Coupling waveguide structure and adjusting method thereof, integrated optical chip and preparation method thereof

Abstract

The invention discloses a coupling waveguide structure, an adjusting method of the coupling waveguide structure, an integrated optical chip and a preparation method of the integrated optical chip, and relates to the field of guided wave optics. The coating layer is prepared on the surface of the substrate; the single-layer waveguide is arranged in the coating layer; the double-layer waveguide is arranged in the coating layer, the structural parameters of the double-layer waveguide and the single-layer waveguide are designed, so that the propagation constants of the double-layer waveguide and the single-layer waveguide are completely matched, and the coupling efficiency of the optical coupling waveguide structure is improved to the greatest extent in a limited design space on the premise that the process complexity is not increased.

Description

Technical Field

[0001] The present invention relates to the field of waveguide optics, and in particular to a coupled waveguide structure and an adjustment method thereof, an integrated optical chip and a preparation method thereof. Background Art

[0002] Integrated optics achieves more complex functions by cascading different optoelectronic devices such as lasers, amplifiers, optical modulators, mode multiplexers / demultiplexers, etc. on the same substrate. Different devices are generally optically interconnected through coupled waveguide structures. Therefore, coupled waveguide structures are widely used in integrated optical systems. In the design of high-power integrated optical systems, coupled waveguide structures are usually used to couple light into / out of optical waveguides. How to improve coupling efficiency, thereby reducing light loss and improving system performance is a current concern.

[0003] The traditional coupled waveguide structure usually includes an upper waveguide and a lower waveguide, and the tip width of the upper and lower waveguides gradually decreases. The traditional coupled waveguide structure usually has the problem of low coupling efficiency and is not suitable for the transition conversion of waveguides with different thicknesses. The existing technology usually optimizes the tip of the upper waveguide through two or more (thin film deposition) processes to prepare a tip structure with gradual thickness and width to improve the coupling efficiency. Since the three-dimensional design of the waveguide has extremely high requirements for the photolithography processing technology and is limited by the processing accuracy, the width of the upper waveguide cannot be reduced indefinitely. Multiple processes make the tip of the waveguide smooth, and the width of the tip is prone to cause reflection, resulting in reduced coupling efficiency.

[0004] Figure 1 This is a Taper structure vertical directional coupler in the prior art, wherein (a), (b), and (c) are cross-sectional views in different directions, and (d) is a schematic diagram of the overall structure of the device; Figure 2 The figure is a schematic diagram of a cutting-edge transition structure in the prior art.

[0005] Reference Figure 1 In order to achieve the transmission of single-mode signal light in the vertical direction in a three-dimensional structure, the existing technology generally adopts a waveguide structure with two layers of mirror symmetry to complete the energy coupling between the upper and lower waveguides. With the change of the width of the Taper tip, the coupling efficiency of the vertical directional coupling structure can be finally obtained to be 97.3%.

[0006] In order to improve the coupling efficiency, the tip transition structure of the upper waveguide can be further optimized. Figure 2 , a tip transition structure with gradual thickness and width is prepared through two (or more) processing processes.

[0007] Although the current design can increase the theoretical value of the coupling efficiency of the three-dimensional waveguide structure to more than 95%, the existing technology still has the following defects:

[0008] 1. Add an upper waveguide with a smaller width above the lower waveguide. The upper waveguide structure is processed twice (or more times) to prepare a tip transition structure. Due to the limitation of processing accuracy, the width of the upper waveguide cannot be infinitely small. The tip structure always tends to be smoothed during the process. The tip will have a certain width. The waveguide with width will always cause reflection at this position, reducing the efficiency of the transition of waveguides with different thicknesses.

[0009] Second, transition to the position where the upper waveguide structure is located to prepare a thickness gradient structure. The preparation of the thickness gradient structure has extremely high process requirements;

[0010] In summary, the existing lithography processing technology of three-dimensional structure solutions is relatively complex and has many processing steps, and it is difficult to achieve the expected coupling effect in actual design and application. Summary of the invention

[0011] The purpose of the present invention is to provide a coupled waveguide structure and an adjustment method thereof, an integrated optical chip and a preparation method thereof, so as to improve the coupling efficiency of the coupled waveguide structure.

[0012] According to a first aspect of an embodiment of the present invention, there is provided a coupled waveguide structure, comprising:

[0013] substrate;

[0014] A coating layer is prepared on the surface of the substrate;

[0015] A single-layer waveguide is disposed in the cladding layer;

[0016] A double-layer waveguide is arranged in the cladding layer, and the structural parameters of the double-layer waveguide and the single-layer waveguide are designed so that the propagation constants of the double-layer waveguide and the single-layer waveguide are completely matched.

[0017] According to a second aspect of an embodiment of the present invention, a method for coupling a propagation constant of a waveguide structure is provided, comprising:

[0018] The structural parameters of the single-layer waveguide and / or the double-layer waveguide in the coupled waveguide structure are adjusted so that the propagation constant of the single-layer waveguide completely matches the propagation constant of the double-layer waveguide.

[0019] According to a third aspect of an embodiment of the present invention, there is provided an integrated optical chip, comprising:

[0020] The coupled waveguide structure described above;

[0021] A main waveguide connected to the double-layer waveguide of the coupling waveguide structure through a first transition structure;

[0022] The optical coupling structure is connected to the single-layer waveguide of the coupling waveguide structure through a second transition structure.

[0023] According to a fourth aspect of an embodiment of the present invention, a method for processing a coupled waveguide structure is provided, comprising:

[0024] Patterning the epitaxial structure to form a double-layer waveguide; forming a single-layer waveguide on the epitaxial structure having the double-layer waveguide;

[0025] Alternatively, the epitaxial structure is patterned to form a double-layer waveguide and a single-layer waveguide;

[0026] The epitaxial structure at least includes a substrate, a cladding layer, and a double-layer waveguide core layer.

[0027] The above technical solution of the present invention has the following beneficial technical effects:

[0028] The coupled waveguide structure provided by the embodiment of the present invention is achieved by arranging a single-layer waveguide and a double-layer waveguide in the cladding layer. During the design process, the structural parameters of the double-layer waveguide and the single-layer waveguide are designed so that the propagation constants of the two waveguides are completely matched. Without increasing the process complexity and within a limited design space, the coupling efficiency of the optical coupling waveguide structure is maximized, and the coupling efficiency is finally increased to 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a Taper structure vertical directional coupler in the prior art;

[0030] Figure 2 It is a tip transition structure of a Taper structure vertical directional coupler in the prior art;

[0031] Figure 3 is a schematic diagram of the relative positions of a single-layer waveguide and a double-layer waveguide of the coupled waveguide structure provided by the present invention;

[0032] Figure 4 It is a schematic diagram of a coupled waveguide structure provided by the present invention based on different design requirements;

[0033] Figure 5 It is a schematic diagram of the relationship between the thickness of the upper waveguide and the propagation constant of the double-layer waveguide provided by the present invention;

[0034] Figure 6 It is a schematic diagram of the relationship between the spacing between the upper waveguide and the lower waveguide and the propagation constant of the double-layer waveguide provided by the present invention;

[0035] Figure 7 It is a schematic diagram of the relationship between the width of the upper waveguide and the propagation constant of the double-layer waveguide provided by the present invention;

[0036] Figure 8 is a schematic top view of an integrated optical chip provided by the present invention;

[0037] Fig. 9 is a top view schematic diagram of another integrated optical chip provided by the present invention;

[0038] Fig.10 The present invention provides a flow chart of a method for processing a coupled waveguide structure based on a prefabricated epitaxial wafer;

[0039] In the figure,

[0040] Substrate 10; single-layer waveguide 20; cladding layer 30; double-layer waveguide 40; lower waveguide 401; upper waveguide 402; first transition structure 51; second transition structure 52; optical coupling structure 61; main waveguide 62; coupling waveguide structure 70; light source module 80. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0042] The terms used in one or more embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit one or more embodiments of the present invention. The singular forms of "a", "said" and "the" used in one or more embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used in one or more embodiments of the present invention refers to and includes any or all possible combinations of one or more associated listed items.

[0043] It should be understood that although the terms first, second, etc. may be used to describe various information in one or more embodiments of the present invention, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of one or more embodiments of the present invention, the first may also be referred to as the second, and similarly, the second may also be referred to as the first. Depending on the context, the word "if" as used herein may be interpreted as "in response to determining".

[0044] Glossary

[0045] Optical coupling: In waveguide optics, the light emitted by the light source enters the optical waveguide. The process of introducing light from one optical waveguide to another is called optical coupling, or simply coupling.

[0046] [Overview of the Invention Principle]

[0047] According to the perturbation theory of optical waveguide coupling, when the guided modes in the two strip waveguides propagate in the same direction (coupled in the same direction), the power P1(z) of waveguide 1 and the power P2(z) of waveguide 2 are calculated as follows:

[0048]

[0049]

[0050] Where z is the propagation distance between the coupled waveguide 1 and waveguide 2 in the propagation direction, K is the coupling coefficient, K 12 , K 21 are the coupling coefficients between the two optical waveguides respectively; when coupling occurs, the difference in propagation constants between the guided modes of waveguide 1 and waveguide 2 is:

[0051] 2Δk=(k1+C1)-(k2+C2)

[0052] C1 is the change in the transmission constant in the coupled waveguide 1, C2 is the change in the transmission constant in the coupled waveguide 2, k1 is the propagation constant of waveguide 1, k2 is the propagation constant of waveguide 2, Δk is also called the phase mismatch factor, and the light wave energy transfer caused by mode coupling can only be achieved when the phase is matched.

[0053] When the size, refractive index and other structural and material parameters of the two waveguides are the same:

[0054] C1=C2,K 12 =K 21 =K

[0055] Then at z = L c To achieve complete power conversion, the corresponding coupling length That is, in the case of perfect phase matching, the guided modes in waveguide 1 and waveguide 2 periodically convert their power completely, and the period along the propagation direction is equal to the coupling length L. c .

[0056] However, in the design of high-power integrated optical systems, the waveguide specifications for optical interconnection between different devices are different. In order to maximize the coupling efficiency of the optical coupling waveguide structure within a limited design space without increasing the process complexity, the applicant repeatedly designed and tested the optical coupling between the two optical waveguides, adjusted the size, structure, position and material of different optical waveguides, and finally proposed a coupling waveguide structure that can increase the coupling efficiency to 100%.

[0057] Based on the same inventive principle, the present application also proposes a method for adjusting the propagation constant of a coupled waveguide structure, which is used to design two optical waveguides of different thicknesses so that the propagation constants of the two are matched. When the thickness of the waveguides connecting different devices is different, a coupled waveguide structure is required to achieve optical interconnection between the devices. The present invention can apply a coupler structure to a transition structure between waveguides of different thicknesses. By utilizing the characteristic that the propagation law of the waveguide structure is related to the thickness and width of the waveguide, the waveguide characteristics can be adjusted based on structural parameters such as thickness and width.

[0058] In the actual structure, the coupled waveguide structure with different thicknesses can be designed as a single-layer and double-layer coupled waveguide structure, wherein the main purpose is to transition from a single-layer waveguide to a double-layer waveguide structure. The waveguide characteristics can be adjusted by adjusting the thickness and width of the single-layer waveguide and / or double-layer waveguide and other related structural parameters so that k1=k2, thereby improving or achieving complete power conversion. Of course, when the signal light transitions from a double-layer waveguide to a single-layer waveguide, it can also be adjusted based on the same inventive principle.

[0059] In the present invention, the structural parameters of the waveguide include the structural parameters of the single-layer waveguide and the structural parameters of the double-layer waveguide, which may specifically include at least: the material / refractive index of the waveguide, the waveguide width, thickness, the distance between the double-layer waveguides (the distance between the upper waveguide and the lower waveguide), the lower cladding thickness, the upper cladding thickness and other parameters.

[0060] The coupled waveguide structure and the method for adjusting the propagation constant thereof provided by the present invention are described below by way of examples.

[0061] First, the present invention can design coupled waveguide structures of different thicknesses as single-layer and double-layer coupled waveguide structures. It should be noted that the present invention can individually adjust the single-layer waveguide characteristics or parameters, including but not limited to the methods provided in Examples 1-3. The present invention can individually adjust the double-layer waveguide characteristics or parameters, including but not limited to the methods provided in Examples 1-1, 1-2, 1-5, and 1-6. The present invention can also simultaneously adjust the single-layer waveguide and double-layer waveguide characteristics or parameters, including but not limited to Examples 1-4. In addition, the present invention can also adjust the single-layer waveguide characteristics and / or double-layer waveguide characteristics in other ways besides the above-mentioned ways, so that coupled waveguide structures of different thicknesses can achieve 100% power conversion at a certain position, and examples will not be given one by one here.

[0062] Secondly, in the embodiment of the present invention, the single-layer waveguide parameters include but are not limited to: the width W1 of the single-layer waveguide 20, the thickness of the single-layer waveguide 20 (not shown in the figure), the distance h1 between the single-layer waveguide 20 and the substrate, etc. The double-layer waveguide parameters include but are not limited to: the width W2 of the lower waveguide 401, the width W3 of the upper waveguide 402, the distance h2 between the lower waveguide 401 and the substrate, the distance h3 between the lower waveguide 401 and the upper waveguide 402 (i.e., the thickness of the middle layer), the thickness h4 of the upper waveguide 402, etc.

[0063] In addition, refer to Figure 3 (a), the present invention can design the single-layer waveguide and the double-layer waveguide so that their projections on the substrate surface are parallel to each other; Figure 3 (b) or (c), the present invention can also design the single-layer waveguide and the double-layer waveguide so that their projections on the substrate surface completely overlap; Figure 3 (d) The present invention can also design the single-layer waveguide and the double-layer waveguide to overlap each other in their projections on the substrate surface.

[0064] It should be noted that the double-layer waveguide may at least include an upper waveguide, a lower waveguide, and an intermediate layer region between the upper waveguide and the lower waveguide; generally speaking, the upper waveguide and the lower waveguide are vertically arranged in a direction perpendicular to the substrate.

[0065] Example 1-1

[0066] Reference Figure 4 (a) A coupled waveguide structure includes: a substrate 10, a single-layer waveguide 20, a cladding layer 30, and a double-layer waveguide 40 (including a lower waveguide 401, an upper waveguide 402, and an intermediate layer region therebetween); wherein the substrate 10 may be silicon or other substrate materials, the single-layer waveguide 20 may be silicon nitride or other waveguide materials, the cladding layer 30 may be silicon dioxide or other materials, the intermediate layer may be silicon dioxide or other materials, the double-layer waveguide 40 may be silicon nitride or other waveguide materials, and the materials of the lower waveguide 401 and the upper waveguide 402 may be the same or different.

[0067] In this embodiment, the waveguide core layer of the single-layer waveguide 20 is relatively thin, and the propagation constant of the single-layer waveguide 20 is k1. The waveguide core layer of the double-layer waveguide 40 is thicker, and the width W2 of the waveguide is reduced, so that W1>W2. In a specific design, the width of the lower waveguide 401 can be wider than that of the upper waveguide 402, that is, W2>W3, so that the propagation constant of the waveguide is k2. When k1=k2, 100% power conversion can be achieved at a certain position.

[0068] Example 1-2

[0069] Reference Figure 4(b) A coupled waveguide structure includes: a substrate 10, a single-layer waveguide 20, a cladding layer 30, and a double-layer waveguide 40 (including a lower waveguide 401, an upper waveguide 402, and an intermediate layer region therebetween); wherein the substrate 10 may be silicon or other substrate materials, the single-layer waveguide 20 may be silicon nitride or other waveguide materials, the cladding layer 30 may be silicon dioxide or other materials, the intermediate layer may be silicon dioxide or other materials, the double-layer waveguide 40 may be silicon nitride or other waveguide materials, and the materials of the lower waveguide 401 and the upper waveguide 402 may be the same or different.

[0070] In this embodiment, the propagation constant of the single-layer waveguide 20 is k1, and the thickness h4' of the upper waveguide 402 of the double-layer waveguide 40 is adjusted so that the propagation constant of the double-layer waveguide is k2. When k1=k2, 100% power conversion can be achieved at a certain position.

[0071] Figure 5 FIG. 4 is a schematic diagram showing the relationship between the structural thickness of the upper waveguide 402 and the propagation constant of the double-layer waveguide 40. Figure 5 As shown, as the structural thickness of the upper waveguide 402 increases, the propagation constant of the double-layer waveguide 40 increases. Therefore, when the propagation constant of the single-layer waveguide 20 is designed to be a fixed value k1, the thickness h4' of the upper waveguide 402 of the double-layer waveguide 40 can be adjusted to adjust the propagation constant of the double-layer waveguide 40 to match k1.

[0072] Examples 1-3

[0073] Reference Figure 4 (c) A coupled waveguide structure includes: a substrate 10, a single-layer waveguide 20, a cladding layer 30, and a double-layer waveguide 40 (including a lower waveguide 401, an upper waveguide 402, and an intermediate layer region therebetween); wherein the substrate 10 may be silicon or other substrate materials, the single-layer waveguide 20 may be silicon nitride or other waveguide materials, the cladding layer 30 may be silicon dioxide or other materials, the intermediate layer may be silicon dioxide or other materials, the double-layer waveguide 40 may be silicon nitride or other waveguide materials, and the materials of the lower waveguide 401 and the upper waveguide 402 may be the same or different.

[0074] In this embodiment, the propagation constant of the double-layer waveguide 40 is k2, and the distance h1' between the bottom surface of the single-layer waveguide 20 and the substrate 10 is adjusted. Since the distance h1' between the single-layer waveguide 20 and the substrate 10 will cause the change of the propagation constant of the single-layer waveguide 20, h1' is adjusted so that the propagation constant of the single-layer waveguide 20 is k1. When k1=k2, 100% power conversion can be achieved at a certain position.

[0075] It should be noted that, in this embodiment, since the distance between the single-layer waveguide and the silicon substrate is relatively large, the loss of light in the waveguide caused by the substrate can be further reduced.

[0076] Examples 1-4

[0077] Reference Figure 4 (d) A coupled waveguide structure includes: a substrate 10, a single-layer waveguide 20, a cladding layer 30, and a double-layer waveguide 40 (including a lower waveguide 401, an upper waveguide 402, and an intermediate layer region therebetween); wherein the substrate 10 may be silicon or other substrate materials, the single-layer waveguide 20 may be silicon nitride or other waveguide materials, the cladding layer 30 may be silicon dioxide or other materials, the intermediate layer may be silicon dioxide or other materials, the double-layer waveguide 40 may be silicon nitride or other waveguide materials, and the materials of the lower waveguide 401 and the upper waveguide 402 may be the same or different.

[0078] In this embodiment, the propagation constant of the single-layer waveguide 20 is k1, and the distance h1" between the bottom surface of the single-layer waveguide 20 and the substrate 10 and the thickness h4" of the upper waveguide 402 are adjusted so that the propagation constant of the single-layer waveguide 20 is k1 and the propagation constant of the double-layer waveguide 40 is k2. When k1=k2, 100% power conversion can be achieved at a certain position.

[0079] It should be noted that, in this embodiment, since the distance between the single-layer waveguide and the silicon substrate is relatively large, the loss of light in the waveguide caused by the substrate can be further reduced.

[0080] Examples 1-5

[0081] Reference Figure 4 (e) A coupled waveguide structure includes: a substrate 10, a single-layer waveguide 20, a cladding layer 30, and a double-layer waveguide 40 (including a lower waveguide 401, an upper waveguide 402, and an intermediate layer region therebetween); wherein the substrate 10 may be silicon or other substrate materials, the single-layer waveguide 20 may be silicon nitride or other waveguide materials, the cladding layer 30 may be silicon dioxide or other materials, the intermediate layer may be silicon dioxide or other materials, the double-layer waveguide 40 may be silicon nitride or other waveguide materials, and the materials of the lower waveguide 401 and the upper waveguide 402 may be the same or different.

[0082] In this embodiment, the propagation constant of the single-layer waveguide 20 is k1, and the spacing h3' between the upper waveguide 402 and the lower waveguide 401 is adjusted so that the propagation constant of the double-layer waveguide 40 is k2. When k1=k2, 100% power conversion can be achieved at a certain position.

[0083] Figure 6Schematic diagram of the relationship between the distance between the upper waveguide 402 and the lower waveguide 401 and the propagation constant of the double-layer waveguide 40. Figure 6 As shown in the figure, as the distance between the upper waveguide 402 and the lower waveguide 401 increases, the propagation constant decreases. Therefore, when the propagation constant of the single-layer waveguide 20 is designed to be a fixed value k1, the distance h3' between the upper waveguide 402 and the lower waveguide 401 can be adjusted, and the propagation constant of the double-layer waveguide 40 changes as shown in the figure. A distance value h3' is selected to match k1 with k2, and 100% power conversion is achieved at a certain position.

[0084] Examples 1-6

[0085] Reference Figure 4 (f) A coupled waveguide structure includes: a substrate 10, a single-layer waveguide 20, a cladding layer 30, and a double-layer waveguide 40 (including a lower waveguide 401, an upper waveguide 402, and an intermediate layer region therebetween); wherein the substrate 10 may be silicon or other substrate materials, the single-layer waveguide 20 may be silicon nitride or other waveguide materials, the cladding layer 30 may be silicon dioxide or other materials, the double-layer waveguide 40 may be silicon nitride or other waveguide materials, and the materials of the lower waveguide 401 and the upper waveguide 402 may be the same or different.

[0086] In this embodiment, the propagation constant of the single-layer waveguide 20 is k1, and the width W3' of the upper waveguide 402 and the height h4'' of the upper waveguide 402 are adjusted so that the propagation constant of the double-layer waveguide 40 is k2. When k1=k2, 100% power conversion can be achieved at a certain position.

[0087] Figure 7 FIG. 4 is a schematic diagram showing the relationship between the width W3 of the upper waveguide 402 and the propagation constant of the double-layer waveguide 40. Figure 7 As shown, as the width W3 of the upper waveguide 402 increases, the propagation constant of the double-layer waveguide 40 decreases. Therefore, when the propagation constant of the single-layer waveguide 20 is designed to be a fixed value k1, a width W3 is selected to match k1 with k2 to achieve 100% power conversion.

[0088] In addition to the methods shown in the above embodiments, the present application can also adjust the waveguide characteristics in other ways. In some embodiments, k1=k2 can be adjusted by adjusting one or several parameters as follows. The double-layer waveguide 40 has multiple structural parameters that can be adjusted to match the propagation constant k2 with the propagation constant k1 of the single-layer waveguide 20. On the other hand, the propagation constant k1 of the single-layer waveguide 20 can also be changed by adjusting the structural parameters of the single-layer waveguide 20. By adjusting the propagation constant k1 of the single-layer waveguide 20, the propagation constant k2 of the double-layer waveguide can be more easily matched thereto.

[0089] Based on the same inventive principle, the present invention also provides an integrated optical chip, which may include modules, components or devices with different functions. In order to achieve optical coupling and optical interconnection between different modules, components or devices, and at the same time improve the coupling efficiency, thereby reducing optical loss, the present invention can apply the above-mentioned coupled waveguide structure to the on-chip system of a high-power integrated optical chip.

[0090] Example 2-1

[0091] Figure 8 is a schematic top view of an integrated optical chip provided in this embodiment, wherein the coupled waveguide structure can be any of the coupled waveguide structures described above or a coupled waveguide structure designed based on the same inventive principle, such as Figure 8 As shown, in this embodiment, the coupling waveguide structure 70 is designed as a structure in which the projections of the single-layer waveguide 20 and the double-layer waveguide 40 on the substrate surface are parallel to each other. The double-layer waveguide 40 may include a lower waveguide 401 and an upper waveguide 402. One end of the double-layer waveguide 40 is connected to one end of the second transition structure (Taper) 52, and the other end of the second transition structure (Taper) 52 is connected to the main waveguide 62 of the integrated optical chip; one end of the single-layer waveguide 20 is connected to one end of the first transition structure (Taper) 51, and the other end of the first transition structure (Taper) 51 is connected to one end of the optical coupling structure 61. The coupling waveguide structure 70 can efficiently couple the signal light transmitted by the optical coupling structure 61 to the main waveguide 62, reducing the optical loss.

[0092] Among them, the optical coupling structure 61 can be specifically an edge coupling structure, and the integrated optical chip can also include a silicon-based substrate (not shown in the figure) and a cladding layer 30, wherein the cladding layer 30 can be silicon dioxide, and the single-layer waveguide 20 and the double-layer waveguide 40 can both be silicon nitride.

[0093] It should be noted that the integrated optical chip provided in this embodiment can also couple the signal light from the double-layer waveguide to the single-layer waveguide. In addition, this embodiment can also design the coupling waveguide structure as a structure in which the projections of the single-layer waveguide 20 and the double-layer waveguide 40 on the substrate surface partially or completely overlap, which will not be repeated here.

[0094] Example 2-2

[0095] Fig. 9 is a top view schematic diagram of another integrated optical chip provided in this embodiment, wherein the coupled waveguide structure can be any of the coupled waveguide structures described above or a coupled waveguide structure designed based on the same inventive principle, such as Fig. 9As shown, in this embodiment, the coupling waveguide structure 70 is designed as a structure in which the projections of the single-layer waveguide 20 and the double-layer waveguide 40 on the substrate surface are parallel to each other. The double-layer waveguide 40 may include a lower waveguide 401 and an upper waveguide 402. One end of the double-layer waveguide 40 is connected to one end of the second transition structure (Taper) 52, and the other end of the second transition structure (Taper) 52 is connected to the main waveguide 62 of the integrated optical chip; one end of the single-layer waveguide 20 is connected to one end of the first transition structure (Taper) 51, and the other end of the first transition structure (Taper) 51 is connected to one end of the optical coupling structure 61, and the other end of the optical coupling structure 61 can be connected to a light source module 80 for providing signal light. The coupling waveguide structure 70 can efficiently couple the signal light provided by the light source module 80 to the main waveguide 62, thereby reducing light loss.

[0096] Among them, the optical coupling structure 61 can be specifically an edge coupling structure, the light source module 80 can be specifically a laser or an optical fiber, and the integrated optical chip can also include a silicon-based substrate (not shown in the figure) and a cladding layer 30, wherein the cladding layer 30 can be silicon dioxide, and the single-layer waveguide 20 and the double-layer waveguide 40 can both be silicon nitride.

[0097] It should be noted that the integrated optical chip provided in this embodiment can also couple the signal light from the double-layer waveguide to the single-layer waveguide. In addition, this embodiment can also design the coupling waveguide structure as a structure in which the projections of the single-layer waveguide 20 and the double-layer waveguide 40 on the substrate surface partially or completely overlap, which will not be repeated here.

[0098] By performing optical power conversion through the coupled waveguide structure provided by the present invention, the power in one waveguide can be completely transferred to another waveguide, achieving a highly efficient transition (single-layer waveguide 20 transferred to double-layer waveguide 40, or double-layer waveguide 40 transferred to single-layer waveguide 20, not limited here). This structure does not require the use of a three-dimensional lithography process and has no special process requirements.

[0099] In order to further simplify the processing and preparation process, the present invention can also provide a processing method for preparing the above-mentioned coupled waveguide structure. The process does not require the use of a complex three-dimensional photolithography process, thereby greatly simplifying the process complexity.

[0100] The present invention can directly pattern a pre-prepared epitaxial wafer to form a coupled waveguide structure; or can form an epitaxial layer on a substrate through an epitaxial process and then pattern the coupled waveguide structure.

[0101] Example 3-1

[0102] Reference Fig.10 This embodiment provides a method for processing a coupled waveguide structure based on a prefabricated epitaxial wafer, and the method may at least include:

[0103] Step S101: patterning the prefabricated epitaxial wafer to form a double-layer waveguide;

[0104] Step S102: forming a single-layer waveguide on the epitaxial wafer having the double-layer waveguide formed thereon.

[0105] The prefabricated epitaxial wafer is a multi-layer epitaxial structure, which includes: a substrate, a lower cladding layer, a double-layer waveguide core layer (lower waveguide core layer, an intermediate layer, and an upper waveguide core layer) in sequence. Specifically, the substrate material can be silicon or other materials, the lower cladding material can be silicon dioxide or other materials, and the double-layer waveguide core layer can be composed of a double-layer silicon nitride waveguide and an intermediate layer, wherein the intermediate layer can be silicon dioxide or other materials.

[0106] Optionally, in order to meet the design parameter requirements of different thicknesses of the double-layer waveguide, after step S102, the method may further include: adjusting the thickness of the upper waveguide in the double-layer waveguide by a thinning process so that k1=k2. Since the actual design parameters are not necessarily completely consistent with the thickness of the thin film deposition (growth) during the prefabricated epitaxial wafer, the thickness of the upper waveguide can be adjusted by a thinning process for the prefabricated epitaxial wafer. Of course, the thickness of the upper waveguide can also be controlled by the thin film deposition step during the prefabricated epitaxial wafer.

[0107] Optionally, after step S102, the method further includes: forming an upper cladding layer on the epitaxial wafer formed with the double-layer waveguide and the single-layer waveguide, and the upper cladding layer may be silicon dioxide or other materials.

[0108] Specifically, the above method can be used to prepare a coupled waveguide structure in which the projections of a single-layer waveguide and a double-layer waveguide on the substrate surface are parallel to each other, and the spacing between the lower waveguide and the substrate is not equal to the spacing between the single-layer waveguide and the substrate (i.e., h2≠h1), such as the above embodiments 1-3 or embodiments 1-4, etc. This process does not require the use of a complex three-dimensional lithography process. On the premise of meeting the design parameters (k1=k2), only simple graphical operations are required to obtain a coupled waveguide structure that can achieve high-efficiency transition, thereby reducing the difficulty of processing and simplifying the process complexity.

[0109] Example 3-2

[0110] This embodiment provides another method for processing a coupled waveguide structure based on a prefabricated epitaxial wafer, which may at least include:

[0111] Step S201: patterning the prefabricated epitaxial wafer to form a double-layer waveguide and a single-layer waveguide.

[0112] The prefabricated epitaxial wafer is a multi-layer epitaxial structure, which includes: a substrate, a lower cladding layer, a double-layer waveguide core layer (lower waveguide core layer, an intermediate layer, and an upper waveguide core layer) in sequence. Specifically, the substrate material can be silicon or other materials, the lower cladding material can be silicon dioxide or other materials, and the double-layer waveguide core layer can be composed of a double-layer silicon nitride waveguide and an intermediate layer, wherein the intermediate layer can be silicon dioxide or other materials.

[0113] Optionally, in order to meet the design parameter requirements of different thicknesses of the double-layer waveguide, after step S102, the method may further include: adjusting the thickness of the upper waveguide in the double-layer waveguide by a thinning process so that k1=k2. Since the actual design parameters are not necessarily completely consistent with the thickness of the thin film deposition (growth) during the prefabricated epitaxial wafer, the thickness of the upper waveguide can be adjusted by a thinning process for the prefabricated epitaxial wafer. Of course, the thickness of the upper waveguide can also be controlled by the thin film deposition step during the prefabricated epitaxial wafer.

[0114] Optionally, after step S201, the method further comprises: forming an upper cladding layer on the epitaxial wafer formed with the double-layer waveguide and the single-layer waveguide, and the upper cladding layer may be silicon dioxide or other materials.

[0115] Specifically, the patterning of the prefabricated epitaxial wafer may specifically include: photolithography process, deep etching process, shallow etching process. The above method can be used to prepare a coupled waveguide structure in which the projections of the single-layer waveguide and the double-layer waveguide on the substrate surface are parallel to each other, and the spacing between the lower waveguide and the substrate is equal to the spacing between the single-layer waveguide and the substrate (i.e., h2=h1), such as the above embodiment 1-1, embodiment 1-2, embodiment 1-5 or embodiment 1-6, etc. In this case, since the lower waveguide is flush with the bottom surface of the single-layer waveguide and has the same thickness, the lower waveguide and the single-layer waveguide can be formed simultaneously by simple deep etching, and shallow etching can be performed according to the design parameters of the upper waveguide to form the double-layer waveguide and the single-layer waveguide at the same time. This process does not require the use of a complex three-dimensional photolithography process. On the premise of meeting the design parameters (k1=k2), only a simple graphic operation is required to process a coupled waveguide structure that can achieve high-efficiency transition, which reduces the difficulty of processing and simplifies the process complexity.

[0116] Example 3-3

[0117] This embodiment provides a method for preparing a coupled waveguide structure, which may at least include:

[0118] Step S301: forming a lower cladding layer on a substrate;

[0119] Step S302: forming a lower waveguide core layer, an intermediate layer and an upper waveguide core layer on the lower cladding layer to form the double-layer waveguide core layer, wherein the double-layer waveguide core layer is composed of the lower waveguide core layer, the intermediate layer and the upper waveguide core layer, specifically, the substrate material can be silicon or other materials, the lower cladding material can be silicon dioxide or other materials, the double-layer waveguide core layer can be composed of a double-layer silicon nitride waveguide and an intermediate layer, wherein the intermediate layer can be silicon dioxide or other materials. Therefore, in this embodiment, an epitaxial layer having the above structure can be prepared through the above steps S301 and S302.

[0120] Step S303: continue to pattern the formed epitaxial layer to form a double-layer waveguide;

[0121] Step S304: forming a single-layer waveguide on the epitaxial wafer having the double-layer waveguide formed thereon.

[0122] Optionally, in order to meet the design parameter requirements of different thicknesses of the double-layer waveguide, after step S304, the method may further include: adjusting the thickness of the upper waveguide in the double-layer waveguide by a thinning process so that k1=k2. Since the actual design parameters are not necessarily completely consistent with the thickness of the thin film deposition (growth) during the formation of the epitaxial layer, the thickness of the upper waveguide can be adjusted by a thinning process for the epitaxial layer. Of course, the thickness of the upper waveguide can also be controlled by the thin film deposition step during the formation of the epitaxial layer.

[0123] Optionally, after step S304, the method further includes: continuing to form an upper cladding layer on the epitaxial structure formed with the double-layer waveguide and the single-layer waveguide, and the upper cladding layer may be silicon dioxide or other materials.

[0124] Specifically, the above method can be used to prepare a coupled waveguide structure in which the projections of a single-layer waveguide and a double-layer waveguide on the substrate surface are parallel to each other, and the spacing between the lower waveguide and the substrate is not equal to the spacing between the single-layer waveguide and the substrate (i.e., h2≠h1), such as the above embodiments 1-3 or embodiments 1-4, etc. This process does not require the use of a complex three-dimensional lithography process. On the premise of meeting the design parameters (k1=k2), only simple graphical operations are required to obtain a coupled waveguide structure that can achieve high-efficiency transition, thereby reducing the difficulty of processing and simplifying the process complexity.

[0125] Embodiment 3-4

[0126] This embodiment provides another method for preparing a coupled waveguide structure, which may at least include:

[0127] Step S401 refers to step S301;

[0128] Step S402 refers to step S302;

[0129] Step S403: patterning the epitaxial layer to form a double-layer waveguide and a single-layer waveguide.

[0130] Optionally, in order to meet the design parameter requirements of different thicknesses of the double-layer waveguide, after step S403, the method may further include: adjusting the thickness of the upper waveguide in the double-layer waveguide by a thinning process so that k1=k2. Since the actual design parameters are not necessarily completely consistent with the thickness of the thin film deposition (growth) during the formation of the epitaxial layer, the thickness of the upper waveguide can be adjusted by a thinning process for the epitaxial layer. Of course, the thickness of the upper waveguide can also be controlled by the thin film deposition step during the formation of the epitaxial layer.

[0131] Optionally, after step S403, the method further includes: forming an upper cladding layer on the epitaxial wafer formed with the double-layer waveguide and the single-layer waveguide, and the upper cladding layer may be silicon dioxide or other materials.

[0132] Specifically, patterning the epitaxial layer may specifically include: photolithography, deep etching, and shallow etching. The above method can be used to prepare a coupled waveguide structure in which the projections of the single-layer waveguide and the double-layer waveguide on the substrate surface are parallel to each other, and the spacing between the lower waveguide and the substrate is equal to the spacing between the single-layer waveguide and the substrate (i.e., h2=h1), such as the above embodiment 1-1, embodiment 1-2, embodiment 1-5 or embodiment 1-6, etc. In this case, since the lower waveguide is flush with the bottom surface of the single-layer waveguide and has the same thickness, the lower waveguide and the single-layer waveguide can be formed simultaneously by simple deep etching, and shallow etching can be performed according to the design parameters of the upper waveguide to form the double-layer waveguide and the single-layer waveguide at the same time. This process does not require the use of a complex three-dimensional photolithography process. On the premise of meeting the design parameters (k1=k2), only a simple graphic operation is required to process a coupled waveguide structure that can achieve high-efficiency transition, which reduces the difficulty of processing and simplifies the process complexity.

[0133] It should be noted that, for Example 3-1 to Example 3-4, a thick silicon nitride layer can also be formed by layered deposition.

[0134] In summary, the coupled waveguide structure prepared by the method for preparing the coupled waveguide structure proposed in the present invention can achieve optical coupling between two optical waveguides (single-layer waveguide and double-layer waveguide) of different thicknesses while simplifying the process complexity, and the coupling efficiency can be increased to 100%.

[0135] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

[0136] It should be noted that, for the convenience of description, the aforementioned method embodiments are all described as a series of action combinations, but those skilled in the art should be aware that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0137] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0138] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The optional embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of the present invention. The present invention selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A coupled waveguide structure, characterized in that: include: substrate; A coating layer is prepared on the surface of the substrate; a single-layer waveguide disposed in the cladding layer; A double-layer waveguide is arranged in the cladding layer, and the structural parameters of the double-layer waveguide and the single-layer waveguide are designed so that the propagation constants of the double-layer waveguide and the single-layer waveguide are completely matched.

2. The coupled waveguide structure according to claim 1, characterized in that: The structural parameters include the refractive index of the waveguide material, the waveguide width, thickness, and the distance between the double-layer waveguides; by adjusting one or more structural parameters of the waveguide, complete matching of the propagation constant is achieved.

3. The coupled waveguide structure according to claim 1, wherein: The projections of the single-layer waveguide and the double-layer waveguide on the substrate surface are parallel to each other; or the projections of the single-layer waveguide and the double-layer waveguide on the substrate surface are partially or completely overlapped; The double-layer waveguide includes an upper waveguide and a lower waveguide, and the upper waveguide and the lower waveguide are vertically arranged.

4. The coupled waveguide structure according to claim 3, characterized in that: When the projections of the single-layer waveguide and the double-layer waveguide on the substrate surface are arranged parallel to each other, the width of the lower waveguide is greater than the width of the upper waveguide, and the thickness of the lower waveguide is less than the thickness of the upper waveguide.

5. The coupled waveguide structure according to any one of claims 1 to 4, characterized in that: The double-layer waveguide is a double-layer silicon nitride waveguide, and the single-layer waveguide is a single-layer silicon nitride waveguide.

6. A method for adjusting the propagation constant of a coupled waveguide structure according to claims 1 to 5, characterized in that: include: The structural parameters of the single-layer waveguide and / or the double-layer waveguide in the coupled waveguide structure are adjusted so that the propagation constant of the single-layer waveguide completely matches the propagation constant of the double-layer waveguide.

7. The adjustment method according to claim 6, characterized in that: The parameters include at least the refractive index of the waveguide material, the waveguide width, thickness, and the distance between the double-layer waveguides; The adjusting the structural parameters specifically includes: adjusting one or more of the parameters so that the propagation constants of the single-layer waveguide and the double-layer waveguide are equal.

8. The adjustment method according to claim 7, characterized in that: The adjusting one or more of the parameters so that the propagation constants of the single-layer waveguide and the double-layer waveguide are equal specifically includes: The propagation constant of the double-layer waveguide is set to k2; the propagation constant of the single-layer waveguide is set to k1 by adjusting the width and / or thickness of the single-layer waveguide so that k1=k2; Alternatively, the propagation constant of the single-layer waveguide is set to k1; the propagation constant of the double-layer waveguide is set to k2 by adjusting the width and / or thickness of the upper waveguide in the double-layer waveguide so that k1=k2; and / or, the propagation constant of the single-layer waveguide is set to k1; the propagation constant of the double-layer waveguide is set to k2 by adjusting the width and / or thickness of the lower waveguide in the double-layer waveguide so that k1=k2; and / or, the propagation constant of the single-layer waveguide is set to k1; the propagation constant of the double-layer waveguide is set to k2 by adjusting the spacing between the upper waveguide and the lower waveguide in the double-layer waveguide so that k1=k2.

9. An integrated optical chip, characterized in that: include: The coupled waveguide structure as claimed in claims 1 to 5; A main waveguide connected to the double-layer waveguide of the coupling waveguide structure through a first transition structure; The optical coupling structure is connected to the single-layer waveguide of the coupling waveguide structure through a second transition structure.

10. The integrated optical chip according to claim 9, characterized in that: The integrated optical chip also includes: A light source module, connected to the optical coupling structure, and used to provide signal light; The coupling waveguide structure is specifically used to transition the coupled input signal light to the main waveguide; and the optical coupling structure is specifically an edge coupling structure.

11. A processing method for preparing a coupled waveguide structure as claimed in claims 1 to 5, characterized in that: include: patterning the epitaxial structure to form a double-layer waveguide; forming a single-layer waveguide on the epitaxial structure having the double-layer waveguide; Alternatively, the epitaxial structure is patterned to form a double-layer waveguide and a single-layer waveguide; Wherein, the epitaxial structure at least includes a substrate, a cladding layer, and a double-layer waveguide core layer.

12. The processing method according to claim 11, characterized in that: Also includes: After forming the double-layer waveguide, it also includes: The thickness of the upper waveguide in the double-layer waveguide is adjusted through a thinning process.

13. The processing method according to claim 11, characterized in that: The epitaxial structure is prepared by the following steps: forming a coating layer on a substrate; forming a lower waveguide core layer, an intermediate layer and an upper waveguide core layer in sequence on the cladding layer to form the double-layer waveguide core layer; The substrate material is silicon, the cladding layer and the intermediate layer material are silicon dioxide, and the lower waveguide core layer and the upper waveguide core layer material are silicon nitride.

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