CN107942436B - Gradient Phase based on single particle realizes the method that Si waveguide unidirectionally scatters - Google Patents
Gradient Phase based on single particle realizes the method that Si waveguide unidirectionally scatters Download PDFInfo
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- CN107942436B CN107942436B CN201711334932.XA CN201711334932A CN107942436B CN 107942436 B CN107942436 B CN 107942436B CN 201711334932 A CN201711334932 A CN 201711334932A CN 107942436 B CN107942436 B CN 107942436B
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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
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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
- G02B2006/12035—Materials
- G02B2006/12061—Silicon
Abstract
The invention discloses a kind of, and the Gradient Phase based on single particle realizes the method that Si waveguide unidirectionally scatters, and switches for solving the problem of that existing Si waveguide unidirectionally scatters the interference depended between multiple structures and can not achieve scattering direction.The spin-orbit interaction that this method passes through single particle, symbol (positive/negative) and the chiral relevant Gradient Phase of incident light are generated in the direction of ducting, it acts on circularly polarized light one wave vector laterally propagated of offer for being equivalent to normal incidence, to realize unidirectional scattering, the switching in different scattering directions may be implemented in chirality by changing incident light, the dependence to interfering between multiple structures is avoided, so that the bandwidth of operation of system, robustness and flexibility are largely increased.
Description
Technical field
The present invention relates to Si optical waveguide technique field, in particular to a kind of Gradient Phase based on single particle realizes Si wave
Lead the method unidirectionally scattered.
Background technique
As the most basic structure of Si-based OEIC, silica-based waveguides are to constitute to interconnect between opto-electronic device and device
Basis.The unidirectional scattering for how realizing Si optical waveguide and one way propagation are to the information exchange in integrated optoelectronic circuit to Guan Chong
It wants.Tradition realizes that the method that Si optical waveguide unidirectionally scatters mainly utilizes the directional scattering characteristic of micro-nano structure in Si optical waveguide, such as
The metal Nano structure of two different lengths due to resonance frequency difference can generate different phase shifts, thus its two sides certain
It is long that one direction generates coherent phase, and generates coherent subtraction in its opposite direction, to realize the directional scattering of Si optical waveguide.It is similar
Design further include that the miniature yagi-uda that is made of multiple metal Nano structures is integrated in Si optical waveguide, utilize it
Coherent interference between cellular construction realizes directional scattering.Above-mentioned design method is based on relevant dry between multiple micro-nano structures
Effect is related to, therefore its performance depends critically upon geometric feature sizes and the relative position of micro-nano structure, the requirement to machining accuracy
It is higher, and can only operate in the bandwidth range of a very little and (be usually less than 50nm in 1550nm operation wavelength attachment), it limits
Its application range.On the other hand, above-mentioned design method can only work under the linear polarization of specific direction, therefore structure is once true
It is fixed, it scatters direction and function is determined immediately, can not achieve flexible switching.
Summary of the invention
For said circumstances, the invention discloses a kind of, and the Gradient Phase based on single particle realizes that Si waveguide unidirectionally scatters
Method, unidirectionally scatter for solving existing Si waveguide dependent on the interference between multiple structures, and can not achieve scattering side
To the problem of switching.This method generates symbol in the direction of ducting by the spin-orbit interaction of single particle
To the chiral relevant Gradient Phase of incident light, the circularly polarized light that effect is equivalent to normal incidence provides a wave laterally propagated
Arrow avoids the dependence to interfering between multiple structures, so that being to realize the switching of unidirectional scattering and different scattering directions
Bandwidth of operation, robustness and the flexibility of system are largely increased.
The technical solution adopted by the present invention to solve the technical problems are as follows: the Gradient Phase based on single particle realizes Si wave
The method unidirectionally scattered is led, this method is generated by the spin-orbit interaction of single particle in the direction of ducting
Symbol is laterally propagated to the chiral relevant Gradient Phase of incident light, the circularly polarized light offer one that effect is equivalent to normal incidence
Wave vector, the transverse direction by changing the size and symbol (positive/negative) of phase gradient caused by single particle, with Si Optical Waveguides
Wave vector matches, to realize the switching of unidirectional scattering and different scattering directions.
Wherein, in Si waveguide only integrate single particle, the particle have arc envelope, make it at the same have anisotropy with
Spatial heterogeneity.
Wherein, the mechanism unidirectionally scattered is the spin-orbit interaction of single particle, in the direction of ducting
Symbol and the chiral relevant Gradient Phase of incident light are generated, the circularly polarized light that effect is equivalent to normal incidence provides one and laterally passes
The wave vector broadcast.
Wherein, the switching in different scattering directions may be implemented by changing the chirality of incident light.
The device have the advantages that being:
A kind of method that the Gradient Phase realization Si waveguide based on single particle unidirectionally scatters is provided, is avoided to multiple
The dependence interfered between structure, so that the bandwidth of operation of system, robustness and flexibility are largely increased.
The present invention is discussed in detail in explanation and specific implementation with reference to the accompanying drawing.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of the method for the present invention；Wherein, 1 is SiO2Substrate, 2 be Si waveguide, and 3 be single catenary,
4 be power monitor 1,5 be power monitor 2；
Fig. 2 is that single catenary is under right-handed rotation irradiation in embodiment, the scattering strength of Si waveguide two sides；
Fig. 3 is that single catenary is under right-handed rotation irradiation in embodiment, the contrast of Si waveguide different directions scattering strength；
Fig. 4 is that electric field strength of the single catenary respectively under right-handed rotation and left-handed rotation irradiation in Si waveguide is divided in embodiment
Cloth；Wherein, Fig. 4 (a) is the single catenary electric-field intensity distribution under right-handed rotation irradiation in Si waveguide respectively, figure in embodiment
4 (b) be catenary single in the embodiment electric-field intensity distribution under left-handed rotation irradiation in Si waveguide respectively；
Fig. 5 is the scattering strength and intensity contrast of Si waveguide two sides in embodiment with the variation of single catenary length Λ
Rule；Wherein, Fig. 5 is the scattering strength of Si waveguide two sides in (a) embodiment with the changing rule of single catenary length Λ, figure
5 (b) be the intensity contrast of Si waveguide two sides in embodiment with the changing rule of single catenary length Λ；
Fig. 6 is the scattering strength and (b) intensity contrast of (a) Si waveguide two sides in embodiment with single catenary width Delta
Changing rule；Wherein, Fig. 6 (a) is the scattering strength of Si waveguide two sides in embodiment with the variation of single catenary width Delta
Rule, Fig. 6 (b) are the intensity contrast of Si waveguide two sides in embodiment with the changing rule of single catenary width Delta；
Fig. 7 is the scattering strength and intensity contrast of Si waveguide two sides in embodiment under (a) asymmetric case and (b) quilt
With the changing rule of wavelength in the case of truncation；Wherein, Fig. 7 (a) is the scattering strength and intensity pair of Si waveguide two sides in embodiment
Than degree with the changing rule of wavelength under asymmetric case, Fig. 7 (b) is the scattering strength and intensity of Si waveguide two sides in embodiment
Contrast is when being truncated with the changing rule of wavelength；
The Si waveguiding structure that Fig. 8 designs for the present embodiment.
Specific embodiment
With reference to the accompanying drawing and the present invention is discussed in detail in specific embodiment.But embodiment below is only limitted to explain this hair
Bright, protection scope of the present invention should include the full content of claim, and pass through following embodiment those skilled in the art
The full content of the claims in the present invention can be thus achieved.
1, as shown in Figure 1, according to embodiment of the present invention a kind of method that Si waveguide unidirectionally scatters, comprising: Si light wave
The single particle led and integrated in waveguide, the particle have certain arc envelope.Here with catenary commonly used in mechanics
For structure, envelope shape can be as follows with function representation,
Wherein, Λ represents the lateral length of catenary, and Δ represents the width of catenary.As can be seen that the particle is actually
It is made of following two catenary area defined,
The angle theta of the positive direction of the envelope and x-axis of the particle changes with the variation of coordinate position, and numerically the angle can
To be indicated with the arctan function of curve,
2, the arc envelope of the particle makes it while having anisotropy and spatial heterogeneity, therefore in circularly polarized light
Spin-orbit interaction can be generated under irradiation, the light after the KPT Scatter includes two parts.The chiral of a part of light keeps
It is constant, therefore there is no phase-modulation, this part light is after particle directly from the substrate (SiO of Si waveguide2) in transmission.And another portion
The chirality of light splitting is changed, and is modulated along with geometric phase, can mathematically be indicated are as follows:
Wherein, it is left-handed scattering light as dextrorotation that σ=1, which represents incident light, and it is left that σ=- 1, which represents incident light and scatters light as dextrorotation,
Rotation.From formula (4) as can be seen that changed light chiral for this part, phase are changed linearly along particle envelope, i.e.,
It attached linear Gradient Phase.Gradient Phase can generate lateral Equivalent Wave Vector kx, can mathematically indicate are as follows:
The transverse direction wave vector k it can be seen from formula (5)xIt is only related with Λ, therefore the size by changing Λ, it can be right
The lateral wave vector k that the rotatory polarization of normal incidence introducesxIt is adjusted, so that it be made to meet the wave vector matching condition with Si optical waveguide.
Due to the k of lateral wave vectorxVectorial property, chirality change this part light only can along with waveguide wave vector matching direction propagate.
Ideal situation is that incident circularly polarized light can be made to be completely converted into phase backhand after KPT Scatter by designing structure appropriate
The light of property, can greatly lift structure capacity usage ratio.
3, in order to avoid the propagation loss of Si material, the present embodiment is quasi- to be nearby designed for operation wavelength 1550nm,
The width that Si waveguide is arranged is 500nm, is highly 220nm, it is made to meet Si optical waveguide single mode transport condition.Grain in Si waveguide
Son can may be dielectric material for metal.Consider it first for gold, dielectric constant can be obtained by Palik optics handbook
?.The structural parameters that gold particle is arranged are Λ=900nm, Δ=100nm, thickness t=90nm.
4, in order to verify the method that the Gradient Phase realization Si waveguide proposed by the present invention based on single particle unidirectionally scatters,
We are using the Three-D limited FD―TD method of business software FDTD Solutions (Canadian Lumerical company) to this hair
Bright embodiment design has carried out simulation calculation.Using two orthogonal total field-scattered fields in emulation (TFSF, phase difference are 90 °)
To simulate circularly polarized light, and two power monitors (Power monitor) records are set not at Si waveguide both ends (at 10 μm)
Equidirectional scattering strength uses perfect matching boundary condition (PML) around to reduce the influence of environment scattering.In order to ensure foot
Enough simulation accuracies, grid (Mesh) precision setting are dx=dy=dz=2nm.Emulate obtain along two sides of Si waveguide or so
To scattering strength (be denoted as T respectively1And T2), as shown in Figure 2.From figure it can clearly be seen that in right-circularly polarized light incidence
In the case of, most of light that scatters is scattered along Si waveguide left direction, and the light along the scattering of Si waveguide left direction can neglect substantially
Slightly (< 10-4)。
5, in order to further analyze the unidirectional scattering property in the present embodiment, it is strong that different directions scattering is defined here
The contrast of degree is 10log (max (T1,T2)/min(T1,T2)), as a result as shown in Figure 3.As can be seen that contrast is in 1550nm
It is greatest around to have reached 25dB, and contrast is more than the bandwidth of operation of 15dB greater than 100nm, is based on multiple micro-nanos much larger than tradition
The bandwidth of operation (usually less than 50nm) of structure coherent interference.
6, in order to which to claim 4 of the invention, the Gradient Phase based on single particle realizes what Si waveguide unidirectionally scattered
Method, which is characterized in that the switching in different scattering directions may be implemented in the chirality by changing incident light, is verified.This reality
It applies example and gives electric-field intensity distribution under the circular polarization incident of different chiralitys, as shown in Figure 4.As can be seen that right-handed rotation is incident
When, the transmission on the left of Si waveguide of wide part is scattered, and when left-handed rotation incidence, the transmission on the right side of Si waveguide of wide part is scattered,
It is changed by the chirality to circularly polarized light, the switching in different scattering directions can be neatly realized.
7, in order to prove method proposed by the invention robustness with higher and processing tolerance, Fig. 5-8 gives respectively
Gone out under Different structural parameters, unidirectional scattering property based on single metal catenary particle Gradient Phase (scattering strength with it is right
Than degree).As can be seen that even biggish change, side proposed by the invention has occurred in the structural parameters of particle, symmetry etc.
Method is still able to achieve the unidirectional scattering greater than 10dB, and bandwidth of operation remains to maintain 50nm or more, it was demonstrated that proposed by the invention
Unidirectional scattering method robustness with higher based on single metal catenary particle Gradient Phase and processing tolerance.
It is worth noting that the embodiment of the present invention is described with above attached drawing, but the present invention not office
It is limited to above-mentioned specific embodiment, above-mentioned embodiment is only schematical, rather than restrictive.Change gold into it
Its metal material (silver, aluminium etc.) or dielectric material (silicon, germanium etc.), or the single particle with catenary envelope is changed into it
The single particle of its arc envelope, or change Si waveguide into SiN waveguide or SOI (silicon-on-insulator) waveguide,
Within right of the presently claimed invention, without departing from not inventing protected interest field.Non-elaborated part of the present invention belongs to
In the well-known technique of those skilled in the art.
Claims (2)
1. the Gradient Phase based on single particle realizes the method that Si waveguide unidirectionally scatters, it is characterised in that: this method passes through list
The spin-orbit interaction of a particle generates symbol and the chiral relevant gradient phase of incident light in the direction of ducting
Position, the circularly polarized light that effect is equivalent to normal incidence provides a wave vector laterally propagated, by changing produced by single particle
Phase gradient size and symbol, match with the lateral wave vector of Si Optical Waveguides, to realize unidirectional scattering and different
Scatter the switching in direction；
The single particle integrated in Si optical waveguide and waveguide has certain arc envelope, which is actually by following two
Catenary area defined composition:
Wherein, Λ represents the lateral length of catenary, and Δ represents the width of catenary, the envelope of the particle and the positive direction of x-axis
Angle theta change with the variation of coordinate position, numerically the angle can be indicated with the arctan function of curve:
The arc envelope of the particle makes it while having anisotropy and spatial heterogeneity, can produce under the irradiation of circularly polarized light
Raw spin-orbit interaction, the light after the KPT Scatter includes two parts, and the chirality of a part of light remains unchanged, and is not had
Phase-modulation, this part light is after particle directly from the SiO of Si waveguide2It is transmitted in substrate, and the chiral of another part light occurs
Change, and modulate along with geometric phase, is expressed mathematically as:
Wherein, σ=1 represent incident light be it is left-handed, scattering light be dextrorotation；σ=- 1 represents incident light as dextrorotation, and scattering light is a left side
Rotation；Changed light chiral for this part, phase are changed linearly along particle envelope, that is, attached linear gradient phase
Position, Gradient Phase can generate lateral Equivalent Wave Vector kx, it is expressed mathematically as:
Transverse direction wave vector kxIt is only related with Λ, it, can be to the lateral wave vector of the rotatory polarization of normal incidence introducing by changing the size of Λ
kxIt is adjusted, to make it meet the wave vector matching condition with Si optical waveguide, due to the k of lateral wave vectorxVectorial property, hand
This part light sexually revised can only be propagated along with waveguide wave vector matching direction.
2. the Gradient Phase according to claim 1 based on single particle realizes the method that Si waveguide unidirectionally scatters, special
Sign is: the switching in different scattering directions may be implemented in the chirality by changing incident light.
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| CN105322287A (en) * | 2015-10-13 | 2016-02-10 | 中国人民解放军空军工程大学 | Phase gradient super-surface based surface plasmon planar antenna |
| CN106168688A (en) * | 2016-09-08 | 2016-11-30 | 复旦大学 | High efficiency and coupling direction adjustable surface phasmon bonder under rotatory polarization incidence |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105322287A (en) * | 2015-10-13 | 2016-02-10 | 中国人民解放军空军工程大学 | Phase gradient super-surface based surface plasmon planar antenna |
| CN106168688A (en) * | 2016-09-08 | 2016-11-30 | 复旦大学 | High efficiency and coupling direction adjustable surface phasmon bonder under rotatory polarization incidence |
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| Catenary optics for achromatic generation of perfect optical angular momentum;Mingbo Pu 等;《Science Advanced》;20151002;全文 * |
| Quasi-continuous metasurface for ultra-broadband and polarization-controlled electromagnetic beam deflection;Yanqin Wang 等;《Scientific Reports》;20151204;全文 * |
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