CN207601358U - A kind of broadband unidirectional transmission structures of photonic crystal - Google Patents
A kind of broadband unidirectional transmission structures of photonic crystal Download PDFInfo
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- CN207601358U CN207601358U CN201721572288.5U CN201721572288U CN207601358U CN 207601358 U CN207601358 U CN 207601358U CN 201721572288 U CN201721572288 U CN 201721572288U CN 207601358 U CN207601358 U CN 207601358U
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- photonic crystal
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Abstract
The utility model discloses a kind of broadband unidirectional transmission structures of photonic crystal, belong to photoelectron technical field.It is designed to provide a kind of broadband unidirectional transmission structures of photonic crystal, a special structure.Changing structural parameters can make reverse transfer efficiency be zero, and adjustment structure size can obtain UDT effects in optional frequency.Realize the broadband unidirectional transmission structures of photonic crystal.It is made of a 2 D photon crystal with dielectric grating.Photonic crystal is designed in point Γ there are one dirac cone, this cone allows vertical incidence optical transport without oblique incident ray is allowed to transmit in certain frequency range.The target of dielectric grating be by vertical incidence optical diffraction be other directions.Therefore, when incident light from a direction with this configuration when, will be completely plugged, and when incident light is from another direction incidence, it will be transmitted.
Description
Technical field
The utility model is related to a kind of broadband unidirectional transmission structures of photonic crystal, belong to photoelectron technical field.Specifically
A kind of excellent one-way transmission apparatus is provided.
Background technology
One-way transmission (UDT) device is the basis of optical computing and information processing.Generally speaking, there are two types of basic methods
It goes to obtain UDT effects：Interactive system and noninteractive system.Break time reversal using Faraday effect and nonlinear effect
Property comparison noninteractive system easy to implement, but huge volume and relevant high intensity require the UDT for making nonreciprocal system
Effect is not suitable for modern integrated optics.In recent years, in the interaction linear system with micro nano structure size, UDT effects are drawn
Sizable concern is played.So far, the UDT structures of various interactions occur in the literature, including asymmetric metallic film, two
Layer metal grating, Single Medium grating, metal grating and various optical materials.However, interaction UDT still occurs two in application
The problem of a practical：
1, because in linear system, optical transport does not have energy threshold, so reverse transfer can not be completely switched off, even if
It is single operation frequency, it is impossible to while meet the following conditions：
T1/T21000 10log (1/T of ＞2) ＞ 20
Wherein T1Represent positive efficiency of transmission, T2Represent reverse transfer efficiency.
2, the most of UDT effects obtained in system is received are based on various resonance effects, they do not have bandwidth, are only existed
Under single or discrete resonant frequency effectively, even if in THz, GHz or even in a other visible frequency, UDT has been able to reality
It is existing, but still without a kind of universal method that UDT can be realized in any frequency, especially broadband UDT.
Utility model content
The purpose of this utility model is to provide a kind of broadband unidirectional transmission structures of photonic crystal, a special knots
Structure.Changing structural parameters can make reverse transfer efficiency be zero, and adjustment structure size can obtain UDT effects in optional frequency.
Specifically, a kind of broadband unidirectional transmission structures for realizing photonic crystal.It is situated between by a 2 D photon crystal and electricity
Matter grating forms.Photonic crystal is designed in point Γ there are one dirac cone, this cone allows in certain frequency range
Vertical incidence optical transport is without allowing oblique incident ray to transmit.The target of dielectric grating be by vertical incidence optical diffraction be its other party
To.Therefore, when incident light from a direction with this configuration when, will be completely plugged, and when incident light enters from another direction
When penetrating, it will be transmitted.
Broadband unidirectional transmission structures further include the dielectric grating being oppositely arranged with photonic crystal, and the photonic crystal is two
Dimensional photonic crystal, on one point there are one dirac cone, dirac cone allows vertically to enter photonic crystal in certain frequency range
Optical transport is penetrated without oblique incident ray is allowed to transmit, it is other directions that dielectric grating, which is used for vertical incidence optical diffraction,.
The refractive index of the dielectric grating is n=2.
H=0.317 μm of the dielectric grating thickness.
The beneficial effects of the utility model are：Photonic crystal/the optical grating construction of the utility model, realizes photonic crystal
Broadband one-way transmission.The device is applicable not only to wideband frequency, it is often more important that can come by adjusting structure size arbitrary
Adjust working frequency.In addition, photonic crystal and grating are all symmetrical structures, and total is all dielectric, therefore is made
It makes and integrates and is very convenient.The utility model is opened using most traditional optical element and material and realizes high efficiency and broad band UDT effects
Approach.
Description of the drawings
Fig. 1 a are photon crystal structures；
Fig. 1 b are the three-dimensional dispersion surfaces of photonic crystal；
Dispersion relation figure when Fig. 1 c are light vertical incidence；
Dispersion relation figure when Fig. 1 d are light oblique incidences；
Fig. 2 is vertical incidence and oblique incidence (Kx=0.1 (2 π/a)) when layer of photonic crystals corresponding transmitted spectrum, it is real
Line represents vertical incidence, and dotted line represents oblique incidence；
Fig. 3 a are unidirectional (UDT) structure diagrams of the utility model broadband forward entrance；
Fig. 3 b are reversed incident unidirectional (UDT) structure diagrams in the utility model broadband；
Transmitted spectrum when Fig. 4 a are H=0.317 μm of arbitrary single grating thickness；
When Fig. 4 b are H=0.317 μm, transmissivity contrast and the relationship of isolation and incident wavelength；
Fig. 4 c are the respective electric field distribution that forward entrance and reversed incidence are when λ=0.65 μm.
Reference numeral is as follows：1st, 2 D photon crystal, 2, photoelectricity sub-gratings, 3, first band gap, the 4, second band gap, 5, Di La
Gram dot frequency.
Specific embodiment
Specific embodiment of the present utility model is illustrated below in conjunction with the accompanying drawings：
The transmission characteristic near dirac point in the photonic crystal based on dispersion relation is analyzed first, then designs one
UDT structures.Its principle is illustrated from the angle of geometric optics, using Finite difference time domain (FDTD) technology, to one-way transmission result
And its property carries out numerical simulation.Fig. 1 a are simple 2 D photon crystals, are made of, scheme the dielectric stick of some arrangement squarelys
In also give cartesian coordinate, in X direction with Y-direction periodic arrangement, their axis arranges dielectric stick along Z-direction, f and R
Representing the radius of lattice constant and stick respectively, ε is the relative dielectric constant of dielectric rod, ε=12.5, first, along the Z direction, I
Calculate first with electricity transverse magnetic (TM) polarised light the photonic crystal three-dimensional dispersion surface, in the calculation, R=
0.2a, then, λ are incident wavelengths.As a result as shown in Figure 1 b, it coincide well with traditional tetragonal photonic crystal dispersion relation.
As can be seen that dirac cone is located at Kx=0, KyDirac point at=0, f=0.541a/ λ, corresponding to the photonic crystal
The Γ points of the first Brillouin-Zone of band structure.Near dirac dot frequency, there is no band gap in the frequency span entirely calculated.So
And this is not meant to do not have band gap on any direction of propagation.When light is propagated in the y-direction, work as Kx=0 (vertical incidence),
Fig. 1 c are obtained from Fig. 1 b, it can be seen that there is no band gap, it means that the frequency of all calculating can be in the photonic crystal
It propagates.If however, Kx≠ 0 (oblique incidence), it is assumed that Kx=0.1 (2 π/a), then dispersion curve is as shown in Figure 1 d, it can be seen that with
Normal incidence is different, and two band gap are appeared in above and below dirac dot frequency, leave a small transmission therebetween
Band.For the frequency in frequency band, it is impossible to be transmitted in the photonic crystal.
In order to verify above-mentioned property, Fig. 2 gives vertical incidence and oblique incidence (Kx=0.1 (2 π/a)) when photon it is brilliant
The corresponding transmitted spectrum of body layer, Fig. 2 include 3 and second band gap 4 of first band gap, wherein a=0.36 μm of lattice constant, and photon is brilliant
10 layers of dielectric rod of thickness selected as of body layer.Solid line and dotted line represent vertical incidence and oblique incidence respectively.Clearly for vertical
Incidence, entire frequency band do not have transmission gap.And for oblique incidence Kx=0.1 (2 π/a), have two beside dirac dot frequency
A apparent transmission gap.For the frequency in these gaps, photonic crystal shows as zero refraction materials (in addition to dirac point
Except frequency, without real zero refractive index).During light vertical incidence, it is almost completely transmitted.When Ray obliquity, it
It is completely reflected.
From above-mentioned analysis it is found that for the frequency in band gap, the direction of incident light determines that can it transmit.Control incident light
There are various methods in the direction of propagation, and optical grating diffraction is one of method the most convenient.Here we select medium diffraction grating real
This existing function.Fig. 3 a, Fig. 3 b show photonic crystal and grating combination structure.Rectangle represents photon crystal 1, and array represents only
Vertical dielectric grating 2 (actually if there is the substrate of the grating with identical material, then not influencing UDT effects), in figure
Including dirac dot frequency 7.As can be seen that for forward entrance, light normally reaches photon crystal 1, it passes through photon crystal 1 layer
And dielectric grating 2 is reached, right side is then diffracted into the different orders of diffraction.Entire transmissivity is the summation of all orders of diffraction.
When light is from rear incident, it is diffracted into many directions first.When these diffraction lights are incident on photonic crystal, in addition to zero
Other than sequence, other diffraction lights are all inclined.This inclined incident light, which can be reflected, to be come.Therefore, if the week of grating
Phase is more than incident wavelength, then is easy to get asymmetric transmission (AT) effect.The order of diffraction is more, and effect is better.In addition, the order of diffraction
Between intensity distribution be influence AT effects another factor.The diffraction efficiency of zero level is lower, and AT effects are better.According to me
Previous studies, by selecting appropriate grating thickness that can the diffraction efficiency of zero level be adjusted to 0, be obtained in this way
Perfect UDT effects.
According to above-mentioned principle, it now devised UDT structures and optimize its parameter.In simulations, one is only calculated by void
The period that line surrounds.Lattice constant and radius remain a=0.36 μm, R=0.2a=0.072 μm, and in incident direction
Still 10 layers of stick are used.For simplicity, grating fill-factor is selected as L/P=0.5, and the refractive index of grating material is n=
2.First, in order to obtain better AT effects, screen periods should be greater than incident wavelength, be set as P=6a=2.16 μm here, about
Three times for incident wavelength.Fig. 4 a give transmitted spectrum during H=0.317 μm of arbitrary single grating thickness.It can be clearly
See, the transmissivity of two opposite directions is very different in certain frequency range.Positive transmissivity is with higher number
The horizontal fluctuation of value, at some frequencies, almost unit 1.And for the inverse direction from 0.62 μm to 0.66 μm, transmissivity
All close to 0. this is because projectile energy is almost diffracted into the band gap of photonic crystal higher-order number by grating.Therefore, it obtains
One-way transmission in the range of certain frequency.
As excellent optical-unidirectional device, poor Δ T=T is transmitted1-T2And reversed transmissivity T2It is sufficiently large.Transmissivity
Contrast (T1/T2) and isolation (D=10log (1/T2)) it is two kinds of parameters for judging UDT device performances.Fig. 4 b are given in H
At=0.317 μm, the relationship of the two parameters and incident wavelength.As can be seen that the peak value of this two curves appears in same position
It puts.Maximum-contrast and isolation respectively reach 8000 and 40.This is because under the wavelength value, meet condition H=λ/2,
The efficiency of zero level is almost 0, therefore reversely transmissivity is very small, causes contrast and isolation angle value maximum.This means that for
Single frequency point can realize perfect UDT effects by optimizing grating thickness.In addition, from this figure, it can be seen that entire
For isolation nearly all higher than 20, contrast is nearly all higher than 1000 in computer capacity.Even for the list in other UDT structures
A wavelength, in certain frequency range, it is also difficult to while meet the two conditions.It undoubtedly demonstrates this UDT structure to wide
General wave band has effect.
In order to further illustrate UDT effects, Fig. 4 c give the respective electric field of two incident directions when λ=0.65 μm
Distribution.FromArbitrarily 0.65 μm is selected, it can be seen that if light, from the incidence of photonic crystal side, light can
To be propagated through total, and it is diffracted into many directions.It can interfere between them, and after by grating
Form certain interference figure.When light is from the incidence of grating side, there are some energy still can enter photonic crystal.But these energy
Amount can be fallen into the band gap of photonic crystal, cannot penetrate photonic crystal.Therefore, transmissivity is almost nil.
For the dispersion surface of the photonic crystal, as shown in Figure 1 b, frequency is normalized by the inverse of lattice constant.This meaning
Taste when total it is proportional when zooming in or out, the dispersion relation of red shift or blue shift remains unchanged, transmission shown in Fig. 2
Spectrum is also such.In addition, can be distributed can also be by optimizing grating thickness control for the diffraction between the order of diffraction, the zero of zero level spreads out
Penetrating efficiency can obtain under any frequency.Therefore, by adjusting structure size, UDT effects can be obtained in arbitrary frequency location
It should.In information processing system, 1.55 μm are generally selected as operation wavelength.Herein, it designs another and is operated in λ=1.55
μm UDT devices, with prove can obtain the UDT effects in any frequency.First, structure size is expanded 1.55/
0.634=2.44 times, parameter becomes a=0.88 μm, R=0.176 μm, P=5.28 μm, L=2.64 μm, H=0.772 μm.It obtains
Obtained identical transmission shape.In order to more convincing, our grating thickness are changed to H=0.775 μm, calculate transmitted light, can be with
Find out, although transmitted spectrum is slightly changed, but still obtain excellent UDT effects when wavelength is 1.55 μm.In addition, pass through
Adjust structure size, obtain microwave, THz, GHz with it is infrared on similar UDT effects.Demonstrating can under any frequency
Obtain UDT effects.
To sum up, unique dirac cone dispersion surface using photonic crystal can obtain efficient UDT structures.
For single operation frequency, positive transmissivity may be up to 95%, while reversely transmissivity is less than 10-4, therefore contrast and isolation
Degree respectively reaches 8000 and 40.Even if in a bigger frequency range, contrast and isolation can also reach simultaneously
1000 and 20.The device is applicable not only to wideband frequency, it is often more important that can carry out arbitrary adjustment work by adjusting structure size
Working frequency.In addition, photonic crystal and grating are all symmetrical structures, and total is all dielectric, therefore manufactures sum aggregate
Into very convenient.The approach for realizing high efficiency and broad band UDT effects is opened using most traditional optical element and material herein.
The above is the preferred embodiment of the utility model, it is noted that for the ordinary skill of the art
For personnel, under the premise of principle described in the utility model is not departed from, several improvements and modifications can also be made, these improvement
The scope of protection of the utility model is also should be regarded as with retouching.
Claims (3)
- A kind of 1. broadband unidirectional transmission structures of photonic crystal, including photonic crystal, which is characterized in that the broadband one-way transmission Structure further includes the dielectric grating being oppositely arranged with photonic crystal, and the photonic crystal is 2 D photon crystal, photonic crystal There are one dirac on one point to bore, and dirac cone allows vertical incidence optical transport oblique without allowing in certain frequency range Optical transport is penetrated, it is other directions that dielectric grating, which is used for vertical incidence optical diffraction,.
- 2. the broadband unidirectional transmission structures of photonic crystal as described in claim 1, which is characterized in that the dielectric grating Refractive index is n=2.
- 3. the broadband unidirectional transmission structures of photonic crystal as claimed in claim 2, which is characterized in that the dielectric grating is thick H=0.317 μm of degree.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110333566A (en) * | 2019-07-12 | 2019-10-15 | 苏州大学 | A kind of all dielectric filter |
| CN112185487A (en) * | 2020-09-28 | 2021-01-05 | 北京环境特性研究所 | Target excitation frequency searching method and device of photonic crystal and readable medium |
-
2017
- 2017-11-22 CN CN201721572288.5U patent/CN207601358U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110333566A (en) * | 2019-07-12 | 2019-10-15 | 苏州大学 | A kind of all dielectric filter |
| CN112185487A (en) * | 2020-09-28 | 2021-01-05 | 北京环境特性研究所 | Target excitation frequency searching method and device of photonic crystal and readable medium |
| CN112185487B (en) * | 2020-09-28 | 2023-05-16 | 北京环境特性研究所 | Target excitation frequency searching method and device for photonic crystal and readable medium |
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Granted publication date: 20180710 Termination date: 20181122 |