Bending waveguide directional coupler with adjustable splitting ratio

Abstract

This application relates to a bend waveguide directional coupler with adjustable splitting ratio and a design method, including: a first waveguide, a second waveguide, a substrate, and an isolation layer; the isolation layer is disposed between the first waveguide and the second waveguide; the minimum waveguide center distance between the first waveguide and the second waveguide is less than the coupling mode distance; the coupling mode distance is the minimum distance for coupling between waveguides; the isolation layer is provided with an accommodation cavity for storing a tuning medium, and the tuning medium is used to adjust the coupling degree between waveguides. When the directional coupler provided in this application is produced, the coupling intensity can be selected according to the combination number of the strong coupling region and the weak coupling region, and the splitting ratio of the coupler can be adjusted.

Description

Technical Field

[0001] This application relates to the field of optical communication technologies, and particularly to a bent waveguide directional coupler with adjustable splitting ratio. Background Art

[0002] As an indispensable device in optical communication, a directional coupler can output optical wave energy from different ports according to a certain ratio. Therefore, a directional coupler is the core part of many integrated optoelectronic devices, such as electro-optic modulators, wavelength division multiplexers, optical switches, rotators, and resonators.

[0003] Among them, a waveguide-type directional coupler is composed of two or more adjacent waveguides, and these waveguides realize the transmission of optical signals through the mutual coupling of optical modes. In a waveguide-type directional coupler, the optical mode of the main waveguide is coupled into the secondary waveguide, so that the optical mode input from the main waveguide is output at the output ends of the main waveguide and the secondary waveguide, and the coupling strength of the optical mode also determines the splitting ratio.

[0004] The coupling strength of the optical mode is related to the interval between adjacent waveguides, the waveguide refractive index, and the cladding material, etc. Therefore, when designing a waveguide-type directional coupler, it is necessary to test and select the waveguide interval, waveguide refractive index, and material.

[0005] In actual production, there are process errors in waveguide-type directional couplers, resulting in the coupling strength of the produced waveguide-type directional couplers not being completely controllable. Therefore, waveguide-type directional couplers are currently still affected by a low yield rate and cannot be actually mass-produced.

[0006] In order to make the coupling strength of the waveguide-type directional coupler meet the design requirements and improve the yield rate, this application provides a bent waveguide directional coupler with adjustable splitting ratio and a design method. Summary of the Invention

[0007] To overcome the problems existing in the related art, a first aspect of this application provides a bent waveguide directional coupler with adjustable splitting ratio, including: a first waveguide, a second waveguide, a substrate, and an isolation layer;

[0008] The first waveguide and the second waveguide are etched and formed on the substrate, and the isolation layer is disposed between the first waveguide and the second waveguide;

[0009] The first waveguide and the second waveguide are arranged in parallel, and two coupling regions are formed according to the interval size between the first waveguide and the second waveguide: a strong coupling region and a weak coupling region;

[0010] The isolation layer is provided with an accommodation cavity for storing a tuning medium, and the tuning medium is used to adjust the coupling degree between the waveguides.

[0011] In one embodiment, it includes: the first waveguide and the second waveguide are curved waveguide structures, and the first waveguide and the second waveguide are symmetric along the optical wave transmission direction.

[0012] In one embodiment, N strong coupling regions and M weak coupling regions are arranged between the first waveguide and the second waveguide; the waveguide spacing in the strong coupling region is smaller than the waveguide spacing in the weak coupling region.

[0013] In one embodiment, the accommodation cavity is arranged in the strong coupling region, and the tuning medium is liquid crystal.

[0014] In one embodiment, the first waveguide includes a first input end and a first output end, and the second waveguide includes a second output end;

[0015] The first input end is connected to an external straight waveguide for optical wave input, and the first output end and the second output end are used for optical wave output.

[0016] In one embodiment, the curved directional coupler is on a thin film lithium niobate platform, and the thickness of the thin film lithium niobate is 200 - 600 nm.

[0017] The second aspect of the present application provides a design method for a tunable splitting ratio curved waveguide directional coupler, including:

[0018] S1. Obtain the structural parameters of each curved waveguide coupler;

[0019] S2. Construct a coupler simulation model according to the structural parameters;

[0020] S3. Perform coupling simulation on the curved waveguide coupler model to obtain the interval coupling strength; the interval coupling strength is the coupling strength value of the differential interval along the optical wave transmission direction.

[0021] S4. Determine the coupling interval length according to the interval coupling strength and the preset splitting ratio.

[0022] In one embodiment, performing coupling simulation on the curved waveguide coupler model to obtain the interval coupling strength specifically includes:

[0023] Calculate the interval coupling length according to the calculation formula of the interval coupling strength; the interval coupling strength calculation formula is:

[0024]

[0025] Among them, is the interval coupling strength, L is the coupling interval length, represents the incident light wavelength, represents the cladding refractive index, is the normalized frequency, and d is the coupling interval.

[0026] The technical solution provided by this application may include the following beneficial effects:

[0027] In the directional coupler provided by this application, the first waveguide and the second waveguide are symmetric and both are curved waveguide structures. A strong coupling region is formed in the region where the waveguide interval between the first waveguide and the second waveguide is the smallest, and a weak coupling region is formed in the region where the waveguide interval is large. When manufacturing the coupler, the coupling strength is selected according to the combination number of the strong coupling region and the weak coupling region, and the coupler is re-etched and processed to adjust the number of coupling regions, so as to design a coupler that meets the splitting ratio.

[0028] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Description of the Drawings

[0029] By describing the exemplary embodiments of this application in more detail in conjunction with the drawings, the above and other objects, features, and advantages of this application will become more obvious. Among them, in the exemplary embodiments of this application, the same reference numerals generally represent the same components.

[0030] Figure 1 is a schematic structural diagram of the curved waveguide directional coupler shown in the embodiment of this application;

[0031] Figure 2 is a schematic flow diagram of the design method of the curved waveguide directional coupler shown in the embodiment of this application;

[0032] Explanation of the reference numerals in the drawings: the first waveguide 1, the first input end 11, the first output end 12, the second waveguide 2, the second output end 21, and the isolation layer 3. Detailed Embodiments

[0033] The following will describe the preferred embodiments of this application in more detail with reference to the drawings. Although the preferred embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make this application more thorough and complete, and to be able to fully convey the scope of this application to those skilled in the art.

[0034] The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "the", and "said" used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0035] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality" means two or more unless otherwise specifically defined.

[0036] Embodiment 1

[0037] In actual production, there are process errors in waveguide-type directional couplers, resulting in the coupling strength of the produced waveguide-type directional couplers not being completely controllable. Therefore, waveguide-type directional couplers are currently still affected by a low yield rate and cannot be actually mass-produced.

[0038] In order to make the coupling strength of the waveguide-type directional coupler meet the design requirements and improve the yield rate, an embodiment of this application provides a bent waveguide directional coupler with an adjustable splitting ratio.

[0039] As Figure 1 shown, a bent waveguide directional coupler with an adjustable splitting ratio includes: a first waveguide 1, a second waveguide 2, a substrate, and an isolation layer 3.

[0040] Specifically, the first waveguide 1 and the second waveguide 2 are etched and formed on the substrate, and the isolation layer 3 is disposed between the first waveguide 1 and the second waveguide 2.

[0041] Furthermore, the minimum waveguide center distance between the first waveguide 1 and the second waveguide 2 is less than the coupling mode distance. The coupling mode distance is the minimum distance for coupling between waveguides.

[0042] The first waveguide 1 and the second waveguide 2 are of a bent waveguide structure, and the first waveguide 1 and the second waveguide 2 are symmetric along the optical wave transmission direction.

[0043] In the embodiment of this application, the first waveguide 1 includes a first input end 11 and a first output end 12, and the second waveguide 2 includes a second output end 21; the first input end 11 is connected to an external straight waveguide for optical wave input, and the first output end 12 and the second output end 21 are for optical wave output.

[0044] Wherein, N strong coupling regions and M weak coupling regions are provided between the first waveguide 1 and the second waveguide 2. The waveguide spacing in the strong coupling regions is greater than the waveguide spacing in the weak coupling regions.

[0045] In the embodiment of the present application, since the first waveguide 1 and the second waveguide 2 are symmetric and both are bent waveguide structures.

[0046] Therefore, a strong coupling region is formed in the region where the waveguide spacing between the first waveguide 1 and the second waveguide 2 is the smallest, and a weak coupling region is formed in the region where the waveguide spacing is large. When manufacturing the coupler, the coupling strength is selected according to the combination number of the strong coupling region and the weak coupling region, and the splitting ratio of the coupler is adjusted.

[0047] In order to further adjust the splitting ratio of the coupler, in the coupler, the isolation layer 3 is provided with a cavity for storing a tuning medium, and the tuning medium is used to adjust the coupling degree between the waveguides.

[0048] Specifically, the cavity is arranged in the strong coupling region, and the tuning medium is liquid crystal.

[0049] In the embodiment of the present application, the refractive index of the liquid crystal is controlled by voltage, the coupling strength between the two waveguides in the strong coupling region is changed, and thus the splitting ratio of the coupler is adjusted again.

[0050] Embodiment Two

[0051] Based on Embodiment One, the embodiment of the present application provides a design method for a tunable splitting ratio bent waveguide directional coupler, including:

[0052] S1. Obtain the structural parameters of each bent waveguide coupler;

[0053] S2. Construct a coupler simulation model according to the structural parameters;

[0054] S3. Perform coupling simulation on the bent waveguide coupler model to obtain the interval coupling strength; the interval coupling strength is the coupling strength value of the differential interval along the optical wave transmission direction;

[0055] Specifically, the calculation formula for the interval coupling strength is:

[0056]

[0057] Wherein, is the interval coupling strength, L is the coupling interval length, represents the incident light wavelength, represents the cladding refractive index, is the normalized frequency, and d is the coupling interval.

[0058] In the embodiment of the present application, the interval coupling strength is a preset parameter, and the preset interval coupling strength is substituted into the above calculation formula to solve the coupling interval length.

[0059] It can be understood that It is a parameter describing the characteristics of waveguide modes, related to the size and refractive index distribution of the waveguide, and obtained through experimental measurement.

[0060] S4. Determine the coupling interval length according to the interval coupling strength and the preset splitting ratio.

[0061] In the embodiments of the present application, by inputting a preset interval coupling strength, the value of the coupling interval length is calculated, and the number of coupling zone combinations of the directional coupler is determined according to the coupling interval length.

[0062] In order to avoid the defect that the directional coupler cannot reach the preset splitting ratio due to process errors. In the embodiments of the present application, a symmetric bent waveguide is designed for directional coupling, which has multiple strong coupling zones and weak coupling zones. After the directional coupler is etched, the structural parameters of each directional coupler are measured, and then the coupling interval length is determined according to the interval coupling strength, and then the etched directional coupler is etched again.

[0063] The solution of the present application has been described in detail above with reference to the accompanying drawings. In the above embodiments, the descriptions of the various embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments. Those skilled in the art should also know that the actions and modules involved in the specification are not necessarily essential to the present application.

[0064] In addition, it can be understood that the steps in the method embodiments of the present application can be adjusted, combined, and deleted according to actual needs, and the modules in the device embodiments of the present application can be combined, divided, and deleted according to actual needs.

[0065] Those skilled in the art will also understand that the various exemplary logical blocks, modules, circuits, and algorithm steps described in connection with the applications herein can be implemented as electronic hardware, computer software, or a combination of both.

[0066] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of the present application. In this regard, each block in the flowchart or block diagram may represent a module, a segment of a program, or a portion of code, which contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than that marked in the accompanying drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, as well as combinations of blocks in the block diagram and / or flowchart, may be implemented by a dedicated hardware-based system that performs the specified functions or operations, or may be implemented by a combination of dedicated hardware and computer instructions.

[0067] The embodiments of the present application have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application, or the improvement of the technology in the market, or to enable other ordinary skill in the technical field to understand the embodiments disclosed herein.

Claims

1. An adjustable splitting ratio bent waveguide directional coupler, characterized in that, Including: A first waveguide, a second waveguide, a substrate, and an isolation layer; The first waveguide and the second waveguide are etched and formed on the substrate, and the isolation layer is disposed between the first waveguide and the second waveguide; The first waveguide and the second waveguide are arranged in parallel, and two coupling regions are formed according to the interval size between the first waveguide and the second waveguide: a strong coupling region and a weak coupling region; The isolation layer is provided with an accommodation cavity for storing a tuning medium, and the tuning medium is used to adjust the coupling degree between the waveguides; The first waveguide and the second waveguide are curved waveguide structures, and the first waveguide and the second waveguide are symmetric along the optical wave transmission direction; A strong coupling region and a weak coupling region are provided between the first waveguide and the second waveguide; The waveguide spacing in the strong coupling region is smaller than the waveguide spacing in the weak coupling region; The accommodation cavity is disposed in the strong coupling region, and the tuning medium is liquid crystal; Both ends of the liquid crystal are metal electrodes, and the metal electrodes are used to change the polarization direction of the liquid crystal.

2. The adjustable splitting ratio bent waveguide directional coupler according to claim 1, wherein The first waveguide includes a first input end and a first output end, and the second waveguide includes a second output end; The first input end is connected to an external straight waveguide for optical wave input, and the first output end and the second output end are used for optical wave output.

3. The bend waveguide directional coupler with adjustable splitting ratio according to claim 2, characterized in that, The curved waveguide directional coupler is on a thin film lithium niobate platform, and the thickness of the thin film lithium niobate is 200 - 600 nm.

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