CN209417328U - A kind of photonic crystal of pair of Defect Modes reflectivity enhancing - Google Patents
A kind of photonic crystal of pair of Defect Modes reflectivity enhancing Download PDFInfo
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- CN209417328U CN209417328U CN201920245931.6U CN201920245931U CN209417328U CN 209417328 U CN209417328 U CN 209417328U CN 201920245931 U CN201920245931 U CN 201920245931U CN 209417328 U CN209417328 U CN 209417328U
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Abstract
The utility model provides the photonic crystal of a kind of pair of Defect Modes reflectivity enhancing, belongs to field of photoelectric technology.A kind of photonic crystal of high reflectance, this photonic crystal include the first dielectric layer, the second dielectric layer, defect layer and graphene layer, and defect layer is located at the middle part of electron crystal；The regularity of distribution of first dielectric layer and the second dielectric layer are as follows: the two sides of defect layer have been alternately arranged several first dielectric layers and several second dielectric layers, and two lateral surfaces of photonic crystal are the first dielectric layer, the two sides close to defect layer are the second dielectric layer；Graphene layer is embedded in defect layer.The utility model has many advantages, such as can be by the way that graphene to be doped in the defect layer of photonic crystal, to improve Defect Modes reflectivity, cause reflection coefficient phase acute variation and the big lateral displacement of the reflected beams.
Description
Technical field
The utility model belongs to photoelectricity technical field, is related to the photonic crystal of a kind of pair of Defect Modes reflectivity enhancing.
Background technique
There are band gap for energy band in photonic crystal.When illumination is mapped on photonic crystal, if the frequency of light is located at band gap
Interior, then it will not penetrate photonic crystal by light, light beam will be totally reflected.But if defect is added in the photonic crystal
Layer, then there are a Defect Modes in the band gap of energy band.When the frequency of incident light is equal to the frequency of Defect Modes, light beam is by areflexia
All by photonic crystal, reflectivity at this time is zero, therefore Defect Modes is also called Transmission Modes.The energy of Defect Modes mainly divides
For cloth in defect layer, the Energy distribution of the center of defect layer is most strong.Extend from defect layer center to photonic crystal both sides, lacks
The Energy distribution for falling into mould exponentially decays.
The lateral displacement of the reflected beams can be widely applied to high sensor and photoswitch etc..But usual situation
Under, the lateral displacement of the reflected beams is smaller, generally with regard to several wavelength or tens wavelength, therefore to the cross for experimentally detecting light beam
Very big difficulty is brought to displacement and practical application.People enhance the lateral displacement of the reflected beams by a variety of methods, such as
Biggish lateral displacement is realized using the band gap edge of photonic crystal, weak loss material and graphene etc..
The lateral displacement of the reflected beams is proportional to reflection coefficient phase to the derivative of wave vector, since the reflectivity of Defect Modes is
Zero, there is uncertainty in the reflection coefficient phase of Defect Modes, therefore there may be biggish lateral positions for the reflected beams of Defect Modes
It moves.But for the photonic crystal of no gain and loss, the reflectivity of Defect Modes is zero, even if there is biggish transverse direction at this time
Displacement, but be actually also meaningless.
Utility model content
The purpose of this utility model is aiming at the above problems existing in the prior art, to provide a kind of photon of high reflectance
Crystal, technical problem to be solved in the utility model be how by the way that graphene is doped in the defect layer of photonic crystal,
To improve reflectivity.
The purpose of this utility model can be realized by the following technical scheme: a kind of photonic crystal of high reflectance, special
Sign is that this photonic crystal includes the first dielectric layer, the second dielectric layer, defect layer and graphene layer, the defect layer position
In the middle part of electron crystal；The regularity of distribution of first dielectric layer and the second dielectric layer are as follows: the two sides of the defect layer
Several first dielectric layers and several second dielectric layers are alternately arranged, and two lateral surfaces of photonic crystal are that the first electricity is situated between
Matter layer, the two sides close to defect layer are the second dielectric layer；The graphene layer is embedded in defect layer.
Dielectric layer one and dielectric layer two can be the common dielectric in this field, such as magnesium fluoride, zinc sulphide.
Graphene is doped in the defect layer of photonic crystal by we, using the weak loss of graphene, weakens photonic crystal
To the transmissivity of Defect Modes, to improve the reflectivity of light beam.Meanwhile the weak loss of graphene can also cause reflection coefficient phase
Change dramatically.It is proportional to reflection coefficient phase change rate according to the reflected beams lateral displacement, is lacked when the incident frequencies of light are located at
When falling near mould, the available biggish lateral displacement of the reflected beams.
The refractive index of first dielectric layer, the second dielectric layer and defect layer is respectively na=1.38, nb=2.35 and nc=
2.35, the thickness of the first dielectric layer, the second dielectric layer and defect layer is respectively da=0.281 μm, db=0.165 μm and dc
=0.33 μm.Incident ray is denoted as 1, reflection light is denoted as 2, and transmitted ray is denoted as 3.By reflection light relative to incidence point
Lateral displacement is denoted as Δ.
Single-layer graphene is entrained in the centre of defect layer, that is, is located at 0 position of z-axis of photonic crystal.Single-layer graphene
The two-dimensional material for disregarding thickness, surface conductivity can be described with nine fort formula (Kuboformula), it is as follows:
Wherein, fd=1/ (1+exp [(ε-μc)/(kBIt T is)]) Fermi-Dirac statistics, ε is particle energy, μcIt is graphite
Alkene chemical potential (is also called fermi level EF)), T is temperature, and e is elementary charge, and τ is momentum relaration time, kBIt is Boltzmann
Constant.
Graphene layer is regarded as with certain thickness dielectric, it is this to wait efficacious prescriptions when equivalent thickness is lower than 1nm
Method is negligible to the influence for calculating reflectivity and transmissivity.We take graphene layer with a thickness of 0.34nm.Graphene
Effective dielectric constant be εg=1+i σgη0/(kdg), wherein k is incident wave vector, η0It is vacuum impedance.Temperature takes T=27 DEG C, moves
Measure relaxation time τ=0.5ps, μc=0.15eV.
Total is (AB)NCGC(BA)N(it is assumed that the first dielectric layer be A, the second dielectric layer be B, defect layer C,
Graphene layer is G), wherein Bragg period number N=5.
If incident light is TM wave, propagated along z-axis.The electromagnetic field at each layer of dielectric both ends can be contacted by transmission matrix
Get up.For example, the electromagnetic field at l layers of dielectric both ends can be got up by following relationship
Wherein, MlIt is l layers of transmission matrix, wherein ηl=εl(ε0/μ0)1/2/(εl-sin2θ)1/2,θ is the incidence angle of light, is set as θ=20 ° here.The transmission matrix of whole system is
Wherein n is total number of plies of structure.Reflection coefficient is
Wherein η1=ηN+1=(ε0/μ0)1/2(1-sin2θ)1/2, the respectively impedance of incidence end and exit end, reflectivity R
=rr*.The band gap of photonic crystal is ωgap=4 ω0arcsin│(nb-na)/(nb+na)│2/ π, wherein ω0=2 π c/ λ0, λ0=
1.55μm。
If undoped with graphene layer, it can be seen that reflectivity is the function of incident light frequency.There are one among reflectance spectrum
A band gap, the light in this band gap will all be reflected.But the reflectivity of the position * Defect Modes is zero, Defect Modes
Light will be transmitted all, therefore also be Transmission Modes.
According to the relationship of the lateral displacement of the reflected beams and reflection coefficient phase
It is recognised that the lateral displacement of the reflected beams near Defect Modes is larger.But reflectivity at this moment is smaller, because
Graphene is doped in defect layer by we for this, obtains biggish reflectivity.
After doped graphene layer, the reflectivity of the position * Defect Modes is not zero, R=0.212.Phase at Defect Modes does not have
There is jump, but changes more violent.Therefore, available reflectivity is not zero, and has the reflected light of relatively larger transverse displacement again
Beam.
When incident light frequency is located at Defect Modes, the lateral displacement of the reflected beams is maximum, and maximum value is Δ=124 λ.
The advantages of the utility model: the doped graphene in Defect Photonic Crystal can greatly improve the reflection of Defect Modes
Rate, in present case, the maximum reflectivity of Defect Modes can reach R=0.212；It can make the lateral displacement maximum value of the reflected beams
Reach 124 λ, improves a magnitude than the lateral displacement in general structure.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of this electron crystal.
Fig. 2 is the reflectivity and reflection coefficient phase of the Defect Modes undoped with graphene.
Fig. 3 is the reflectivity and reflection coefficient phase of the Defect Modes of doped graphene.
Fig. 4 is the lateral displacement of the reflected beams in the Defect Photonic Crystal of doped graphene.
In figure, A, the first dielectric layer；B, the second dielectric layer；C, defect layer；G, graphene layer.
Specific embodiment
It is specific embodiment of the utility model and in conjunction with attached drawing below, the technical solution of the utility model is made further
Description, but the utility model is not limited to these examples.
This photonic crystal includes the first dielectric layer A, the second dielectric layer B, defect layer C and graphene layer G, defect layer C
Positioned at the middle part of electron crystal；The regularity of distribution of first dielectric layer A and the second dielectric layer B are as follows: the two sides of defect layer C replace
Several first dielectric layer A and several second dielectric layer B are arranged with, and two lateral surfaces of photonic crystal are the first dielectric
Layer A, the two sides close to defect layer C are the second dielectric layer B；Graphene layer G is embedded in defect layer C.
As shown in Figure 1, the refractive index of the first dielectric layer A, the second dielectric layer B and defect layer C is respectively na=1.38,
nb=2.35 and ncThe d that the thickness of=2.35, the first dielectric layer A, the second dielectric layer B and defect layer C are respectivelya=
0.281, db=0.165 and dc=0.33 μm.Incident ray is 1, reflection light 2, transmitted ray 3.Reflection light relative to
There are the displacements of a transverse direction for incidence point.
Graphene is entrained in the centre of defect layer, i.e. the 0 of z-axis position.Graphene is the two-dimensional material of not thickness,
Surface conductivity can be described with nine fort formula (Kuboformula), it is as follows:
Wherein, fd=1/ (1+exp [(ε-μc)/(kBIt T is)]) Fermi-Dirac statistics, ε is particle energy, μcIt is graphite
Alkene chemical potential (is also called fermi level EF)), T is temperature, and e is elementary charge, and τ is momentum relaration time, kBIt is Boltzmann
Constant.
Graphene is regarded as with certain thickness dielectric, when equivalent thickness is lower than 1nm, this equivalent method
It is negligible to the influence for calculating reflectivity and transmissivity.Here we take graphene with a thickness of 0.34nm.Graphene
Effective dielectric constant be εg=1+i σgη0/(kdg), wherein k is incident wave vector, η0It is vacuum impedance.Temperature takes T=27 DEG C, moves
Measure relaxation time τ=0.5ps, μc=0.15eV.
Total is (AB)NCGC(BA)N, wherein Bragg period number N=5.
If incident light is TM wave, propagated along z-axis.The electromagnetic field at each layer of dielectric both ends can be contacted by transmission matrix
Get up.For example, the electromagnetic field at l layers of dielectric both ends can be got up by following relationship
Wherein MlIt is l layers of transmission matrix, wherein ηl=εl(ε0/μ0)1/2/(εl-sin2θ)1/2,θ is the incidence angle of light, is set as θ=20 ° here.The transmission matrix of whole system is
Wherein n is total number of plies of structure.Reflection coefficient is
Wherein η1=ηN+1=(ε0/μ0)1/2(1-sin2θ)1/2, the respectively impedance of incidence end and exit end, reflectivity R
=rr*.The band gap of photonic crystal is ωgap=4 ω0arcsin│(nb-na)/(nb+na)│2/ π, wherein ω0=2 π c/ λ0, λ0=
1.55μm。
(a) is the reflectivity of Defect Modes in the Defect Photonic Crystal undoped with graphene in Fig. 2.It can be seen that reflectivity
It is the function of incident light frequency.There are a band gap among reflectance spectrum, and the light in this band gap will all be reflected.But
It is that the reflectivity of the position * Defect Modes is zero, the light of Defect Modes will be transmitted all, therefore also be Transmission Modes.It is by reflection
Number is write as the form of indexWhereinIt is the phase of reflection coefficient.(b) is undoped with graphene in Fig. 2
The reflection coefficient phase of Defect Modes in Defect Photonic Crystal, it can be seen that have the phase hit of a π at Defect Modes position.Cause
Reflectivity for Defect Modes is zero, therefore there are the phases of reflection coefficient there is uncertainty.Meanwhile near Defect Modes, instead
It is more violent to penetrate coefficient phase variation.According to the relationship of the lateral displacement of the reflected beams and reflection coefficient phase
It is recognised that the lateral displacement of the reflected beams near Defect Modes is larger.But reflectivity at this moment is smaller, because
Graphene is doped in defect layer by we for this, obtains biggish reflectivity.
Fig. 3 (a) is the reflectivity of Defect Modes in the Defect Photonic Crystal of doped graphene.It can be seen that the position * defect
The reflectivity of mould is not zero, in present case, the maximum reflectivity R=0.212 of Defect Modes.Fig. 3 (b) is lacking for doped graphene
Fall into the reflection coefficient phase of Defect Modes in photonic crystal.It can be seen that the phase at Defect Modes does not jump, but variation is compared
Acutely, therefore available reflectivity is not zero, and the reflected beams with relatively larger transverse displacement.
Fig. 4 is the lateral displacement of the reflected beams in the Defect Photonic Crystal of doped graphene.It can be seen that when incident optical frequency
When rate is located at Defect Modes, the lateral displacement of the reflected beams is maximum, and maximum value is Δ=124 λ.
So visible: the doped graphene in Defect Photonic Crystal can greatly improve the reflectivity of Defect Modes, present case
In, the maximum reflectivity of Defect Modes can reach R=0.212；The lateral displacement maximum value of the reflected beams can be made to reach 124 λ, than
Lateral displacement in general structure improves a magnitude.
The specific embodiments described herein are merely examples of the spirit of the present invention.The utility model institute
Belonging to those skilled in the art can make various modifications or additions to the described embodiments or using similar
Mode substitute, but without departing from the spirit of the present application or beyond the scope of the appended claims.
Claims (2)
1. the photonic crystal of a kind of pair of Defect Modes reflectivity enhancing, which is characterized in that this photonic crystal includes the first dielectric layer
(A), the second dielectric layer (B), defect layer (C) and graphene layer (G), the defect layer (C) are located at the middle part of electron crystal；Institute
State the regularity of distribution of the first dielectric layer (A) and the second dielectric layer (B) are as follows: the two sides of the defect layer (C) have been alternately arranged
Several first dielectric layers (A) and several second dielectric layers (B), and two lateral surfaces of photonic crystal are the first dielectric layer
It (A), is the second dielectric layer (B) close to the two sides of defect layer (C)；The graphene layer (G) is embedded in defect layer (C).
2. the photonic crystal of a kind of pair of Defect Modes reflectivity enhancing according to claim 1, which is characterized in that the first dielectric
The refractive index of layer (A), the second dielectric layer (B) and defect layer (C) is respectively na=1.38, nb=2.35 and nc=2.35, first
The thickness of dielectric layer (A), the second dielectric layer (B) and defect layer (C) is respectively da=0.281 μm, db=0.165 μm and dc
=0.33 μm.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109669227A (en) * | 2019-02-27 | 2019-04-23 | 湖北科技学院 | A kind of photonic crystal of pair of Defect Modes reflectivity enhancing |
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| CN109669227A (en) * | 2019-02-27 | 2019-04-23 | 湖北科技学院 | A kind of photonic crystal of pair of Defect Modes reflectivity enhancing |
| CN109669227B (en) * | 2019-02-27 | 2024-04-05 | 湖北科技学院 | Photonic crystal with enhanced reflectivity to defect mode |
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