waveguide 1 is preferably 210 nm to 220 nm, and the thickness of the upper waveguide 2 is preferably 200 nm to 500 nm.

[0027] Through the above structural design, low transmission loss and low reflection in the silicon-based waveguide, as well as low crosstalk between the silicon nitride waveguide and the silicon nitride waveguide are achieved.

[0028] Figure 3 (a)-3(d) is Figure 1 Loss calculation results obtained from the simulation design of the existing cross-structure waveguide shown in (a)-1(b). Figure 1 In the example of (b), the distance between the upper and lower waveguides is 80nm, the width of the upper waveguide (silicon nitride waveguide) is 700nm, and the width of the lower waveguide (silicon-based waveguide) is 400nm. From the calculation of the simulation design, it can be seen that Figure 1 The typical crossover structure of the prior art shown in (a)-1(b) has a loss of up to 0.04 dB and a light wave reflection of up to 21.5 dB. Figure 3 (b)-3(c) as shown. Figure 3 As shown in (d), the crosstalk between different waveguides can be ignored.

[0029] Figure 4(a)-4(c) are the loss calculation results obtained from the simulation design of the cross-structure waveguide of the present invention shown in Figures 2(a)-2(b). Figure 4 (a)-4(c) Waveguide structure, the distance between the upper and lower waveguides is Figure 1 (b) is the same, also 80nm. The width of the upper waveguide (silicon nitride waveguide) is 700nm. The width of the first fixed segment 1-1 and the third fixed segment 1-5 of the lower waveguide (silicon-based waveguide) are 400nm, the width of the second fixed segment 1-3 is 300nm, and the lengths of the first and second width gradient segments 1-2 and 1-4 are 50µm. As can be seen from the figure, the loss of the waveguide cross structure designed by the present invention is reduced to 0.01dB. Figure 4 As shown in (a), the requirements for cross-structure waveguide loss are fully met; Figure 4 As shown in (b), the light wave reflection is reduced to -38dB. The crosstalk suppression between different waveguides is 57dB. Figure 4 (c) shows better performance.

[0030] Figure 5 (a)-5(b) show the simulation calculation results of the second fixed-width segment 1-3 with a width of 200nm and 400nm, when the other structures and dimensions are the same as those of the embodiment of Figures 2(a)-2(b). From the calculation results, it can be seen that the loss reaches 0.8dB and 0.85dB respectively, which is too large to meet the requirements of waveguide design.

[0031] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0032] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A waveguide crossing device made of different materials for a silicon photonic chip, comprising an upper waveguide and a lower waveguide that cross each other, characterized in that: The lower waveguide includes, in sequence, a first fixed-width section, a first gradually changing width section, a second fixed-width section, a second gradually changing width section, and a third fixed-width section; the first gradually changing width section and the second gradually changing width section are linearly gradually changing trapezoidal structures, and the width of the first gradually changing width section gradually decreases from the second fixed-width section until its width is the same as that of the second fixed-width section; the width of the second gradually changing width section gradually increases from the second fixed-width section until its width is the same as that of the third fixed-width section; the second fixed-width section is located below the upper waveguide, and its length is the same as that of the upper waveguide; the width of the second fixed-width section is 300 nm; the lengths of the first gradually changing width section and the second gradually changing width section are the same, ranging from 50 µm to 500 µm.

2. The waveguide intersection device of different materials for silicon photonic chips according to claim 1, characterized in that: The first fixed-width section and the third fixed-width section have the same width.

3. The waveguide intersection device of different materials for silicon photonic chips according to claim 1, characterized in that: The width of the widest part of the first width gradual change section is the same as the width of the first fixed width section, and the width of the widest part of the second width gradual change section is the same as the width of the third fixed width section.

4. The waveguide intersection device of different materials for silicon photonic chips according to claim 1, characterized in that: The width of the upper waveguide is 700nm-800nm.

5. The waveguide intersection device of different materials for silicon photonic chip according to claim 1 or 2, characterized in that: The widths of the first fixed-width segment and the third fixed-width segment are 400 nm-500 nm.

6. The waveguide intersection device of different materials for silicon photonic chips according to claim 1, characterized in that: The upper waveguide is a silicon nitride waveguide, and the lower waveguide is a silicon-based waveguide.

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