End face coupler, preparation method of end face coupler and photon chip

Abstract

The invention relates to the field of integrated optics, and discloses an end face coupler, a preparation method of the end face coupler and a photon chip. The end face coupler comprises a coupling region, a mode field transition region and a waveguide transmission region. And the widths of the coupling region, the mode field transition region and the waveguide transmission region are sequentially reduced. The first end of the mode field transition region is connected with the coupling region. The second end of the mode field transition region is connected with the waveguide transmission region; and the surface of the second end of the mode field transition region is a cambered surface.

Description

Technical Field

[0001] The present application relates to the field of integrated optics, and in particular to an end coupler, a method for preparing the end coupler, and a photonic chip. Background Art

[0002] Photonic chips are integrated circuits based on photonics, which integrate photonic devices on the chip and use light waves as information carriers to achieve optical interconnection. Compared with electronic integrated circuits or electrical interconnection technology, photonic integrated circuits and optical interconnection show lower transmission loss, wider transmission bandwidth, smaller time delay, and stronger anti-electromagnetic interference ability.

[0003] The edge coupler is an important I / O interface (Input / Output Interface) component in the photonic chip. It is located at the edge of the photonic chip and is used to realize the optical signal transmission between the optical fiber and the photonic chip. The edge coupler has the advantages of high coupling efficiency, large working bandwidth, low insertion loss (less than 0.5dB) and polarization insensitivity.

[0004] However, there are certain risks in the process of preparing the end face coupler, which may cause cracks that penetrate the end face coupler and affect the quality of the end face coupler. Summary of the invention

[0005] In view of this, the embodiments of the present application provide an end face coupler, a method for preparing the end face coupler, and a photonic chip, which can avoid the generation of cracks and improve the quality.

[0006] The technical solution of the embodiment of the present application is implemented as follows:

[0007] An embodiment of the present application provides an end face coupler, which includes: a coupling region, a mode field transition region and a waveguide transmission region; the widths of the coupling region, the mode field transition region and the waveguide transmission region decrease in sequence; the first end of the mode field transition region is connected to the coupling region; the second end of the mode field transition region is connected to the waveguide transmission region; and the surface of the second end of the mode field transition region is an arc surface.

[0008] In some embodiments of the present application, the second end of the mode field transition zone includes: a first connecting structure; the first connecting structure is conical, and the connecting angle is rounded; the thinner end of the first connecting structure is connected to the waveguide transmission zone, and the thicker end of the first connecting structure is connected to the mode field transition zone.

[0009] In some embodiments of the present application, the Y-axis height of the first connecting structure is first-order continuously differentiable with respect to the X-axis length.

[0010] In some embodiments of the present application, the second end of the mode field transition zone further includes: a second connecting structure; the second connecting structure is annular and surrounds the first connecting structure; the second connecting structure is close to the surface of the waveguide transmission zone and is a convex arc surface.

[0011] In some embodiments of the present application, the end face coupler is made of thin film lithium niobate.

[0012] In some embodiments of the present application, the length of the end face coupler is 50um to 1000um; wherein the length of the mode field transition zone is 30um to 800um.

[0013] An embodiment of the present application also provides a method for preparing an end face coupler, the method comprising: providing a substrate; performing photolithography and etching on the substrate to form a waveguide transmission region, a mode field transition region and a coupling region; wherein the widths of the coupling region, the mode field transition region and the waveguide transmission region decrease in sequence; the first end of the mode field transition region is connected to the coupling region; the second end of the mode field transition region is connected to the waveguide transmission region; and the surface of the second end of the mode field transition region is an arc surface.

[0014] In some embodiments of the present application, photolithography and etching are performed on the substrate, including: performing a first photolithography and a first etching on the substrate to form the waveguide transmission region and a first connecting structure; wherein the first connecting structure is tapered and the connecting angle is rounded; a thinner end of the first connecting structure is connected to the waveguide transmission region, and a thicker end of the first connecting structure is connected to the mode field transition region.

[0015] In some embodiments of the present application, photolithography and etching are performed on the substrate, and also include: performing a second photolithography and a second etching on the substrate to form the coupling region and a second connecting structure; wherein the second connecting structure is annular and surrounds the first connecting structure; the second connecting structure is close to the surface of the waveguide transmission region and is a convex arc surface.

[0016] An embodiment of the present application also provides a photonic chip, which includes the end face coupler described in the above solution.

[0017] It is understandable that the design of the curved surface can avoid the existence of sharp figures in the photolithography pattern, thereby avoiding the cracking of the figure caused by the stress concentration of the photoresist layer. Furthermore, since the size of the waveguide transmission area is relatively thin (i.e., the width is relatively small), the second end of the mode field transition area connected to the waveguide transmission area is more prone to cracks. Therefore, in the embodiment of the present application, the surface of the second end of the mode field transition area is designed as a curved surface, which can specifically avoid the generation of cracks and improve the quality of the end face coupler. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 An electron microscope photograph of an end coupler in the related art;

[0020] Figure 2 Schematic diagram of the structure of the end coupler provided in the embodiment of the present application Figure 1 ;

[0021] Figure 3 Schematic diagram of the structure of the end coupler provided in the embodiment of the present application Figure 2 ;

[0022] Figure 4 Schematic diagram of the structure of the end coupler provided in the embodiment of the present application Figure 3 ;

[0023] Figure 5 A flow chart of a method for preparing an end face coupler provided in an embodiment of the present application;

[0024] Figure 6 Schematic diagram of the method for preparing the end coupler provided in the embodiment of the present application Figure 1 ;

[0025] Figure 7 Schematic diagram of the method for preparing the end coupler provided in the embodiment of the present application Figure 2 ;

[0026] Figure 8 Schematic diagram of the method for preparing the end coupler provided in the embodiment of the present application Figure 3 ;

[0027] Fig. 9 Schematic diagram of the method for preparing the end coupler provided in the embodiment of the present application Figure 4 ;

[0028] Fig.10 A schematic diagram of the structure of the photonic chip provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] The exemplary embodiments disclosed in the present application will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the specific embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope disclosed in the present application to those skilled in the art.

[0030] In the following description, a large number of specific details are given to provide a more thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present application, some technical features known in the art are not described; that is, all features of the actual embodiments are not described here, and well-known functions and structures are not described in detail.

[0031] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0032] It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below can be represented as a second element, component, region, layer or part. When the second element, component, region, layer or part is discussed, it does not indicate that the present application necessarily has a first element, component, region, layer or part.

[0033] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present application. When used herein, the singular "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "composition" and / or "comprising" when used in this specification determine the existence of the features, integers, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items. All numerical ranges herein include endpoint values.

[0034] It should be noted that the photolithography-dry etching process is used to form the end coupler, which requires forming a patterned photoresist layer, transferring the pattern to the hard mask, and then etching. Since the hard mask material includes silicon nitride, silicon oxide, chromium metal, diamond film, etc., which are difficult to etch, it is necessary to form a thicker (more than 1um) photoresist layer to transfer the pattern. However, the thicker the photoresist layer, the greater its internal stress. Figure 1 As shown, if there are relatively sharp figures in the photolithography pattern, it is easy to cause the pattern to crack, thereby possibly forming cracks that penetrate the end face coupler, affecting the quality of the end face coupler.

[0035] Figures 2 to 4 The schematic diagrams of the structure of the end face coupler provided in the embodiments of the present application are all top views. Figure 3 and Figure 4 They are Figure 2 Schematic diagram of the structure of the middle part. In integrated circuit design, you can refer to Figures 2 to 4 To design a layout to prepare the end face coupler provided in the embodiment of the present application.

[0036] The present application embodiment provides an end face coupler, such as Figure 2 As shown, the end face coupler includes: a coupling region, a mode field transition region and a waveguide transmission region. The widths of the coupling region, the mode field transition region and the waveguide transmission region (i.e., the size along the second direction Y) decrease in sequence. The first end of the mode field transition region is connected to the coupling region, and the second end of the mode field transition region is connected to the waveguide transmission region.

[0037] It should be noted that the coupling region is used to couple light to generate an on-chip propagation light field. The mode field transition region is used to compress the light field and maintain low loss during transmission. The waveguide transmission region is connected to the optical waveguides of other devices and is used to transmit the compressed light field.

[0038] In the present application examples, reference Figure 2 , the surface of the second end of the mode field transition zone is an arc surface. That is to say, in the process of preparing the end face coupler, the photolithography pattern corresponding to the second end of the mode field transition zone does not include a sharp pattern.

[0039] It is understandable that the design of the curved surface can avoid the existence of sharp graphics in the photolithography pattern, thereby avoiding the pattern cracking phenomenon caused by stress concentration of the photoresist layer.

[0040] Furthermore, since the size of the waveguide transmission area is relatively small (i.e., the width is relatively small), the second end of the mode field transition area connected to the waveguide transmission area is more likely to have cracks. Therefore, in the embodiment of the present application, the surface of the second end of the mode field transition area is designed to be a curved surface, which can specifically avoid the generation of cracks and improve the quality of the end face coupler.

[0041] In some embodiments of the present application, Figure 3 As shown, the second end of the mode field transition zone includes: a first connection structure. The first connection structure is tapered, and the connection angle is rounded, so that sharp patterns in the photolithography pattern can be avoided and cracks can be avoided. The thinner end of the first connection structure is connected to the waveguide transmission zone, and the thicker end of the first connection structure is connected to the mode field transition zone.

[0042] In some embodiments of the present application, reference Figure 3 , the Y-axis height (the dimension along the second direction Y) of the first connecting structure is first-order continuously differentiable with respect to the X-axis length (the dimension along the first direction X).

[0043] It can be understood that the Y-axis height of the first connecting structure is first-order continuously differentiable with respect to the X-axis length, which can ensure that there is no mutation point in the first connecting structure and reduce stress; if the first-order derivative of the Y-axis height of the first connecting structure with respect to the X-axis length is less than 1, the size change of the first connecting structure is relatively gentle, thereby being able to reduce the refractive index mutation of the light field in the first connecting structure, which is beneficial to reducing the loss during transmission.

[0044] In some embodiments of the present application, reference Figure 4 The second end of the mode field transition region further includes: a second connection structure. The second connection structure is annular and surrounds the first connection structure. The second connection structure is close to the surface of the waveguide transmission region and is a convex arc surface. Such a design can avoid the existence of sharp figures in the lithography pattern and avoid the generation of cracks.

[0045] In some embodiments of the present application, the end coupler is made of thin film lithium niobate (TFLN).

[0046] It should be noted that lithium niobate crystals have excellent electro-optical, piezoelectric and nonlinear optical properties, and have the ability to manipulate photons in multiple dimensions. Optoelectronic devices made from thin-film lithium niobate have excellent performance.

[0047] The processing method of thin-film lithium niobate is mainly based on dry etching technology. Specifically, first, a patterned photoresist layer can be formed; then, the pattern can be transferred to a hard mask formed by materials such as silicon nitride, silicon oxide, chromium metal or diamond film; finally, argon ion bombardment etching can be used to process the waveguide, or the thin-film lithium niobate can be directly etched using the photoresist as a mask. Since thin-film lithium niobate and hard masks such as silicon nitride, silicon oxide, chromium metal or diamond film are difficult to etch, a photoresist with a thickness of more than 1um is required to transfer the pattern.

[0048] In some embodiments of the present application, reference Figure 2, the length of the end face coupler (ie, the dimension along the first direction X) is 50um to 1000um; wherein, the length of the mode field transition zone (ie, the dimension along the first direction X) is 30um to 800um.

[0049] Figure 5 The schematic diagram of the process of preparing the end coupler provided in the embodiment of the present application is as follows. Figure 5 As shown, the preparation method includes steps S101 to S102, which will be described in conjunction with each step.

[0050] It should be noted that Figures 6 to 9 An intermediate structure in the method for preparing an end face coupler provided in an embodiment of the present application is shown, which is used to describe and clearly illustrate the steps of the method for preparing the end face coupler.

[0051] S101. Provide a substrate.

[0052] In the present application examples, reference Figure 6 A layer of light-transmitting material is formed on the substrate. The thickness of the light-transmitting material can reach 400um. The light-transmitting material can be thin-film lithium niobate (TFLN). Through photolithography and etching, the light-transmitting material can be processed into end couplers and other photonic devices.

[0053] S102, performing photolithography and etching on the substrate to form a waveguide transmission region, a mode field transition region and a coupling region.

[0054] In the present application examples, reference Figure 2 The widths of the coupling region, the mode field transition region and the waveguide transmission region decrease in sequence. The first end of the mode field transition region is connected to the coupling region. The second end of the mode field transition region is connected to the waveguide transmission region; and the surface of the second end of the mode field transition region is an arc surface.

[0055] It is understandable that the design of the curved surface can avoid the existence of sharp graphics in the photolithography pattern, thereby avoiding the pattern cracking phenomenon caused by stress concentration of the photoresist layer.

[0056] Furthermore, since the size of the waveguide transmission area is relatively small (i.e., the width is relatively small), the second end of the mode field transition area connected to the waveguide transmission area is more likely to have cracks. Therefore, in the embodiment of the present application, the surface of the second end of the mode field transition area is designed to be a curved surface, which can specifically avoid the generation of cracks and improve the quality of the end face coupler.

[0057] In some embodiments of the present application, reference Figure 7, a first photolithography and a first etching can be performed on the substrate to form a waveguide transmission region and a first connection structure. The first connection structure is tapered, and the connection angle is rounded; the thinner end of the first connection structure is connected to the waveguide transmission region, and the thicker end of the first connection structure is connected to the mode field transition region.

[0058] In some embodiments of the present application, reference Figure 8 After the first etching is completed, a second photolithography can be performed on the substrate, and a second etching can be performed to form a coupling region and a second connection structure. The second connection structure is annular and surrounds the first connection structure; the second connection structure is close to the surface of the waveguide transmission region and is a convex arc surface.

[0059] In the present application examples, reference Fig. 9 After the end coupler and other photonic devices are prepared on the substrate, a dielectric layer can be covered on each photonic device to encapsulate and protect each photonic device.

[0060] The present application also provides a photonic chip. Fig.10 As shown, the photonic chip includes an end coupler, wherein the end coupler includes the technical features in the above-mentioned embodiment.

[0061] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0062] The serial numbers of the embodiments of the present application are for description only and do not represent the advantages and disadvantages of the embodiments. The methods disclosed in the several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments. The features disclosed in the several product embodiments provided in this application can be arbitrarily combined without conflict to obtain new product embodiments. The features disclosed in the several method or device embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments or device embodiments.

[0063] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. An end coupler, characterized in that: The end face coupler comprises: a coupling region, a mode field transition region and a waveguide transmission region; The widths of the coupling region, the mode field transition region and the waveguide transmission region decrease in sequence; The first end of the mode field transition zone is connected to the coupling zone; the second end of the mode field transition zone is connected to the waveguide transmission zone; and the surface of the second end of the mode field transition zone is an arc surface.

2. The end coupler according to claim 1, characterized in that: The second end of the mode field transition region includes: a first connection structure; The first connection structure is tapered, and the connection angle is rounded; A thinner end of the first connection structure is connected to the waveguide transmission region, and a thicker end of the first connection structure is connected to the mode field transition region.

3. The end coupler according to claim 2, characterized in that: The Y-axis height of the first connecting structure is first-order continuously differentiable with respect to the X-axis length.

4. The end coupler according to claim 2, characterized in that: The second end of the mode field transition region further includes: a second connecting structure; The second connecting structure is annular and surrounds the first connecting structure; The second connection structure is close to the surface of the waveguide transmission area and is a convex arc surface.

5. The end coupler according to claim 1, characterized in that: The end face coupler is made of thin film lithium niobate.

6. The end coupler according to claim 1, characterized in that: The length of the end face coupler is 50um to 1000um; wherein the length of the mode field transition zone is 30um to 800um.

7. A method for preparing an end coupler, characterized in that: The preparation method comprises: providing a substrate; Photolithography and etching are performed on the substrate to form a waveguide transmission region, a mode field transition region and a coupling region; wherein the widths of the coupling region, the mode field transition region and the waveguide transmission region decrease in sequence; the first end of the mode field transition region is connected to the coupling region; the second end of the mode field transition region is connected to the waveguide transmission region; and the surface of the second end of the mode field transition region is an arc surface.

8. The method for preparing an end coupler according to claim 7, characterized in that: Performing photolithography and etching on the substrate, comprising: A first photolithography and a first etching are performed on the substrate to form the waveguide transmission region and a first connection structure; wherein the first connection structure is tapered and the connection angle is rounded; a thinner end of the first connection structure is connected to the waveguide transmission region, and a thicker end of the first connection structure is connected to the mode field transition region.

9. The method for preparing an end coupler according to claim 8, characterized in that: Performing photolithography and etching on the substrate, further comprising: A second photolithography and a second etching are performed on the substrate to form the coupling region and a second connection structure; wherein the second connection structure is annular and surrounds the first connection structure; and the second connection structure is close to the surface of the waveguide transmission region and is a convex arc surface.

10. A photonic chip, characterized in that: The photonic chip comprises the end coupler according to any one of claims 1 to 6.

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