CN108254829A - A kind of design method of the vertical pattern converter of double, asymmetrical - Google Patents
A kind of design method of the vertical pattern converter of double, asymmetrical Download PDFInfo
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- CN108254829A CN108254829A CN201810013649.5A CN201810013649A CN108254829A CN 108254829 A CN108254829 A CN 108254829A CN 201810013649 A CN201810013649 A CN 201810013649A CN 108254829 A CN108254829 A CN 108254829A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/14—Mode converters
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
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Abstract
The present invention provides a kind of design method of the vertical pattern converter of double, asymmetrical, this method is using lateral (horizontal direction) and the directional coupling structure of the double, asymmetrical of longitudinal direction (vertical direction), both the effective refractive index matching of two patterns had been ensure that, also the orthogonality between vertical pattern has been broken, so as to realize the arbitrary conversion between the vertical pattern of high-order and basic mode.
Description
Technical field
The present invention relates to optical communication field, more particularly, to a kind of design method of vertical pattern conversion.
Background technology
With the fast development of the technologies such as cloud computing, big data, Internet of Things, mobile Internet, information-intensive society is just from IT
(Information Time) epoch, demand of the people to network data was increasing, to DT (Data Time) era development
Information transmission is asked to have the capacity of bigger, faster speed, more economical expense.Information multiplexing is a kind of common, is used
To improve the technology of transmission medium data capacity.Existing wavelength-division multiplex (Wavelength Division Multiplexing)
With dense wave division multipurpose (Dense WDM) commercial utilization, and good benefit is achieved.Although however, simple optical fiber
Can be with the flashlight of the different wavelength of simultaneous transmission, but be not unlimited bandwidth, there are one shannon limits.In order to overcome
The constraint of shannon limit, further improves the transmission capacity of simple optical fiber, occurs a new technology now --- and mould point is multiple
With (Mode-division multiplexing) technology.
Mode division multiplexing (MDM) orthogonal pattern limited in referring to by the use of multimode fibre or less fundamental mode optical fibre is as solely
Vertical channel transmission information allows the different mode of each wavelength to carry different information, is multiplexed and is demultiplexed.It is multiple using mould point
After technology, the capacity of optical transport can be with the pattern count growth at double of multiplexing, in conjunction with other Optical multiplexing technologies, energy
Enough significant raising light transmission capacities, and very high spectrum efficiency can be obtained, it is the preferential of following large capacity development of optical network
Technical solution.
Mode division multiplexing (MDM) can be directed to transverse multimode waveguide or longitudinal multimode waveguide two ways, i.e., used
Multimode waveguide has multi-mode distribution on lateral or vertical.It proposes under study for action at present a kind of using etched diffraction grating
Method, be used as the multiplexing demultiplexing device part of longitudinal multimode waveguide, all mode passageways can be simultaneously by one
Grating device detaches, similar to the wavelength division multiplex device in corresponding WDM technology.
It is basic although the mode signal being separated from each other after etched diffraction grating pattern demultiplexer
All or high-order pattern, it is contemplated that transmission and bending loss, crosstalk and with optical fiber the problems such as docking when, it is sometimes desirable to
These longitudinal directions, higher order mode is converted to basic mode.For this purpose, we carry out pattern conversion using asymmetrical directional coupler (ADC).
When the distance between two parallel waveguides are small to a certain extent, respectively into the region where the evanescent field of other side's guided mode when, wave
Coupling will be generated between the pattern led, this Power Exchange occurred between the guided mode of adjacent waveguide is known as orienting coupling
It closes.The asymmetrical directional coupler of transverse mode is widely used.Such ADC devices have same duct height, still
The width of waveguide is different, so as to reach the matching of the effective refractive index between different mode.But has longitudinal multi-mode
The situation that ADC but has its special.Difference lies in spatially having overturn 90 degree between vertical pattern and transverse mode, but in device
In part design but exactly because 90 degree of this overturning and cause one it is new the problem of, i.e. relationship between two patterns to be coupled by
Being overlapped and becoming orthogonal originally, cannot intercouple and convert so as to cause the pattern in two waveguides.Fig. 1
For the ADC devices of traditional transverse multimode, input waveguide of the left side for the lateral single order pattern of transmission, right side is need to be converted into basic mode
The coupled waveguide being transmitted, the symmetrical centres of two patterns in left and right are therefore nonopiate each other in the horizontal direction there are one deviating
(overlap integral of electric field distribution function both i.e. is not zero) can intercouple between pattern.For longitudinal multimode waveguide,
Structure in Fig. 3 is similar with Fig. 1, is equivalent to entirety and has rotated 90 degree around a basic point, the two situation is equivalent, and coupling can also occur
It closes.However device making technics requirement input is located at output waveguide in same level layer, as shown in Fig. 2, left side inputs at this time
Longitudinal First-Order Mode in waveguide and the symmetrical centre of the basic mode in the coupled waveguide of right side are not deviated in vertical direction, two different moulds
(i.e. the overlap integral of the electric field distribution function of the two is zero) orthogonal between formula, can not couple.
Invention content
The present invention is proposed based on the above-mentioned fact, it is intended that a kind of design method of vertical pattern conversion is provided,
After this method is for EDG demultiplexings, the multiple higher order modes in longitudinal direction in waveguide carry out the conversion to basic mode, and using dual non-
The design pattern of symmetric directional coupler, can break the orthogonality between vertical pattern, change the longitudinal direction height of output waveguide, then
The secondary weight that increases in the longitudinal direction is asymmetric, this horizontal and vertical double asymmetric, can make it is non-orthogonal between vertical pattern, and
Effective refractive index between different mode is adjusted to identical, is converted so as to fulfill Mode Coupling.
In order to reach above-mentioned technique effect, the present invention provides a kind of designs of the vertical pattern converter of double, asymmetrical
Method, it is characterised in that：Include the following steps：
S1：The longitudinal multimode input waveguide structure of design, the multimode waveguide prop up on longitudinal direction (perpendicular to chip surface direction)
Hold two or more multiple communication modes；
Its waveguide material is that the oxide, nitride or III/V compound semiconductors, waveguide core layer of silicon and silicon exist
Short transverse supports more than two communication modes, can be calculated in this vertical direction i.e. short transverse according to the communication mode
The effective refractive index of supported multiple communication modes；
By taking silicon-on-insulator (SOI) material system as an example, silica is chosen as substrate, using silicon as waveguide core layer, is covered
Cap rock is silica, and when waveguide core layer height is more than single mode condition, there are more than one communication mode, meters in the longitudinal direction
Calculate the effective refractive index of supported multiple communication modes；
S2：Design the directional coupler of double, asymmetrical structure：
Using the waveguiding structure designed in S1, by changing the lateral width of coupled waveguide and the height of longitudinal direction,
Change the effective refractive index of its waveguide, the waveguide to match so as to design effective refractive index and input waveguide carrys out implementation pattern and turns
It changes；
Wherein, the detailed process for designing the dual non-directional coupler for piling structure is as follows：
S21：Width, the height of the input waveguide of higher order mode are determined, so that it is determined that effective folding of the high-order mode of its input
Penetrate rate；
S22：The coupled waveguide of double, asymmetrical is designed, first longitudinally an asymmetric design is being done, by changing coupled wave
The height led breaks the orthogonality of two vertical patterns in two waveguides；
S23：Try again lateral asymmetric design, changes the width of coupled waveguide, so as to further change waveguide
Effective refractive index so that the effective refractive index of coupled waveguide basic mode is equal to the effective refractive index of the high-order mode of input waveguide；
S24：According to directional couple principle：
When the effective refractive index of two patterns in two waveguides is equal, and it is close to each other when two patterns mould field it is non-just
Hand over, when overlap integral is not zero, two patterns can be converted mutually, pass through the power of waveguide I | A (z) |2With the power of waveguide II
|B(z)|2, they and input power | A (0) |2The ratio between be respectively：
Wherein,
F is maximum transfer power.By above formula (3) it is known that maximum transfer power F depends on the size of coefficient of coup κ
And the synchronization extent of two mould phase velocities；When two moulds being coupled are asynchronous, the phase velocity of two moulds is different, reflects phase velocity
δ ≠ 0 of the difference of degree, F are less than 1, i.e., cannot reach complete coupling；Only when two moulds synchronize, phase velocity is equal, there is δ at this time
=0, F are just equal to 1；So as to be determined to reach corresponding coupling length when complete pattern is converted according to formula；
S25：According to more than parameter designing double, asymmetrical vertical pattern converter.
Description of the drawings
Fig. 1 is the lateral asymmetric coupled waveguide cross-sectional view of tradition.
Fig. 2 is the longitudinal asymmetric coupled waveguide schematic diagram that traditional approach is placed.
Fig. 3 rotates integrally 90 degree of resulting structures schematic diagrames for transverse coupling waveguide around same center.
Fig. 4 is double, asymmetrical coupled waveguide cross-sectional view proposed by the present invention.
Specific embodiment
The attached figures are only used for illustrative purposes and cannot be understood as limitating the patent；
In order to more preferably illustrate the present embodiment, the certain components of attached drawing have omission, zoom in or out, and do not represent actual product
Size；
To those skilled in the art, it is to be appreciated that certain known features and its explanation, which may be omitted, in attached drawing
's.
With reference to embodiment, the following further describes the technical solution of the present invention.
Waveguiding structure is selected using silica as substrate, using silicon as waveguide core layer, coating is silica, waveguide core layer
It is highly 1.2um, the wavelength for choosing 1550nm is the correspondence operation wavelength of the device, and calculating can prop up under transverse electric (TE) polarization
Hold 3 communication modes effective refractive index n corresponding with them1, n2, n3。
After above-mentioned input waveguide structural parameters are selected, the coupled waveguide of matching double, asymmetrical is designed, is first existed
An asymmetric design is done in longitudinal direction, by changing the height of coupled waveguide, breaks in two waveguides the orthogonal of two vertical patterns
Property.Then it does an asymmetric design in the horizontal again, changes the width of coupled waveguide, make to have between two patterns of needs conversion
Index matching is imitated, so as to fulfill the purpose of pattern conversion.
Such as need to realize conversion of the First-Order Mode to basic mode in input waveguide, two patterns are first broken by longitudinal asymmetric
Intermode it is orthogonal, preferably make that left side duct height h is the right duct height h1 two times, h=1.2um, then h1=0.6um, h
=2*h1.Again by laterally asymmetric so that two pattern effective refractive indexs are equal, and left side waveguide transmission is First-Order Mode, wave
Width is led as w=350nm, the right is basic mode and the matched waveguide of the First-Order Mode, width w1=337.9nm, at this time its base
The propagation constant and effective refractive index of mould are equal with left side waveguide First-Order Mode, can reach maximum conversion efficiency, F=1.
Transfer principle and above consistent, left side duct height h preferably the right duct height h2 of the second order mode to basic mode
Three times, h=1.2um, h2=0.4um, h=3*h2.Again by laterally asymmetric, adjusting duct width causes two patterns to have
Effect refractive index is equal, and left side waveguide transmission is second order mode, and width is taken as w=350nm.Basic mode and its second order in the waveguide of the right
Mould matches, and width w2=307.2nm, its effective refractive index is equal with the second order mode of left side waveguide at this time, can reach maximum
Transfer efficiency.
Longitudinal ADC uses the structure of lateral, longitudinal double, asymmetrical.When the higher order mode and coupled waveguide of input waveguide
When effective index of fundamental mode is equal, two patterns are nonopiate, and pattern match, and mutual coupling conversion can occur.One
It is transfer efficiency maximum at 9um that rank mould, which turns basic mode in coupling length, and at this time close to conversion completely, coupling efficiency is in periodical later
Oscillation, the period is 9um.Therefore when progress First-Order Mode converts basic mode, the length of waveguide coupling regime is preferably 9um, at this time
All structural parameters of entire mode converter part are it has been determined that device can realize maximum mode conversion efficiency.Second order mode turns
Basic mode is maximum for transfer efficiency at 10um in coupling length, and transmission light field is also alternately shaken as the period between two waveguides later
It swings, therefore second order mode is to the conversion of basic mode that its coupling length is preferably 10um, there is maximum conversion efficiency at this time.It can by designing above
To realize all higher order modes are converted to basic mode in input waveguide purpose.
The same or similar label correspond to the same or similar components；
Position relationship is only for illustration described in attached drawing, it is impossible to be interpreted as the limitation to this patent；
Obviously, the above embodiment of the present invention be only to clearly illustrate example of the present invention, and not be pair
The restriction of embodiments of the present invention.For those of ordinary skill in the art, may be used also on the basis of the above description
To make other variations or changes in different ways.There is no necessity and possibility to exhaust all the enbodiments.It is all this
All any modification, equivalent and improvement made within the spirit and principle of invention etc., should be included in the claims in the present invention
Protection domain within.
Claims (2)
1. the design method of the vertical pattern converter of a kind of double, asymmetrical, which is characterized in that include the following steps：
S1：The longitudinal multimode input waveguide structure of design, the multimode waveguide support multiple communication modes in the longitudinal direction；
Its waveguide material is the oxide, nitride or III/V compound semiconductors of silicon and silicon, and waveguide core layer is in height
More than two communication modes are supported in direction, calculated according to the communication mode supported in vertical direction i.e. short transverse it is more
The effective refractive index of a communication mode；
S2：Design the directional coupler of double, asymmetrical structure：
Using the waveguiding structure designed in S1, by changing the lateral width of coupled waveguide and the height of longitudinal direction, change
The effective refractive index of its waveguide, the coupled waveguide to match so as to choose effective refractive index and input waveguide carry out implementation pattern and turn
It changes.
2. a kind of design method of the vertical pattern converter of double, asymmetrical according to claim 1, which is characterized in that
The detailed process of the step S2 is as follows：
S21：Determine width, the height of the input waveguide of higher order mode, and according to its used Refractive Index of Material, so that it is determined that
The effective refractive index of its high-order mode inputted；
S22：The coupled waveguide of double, asymmetrical is designed, first longitudinally an asymmetric design is being done, by changing coupled waveguide
Highly, break the orthogonality of two vertical patterns in two waveguides；
S23：Try again lateral asymmetric design, changes the width of coupled waveguide, so as to further change the effective of waveguide
Refractive index so that the effective refractive index of coupled waveguide basic mode is equal to the effective refractive index of the high-order mode of input waveguide；
S24：According to directional couple principle：
When the effective refractive index of two patterns in two waveguides is equal, and it is close to each other when, the mould field of two patterns is nonopiate,
When overlap integral is not zero, two patterns can be converted mutually；Pass through the power of waveguide I | A (z) |2With the power of waveguide II | B
(z)|2, the power of waveguide I, the power and input power of waveguide II | A (0) |2The ratio between be respectively：
Wherein,
F is maximum transfer power；By above formula (3) it is known that when two moulds being coupled are asynchronous, δ ≠ 0, maximum transfer
Power F is depending on the size of coefficient of coup κ and the synchronization extent of two mould phase velocities, and only as δ=0, F is just equal to 1；So as to
Determine the coupling length of complete pattern conversion；
S25：According to more than parameter designing double, asymmetrical vertical pattern converter.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109726448A (en) * | 2018-12-11 | 2019-05-07 | 中国人民解放军63653部队 | A kind of segmented mode converter designs method based on iterative method |
| CN114114540A (en) * | 2021-12-09 | 2022-03-01 | 南通大学 | Design method of efficient compact adiabatic mode converter |
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| CN1629663A (en) * | 2003-12-18 | 2005-06-22 | 中国科学院半导体研究所 | Silicon ridge optical waveguide with novel crosssectional shape on an insulator and method for manufacturing the same |
| CN106842430A (en) * | 2017-04-05 | 2017-06-13 | 电子科技大学 | A kind of asymmetrical directional coupler |
| WO2017142076A1 (en) * | 2016-02-18 | 2017-08-24 | 日本電信電話株式会社 | Optical multiplexing circuit |
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| CN1629663A (en) * | 2003-12-18 | 2005-06-22 | 中国科学院半导体研究所 | Silicon ridge optical waveguide with novel crosssectional shape on an insulator and method for manufacturing the same |
| WO2017142076A1 (en) * | 2016-02-18 | 2017-08-24 | 日本電信電話株式会社 | Optical multiplexing circuit |
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Cited By (3)
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| CN109726448A (en) * | 2018-12-11 | 2019-05-07 | 中国人民解放军63653部队 | A kind of segmented mode converter designs method based on iterative method |
| CN114114540A (en) * | 2021-12-09 | 2022-03-01 | 南通大学 | Design method of efficient compact adiabatic mode converter |
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