Double-gradient waveguide vertical space optical coupler

Abstract

The invention discloses a double-gradient waveguide vertical space optical coupler, and belongs to the technical field of photonic integrated chips. The filter comprises a bus waveguide and a coupling waveguide, and can be divided into an input area, a coupling area and a transition output area in the transmission direction according to functions. The widths of the bus waveguide and the coupling waveguide change reversely in the coupling area, so that the coupling mode is closer to the transmission mode of the input / output end, the loss is reduced, the coupling ratio is improved, the coupling length is reduced, and the bandwidth is increased. The spatial optical coupler is simple in structure, compact in size, suitable for optical waveguide devices made of various materials and beneficial to large-scale preparation and integration.

Description

Technical Field

[0001] The invention relates to a double-gradient waveguide vertical space optical coupler, belonging to the technical field of photon integrated chips. Background Art

[0002] In recent years, with the explosive growth of information in modern society, information processing and transmission are facing the challenges of large capacity and high speed. Photonic integrated chips use photons as information carriers and are compatible with mature CMOS processes. Compared with electronic chips, they have great advantages in speed, energy consumption and cost, and have been widely used in data centers, optical computing, optical communications and other fields.

[0003] The function of the spatial optical coupler in the photonic integrated chip is to control the transmission of light between different waveguide layers. It is commonly used in chips such as on-chip lasers and on-chip amplifiers that require multiple waveguide layers. Due to the limitations of the switching function and the minimum line width of the process, the spatial optical coupler used in the optical switch array chip needs to ensure that the bus waveguide is turned on at the output end, that is, it cannot be cut off; at the same time, the minimum width of the tip of the coupling waveguide is limited and cannot be too small. Therefore, in order to achieve a higher coupling efficiency, the current spatial optical coupler generally has a structure in which the bus waveguide width remains unchanged and the coupling waveguide width gradually increases from a smaller value.

[0004] In order to ensure high coupling efficiency and prevent the coupling process from exciting high-order modes, the width of the coupling waveguide should change as slowly as possible, that is, the length of the gradient region should not be too short. This limits the further reduction of the size of spatial optical coupling devices and the improvement of the integration of large-scale optical switch chips. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a dual-gradient waveguide vertical space optical coupler to solve the problem that in order to ensure a high coupling efficiency and not to excite high-order modes during the coupling process, the width of the coupling waveguide should change as slowly as possible, which limits the further reduction of the size of the space optical coupling device and the integration of large-scale optical switch chips. In order to achieve the above purpose / solve the above technical problems, the present invention is implemented by adopting the following technical solutions: A double gradient waveguide vertical space optical coupler, comprising a bus waveguide and a coupling waveguide; The bus waveguide has an input port at one end as an input region, and an output port at the other end. The coupling waveguide has a coupling port. The output port of the bus waveguide and the coupling port of the coupling waveguide serve as an output region, and the overlapping portion of the output port and the coupling port of the coupling waveguide serve as a coupling region. The coupling waveguide is arranged above the bus waveguide. In the on state, the distance between the bus waveguide and the coupling waveguide in the coupling area is the minimum fixed value, and the distance between the bus waveguide and the coupling waveguide in the output area gradually increases, and the waveguide width remains unchanged; In the closed state, the bus waveguide and the coupling waveguide in the coupling region are far away from each other, and light is only transmitted in the bus waveguide, realizing the 1×2 port optical switch function.

[0006] Optionally, in the input region, the bus waveguide width gradually increases.

[0007] Optionally, in the coupling region, the bus waveguide width gradually decreases and the coupling waveguide width gradually increases.

[0008] Optionally, types of the bus waveguide and the coupling waveguide include strip waveguide and ridge waveguide, wherein the waveguide width of the ridge waveguide refers to the ridge width.

[0009] Optionally, the ridge silicon waveguide is made of insulating silicon dioxide material, and the material refractive index of silicon dioxide is 3.47638.

[0010] Optionally, the silicon dioxide substrate has a thickness of 3 μm, a refractive index of silicon dioxide of 1.444, and an air sheath with a refractive index of 1 is formed on the silicon dioxide layer.

[0011] Optionally, the bus waveguide is a shallow etched ridge waveguide with a waveguide thickness of 220 nm, an etching depth of 60 nm, an input region ridge width of 600 nm, a coupling region ridge width of 1000 nm, and an output region ridge width of 600 nm.

[0012] Optionally, the coupling waveguide is a deep etched ridge waveguide with a waveguide thickness of 300nm, an etching depth of 200nm, a ridge width of 150nm in the coupling area, a ridge width of 1000nm in the output area, a waveguide length of 23μm, an upper and lower waveguide spacing of 130nm in the coupling area in the open state, and a waveguide spacing of 1000nm in the closed state.

[0013] Compared with the prior art, the present invention has the following beneficial effects: the device structure of the present invention is composed of a bus waveguide and a coupling waveguide, which can be divided into an input region, a coupling region and a transition output region according to the function in the transmission direction. In the coupling region, the widths of the bus waveguide and the coupling waveguide change in opposite directions, making the coupling mode closer to the transmission mode at the input and output ends, reducing the loss, improving the coupling ratio, and reducing the coupling length and increasing the bandwidth. The spatial optical coupler has a simple structure and compact size, is suitable for optical waveguide devices of various materials, and is conducive to large-scale preparation and integration; The present invention realizes the 1×2 port optical switch function, meets the functional and performance requirements of large-scale optical switch array chips for single optical switch functional devices, and due to the structural optimization, the device size is significantly reduced, which helps to improve the integration of large-array optical switch array chips. At the same time, compared with traditional structure space couplers, the wavelength bandwidth of coupling efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The figure shows a schematic diagram of the structure of the double gradient waveguide vertical space optical coupler of the present invention; Figure 2 Shown is a three-dimensional schematic diagram of the coupling region of the dual gradient waveguide vertical spatial optical coupler of the present invention.

[0015] In the figure: 1. Bus waveguide; 2. Coupled waveguide. DETAILED DESCRIPTION

[0016] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0017] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0018] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0019] The present invention proposes a dual-gradient waveguide vertical space optical coupler. In the on state, the bus waveguide and the coupling waveguide in the coupling area are close to each other, and almost all the light in the bus waveguide is coupled to the coupling waveguide. In the off state, the bus waveguide and the coupling waveguide in the coupling area are far away from each other, and the light is only transmitted in the bus waveguide, realizing the 1×2 port optical switch function, meeting the function and performance requirements of a large-scale optical switch array chip for a single optical switch function device, and due to the structural optimization, the device size is significantly reduced, which is helpful to improve the integration of a large array optical switch array chip, and at the same time, compared with the traditional structure space coupler, the wavelength bandwidth of the coupling efficiency is improved.

[0020] Specifically, it comprises a bus waveguide 1 and a coupling waveguide 2. The bus waveguide is provided with an input port at one end as an input region, and an output port at the other end. The coupling waveguide is provided with a coupling port. The output port of the bus waveguide and the coupling port of the coupling waveguide serve as an output region, and the overlapping portion of the two is a coupling region. The coupling waveguide is provided above the bus waveguide. In the on state, the distance between the bus waveguide and the coupling waveguide in the coupling area is the minimum fixed value, and the distance between the bus waveguide and the coupling waveguide in the output area gradually increases, and the waveguide width remains unchanged; In the closed state, the bus waveguide and the coupling waveguide in the coupling region are far away from each other, and light is only transmitted in the bus waveguide, realizing the 1×2 port optical switch function.

[0021] like Figure 1 As shown, the dark waveguide is the bus waveguide and the light waveguide is the coupling waveguide. For the sake of convenience, the waveguide width direction is defined as the x-axis, the height direction is defined as the y-axis, the light transmission direction in the waveguide is defined as the z-axis, the bus waveguide is located in the lower layer in the y-direction, and the coupling waveguide is located in the upper layer. Positions 1 to 2 in the z-direction are the input area, with only the bus waveguide, and the bus waveguide width gradually increases; positions 2 to 3 are the coupling area, with the bus waveguide width gradually decreasing and the coupling waveguide width gradually increasing. In the on state, the distance between the bus waveguide and the coupling waveguide in the coupling area is a small fixed value; positions 3 to 4 are the transition and output areas, and in the on state, the distance between the bus waveguide and the coupling waveguide in this area gradually increases, and the waveguide width remains unchanged.

[0022] The core area of ​​the present invention is the coupling area, and the three-dimensional schematic diagram of the coupling area is as follows: Figure 2 As shown in the figure, the widths of the bus waveguide and the coupling waveguide in this region change in opposite trends, which can accelerate the adiabatic coupling effect. In the design, it is necessary to optimize the bus waveguide and coupling waveguide parameters in the coupling region, including waveguide type, waveguide material and refractive index, waveguide width and coupling length, so as to achieve the design goal of high coupling efficiency with a shorter coupling length.

[0023] In the specific implementation process of this embodiment: A ridge silicon waveguide made of silicon on insulator (SOI) material is selected. The material refractive index of silicon is 3.47638, the thickness of the silicon dioxide substrate is 3 μm, the refractive index of silicon dioxide is 1.444, and there is an air cladding on the silicon dioxide layer, and the refractive index of air is 1.

[0024] The specific parameters of the double gradient waveguide vertical coupler are as follows: the lower bus waveguide is a shallow etched ridge waveguide with a waveguide thickness of 220nm, an etching depth of 60nm, a ridge width of 600nm at position 1, a ridge width of 1000nm at position 2, and a ridge width of 600nm at positions 3-4; the upper coupling waveguide is a deep etched ridge waveguide with a waveguide thickness of 300nm, an etching depth of 200nm, a ridge width of 150nm at position 2, and a ridge width of 1000nm at positions 3-4. The length of the coupling region, i.e., 2-3, is 23μm. When the coupling region is in the on state, the upper and lower waveguides are spaced 130nm apart, and when it is in the off state, the waveguide spacing is 1000nm.

[0025] The coupling function is realized in the following way: based on the finite element simulation of the waveguide cross-sections at different positions of the double-gradient waveguide vertical spatial optical coupler, the normalized light field distribution at different positions is obtained. The closer the color is to white, the higher the light field intensity is, and the closer it is to black, the lower the light field intensity is. Figure 1 It means that since there is no coupling waveguide in the input region, the light field is only concentrated in the bus waveguide, that is, the light is stably transmitted in the bus waveguide; Figure 2 It means that at the beginning of the coupling area, the coupling waveguide and the bus waveguide are close to each other, resulting in coupling, which stimulates a coupling mode in which the light field is distributed in the two waveguides. However, since the width of the coupling waveguide is extremely small at this position, most of the light field is concentrated in the bus waveguide. As the width of the coupling waveguide gradually increases and becomes larger than the width of the bus waveguide, the light field is concentrated in the coupling waveguide, and the light is coupled from the bus waveguide to the coupling waveguide. After the waveguide spacing gradually increases, the coupling waveguide moves away from the bus waveguide, and the light field is completely concentrated in the coupling waveguide, indicating that in the on state, light enters the spatial optical coupler from the input end, and light is output only at the coupling end.

[0026] Since the width of the coupling waveguide is small, the influence on the coupling mode light field is weak, so the mode mismatch between the coupling mode and the transmission mode of the adjacent input region is small, and the device loss is low.

[0027] After the waveguide spacing in the transition output region changes slowly, the coupling mode slowly transitions to the output mode, further improving the coupling ratio and reducing device loss.

[0028] The finite time-domain difference method is used to perform three-dimensional simulation of the double gradient waveguide vertical spatial optical coupler under the above parameters. The simulation wavelength is set to a wide spectrum range of 1.4μm-1.7μm. A fundamental mode light source is input at the input end of the bus waveguide, and the light transmittance output from the coupled end of the coupled waveguide is monitored, that is, the coupling ratio. As shown in the figure, according to the simulation results, the coupling ratio of the device is greater than 98% in the wavelength range of 1.44-1.64μm, while achieving a compact device structure, high coupling ratio and large bandwidth.

[0029] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A dual gradient waveguide vertical spatial optical coupler, characterized in that: Including bus waveguide and coupled waveguide; The bus waveguide has an input port at one end as an input region, and an output port at the other end. The coupling waveguide has a coupling port. The output port of the bus waveguide and the coupling port of the coupling waveguide serve as an output region, and the overlapping portion of the output port and the coupling port of the coupling waveguide serve as a coupling region. The coupling waveguide is arranged above the bus waveguide. In the on state, the distance between the bus waveguide and the coupling waveguide in the coupling area is the minimum fixed value, and the distance between the bus waveguide and the coupling waveguide in the output area gradually increases, and the waveguide width remains unchanged; In the closed state, the bus waveguide and the coupling waveguide in the coupling region are far away from each other, and light is only transmitted in the bus waveguide, realizing the 1×2 port optical switch function.

2. The dual gradient waveguide vertical spatial optical coupler according to claim 1, characterized in that: In the input region, the bus waveguide width gradually increases.

3. The dual gradient waveguide vertical spatial optical coupler according to claim 1, characterized in that: In the coupling region, the bus waveguide width gradually decreases and the coupling waveguide width gradually increases.

4. The dual gradient waveguide vertical spatial optical coupler according to claim 1, characterized in that: The types of the bus waveguide and the coupling waveguide include strip waveguide and ridge waveguide, wherein the waveguide width of the ridge waveguide refers to the ridge width.

5. The dual gradient waveguide vertical spatial optical coupler according to claim 4, characterized in that: The ridge silicon waveguide is made of insulating silicon dioxide material, and the material refractive index of silicon dioxide is 3.47638.

6. The dual gradient waveguide vertical spatial optical coupler according to claim 5, characterized in that: The silicon dioxide substrate has a thickness of 3 μm, a refractive index of silicon dioxide of 1.444, and an air envelope with a refractive index of 1 is formed on the silicon dioxide layer.

7. The dual gradient waveguide vertical spatial optical coupler according to claim 1, characterized in that: The bus waveguide is a shallow etched ridge waveguide with a waveguide thickness of 220nm, an etching depth of 60nm, a ridge width of 600nm in the input region, a ridge width of 1000nm in the coupling region, and a ridge width of 600nm in the output region.

8. The dual gradient waveguide vertical spatial optical coupler according to claim 1, characterized in that: The coupling waveguide is a deep etched ridge waveguide with a waveguide thickness of 300nm, an etching depth of 200nm, a ridge width of 150nm in the coupling area, a ridge width of 1000nm in the output area, a waveguide length of 23μm, an upper and lower waveguide spacing of 130nm in the coupling area in the open state, and a waveguide spacing of 1000nm in the closed state.

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