Bent waveguide directional coupler with adjustable splitting ratio and design method

Abstract

The invention relates to a bending waveguide directional coupler with an adjustable splitting ratio and a design method. The bending waveguide directional coupler comprises a first waveguide, a second waveguide, a substrate and an isolation layer, the isolation layer is arranged between the first waveguide and the second waveguide; the minimum waveguide center distance between the first waveguide and the second waveguide is smaller than the coupling mode distance. The coupling mode distance is the minimum distance for coupling between waveguides; the isolation layer is provided with an accommodating cavity for storing a tuning medium, and the tuning medium is used for adjusting the coupling degree between the waveguides. When the directional coupler provided by the invention is produced, the coupling strength can be selected according to the combination number of the strong coupling regions and the weak coupling regions, and the splitting ratio of the coupler is adjusted.

Description

Technical Field

[0001] The present application relates to the field of optical communication technology, and in particular to a bent waveguide directional coupler with adjustable splitting ratio and a design method thereof. Background Art

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

[0003] Among them, the waveguide type directional coupler is composed of two or more adjacent waveguides, which realize the transmission of optical signals through the mutual coupling of optical modes. In the waveguide type directional coupler, the optical mode of the main waveguide is coupled to the slave waveguide, so that the optical mode input to the main waveguide is output at the output end of the main waveguide and the slave 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 spacing between adjacent waveguides, the waveguide refractive index, and the cladding material. Therefore, when designing a waveguide directional coupler, it is necessary to test and select the waveguide spacing, waveguide refractive index, and material.

[0005] In actual production, waveguide directional couplers have process errors, which result in the coupling strength of the produced waveguide directional couplers not being fully controllable. Therefore, waveguide directional couplers are currently still subject to the influence of low yield 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, the present application provides a curved waveguide directional coupler with adjustable splitting ratio and a design method. Summary of the invention

[0007] In order to overcome the problems existing in the related art, the first aspect of the present application provides a bent waveguide directional coupler with adjustable splitting ratio, comprising: 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 arranged 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 between the first waveguide and the second waveguide: a strong coupling region and a weak coupling region;

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

[0011] In one embodiment, the first waveguide and the second waveguide are curved waveguide structures, and the first waveguide and the second waveguide are symmetrical along a light 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; and the waveguide spacing in the strong coupling region is smaller than the waveguide spacing in the weak coupling region.

[0013] In one embodiment, the accommodating 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 light wave input, and the first output end and the second output end are used for light 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] A second aspect of the present application provides a method for designing a bent waveguide directional coupler with an adjustable splitting ratio, comprising:

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

[0019] S2, constructing a coupler simulation model according to the structural parameters;

[0020] S3. Perform coupling simulation on the curved waveguide coupler model to obtain interval coupling strength; the interval coupling strength is the coupling strength value between micro-regions along the light wave transmission direction.

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

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

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

[0024]

[0025] Where R is the coupling strength of the interval, L is the length of the coupling interval, λ is the wavelength of the incident light, n2 is the refractive index of the cladding, V i is the normalized frequency, and d is the coupling interval.

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

[0027] The first waveguide and the second waveguide of the directional coupler provided by the present application are symmetrical 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 the coupler is produced, the coupling strength is selected according to the combined number of the strong coupling region and the weak coupling region, the coupler is re-etched, and the number of coupling regions is adjusted, so as to design a coupler that meets the splitting ratio.

[0028] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and other objects, features and advantages of the present application will become more apparent through a more detailed description of exemplary embodiments of the present application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present application.

[0030] Figure 1 It is a structural schematic diagram of a bent waveguide directional coupler shown in an embodiment of the present application;

[0031] Figure 2 A schematic diagram of a flow chart of a method for designing a curved waveguide directional coupler according to an embodiment of the present application;

[0032] Description of the accompanying drawings: first waveguide 1 , first input end 11 , first output end 12 , second waveguide 2 , second output end 21 , isolation layer 3 . DETAILED DESCRIPTION

[0033] The preferred embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the preferred 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 embodiments described herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0034] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application 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 herein refers to and includes any or all possible combinations of one or more 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, this 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 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, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0036] Embodiment 1

[0037] In actual production, waveguide directional couplers have process errors, which result in the coupling strength of the produced waveguide directional couplers not being fully controllable. Therefore, waveguide directional couplers are currently still subject to the influence of low yield 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, the embodiment of the present application provides a bent waveguide directional coupler with an adjustable splitting ratio.

[0039] like Figure 1 As shown, a bent waveguide directional coupler with 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 arranged 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 curved waveguide structures, and the first waveguide 1 and the second waveguide 2 are symmetrical along the light wave transmission direction.

[0043] In the embodiment of the present 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 light wave input, and the first output end 12 and the second output end 21 are used for light wave output.

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

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

[0046] Therefore, a strong coupling region is formed in the region where the waveguide interval is the smallest between the first waveguide 1 and the second waveguide 2, and a weak coupling region is formed in the region where the waveguide interval is large. When the coupler is produced, the coupling strength is selected according to the number of combinations 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 receiving cavity for storing a tuning medium, and the tuning medium is used to adjust the coupling degree between the waveguides.

[0048] Specifically, the accommodating 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 to change the coupling strength between the two waveguides in the strong coupling region, thereby adjusting the splitting ratio of the coupler.

[0050] Embodiment 2

[0051] Based on the first embodiment, the present application provides a method for designing a bent waveguide directional coupler with an adjustable splitting ratio, including:

[0052] S1. Obtaining structural parameters of each curved waveguide coupler;

[0053] S2, constructing a coupler simulation model according to the structural parameters;

[0054] S3, performing coupling simulation on the curved waveguide coupler model to obtain the interval coupling strength; the interval coupling strength is the coupling strength value between the micro-regions along the light wave transmission direction;

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

[0056]

[0057] Where R is the coupling strength of the interval, L is the length of the coupling interval, λ is the wavelength of the incident light, n2 is the refractive index of the cladding, V i 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] Understandably, V i It is a parameter that describes the characteristics of the waveguide mode, which is related to the size and refractive index distribution of the waveguide and is obtained through experimental measurement.

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

[0061] In the embodiment of the present application, a preset interval coupling strength is input to calculate the value of the coupling interval length, 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 achieve the preset splitting ratio due to process errors. The embodiment of the present application performs directional coupling by designing a symmetrical curved waveguide, which has multiple strong coupling regions and weak coupling regions. After the directional coupler is etched, the structural parameters of each directional coupler are measured, and then the length of the coupling interval is determined according to the interval coupling strength, and then the directional coupler that has been etched is re-etched.

[0063] The scheme of the present application has been described in detail above with reference to the accompanying drawings. 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, please refer to the relevant description of other embodiments. Those skilled in the art should also be aware that the actions and modules involved in the description are not necessarily required for the present application.

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

[0065] Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the application herein may be implemented as electronic hardware, computer software, or combinations of both.

[0066] The flow chart and block diagram in the accompanying drawings show the possible architecture, function and operation of the system and method according to multiple embodiments of the present application. In this regard, each square box in the flow chart or block diagram can represent a part of a module, a program segment or a code, and the part of the module, the program segment or the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the square box can also occur in a sequence different from that marked in the accompanying drawings. For example, two continuous square boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each square box in the block diagram and / or the flow chart, and the combination of the square boxes in the block diagram and / or the flow chart can be implemented with a dedicated hardware-based system that performs the specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0067] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A curved waveguide directional coupler with adjustable splitting ratio, characterized in that: include: 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 arranged 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 between the first waveguide and the second waveguide: a strong coupling region and a weak coupling region; The isolation layer is provided with a receiving cavity for storing a tuning medium, and the tuning medium is used to adjust the coupling degree between the waveguides.

2. The bent waveguide directional coupler with adjustable splitting ratio according to claim 1, characterized in that: include: The first waveguide and the second waveguide are bent waveguide structures, and the first waveguide and the second waveguide are symmetrical along a light wave transmission direction.

3. The bent waveguide directional coupler with adjustable splitting ratio according to claim 2, characterized in that: 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.

4. The bent waveguide directional coupler with adjustable splitting ratio according to claim 3, characterized in that: The accommodating cavity is arranged in the strong coupling region, and the tuning medium is liquid crystal; The two ends of the liquid crystal are metal electrodes, and the metal motor is used to change the polarization direction of the liquid crystal.

5. The bent waveguide directional coupler with adjustable splitting ratio according to claim 4, characterized in that: 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 light wave input, and the first output end and the second output end are used for light wave output.

6. The bent waveguide directional coupler with adjustable splitting ratio according to claim 5, characterized in that: The bent directional coupler is on a thin-film lithium niobate platform, and the thickness of the thin-film lithium niobate is between 200 and 600 nm.

7. A method for designing a curved waveguide directional coupler with adjustable splitting ratio, characterized in that: A method for designing a bent waveguide directional coupler according to any one of claims 1 to 6, comprising: S1. Obtaining structural parameters of each curved waveguide coupler; S2, constructing a coupler simulation model according to the structural parameters; S3, performing coupling simulation on the curved waveguide coupler model to obtain the interval coupling strength; the interval coupling strength is the coupling strength value between the micro-regions along the light wave transmission direction; S4. Determine the length of the coupling interval according to the interval coupling strength and the preset splitting ratio.

8. The method for designing a bent waveguide directional coupler with adjustable splitting ratio according to claim 7, characterized in that: The bending waveguide coupler model is subjected to coupling simulation to obtain the interval coupling strength, specifically including: The interval coupling length is calculated according to the calculation formula of the interval coupling strength; the calculation formula of the interval coupling strength is: Where R is the coupling strength of the interval, L is the length of the coupling interval, λ is the wavelength of the incident light, n2 is the refractive index of the cladding, V i is the normalized frequency, and d is the coupling interval.

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