A double-layer cross waveguide structure

Abstract

The application provides a double-layer cross waveguide structure, which effectively controls the mode field distribution of the waveguide at the cross point region through collaborative thinning and widening processing of the waveguide, and the center of the mode field is lowered to significantly increase the effective distance between the lower waveguide and the upper waveguide, and the flattening of the mode field significantly reduces the mode overlap in the vertical direction, thereby achieving excellent crosstalk suppression effect. At the same time, the waveguide cross section is controlled by adiabatic evolution, avoiding light scattering loss caused by structural mutation, reducing insertion loss, improving transmittance, and significantly improving light transmission efficiency. The application is suitable for all interlayer coupling application scenarios, and the effect is particularly significant when the interlayer distance is small.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a double-layer cross-waveguide structure. Background Technology

[0002] As photonic integrated chips develop towards higher density and more multifunctionality, multilayer waveguide structures have become a key technology for improving integration. In such structures, interlayer couplers are required extensively to achieve vertical optical signal interconnection. To achieve high interlayer coupling efficiency, the spacing between waveguide layers (layer spacing) is typically designed to be small to meet the requirements of low loss and compact structure.

[0003] However, while this smaller interlayer spacing facilitates interlayer coupling, it also presents a significant crosstalk challenge for spatially intersecting double-layer waveguides. Optical signals experience crosstalk at the intersection points due to mode field coupling, leading to increased insertion loss and severely impacting chip performance. In existing technologies, when faced with even smaller interlayer spacings, the performance improvement is often limited due to the difficulty in effectively controlling the distribution and overlap of mode fields in the vertical direction, making it difficult to simultaneously achieve low insertion loss and high crosstalk suppression. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a double-layer cross waveguide structure to solve the problem of crosstalk caused by high overlap of mode fields in the vertical direction in the prior art.

[0005] To achieve the above and other related objectives, the present invention provides a double-layer cross-waveguide structure, wherein the double-layer cross-waveguide structure comprises at least:

[0006] The lower waveguide includes a first waveguide, a second waveguide, a third waveguide, a fourth waveguide, and a fifth waveguide that are sequentially contacted along the optical transmission direction. The first waveguide and the fifth waveguide have the same structure. The width of the third waveguide in the direction perpendicular to the optical transmission direction is greater than the width of the first waveguide and the fifth waveguide. The fourth waveguide has the same structure as the second waveguide and is symmetrically distributed along the axis of the third waveguide.

[0007] The second waveguide segment includes a first layer, a second layer, and a third layer. The second layer is located at the bottom of the first layer, and the length of the second layer along the optical transmission direction is greater than the length of the first layer. In the direction perpendicular to the optical transmission direction, the width of both the first layer and the second layer decreases continuously from the end that contacts the first waveguide segment. The third layer is located at the bottom of the second layer, and in the direction perpendicular to the optical transmission direction, the width of the third layer increases continuously from the end that contacts the first waveguide segment until it is the same as the width of the third waveguide segment.

[0008] The upper waveguide and the lower waveguide are spatially intersected, with the intersection area located directly above the third waveguide segment.

[0009] Preferably, the thickness of the third waveguide segment is the same as the thickness of the third layer.

[0010] Preferably, along the direction of light transmission, the length of the third layer is greater than or equal to the length of the second layer.

[0011] Preferably, the upper waveguide and the lower waveguide intersect perpendicularly in space.

[0012] Preferably, the upper waveguide is made of silicon nitride, and the lower waveguide is made of silicon nitride.

[0013] Preferably, the structure of the upper waveguide is the same as that of the lower waveguide.

[0014] Preferably, the upper waveguide comprises a straight waveguide.

[0015] Preferably, the structure of the upper waveguide is interchangeable with the structure of the lower waveguide.

[0016] Preferably, it further includes an interlayer dielectric, which is located between the upper waveguide and the lower waveguide.

[0017] Preferably, the method for forming the upper waveguide includes a deposition method, and the method for forming the lower waveguide includes an etching method and / or a deposition method.

[0018] As described above, the double-layer cross waveguide structure of the present invention has the following beneficial effects:

[0019] 1. This invention regulates the mode field distribution of the lower waveguide in the crossover region through synergistic thinning and widening processes. The downward shift of the mode field center effectively increases the spacing between the lower waveguide and the upper waveguide. At the same time, the flattening of the mode field significantly reduces mode overlap in the vertical direction, achieving excellent crosstalk suppression effect.

[0020] 2. This invention modulates the waveguide cross-section through adiabatic evolution, effectively avoiding light scattering loss caused by structural abrupt changes, thereby reducing insertion loss, increasing transmittance, and significantly improving optical transmission efficiency.

[0021] 3. This invention is applicable to all interlayer coupling applications, and its effect is particularly significant when the interlayer spacing is small. At different operating wavelengths, the structure of this invention exhibits comprehensive advantages over traditional structures in terms of transmittance and crosstalk performance, fully demonstrating its technical effectiveness and robustness. Attached Figure Description

[0022] Figure 1 The diagram shown is a top view of a double-layered cross-waveguide structure in the prior art.

[0023] Figure 2 The diagram shown is a front view of a cross-sectional view of a double-layered cross-waveguide structure in the prior art.

[0024] Figure 3 The diagram shown is a top view of the double-layer cross waveguide structure in an embodiment of the present invention.

[0025] Figure 4 The diagram shown is a front view of the cross-sectional view of the double-layer cross waveguide structure in an embodiment of the present invention.

[0026] Figure 5 The graph shows the transmittance curves of the embodiments of the present invention and the conventional structure.

[0027] Figure 6 The diagram shows the crosstalk curves of the embodiments of the present invention and the conventional structure.

[0028] Component designation explanation

[0029] 10 Lower waveguide 20 upper waveguide 100 Lower waveguide 110 First waveguide segment 120 Second waveguide 121 First layer 122 Second floor 123 Third layer 130 Third waveguide 140 Fourth waveguide 150 Fifth waveguide 200 upper waveguide Detailed Implementation

[0030] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0031] Please see Figures 1 to 6 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0032] In the context of this application, "along the optical transmission direction" is defined as follows: Figures 1 to 4 In the context of the X-direction, the length of the lower waveguide refers to its dimension in the X-direction, its width in the Y-direction, and its thickness in the Z-direction. Similarly, the length of the upper waveguide refers to its dimension in the Y-direction, its width in the X-direction, and its thickness in the Z-direction.

[0033] like Figure 1 and Figure 2As shown, the existing double-layer cross waveguide structure includes an upper waveguide 20 and a lower waveguide 10, and also includes an interlayer dielectric filled between the upper waveguide 20 and the lower waveguide 10. The upper waveguide 20 and the lower waveguide 10 are arranged crosswise in space, specifically, as shown... Figure 1 As shown, in the top view, the upper waveguide 20 and the lower waveguide 10 intersect in the X and Y directions, as... Figure 2 As shown, there is a specific spacing between the upper waveguide 20 and the lower waveguide 10 in the Z direction. Both the upper waveguide 20 and the lower waveguide 10 are straight waveguides with the same width (W0) and the same thickness (D0). To achieve high interlayer coupling efficiency, the spacing between the two lower waveguides 10 is designed to be small to meet the requirements of low loss and compact structure. However, while this small spacing facilitates interlayer coupling, it also presents a severe crosstalk challenge for the spatially intersecting double waveguides. In the intersection region, the optical signal will leak energy due to mode field coupling, leading to increased insertion loss and worsened crosstalk, which seriously affects chip performance.

[0034] like Figure 3 and Figure 4 As shown, an embodiment of the present invention provides a double-layer cross-waveguide structure, the double-layer cross-waveguide structure comprising at least:

[0035] The lower waveguide 100 includes a first waveguide 110, a second waveguide 120, a third waveguide 130, a fourth waveguide 140, and a fifth waveguide 150 that are sequentially contacted along the optical transmission direction. The first waveguide 110 and the fifth waveguide 150 have the same structure. The width of the third waveguide 130 in the direction perpendicular to the optical transmission direction is greater than the width of the first waveguide 110 and the fifth waveguide 150. The fourth waveguide 140 has the same structure as the second waveguide 120 and is symmetrically distributed along the axis of the third waveguide 130.

[0036] The second waveguide 120 includes a first layer 121, a second layer 122, and a third layer 123. The second layer 122 is located at the bottom of the first layer 121, and the length of the second layer 122 along the optical transmission direction is greater than the length of the first layer 121. In the direction perpendicular to the optical transmission, the width of both the first layer 121 and the second layer 122 decreases continuously from the end that contacts the first waveguide 110. The third layer 123 is located at the bottom of the second layer 122, and the width of the third layer 123 in the direction perpendicular to the optical transmission increases continuously from the end that contacts the first waveguide 110 until it is the same as the width of the third waveguide 130.

[0037] The upper waveguide 200 and the lower waveguide 100 are spatially intersected, with the intersection area located directly above the third waveguide 130.

[0038] Specifically, the first waveguide 110 is the signal input terminal, and the fifth waveguide 150 is the signal output terminal. Alternatively, the first waveguide 110 can also be a signal output terminal, and the fifth waveguide 150 can also be a signal input terminal. This is determined by actual needs. The signal in the upper waveguide 200 can be transmitted from the upper end to the lower end, or vice versa, depending on the specific requirements.

[0039] As an example, the first waveguide 110 may include a straight waveguide, but is not limited thereto. In this embodiment, the first waveguide 110 is preferably a straight waveguide.

[0040] As an example, the first waveguide 110 has a width of W0 and a thickness of D0. The first waveguide 110 and the fifth waveguide 150 have the same structure, with the fifth waveguide 150 having a width of W0 and a thickness of D0. The third waveguide 130 has a width of W and a thickness of D2.

[0041] As an example, in the second waveguide 120, the widths of both the first layer 121 and the second layer 122 decrease progressively from the end in contact with the first waveguide 110. The width of the first layer 121 gradually decreases from the width W0 of the first waveguide 110, and the width of the second layer 122 gradually decreases from the width W0 of the first waveguide 110. The widths of the ends of both the first layer 121 and the second layer 122 away from the first waveguide 110 are both greater than or equal to zero, and the widths of the ends of both the first layer 121 and the second layer 122 in contact with the first waveguide 110 are both greater than the widths of the ends away from the first waveguide 110. The fourth waveguide 140 is also symmetrical about the third waveguide 130.

[0042] As an example, the thickness of the third waveguide 130 is the same as the thickness of the third layer 123.

[0043] Specifically, along the direction of light transmission, the width of the third layer 123 of the second waveguide 120 gradually changes from the width W0 of the first waveguide 110 to the width W of the third waveguide 130, and the width of the third layer 123 of the fourth waveguide 140 gradually changes from the width W of the third waveguide 130 to the width W0 of the fifth waveguide 150.

[0044] Specifically, along the direction of light transmission, the thickness of the second waveguide 120 decreases layer by layer from the thickness D0 of the first waveguide 110 to the thickness D2 of the third waveguide 130, and the thickness of the fourth waveguide 140 increases layer by layer from the thickness D2 of the third waveguide 130 to the thickness D0 of the fifth waveguide 150.

[0045] Among them, such as Figure 4 As shown, the thickness of the second waveguide 120 in the region of the first layer 121 is D0, achieving thermal removal of the top of the second waveguide 120, causing the total thickness of the second waveguide 120 to begin to thin, and providing a path for the mode field energy of this part to transfer downwards. The thickness of the second waveguide 120 in the region of the second layer 122 is D1, and the material of the second waveguide 120 is further removed thermally, further reducing the total thickness of the second waveguide 120, and causing the mode field center to continue to shift downwards. The thickness of the second waveguide 120 in the region of the second layer 122 is D2, forming a wide platform at the bottom of the second waveguide 120, effectively dispersing the remaining mode field energy, especially reducing the concentration of energy in the thickness direction. The fourth waveguide 140 shown is the same.

[0046] Specifically, in the second waveguide 120, the length of the first layer 121 is L1, the length of the second layer 122 is L2, and the length of the third layer 123 is L3. The length of the third waveguide 130 is L4. The fourth waveguide 140 is the same as the second waveguide 120.

[0047] As an example, along the direction of light transmission, the length of the third layer 123 is greater than or equal to the length of the second layer 122.

[0048] As an example, the material of the upper waveguide 200 may include silicon nitride, but is not limited thereto, and the material of the lower waveguide 100 may include silicon nitride, but is not limited thereto.

[0049] In this embodiment, the upper waveguide 200 is preferably made of silicon nitride, and the lower waveguide 100 is preferably made of silicon nitride.

[0050] As an example, the structure of the upper waveguide 200 is the same as that of the lower waveguide 100.

[0051] Specifically, the upper waveguide 200 and the lower waveguide 100 may have the same structure. The upper waveguide 200 and the lower waveguide 100 may have a cross-section that becomes thinner and wider. After the intersection area, they will be restored to the initial width and thickness on the other side through a symmetrical and opposite adiabatic evolution process.

[0052] As an example, the upper waveguide 200 may include a straight waveguide, but is not limited thereto. In this embodiment, the upper waveguide 200 is preferably a straight waveguide.

[0053] As an example, the structure of the upper waveguide 200 is interchangeable with the structure of the lower waveguide 100.

[0054] Specifically, when the upper waveguide 200 is a straight waveguide, the lower waveguide 100 has a segmented evolution structure. The lower waveguide 100 can be designed as a straight waveguide, and the upper waveguide 200 as a segmented evolution structure, depending on actual needs.

[0055] As an example, the upper waveguide 200 and the lower waveguide 100 are perpendicular to each other in space.

[0056] Specifically, such as Figure 3 As shown in the top view, the upper waveguide 200 and the lower waveguide 100 intersect perpendicularly in the X and Y directions, as... Figure 4 As shown, there is a specific distance between the upper waveguide 200 and the lower waveguide 100 in the Z direction.

[0057] As an example, it also includes an interlayer medium (not shown) located between the upper waveguide 200 and the lower waveguide 100.

[0058] Specifically, the interlayer dielectric fills the gap between the upper waveguide 200 and the lower waveguide 100 in the Z direction.

[0059] As an example, the interlayer medium may include silicon dioxide, but is not limited thereto. In this embodiment, the interlayer medium is preferably silicon dioxide.

[0060] As an example, the method for forming the upper waveguide 200 includes deposition, and the method for forming the lower waveguide 100 includes etching and / or deposition.

[0061] Specifically, the upper waveguide 200 can be formed into a straight waveguide or a segmented evolution structure using a deposition method. The lower waveguide 100 can be formed into a straight waveguide using a deposition method, or into a segmented evolution structure using a deposition and etching method.

[0062] Example 1

[0063] This embodiment illustrates the implementation of the present invention in detail using a specific preferred embodiment. This embodiment uses a silicon-based silicon nitride optical chip platform as an example, but the present invention is not limited thereto.

[0064] In this embodiment, a silicon substrate is provided. On the silicon substrate, the lower waveguide 100 is fabricated, silicon dioxide is deposited as an interlayer dielectric, and then the upper waveguide 200 is fabricated. The silicon dioxide thickness (i.e., interlayer spacing) between the upper and lower waveguides 100 is 100 nm.

[0065] In this embodiment, the core material of the lower waveguide 100 and the upper waveguide 200 is silicon nitride (SiN), with a refractive index of approximately 2.0. The interlayer dielectric material is silicon dioxide (SiO2), with a refractive index of approximately 1.44. The operating wavelength range of the double-layer cross waveguide structure is 1260 nm to 1360 nm (O-band), with a center wavelength of 1310 nm.

[0066] In this embodiment, the upper waveguide 200 is a straight waveguide, and the lower waveguide 100 shown is a segmented evolution structure.

[0067] In this embodiment, the thickness D0 of the upper waveguide 200 is 400nm and the width W0 is 500nm.

[0068] In this embodiment, the first waveguide 110 and the fifth waveguide 150 in the lower waveguide 100 are straight waveguides, with a thickness D0 of 400 nm and a width W0 of 500 nm. The third waveguide 130 has a width W of 2000 nm and a length L4 of 3 μm.

[0069] In this embodiment, the lower waveguide 100 undergoes multiple photolithography and etching processes. First, a 400nm thick silicon nitride layer is deposited. The first photolithography step defines the basic outline and width variation region of the lower waveguide 100. A first etching step (shallow etching to 340nm) is performed. A second photolithography step aligns the areas requiring deep etching and patterns them. A second etching step (deep etching to 280nm) is performed, ultimately forming the desired thermal cross-section evolution structure. In the lower waveguide 100, the thickness D0 of the second waveguide 120 in the region of the first layer 121 is 400nm, the thickness D1 of the second waveguide 120 in the region of the second layer 122 is 340nm, and the thickness D2 of the second waveguide 120 in the region of the second layer 122 is 280nm. The thickness D2 of the third waveguide 130 is also 280nm.

[0070] In this embodiment, the length L1 of the first layer 121 of the second waveguide segment in the lower waveguide 100 is 10 μm, the length L2 of the second layer 122 is 20 μm, and the length L3 of the third layer 123 is 20 μm.

[0071] In this embodiment, the performance of the structure of the present invention is compared with that of the conventional double-layer cross waveguide structure in the prior art. Figure 5As shown, at a wavelength of 1310 nm, the insertion loss of the structure described in this invention is reduced from -0.7 dB of the conventional structure to -0.43 dB, effectively improving the optical transmission efficiency and operating performance of the device. Figure 6 As shown, the structure described in this invention can optimize crosstalk from -36dB in the traditional structure to -52dB, significantly improving the crosstalk suppression effect. Throughout the entire O-band, the double-layer cross-waveguide structure of this invention exhibits a significant and stable performance improvement.

[0072] In summary, this invention provides a double-layer cross-waveguide structure. By synergistically thinning and widening the waveguides, the mode field distribution in the cross-point region is effectively controlled. Simultaneously, shifting the mode field center downwards significantly increases the effective spacing between the lower and upper waveguides, while the flattening of the mode field significantly reduces mode overlap in the vertical direction, thus achieving excellent crosstalk suppression. Furthermore, by controlling the waveguide cross-section through adiabatic evolution, light scattering loss caused by abrupt structural changes is avoided, insertion loss is reduced, transmittance is increased, and optical transmission efficiency is significantly improved. This invention is applicable to all interlayer coupling applications, and its effects are particularly significant when the interlayer spacing is small. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0073] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A double-layer cross-waveguide structure, characterized in that, The double-layer cross waveguide structure includes at least: The lower waveguide includes a first waveguide, a second waveguide, a third waveguide, a fourth waveguide, and a fifth waveguide that are sequentially contacted along the optical transmission direction. The first waveguide and the fifth waveguide have the same structure. The width of the third waveguide in the direction perpendicular to the optical transmission direction is greater than the width of the first waveguide and the fifth waveguide. The fourth waveguide has the same structure as the second waveguide and is symmetrically distributed along the axis of the third waveguide. The second waveguide segment includes a first layer, a second layer, and a third layer. The second layer is located at the bottom of the first layer, and the length of the second layer along the optical transmission direction is greater than the length of the first layer. In the direction perpendicular to the optical transmission direction, the width of both the first layer and the second layer decreases continuously from the end that contacts the first waveguide segment. The third layer is located at the bottom of the second layer, and the width of the third layer in the direction perpendicular to the optical transmission direction increases continuously from the end that contacts the first waveguide segment until it is the same as the width of the third waveguide segment. The thickness of the second waveguide segment decreases layer by layer from the thickness of the first waveguide segment to the thickness of the third waveguide segment. The upper waveguide includes a straight waveguide, and the upper waveguide and the lower waveguide are spatially intersected, with the intersection area located directly above the third waveguide segment.

2. The double-layer cross-waveguide structure according to claim 1, characterized in that: The thickness of the third waveguide segment is the same as the thickness of the third layer.

3. The double-layer cross-waveguide structure according to claim 1, characterized in that: Along the direction of light transmission, the length of the third layer is greater than or equal to the length of the second layer.

4. The double-layer cross-waveguide structure according to claim 1, characterized in that: The upper waveguide and the lower waveguide are perpendicularly intersecting each other in space.

5. The double-layer cross-waveguide structure according to claim 1, characterized in that: The upper waveguide is made of silicon nitride, and the lower waveguide is made of silicon nitride.

6. The double-layer cross-waveguide structure according to claim 1, characterized in that: The structure of the upper waveguide is the same as that of the lower waveguide.

7. The double-layer cross-waveguide structure according to claim 1, characterized in that: The structure of the upper waveguide is interchanged with the structure of the lower waveguide.

8. The double-layer cross-waveguide structure according to claim 1, characterized in that: It also includes an interlayer medium located between the upper waveguide and the lower waveguide.

9. The double-layer cross-waveguide structure according to claim 1, characterized in that: The method for forming the upper waveguide includes deposition, and the method for forming the lower waveguide includes etching and / or deposition.

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