CN114019606B - Small broadband mode conversion device - Google Patents
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- CN114019606B CN114019606B CN202210010395.8A CN202210010395A CN114019606B CN 114019606 B CN114019606 B CN 114019606B CN 202210010395 A CN202210010395 A CN 202210010395A CN 114019606 B CN114019606 B CN 114019606B
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
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Abstract
The invention discloses a small broadband mode conversion device. The optical waveguide comprises a substrate, a signal input waveguide, a signal output waveguide and a mode conversion region; the signal input waveguide, the signal output waveguide and the mode conversion region are all arranged on the substrate; the mode conversion region is connected between the signal input waveguide and the signal output waveguide through topology optimization reverse design; the signal of the TE0 mode is input through the input waveguide, and is converted into a TE1 mode signal to be output after passing through the mode conversion region. The invention carries out topological optimization reverse design on the device based on the companion source method, realizes the mode conversion function of the broadband, and solves the problems of large occupied area, unstable performance and narrow bandwidth in the traditional on-chip mode conversion device.
Description
Technical Field
The invention belongs to a broadband mode conversion device in the technical field of optical communication, and particularly relates to a small chalcogenide broadband mode conversion device based on topological optimization reverse design.
Background
In the past decades, with the progress of integrated photonics circuits, erbium-doped fiber amplifiers, and communication multiplexing technologies, the capacity of optical communication networks has been greatly increased, however, recent scientific research has confirmed that the transmission capacity of conventional single-mode fiber communication systems has been increasingly approaching its nonlinear shannon limit, and thus, in order to increase the capacity of communication systems and meet the needs of people for service bandwidth, the modular division multiplexing technology has emerged. The mode division multiplexing device can increase the capacity of the optical communication system by several times by multiplexing different modes in the communication system, but the mode division multiplexing does not separate the conversion of the modes. The traditional mode conversion device is mainly realized by a block optical device, an optical fiber and an optical waveguide, the devices need strict processing and arrangement, and simultaneously can introduce great insertion loss, and the traditional mode conversion device also has the defects of overlarge size, small working bandwidth, lack of flexibility in device functions and the like.
Most importantly, most designs are based on silicon-based photonic devices and work in the near infrared band, but besides silicon, chalcogenide materials are also one of important platforms for integrated photonics, limited by the transparent window of quartz fibers, the gain spectrum of erbium-doped fiber amplifiers and the CMOS process. Chalcogenide materials are compounds containing "chalcogenide elements" from group VI of the periodic Table of the elements, commonly referred to as S, Se and Te. Compared with silicon materials, the chalcogenide materials have important application values in optical communication, medical treatment and defense industries due to the characteristics of multiple photosensitivity, wide infrared window and high optical nonlinearity. Due to the appearance of broadband hollow fibers and thulium-doped fiber amplifiers, mid-infrared communication becomes a hot spot of current research, chalcogenide materials have a very wide transparent window in the mid-infrared, and the preparation of a sulfur-based photonic device is compatible with the current CMOS process, but for the sulfur-based photonic device, since the refractive index of chalcogenide glass is smaller than that of silicon, the device structure is larger than that of silicon, the increase of the operating wavelength also brings about the increase of the mode field area and more mode field leakage, which all make the sulfur-based photonic device challenging.
Disclosure of Invention
In order to solve the problems existing in the background art, an object of the embodiments of the present invention is to provide a compact chalcogenide broadband mode switching device based on topology optimization reverse design, so as to overcome the defects of the prior art.
The invention comprises a photonic device based on a chalcogenide medium to realize the function of transmitting a low-loss signal in a middle infrared band; the device is subjected to topological optimization reverse design based on a adjoint source method, so that broadband waveguide mode conversion of signals with the central wavelength of 2025nm is realized, mutual conversion from a TE0 mode to a TE1 mode is realized, and the blank of design of a chalcogenide mode conversion device is filled.
The technical scheme adopted by the invention comprises the following steps:
a substrate;
a signal input waveguide disposed on the substrate;
a signal output waveguide disposed on the substrate;
a mode conversion region disposed on the substrate, the mode conversion region being divided into cells and connected between the signal input waveguide and the signal output waveguide through a topology optimization reverse design; signals of a TE0 mode are input from the signal input waveguide, converted into TE1 mode signals after passing through the mode conversion region and output from the signal output waveguide; the signal of the TE1 mode is input through the signal output waveguide, is converted into a TE0 mode signal after passing through the mode conversion region, and is output from the signal input waveguide.
By "small" as used herein is meant less than 10 x 10 microns in size.
The "broadband" of the invention refers to the working bandwidth which is more than or equal to 100 nanometers.
The substrate is made of silicon dioxide.
The signal input waveguide and the signal output waveguide are made of chalcogenide glass materials. The chalcogenide material has the characteristics of multiple photosensitivities, wide infrared window and high optical nonlinearity, so that the device can work in an infrared band at low loss.
The mode conversion region is divided into n × n unit cuboids in a three-dimensional space, each unit cuboid having two possible material states, which are classified as air or chalcogenide glass materials.
The mode conversion area is optimized and determined through topology optimization reverse design by adopting the following specific method:
the following objective function is established according to the ratio between the signal output power of the TE1 mode of the signal output waveguide and the signal input power of the TE0 mode of the signal input waveguide:
FOM=(|a out_te1|2 N out_te1)/(| a out_te0|2 N out_te0)
am=0.25·((∫dS×E×H* m)/Nm+(∫dS×E* m×H)/N* m)
Nm=0.5·∫dS×Em×H* m
∇×μ 0 -1∇×E-ω 2 ε(P)E=-iωJ
c=λ·ω/(2π)
ε(P)=(ε(p1),ε(p2),⋯,ε(pn×n))
in the formula, the first and second organic solvents are,FOMan objective function representing the overall device is shown,a m = a out_te1 、a in_te0，N m = N out_te1 、N in_te0；a out_te1is the complex transmission coefficient of the TE1 mode signal in the signal output waveguide;N out_te1is the signal power of the TE1 mode in the signal output waveguide;a in_te0complex transmission system of TE0 mode in signal input waveguideThe number of the first and second groups is,N in_te0is the signal power of the TE0 mode in the signal input waveguide;Eis the distribution of the electric field in space,His the magnetic field distribution in space;E m = E out_te1 、E in_te0，H m = H out_te1 、H in_te0，E out_te1for the electric field distribution of the signal output waveguide in the TE1 mode,E in_te0the electric field distribution of the waveguide in TE0 mode for the signal input;H out_te1for the magnetic field distribution of the signal output waveguide in the TE1 mode,H in_te0the magnetic field distribution of the waveguide in TE0 mode for the signal input;μ 0 is the magnetic permeability in free space and,ωis a wavelengthλThe corresponding angular frequency of the frequency,Jfor the current density of the signal input into the waveguide,irepresenting imaginary units, ∇ representing gradient operators,crepresents the vacuum light speed;ε(P) Which represents a vector of the dielectric constant,ε(p 1 )represents a dielectric constant parameter of the 1 st unit cube; s represents the sectional area of the waveguide; whereinE out_te1Anda out_te1in response to this, the mobile terminal is allowed to,E in_te0anda in_te0in response to this, the mobile terminal is allowed to,H out_te1andN out_te1in response to this, the mobile terminal is allowed to,H in_te0andN in_te0and (7) corresponding.
Establishing the target and the relation of mode conversion for the whole device according to the target function, wherein the target and the relation are expressed as the following relation:
FOM→1
wherein → 1 represents approach 1;
and solving under the target of the objective function to obtain the optimal distribution of the dielectric constant of each unit cube, and further manufacturing a mode conversion region according to the optimal distribution.
The design of the present invention is one of the important components of an on-chip optical communication system. Because the traditional mode conversion device is mainly realized by a block optical device, an optical fiber and an optical waveguide, the devices need strict processing and arrangement, and simultaneously introduce great insertion loss, and simultaneously face the defects of too large size, small working bandwidth, lack of flexibility of device functions and the like, the miniaturization of the device structure cannot be realized, the integration is not facilitated, meanwhile, all the designs are based on a silicon-based photonic device and work in a near infrared band, and the design of the mode conversion device is blank in a middle infrared band taking 2025 nanometers as a central wavelength. Therefore, how to realize the miniaturization of the device, improve the working performance, and realize the design of the chalcogenide mode conversion device with high conversion efficiency, low insertion loss and large working bandwidth is very important and very challenging.
The design of the present invention scales device performance by establishing an objective function. The ratio of the signal energy of the TE1 mode at the output of the signal output waveguide to the signal energy of the TE0 mode in the device signal input waveguide is taken as the objective function and is denoted as FOM. In order for the device to realize mode conversion in a broadband with a central wavelength of 2025nm, the objective function needs to satisfy a certain relationship. When the input signal mode is the TE0 mode, it should be completely converted into the TE1 mode, and output from the signal output waveguide, i.e. the FOM should approach 1.
The mode-switching region was spatially divided into 250 × 250 cell structures, each cell structure having a size of 20 × 500nm, and there were two possible material properties for each cell structure, air or chalcogenide glass material. The material properties of all the unit structures are combined to form the structural shape of the mode conversion region, which has a total of 262500And possible structural arrangements. Each structure arrangement corresponds to a group of objective functions, the relationship between the objective functions and the material properties of each unit structure is established through an adjoint method, the variation gradient of the dielectric constant of each unit structure meeting the objective function relationship is solved, the material properties of each unit structure are determined, and finally the structure of the mode conversion region is determined.
The technical scheme provided by the embodiment of the invention can have the following beneficial effects:
the invention designs the chalcogenide broadband mode conversion device by using a continuous parameter associated source optimization method, realizes the mode conversion of which the central wavelength is 2025 nanometers and the working bandwidth is 100 nanometers, realizes the broadband mode conversion, overcomes the problems of large structural size, difficult integration and narrow working bandwidth of the mode conversion device, and fills the blank of the design of the chalcogenide mode conversion device.
The invention comprises a function of realizing intermediate infrared long-wave low-loss signal transmission by a photonic device based on a chalcogenide medium, and a function of realizing broadband mode conversion by performing topology optimization reverse design on the device based on an adjoint source method, and solves the problems of large occupied area, unstable performance and narrow working bandwidth in the traditional on-chip mode conversion device.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
Fig. 1 is a schematic diagram illustrating a structure of a compact broadband mode conversion device according to an exemplary embodiment.
Fig. 2 is a schematic cross-sectional view of an input/output waveguide shown in accordance with an example embodiment.
Fig. 3 is a schematic diagram illustrating a mode conversion region of a compact broadband mode conversion device according to an exemplary embodiment.
FIG. 4 is a flowchart illustrating a reverse design method for topology optimization according to an exemplary implementation.
FIG. 5 is an electric field profile of different waveguide modes of a cross-section of an input-output waveguide shown in accordance with an exemplary implementation.
Fig. 6 is a graph illustrating an electric field profile of a device at an operating wavelength according to an exemplary implementation.
FIG. 7 illustrates the conversion efficiency for an output TE1 when the input mode is TE0, according to an exemplary implementation.
In the figure: a substrate 1, a signal input waveguide 2, a signal output waveguide 3, and a mode conversion region 4.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
As shown in fig. 1, the structure of the embodied device includes:
a substrate 1;
a signal input waveguide 2 disposed on the substrate 1;
a signal output waveguide 3 disposed on the substrate 1;
in a specific implementation, the signal output waveguide 3 is located on the same axis as the signal input waveguide 2.
A mode conversion region 4, which is arranged on the substrate 1, wherein the mode conversion region 4 is connected between the signal input waveguide 2 and the signal output waveguide 3 through topology optimization reverse design; a signal of a TE0 mode is input from the signal input waveguide 2, passes through the mode conversion region 4, is converted into a TE1 mode signal, and is output from the signal output waveguide 3; the signal of the TE1 mode is input through the signal output waveguide 3, passes through the mode conversion region 4, is converted into a TE0 mode signal, and is output from the signal input waveguide 2.
In the specific implementation, the substrate 1 is made of silicon dioxide, and the signal input waveguide 2 and the signal output waveguide 3 are made of chalcogenide glass materials.
In a specific implementation, the width W _ input of the signal input waveguide 2 and the signal output waveguide 3 is 1800 nm, and the thickness H _ input is 500 nm.
The mode switching region 4 is divided into n × n unit cuboids on average in a three-dimensional space, each unit cuboid having two possible material states, which are classified as air or chalcogenide glass materials.
In a specific implementation, the width W0 of the mode-converting region 4 is 5 microns, the length L0 is 5 microns, and the thickness H0 is 500 nanometers. The mode switching region 4 was divided into 250 × 250 unit cuboids, each unit cuboid having a length of 20 nm, a width of 20 nm, and a thickness of 500 nm.
There are two possible material states, air or chalcogenide glass material, for each unit cube of the mode conversion region.
The mode conversion area 4 is optimized and determined through topology optimization reverse design by adopting the following specific method:
establishing the following objective function according to the ratio between the signal output power of the TE1 mode of the signal output waveguide and the signal input power of the TE0 mode of the signal input waveguide, by which the performance of the device is optimized:
FOM=(|a out_te1|2 N out_te1)/(|a out_te0|2 N out_te0)
am=0.25·((∫dS×E×H* m)/Nm+(∫dS×E* m×H)/N* m)
Nm=0.5·∫dS×Em×H* m
∇×μ 0 -1∇×E-ω 2 ε(P)E=-iωJ
c=λ·ω/(2π)
ε(P)=(ε(p1),ε(p2),⋯,ε(pn×n))
in the formula, the first and second organic solvents are,FOMrepresenting the wholeAn objective function of the devicea out_te1|2 N out_te1Representing the forward transmission power of TE1 mode signal in the signal output waveguide 3a out_te0|2 N out_te0The forward transmission power of the TE0 mode signal in the signal input waveguide 2, i.e. the signal power fed into the system, is shown;a m = a out_te1 、a in_te0，N m = N out_te1 、N in_te0；a out_te1is the complex transmission coefficient of the TE1 mode signal in the signal output waveguide 3;N out_te1is the signal power of the TE1 mode in the signal output waveguide 3;a in_te0is the complex transmission coefficient of the TE0 mode in the signal input waveguide 2,N in_te0is the signal power of the TE0 mode in the signal input waveguide 2;Eis the distribution of the electric field in space,His the magnetic field distribution in space;E m = E out_te1 、E in_te0，H m = H out_te1 、 H in_te0，E out_te1for the electric field distribution of the signal output waveguide 3 in the TE1 mode,E in_te0the electric field distribution of the signal input waveguide 2 in the TE0 mode;H out_te1for the magnetic field distribution of the signal output waveguide 3 in the TE1 mode,H in_te0the magnetic field distribution in TE0 mode for signal input waveguide 2;μ 0 is the magnetic permeability in free space and,ωis a wavelengthλThe corresponding angular frequency of the frequency of,Jfor the current density of the signal input into the waveguide,irepresenting imaginary units, ∇ representing gradient operators,crepresents the vacuum light speed;ε(P) Which represents a vector of the dielectric constant,ε (p 1 )denotes a dielectric constant parameter of the 1 st unit cube, S denotes a sectional area of the waveguide;
establishing the target and the relation of mode conversion for the whole device according to the target function, wherein the target and the relation are expressed as the following relation:
FOM→1
wherein → 1 represents approximately 1, or 1;
that is, the signals of the TE0 mode in the signal input waveguide 2 are all converted into the TE1 mode signals, and are output from the signal output waveguide 3, thereby realizing the function of one signal mode conversion.
Solving is performed under the objective of the objective function to obtain the optimal distribution of the dielectric constants of the unit cubes, and then the mode conversion region 4 is manufactured according to the optimal distribution.
In this embodiment, fig. 2 is a cross-sectional schematic diagram of an input/output waveguide shown in accordance with an exemplary implementation. Specifically, the signal input/output waveguide width W _ input is 1800 nm. The signal input waveguide thickness H _ input is 500 nm.
In this embodiment, fig. 3 is a schematic diagram of a mode conversion region of a small broadband mode conversion device according to an exemplary embodiment, the mode conversion region is spatially divided into 250 × 250=62500 unit structures, each unit structure has a size of 20 × 500nm, and there are two possible material properties of each unit structure, air or chalcogenide glass material. The material properties of all the unit structures are combined to form the structural shape of the mode conversion region, which has a total of 262500And possible structural arrangements. Each structural arrangement corresponds to a set of objective functions.
In this embodiment, fig. 4 is a flowchart illustrating a reverse design method for topology optimization according to an exemplary implementation. The ratio of the signal energy of the TE1 mode at the output of the output waveguide to the signal energy of the TE0 mode at the input waveguide of the device is taken as the target function, denoted as FOM. In order for the device to realize broadband mode conversion with a central wavelength of 2025nm, the objective function needs to satisfy a certain relationship. When signals of a TE0 mode in the signal input waveguide 2 are all converted into signals of a TE1 mode and are output from the signal output waveguide 2, a signal mode conversion function is realized, and FOM is required to approach 1.
Establishing a link between the objective function and the material property of each unit structure of the mode conversion region by an adjoint method, determining the material property (selected as air or chalcogenide glass material) of each unit cube, representing the set of dielectric constants of the respective unit cubes by a dielectric constant vector P:
ε(P)= (ε(p 1), ε(p 2), …,ε(p 62500))，ε(p 1) And (2) the glass is not less than 1^2 (air) or 2.71^2 (chalcogenide glass).
In a specific implementation, the TE1 mode is used as the target mode of the signal output waveguide 3, and the TE0 mode is used as the target mode of the signal input waveguide 2.
The following, objective function conditions were established:
FOM→1
the relationship between the objective function FOM and the dielectric constant of each unit cube in the mode conversion region 4 satisfies the following formula:
∇ε(P)FOM=(dFOM/dε(p 1), ⋯, dFOM/dε(p 62500))
wherein, ∇ ε P()Representing the gradient of variation of the objective function with respect to the dielectric constant of each cell in the mode conversion region 4,ε(p i) Denotes the dielectric constant of the unit cube, i denotes the serial number of the unit cube,ε(p 1) And (2) the glass is not less than 1^2 (air) or 2.71^2 (chalcogenide glass).
In this embodiment, fig. 5 is an electric field distribution diagram of different modes of a cross section of the input-output waveguide at an operating wavelength of 2025nm according to an exemplary implementation, where fig. 5 (a) is a TE0 mode and fig. 5 (b) is a TE1 mode. After determining the structural dimension and material properties of the input/output waveguide, the input/output waveguide is simulated, and the mode electric field distribution of the waveguide cross sections TE0 and TE1 at the working wavelength (2025 nm) is shown in the figure.
In this embodiment, fig. 6 is a diagram illustrating the electric field distribution of the structure at different wavelengths according to an exemplary embodiment. As seen from the results, when a signal of the TE0 mode is input through the input waveguide, it is converted into a TE1 mode signal after passing through the mode conversion region, and is output from the output waveguide. If the TE1 mode signal is reversely input through the output waveguide, the TE0 mode signal is converted to be output from the input waveguide after passing through the mode conversion region.
In this embodiment, FIG. 7 illustrates the conversion efficiency for an output of TE1 when the input mode is TE0, according to an exemplary implementation. It can be seen from the results that when the signal of TE0 mode is input through the input waveguide, and is converted into the signal of TE1 mode after passing through the mode conversion region, and is output from the output waveguide, the conversion efficiency can be almost 100% in the wavelength range of 100 nm. From the results, it is seen that the device achieves a high conversion efficiency, low insertion loss, large operating bandwidth conversion function.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (4)
1. A compact broadband mode conversion device, comprising:
a substrate (1);
a signal input waveguide (2) arranged on the substrate (1);
a signal output waveguide (3) arranged on the substrate (1);
a mode conversion region (4) disposed on the substrate (1), the mode conversion region (4) being divided into cells and connected between the signal input waveguide (2) and the signal output waveguide (3) by a topology-optimized reverse design;
the mode conversion region (4) is divided into n x n unit cuboids in a three-dimensional space, each unit cuboid has two possible material states which are divided into air or chalcogenide glass materials;
the mode conversion area (4) is reversely designed through topology optimization, and is specifically determined through optimization in the following mode:
the following objective function is established according to the ratio between the signal output power of the TE1 mode of the signal output waveguide and the signal input power of the TE0 mode of the signal input waveguide:
FOM=(|a out_te1|2 N out_te1)/(|a in_te0|2 N in_te0)
a out_te1=0.25·((∫dS×E×H* out_te1)/N out_te1+(∫dS×E* out_te1×H)/N* out_te1)
N out_te1=0.5·∫dS×E out_te1×H* out_te1
a in_te0=0.25·((∫dS×E×H* in_te0)/N in_te0+(∫dS×E* in_te0×H)/N* in_te0)
N in_te0=0.5·∫dS×E in_te0×H* in_te0
∇×μ 0 -1∇×E-ω 2 ε(P)E=-iωJ
c=λ·ω/(2π)
ε(P)=(ε(p1),ε(p2),⋯,ε(pn×n))
in the formula, the first and second organic solvents are,FOMan objective function representing the overall device is shown,a out_te1is a complex transmission system of TE1 mode signal in the signal output waveguide (3)Counting;N out_te1is the signal power of the TE1 mode in the signal output waveguide (3);a in_te0is the complex transmission coefficient of the TE0 mode in the signal input waveguide (2),N in_te0is the signal power of the TE0 mode in the signal input waveguide (2);Eis the distribution of the electric field in space,His the magnetic field distribution in space; E out_te1for the electric field distribution of the signal output waveguide (3) in the TE1 mode,E in_te0electric field distribution of the signal input waveguide (2) in the TE0 mode;H out_te1for the magnetic field distribution of the signal output waveguide (3) in the TE1 mode,H in_te0a magnetic field distribution in TE0 mode for the signal input waveguide (2);μ 0 is the magnetic permeability in free space and,ωis a wavelengthλThe corresponding angular frequency of the frequency of,Jfor the current density of the signal input into the waveguide,irepresenting imaginary units, ∇ representing gradient operators,crepresents the vacuum light speed;ε(P) Which represents a vector of the dielectric constant,ε(p 1 )represents a dielectric constant parameter of the 1 st unit cube; s represents the sectional area of the waveguide;
establishing the target and the relation of mode conversion for the whole device according to the target function, wherein the target and the relation are expressed as the following relation:
FOM→1
wherein → 1 represents approach 1;
solving under the target of the objective function to obtain the optimal distribution of the dielectric constant of each unit cube, and further manufacturing a mode conversion region (4) according to the optimal distribution;
the broadband refers to the working bandwidth which is more than or equal to 100 nanometers, and the central wavelength of the device is 2025 nm;
each structure arrangement corresponds to a group of objective functions, the relationship between the objective functions and the dielectric constant of each unit structure is established through an adjoint method, the change gradient of the dielectric constant of each unit structure meeting the objective function relationship is solved, the dielectric constant of each unit structure is determined, and finally the structure of a mode conversion region is determined;
the relationship between the objective function FOM and the dielectric constant of each cell cube in the mode conversion region (4) satisfies the following formula:
∇ε(P)FOM=(dFOM/dε(p 1), ⋯, dFOM/dε(p 62500))
wherein, ∇ ε P()Representing the gradient of variation of the objective function with respect to the dielectric constant of each cell in the mode conversion region (4),ε(p i) Denotes the dielectric constant of the unit cube, i denotes the serial number of the unit cube;
by small is meant less than 10 x 10 microns in size.
2. A compact broadband mode conversion device according to claim 1, wherein:
in the mode conversion region (4), a TE0 mode signal is input from the signal input waveguide (2), converted into a TE1 mode signal after passing through the mode conversion region (4), and output from the signal output waveguide (3); the TE1 mode signal is input through the signal output waveguide (3), passes through the mode conversion region (4), is converted into the TE0 mode signal and is output from the signal input waveguide (2).
3. A compact broadband mode conversion device according to claim 1, wherein:
the substrate (1) is made of silicon dioxide.
4. A compact broadband mode conversion device according to claim 1, wherein:
the signal input waveguide (2) and the signal output waveguide (3) are made of chalcogenide glass materials.
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| CN112180592A (en) * | 2020-10-14 | 2021-01-05 | 兰州大学 | Rapid optimization method for optical reverse design |
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