CN115548690A - Dual-tuned absorber based on dirac semimetal and strontium titanate - Google Patents

Dual-tuned absorber based on dirac semimetal and strontium titanate Download PDF

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CN115548690A
CN115548690A CN202211474008.2A CN202211474008A CN115548690A CN 115548690 A CN115548690 A CN 115548690A CN 202211474008 A CN202211474008 A CN 202211474008A CN 115548690 A CN115548690 A CN 115548690A
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absorber
double
tuned
bds
layer
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胡宝晶
胡朋
杨利
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Yunnan Agricultural University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
    • H01Q15/002—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective said selective devices being reconfigurable or tunable, e.g. using switches or diodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
    • H01Q15/0026—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective said selective devices having a stacked geometry or having multiple layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/0086—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems

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Abstract

The invention discloses a double-tuned absorber based on a dirac semimetal and strontium titanate, which belongs to the technical field of devices, wherein the top layer of the double-tuned absorber is a BDS nanorod resonator, a middle dielectric layer is composed of STO, the bottom of the double-tuned absorber is a ground layer, and all the layers are tightly and seamlessly attached to each other to form a structural body. Compared to monoatomic layer graphene, BDS is more robust to environmental defects or excessive conductor states.

Description

Dual-tuned absorber based on dirac semimetal and strontium titanate
Technical Field
The invention belongs to the technical field of metamaterial devices, and particularly relates to a dual-tuned absorber based on a dirac semimetal and strontium titanate.
Background
Terahertz (THz) waves have attracted considerable interest to researchers because they have the advantages of both microwave and visible light waves. In recent years, terahertz absorbers (THz absorbers) have been a research hotspot in many fields. However, due to natural limitations of natural materials in the terahertz range, it remains a great challenge to realize a high-performance absorber using natural materials in the terahertz frequency band. The metamaterial is an artificial composite material with a periodic arrangement and has outstanding electromagnetic properties. Since the first narrow-band wave absorber based on a Metamaterial designed by Landy et al in 2008, the development of a terahertz frequency band Metamaterial wave absorber (Metamaterial absorber) has made a great progress, and the terahertz frequency band Metamaterial wave absorber is developed from a single band and a double band to a multiband and a wide band. However, most absorbers are difficult to change in spectral characteristics and bandwidth once they are fabricated, which greatly limits their applications and developments. Therefore, the development of dynamically tunable absorbers is highly desirable for many intelligent systems.
In order to design absorbers with dynamically tunable properties, many new materials are available such as: semiconductors, vanadium dioxide and liquid water are all applied to the research and design of wave absorbers. However, these materials generally have the disadvantages of low efficiency, inconvenient operation, etc. Graphene shows great application potential as a two-dimensional (2D) material with excellent electromagnetic properties. Unfortunately, however, graphene absorbers are often difficult to manufacture due to their natural 2D structure. Therefore, a material that can replace graphene must be found. In recent years, dirac semimetal (BDS), which is a 3D analog of graphene, has been applied to the design of metamaterial absorbers. Like graphene, the dielectric constant of BDS can be dynamically tuned by changing the fermi energy. Meanwhile, BDS has higher mobility under the same conditions and is easier to manufacture and stable than graphene. These features mean that BDS is more suitable than graphene for designing dynamically tunable terahertz devices. In addition to BDS, strontium Titanate (STO) is also a ferroelectric material with a high dielectric constant and low dielectric loss. The response of STO to terahertz waves is determined by a strongly polar soft vibration mode, and its relative dielectric constant can be modulated by temperature.
Due to the electrically tunable nature of the BDS and the temperature tunable nature of the STO. In recent years, a wave absorber for realizing dynamic double tuning by using BDS and STO has become a research hotspot of the scientific community. In 2020, xiong et al proposed a double tuned absorber consisting of a BDS disc with discontinuous rings and an STO. In the same year, they have proposed a double tuned absorber consisting of a rosette-shaped BDS resonator and an STO. In 2021, wu et al also designed a terahertz double-tuned absorber composed of a BDS resonator and an STO with an arrow ring hybrid structure. However, it can be found by comparison that the dynamic double-tuned absorber model based on BDS and STO proposed in the prior art is very complex in structure, which adds great difficulty to subsequent experimental preparation and device processing.
Disclosure of Invention
The invention provides a dynamic double-tuned metamaterial wave absorber based on simple BDS cross-shaped nanorods and STO. First, dynamic double tuning of the absorption frequency and the absorption rate magnitude of the absorber can be achieved by varying the BDS Fermi energy and the STO temperature. Secondly, the performance of the wave absorber is theoretically analyzed through a Coupling Mode Theory (CMT) and an Equivalent Circuit Model (ECM) respectively. Finally, the influence of the electric field distribution and the incident light polarization angle of the absorber on the absorption effect of the absorber is discussed. This provides a theoretical basis for the design of double-tuned filters and wave absorbers.
In order to realize the purpose, the invention is realized by adopting the following technical scheme: the top layer of the double-tuned wave absorber is a BDS nanorod resonator, the middle dielectric layer is formed by STOs, the bottom of the double-tuned wave absorber is a grounding layer, the top layer is a cross-shaped BDS nanorod resonator, the bottom layer is a gold grounding layer, and the layers are tightly and seamlessly attached to each other to form a structural body.
Further, the length of the top cross-shaped BDS nano rod
Figure 605908DEST_PATH_IMAGE001
Width of
Figure 571983DEST_PATH_IMAGE002
With a thickness of
Figure 882879DEST_PATH_IMAGE003
Initial fermi energy
Figure 809246DEST_PATH_IMAGE004
。
Further, the interlayer dielectric layerInitial temperature T of 250K to 400K and thickness of
Figure 171089DEST_PATH_IMAGE005
(ii) a The conductivity of the bottom gold grounding layer is
Figure 524710DEST_PATH_IMAGE006
With a thickness of
Figure 322901DEST_PATH_IMAGE007
。
Further, the double-tuned absorber equivalent circuit is as follows:
the bottom gold thin film layer is equivalent to a short-circuit device; when incident light is X polarized light, only the nanorods in the X direction can interact with incident waves, the nanorods in the Y direction cannot interact with the incident light because the polarization direction is vertical to the long axis of the nanorods, and the top cross BDS nanorods can be represented by a RLC series circuit connected in parallel; RLC series circuit route R 1 ,L 1 ,C 1 And RLC are connected in series and then connected with the short-circuit device in parallel.
The input impedance of the double tuned absorber can be expressed as:
Figure 318539DEST_PATH_IMAGE008
wherein, in the step (A),
Figure 767844DEST_PATH_IMAGE009
represent
Figure 292366DEST_PATH_IMAGE010
A series circuit equivalent impedance;
Figure 843433DEST_PATH_IMAGE011
representing the characteristic impedance of the short-circuited transmission line;
Figure 862336DEST_PATH_IMAGE012
which represents the impedance of the wave in free space,
Figure 916880DEST_PATH_IMAGE013
respectively representing the relative dielectric constant and thickness of the STO layer,
Figure 877882DEST_PATH_IMAGE014
representing the free space wavenumber; therefore, the reflection coefficient of the double-tuned absorber
Figure 916246DEST_PATH_IMAGE015
Can be expressed as:
Figure 974725DEST_PATH_IMAGE016
(ii) a The equivalent impedance of the absorber can be expressed as:
Figure 149354DEST_PATH_IMAGE017
(ii) a According to the impedance matching theory, when the equivalent impedance of the absorber
Figure 15679DEST_PATH_IMAGE018
The wave absorber reflectivity will be equal to 0 and the absorption will be close to 1.
Further, the absorption rate of the double-tuned absorber is more than 99%.
Further, BDS Fermi energy
Figure 292071DEST_PATH_IMAGE019
Is selected at
Figure 902044DEST_PATH_IMAGE020
In the meantime, the resonance frequency and the absorption rate at the absorption peak can be dynamically adjusted.
Further, the STO temperature T is selected to be
Figure 931179DEST_PATH_IMAGE021
The resonance frequency and the absorption rate at the absorption peak can be dynamically adjusted.
The invention has the beneficial effects that:
1. the invention adopts the Dirac semimetal (BDS) metamaterial, and compared with the common material, the Dirac semimetal is relatively easy to manufacture and has lower inherent loss and more stable physical characteristics in the terahertz waveband. Compared to monoatomic layer graphene, BDS is more robust to environmental defects or excessive conductor states.
2. The invention adopts the resonance structure of the Dirac semimetal (BDS) cross nano rod, has simple structure, can realize the perfect wave-absorbing effect independent of polarization, and has the absorption rate of over 99 percent.
3. The invention uses BDS Fermi energy
Figure 233985DEST_PATH_IMAGE022
The selected range is 0.04 eV-0.1 eV, the resonance frequency and the absorption rate at the absorption peak can be dynamically adjusted.
4. According to the invention, strontium Titanate (STO) is set as a model medium layer, the temperature T is selected to be between 250K and 400K, and the resonance frequency at the absorption peak can be dynamically adjusted by changing the temperature control characteristic of the STO layer and by changing the temperature of the STO layer.
5. The invention adopts all-dielectric material, so the structure is simple and convenient, and the processing is easy.
Drawings
FIG. 1 is a graph showing the change of the real part (a) of the dielectric constant of BDS when the Fermi energy of BDS is increased from 40 mev to 100 mev;
FIG. 2 is a graph of the change in dielectric constant and imaginary part (b) of BDS as the Fermi energy of BDS increases from 40 mev to 100 mev;
FIG. 3 is a graph showing the change of the real part (c) of the STO dielectric constant when the Fermi energy of the BDS is increased from 40 mev to 100 mev;
FIG. 4 is a graph of the change in the imaginary part (d) of the STO dielectric constant when the BDS Fermi energy increases from 40 mev to 100 mev;
FIG. 5 is a view showing the structure of an absorbent body of the present invention;
FIG. 6 is an equivalent circuit diagram of the present invention;
FIG. 7 shows the transmission, reflection, absorption and CMT theoretical analysis results of a double tuned absorber.
FIG. 8 is a graph of the absorption rate of a double tuned absorber as a function of the polarization angle of incident light;
FIG. 9 is a graph comparing the numerical absorption rate of a double tuned absorber with the theoretical results of an ECM;
FIG. 10 is a graph showing the variation of the impedance of the double-tuned absorber with frequency;
FIG. 11 is the electric field distribution of a double tuned absorber at (a) 2.1608 THz in the X-Y plane under X-polarized wave conditions;
FIG. 12 shows the electric field distribution of a double tuned absorber at (b) 1.0301THz in the X-Y plane under X-polarized wave conditions;
FIG. 13 is a diagram showing an electric field distribution at (c) 2.1608 THz of a double-tuned absorber in an X-Y plane under a Y-polarized wave condition
FIG. 14 is a graph showing an electric field distribution at (d) 2.1608 THz of a double-tuned absorber in an X-Y plane under a Y-polarized wave condition;
FIG. 15 shows the electric field distribution of a double-tuned absorber at (a) 2.1608 THz in the Y-Z plane under X-polarized wave conditions
FIG. 16 is the electric field distribution of the double tuned absorber at (b) 1.0301THz in the Y-Z plane under X-polarized wave conditions;
FIG. 17 is a graph showing the electric field distribution of a double-tuned absorber at (c) 2.1608 THz in the X-Z plane under Y-polarized wave conditions;
FIG. 18 is a graph showing the electric field distribution of a double tuned absorber at (d) 1.0301THz in the X-Z plane under the condition of Y polarized wave;
FIG. 19 is an infrared plot of absorber absorption rate as a function of BDS fermi energy;
FIG. 20 is a line graph of the law of absorber absorption rate as a function of BDS fermi energy;
fig. 21 is a graph of the absorption rate of the absorber as a function of temperature of the fermi energy STO.
Detailed Description
The present invention will be described in detail below with reference to the attached drawings, and the technical solutions in the embodiments of the present invention will be clearly and completely described. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
As shown in FIG. 5, the top layer of the double-tuned absorber is BDS nanorod resonator, the middle dielectric layer is STO, and the bottom of the double-tuned absorber isThe BDS nano-rod resonator is a grounding layer, wherein the top layer is a cross-shaped BDS nano-rod resonator, the bottom layer is a gold grounding layer, and the layers are tightly and seamlessly attached to each other to form a structural body. The top layer is a cross-shaped BDS nanorod resonator, the middle dielectric layer is composed of STO, and the bottom is a gold grounding layer. In FIG. 5 (b), the length of the top BDS cross-shaped nanorods
Figure 230629DEST_PATH_IMAGE023
Width of
Figure 909872DEST_PATH_IMAGE024
A thickness of
Figure 793514DEST_PATH_IMAGE025
Initial fermi energy
Figure 17953DEST_PATH_IMAGE026
. Initial temperature of intermediate STO layer
Figure 987046DEST_PATH_IMAGE027
A thickness of
Figure 938822DEST_PATH_IMAGE028
. The conductivity of the bottom gold film is
Figure 208129DEST_PATH_IMAGE029
A thickness of
Figure 116653DEST_PATH_IMAGE030
. The period of the model is
Figure 573042DEST_PATH_IMAGE031
. Numerical simulations were done by means of commercial FDTD Solutions. The two-dimensional structure shown in fig. 5 (b) has periodic boundary conditions in the X and Y directions and Perfectly Matched Layer (PML) absorption boundary conditions in the Z direction. The incident wave is linearly polarized wave, the incident direction is-Z direction, and the polarization direction is X direction.
The double-tuned wave absorber equivalent circuit is as follows:
according to the transmission line theoryAn Equivalent Circuit Model (ECM) of a double tuned absorber is shown in fig. 6. The bottom gold thin film layer in the ECM may be equivalent to a shorting device. Meanwhile, when the incident light is X polarized light, only the nanorods in the X direction can interact with the incident wave, and the nanorods in the Y direction cannot interact with the incident light because the polarization direction is perpendicular to the long axis of the nanorods. Thus, the top cross BDS nanorod can be represented by a parallel RLC series circuit. RLC series circuit routing
Figure 328508DEST_PATH_IMAGE032
The RLC are connected in series and then connected with the short-circuit device in parallel.
The input impedance of the double tuned absorber can be expressed as:
Figure 921164DEST_PATH_IMAGE033
wherein, in the step (A),
Figure 487405DEST_PATH_IMAGE034
to represent
Figure 696670DEST_PATH_IMAGE035
A series circuit equivalent impedance;
Figure 255827DEST_PATH_IMAGE036
representing the characteristic impedance of the short-circuited transmission line;
Figure 217836DEST_PATH_IMAGE037
which represents the impedance of the wave in free space,
Figure 938667DEST_PATH_IMAGE038
respectively representing the relative dielectric constant and thickness of the STO layer,
Figure 369649DEST_PATH_IMAGE039
representing the free space wavenumber; thus, the reflection coefficient of the double tuned absorber
Figure 466918DEST_PATH_IMAGE015
Can be expressed as:
Figure 316056DEST_PATH_IMAGE040
(ii) a The equivalent impedance of the absorber can be expressed as:
Figure 207789DEST_PATH_IMAGE041
(ii) a According to the impedance matching theory, when the equivalent impedance of the absorber
Figure 126066DEST_PATH_IMAGE042
The absorber reflectivity will be equal to 0 and the absorption will be close to 1. The absorptivity of the double-tuned wave absorber is more than 99%.
BDS Fermi energy
Figure 27026DEST_PATH_IMAGE043
Is selected at
Figure 700977DEST_PATH_IMAGE020
In the meantime, the resonance frequency and the absorption rate at the absorption peak can be dynamically adjusted.
The STO temperature T is chosen between 250K and 400K, and the resonance frequency and the absorption rate at the absorption peak can be dynamically adjusted.
The design process of the double-tuned wave absorber is as follows:
kubo formula is used in random phase approximation theory (RPA) at long wavelength limits
Figure 29190DEST_PATH_IMAGE044
Under the conditions, the dynamic conductivity of BDS is expressed as:
Figure 169185DEST_PATH_IMAGE045
(1)
Figure 873836DEST_PATH_IMAGE046
(2)
wherein
Figure 166408DEST_PATH_IMAGE047
，
Figure 931101DEST_PATH_IMAGE048
Which is a function of the fermi distribution,
Figure 558392DEST_PATH_IMAGE049
which represents the energy in the fermi range,
Figure 50422DEST_PATH_IMAGE050
which is indicative of the fermi momentum,
Figure 446768DEST_PATH_IMAGE051
which is indicative of the fermi rate,
Figure 116784DEST_PATH_IMAGE052
represents a factor of degeneracy, and represents,
Figure 231371DEST_PATH_IMAGE053
to cut off the energy, the dirac spectrum will then no longer be linear.
For further calculations, drude damping should be considered in the equations, i.e. using alternatives in equations (1) and (2)
Figure 762977DEST_PATH_IMAGE054
In which
Figure 279409DEST_PATH_IMAGE055
Is derived from the carrier mobility
Figure 385905DEST_PATH_IMAGE056
The determined scattering ratio.
Finally, the dielectric constant of the BDS can be written as
Figure 987788DEST_PATH_IMAGE057
(3)
Wherein the content of the first and second substances,
Figure 824550DEST_PATH_IMAGE058
is a dielectric constant of a vacuum, and,
Figure 195489DEST_PATH_IMAGE059
is effectively the background dielectric constant when
Figure 207307DEST_PATH_IMAGE060
When the temperature of the water is higher than the set temperature,
Figure 30907DEST_PATH_IMAGE061
it represents AlCuFe quasi-crystal.
On the other hand, as a temperature-dependent material, the dielectric constant of STO in the terahertz range can be expressed as:
Figure 169895DEST_PATH_IMAGE062
(4)
wherein
Figure 660919DEST_PATH_IMAGE063
Representing the high frequency bulk constant.
Figure 843639DEST_PATH_IMAGE064
Representing the incident angular frequency.
Figure 669381DEST_PATH_IMAGE065
Is the oscillator strength independent of temperature.
Figure 595749DEST_PATH_IMAGE066
And
Figure 675701DEST_PATH_IMAGE067
respectively representing the soft mode frequency and the damping factor. By means of the law of the kokelen law,
Figure 294901DEST_PATH_IMAGE066
and
Figure 843825DEST_PATH_IMAGE067
can be expressed as:
Figure 839463DEST_PATH_IMAGE068
(5)
Figure 773921DEST_PATH_IMAGE069
(6)
according to the equations (1) - (6), fig. 1-4 show the change rule of BDS and STO dielectric constants with incident light frequency under different BDS fermi energies and different STO temperatures. It can be seen from fig. 1 and 2 that the dielectric constant of BDS is very sensitive to fermi energy over the frequency range of interest. In fig. 1, the real part of the dielectric constant of the BDS gradually increases from a negative value to zero, indicating that the BDS exhibits metallic characteristics in this frequency range. In fig. 2, the imaginary part of the dielectric constant of the BDS decreases significantly up to near zero with increasing frequency, which means that the loss of the BDS is very low in the high frequency range. In FIGS. 3 and 4, when the STO temperature is constant, the real part of the STO dielectric constant increases slowly with increasing frequency, but the imaginary part increases significantly with increasing frequency. Meanwhile, when the STO temperature changes, both the real part and the imaginary part of the STO dielectric constant increase with the STO temperature at the same frequency, but the increment of the real part is much larger than that of the imaginary part.
Example 1
FIG. 7 shows the Fermi energy when BDS is used
Figure 564022DEST_PATH_IMAGE070
STO temperature
Figure 101707DEST_PATH_IMAGE027
The absorption, reflection and transmission spectra of the double tuned absorber. It can be seen that the absorption rate of the double tuned absorber at 2.1608 THz reaches 99.8%, and the "perfect" absorption is realized. Meanwhile, at this frequency point, the reflectivity of the absorber is close to 0. Furthermore, the transmission of the absorber is always close to 0 throughout the analysis frequency range. This is because the thickness of the bottom gold thin film layer is greater than the skin depth of incident light in the terahertz range, which can block all transmitted waves and act as a reflective layer in the model. At this time, the absorption rate of the wave absorber
Figure 369878DEST_PATH_IMAGE071
And reflectivity
Figure 424421DEST_PATH_IMAGE072
The relationship of (1) is:
Figure 385424DEST_PATH_IMAGE073
。
according to the coupled mode theory (coupled mode the CMT), for a "perfect" wave absorbing system, the physical mechanism can be represented by the following formula:
Figure 643361DEST_PATH_IMAGE074
(7)
Figure 980802DEST_PATH_IMAGE075
(8)
here, the first and second liquid crystal display panels are,
Figure 155431DEST_PATH_IMAGE076
representing the normalized amplitude of the guided resonance,
Figure 271023DEST_PATH_IMAGE077
the normalized input and output amplitudes are described separately,
Figure 531103DEST_PATH_IMAGE078
indicating the inherent loss and external leakage of the system,
Figure 141076DEST_PATH_IMAGE079
is the resonant frequency. The reflection coefficient of the coupled system model can be expressed as:
Figure 435791DEST_PATH_IMAGE080
(9)
when the transmission coefficient is equal to zero, the absorption coefficient of the system can be expressed as:
Figure 223750DEST_PATH_IMAGE081
(10)
as can be seen from the formula (9), when
Figure 971126DEST_PATH_IMAGE082
When is at
Figure 384790DEST_PATH_IMAGE083
Here, the system reflectivity is minimized and the absorption is maximized. The theoretical absorption spectrum of the CMT model is shown in fig. 7. It was found by comparison that it matched well with the numerical absorption spectrum of FDTD.
The full width at half maximum (FWHM) of the double tuned absorber can be calculated in the FDTD numerical absorption spectrum of FIG. 7
Figure 268432DEST_PATH_IMAGE084
Absorption frequency of
Figure 982617DEST_PATH_IMAGE085
. Therefore, the quality factor of the wave absorber
Figure 951711DEST_PATH_IMAGE086
. On the other hand, in the CMT theoretical model, the system inherent loss
Figure 903486DEST_PATH_IMAGE087
External leakage of
Figure 907214DEST_PATH_IMAGE088
. Theoretical figure of merit for a system
Figure 36975DEST_PATH_IMAGE089
. Wherein the content of the first and second substances,
Figure 758944DEST_PATH_IMAGE090
，
Figure 514410DEST_PATH_IMAGE091
. Therefore, the theoretical figure of merit of the system
Figure 621912DEST_PATH_IMAGE092
In close proximity to the numerical results, this demonstrates that the "perfect" absorption effect of the double tuned absorber is based on critical coupling.
FIG. 8 shows the polarization angle of incident light
Figure 437421DEST_PATH_IMAGE093
And when the change is carried out, the change rule of the absorption effect of the double-tuned wave absorber is changed.
Figure 381107DEST_PATH_IMAGE093
Is defined as the angle between the incident electric field direction and the X-axis direction. It can be seen from the figure that due to the symmetry of the model, the polarization angle of the incident light is changed from
Figure 674685DEST_PATH_IMAGE094
Is increased to
Figure 138158DEST_PATH_IMAGE095
In the process, the absorption frequency and the absorption rate of the wave absorber are basically kept unchanged, and the polarization insensitivity is shown.
To further theoretically analyze the physical properties of the double-tuned absorber, fig. 9 and 10 show the analysis results of an Equivalent Circuit Model (ECM). As can be seen from fig. 9, the theoretical absorption spectrum of the ECM model agrees well with the numerical absorption spectrum of FDTD. In FIG. 10, the double tuned absorber is at the absorption frequency
Figure 390148DEST_PATH_IMAGE096
Equivalent impedance of
Figure 821129DEST_PATH_IMAGE097
And the impedance matching condition is satisfied. Therefore, the wave absorber is in
Figure 918398DEST_PATH_IMAGE098
The absorption rate is close to 1, and 'perfect' is realized "And (4) absorbing.
FIGS. 11-14 and 15-18 show the incident wave as X-polarized wave (respectively)
Figure 737843DEST_PATH_IMAGE094
) And Y polarized wave (
Figure 895155DEST_PATH_IMAGE095
) Under the condition, the electric field distribution of the double-tuned wave absorber under an X-Y plane, an X-Z plane and a Y-Z plane.
As can be seen from fig. 11 and 12, under the X-polarized wave condition, when the frequency is equal to 2.1608 THz, only the lateral BDS nanorods can interact with the incident light and the absorption at this point is close to 1. Therefore, in the X-Y plane, the electric field at this point is mainly distributed near the transverse nanorods in a dipole mode, and the electric field value is maximum. Whereas at 1.0301THz, the electric field value at this point is significantly less than at 2.1608 THz, since the absorption is close to 0, but also approximately exhibits a dipole mode distribution. In fig. 13 and 14, under the Y polarized wave condition, the electric field distribution of the wave absorber in the X-Y plane is perpendicular to that under the X polarized wave condition, but the distribution rule is approximately the same.
Similarly, in fig. 15, for the X-polarized wave, the absorption rate is maximum at 2.1608 THz. Therefore, in the Y-Z plane, the electric field value of the wave absorber at this point is maximum and is distributed intensively near the BDS nanorods and inside the STO layer. Whereas at 1.0301THz, the absorption is less. Therefore, the value of the electric field at the point of change is much less than that at 2.1608 THz. In fig. 17 and 18, the electric field distribution law in the X-Z plane for the Y-polarized wave is approximately the same as that of fig. 11 and 12.
Finally, in order to verify the dynamic double-tuning performance of the absorber, fig. 19-20 and fig. 21 respectively show the change law of the absorption rate of the absorber under different BDS fermi energy and STO temperature conditions.
As shown in fig. 1 and 2, as the fermi energy increases, the real part of the dielectric constant of the BDS gradually decreases and the imaginary part gradually increases, and the decrease of the dielectric constant according to perturbation theory will result in an increase of the resonant frequency. Thus, as the fermi energy of the BDS increases,the absorption frequency of the absorber increases gradually. At the same time, an increase in the imaginary part will lead to an increase in losses, so the inherent losses in the CMT theoretical model
Figure 813433DEST_PATH_IMAGE099
And the absorption rate will gradually decrease as the system changes from the critical coupling state to the under coupling (under coupling) state.
Thus, in FIG. 19, the Fermi energy of the BDS is as high as
Figure 465125DEST_PATH_IMAGE100
Is gradually increased to
Figure 152458DEST_PATH_IMAGE101
In this case, the absorption frequency of the wave absorber gradually increases, and a blue shift occurs. At the same time, the absorption rate gradually decreases. Specifically, it can be seen from FIG. 20 that the Fermi energy of BDS is as low as possible
Figure 480671DEST_PATH_IMAGE100
Is gradually increased to
Figure 620666DEST_PATH_IMAGE102
In time, the absorption frequency of the wave absorber is increased from 2.1608 THz to 2.3266 THz, and the absorption rate is reduced from 99.8% to 87.3%.
Similarly, in fig. 1 and 2, the real part of the STO dielectric constant is decreasing as the temperature increases. Thus, in FIGS. 19 and 20, when the STO temperature is changed from
Figure 840163DEST_PATH_IMAGE103
Is increased to
Figure 382003DEST_PATH_IMAGE104
In the meantime, the absorption frequency of the absorber also increased from 1.9347 THz to 2.5377 THz, and blue-shifted. However, since the imaginary part of the STO dielectric constant changes very little during temperature variations, the absorption of the absorber remains approximately constant with increasing temperature, always greater than 99%.
Thus, dynamic double tuning of the absorption frequency and the absorption rate magnitude of the absorber can be achieved by varying the BDS Fermi energy and the STO temperature.
The analysis shows that the Fermi energy of BDS is based on the critical coupling effect
Figure 881117DEST_PATH_IMAGE100
STO temperature
Figure 524720DEST_PATH_IMAGE105
In the process, the wave absorber has an absorption rate of 99.8% at the 2.1608 THz position, and perfect absorption is realized. Second, when the STO temperature is high
Figure 501903DEST_PATH_IMAGE105
BDS Fermi energy from
Figure 163828DEST_PATH_IMAGE100
Is increased to
Figure 833844DEST_PATH_IMAGE106
In the process, the absorption frequency of the wave absorber can be increased from 2.1608 THz to 2.3266 THz, and the absorption magnitude can be reduced from 99.8% to 87.3%. Third, when BDS Fermi energy
Figure 200628DEST_PATH_IMAGE107
The STO temperature is from
Figure 981502DEST_PATH_IMAGE108
Is increased to
Figure 763513DEST_PATH_IMAGE109
In the process, the absorption frequency of the wave absorber can be increased from 1.9347 THz to 2.5377 THz, and the absorption rate is always greater than 99%.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.

Claims (7)

1. Double-tuned wave absorber based on Dirac semimetal and strontium titanate, its characterized in that: the top layer of the double-tuned wave absorber is a Dirac semimetal BDS nanorod resonator, the middle dielectric layer is composed of strontium titanate STO, the bottom of the double-tuned wave absorber is a grounding layer, the top layer is a cross-shaped Dirac semimetal BDS nanorod resonator, the bottom layer is a gold grounding layer, and the layers are tightly and seamlessly attached to each other to form a structural body.
2. The dirac semimetal and strontium titanate-based double tuned absorber of claim 1, wherein: the length of the top cross-shaped BDS nanorod
Figure 262509DEST_PATH_IMAGE001
Width of
Figure 274328DEST_PATH_IMAGE002
A thickness of
Figure 973293DEST_PATH_IMAGE003
Initial fermi energy
Figure 361549DEST_PATH_IMAGE004
。
3. The dirac semimetal and strontium titanate-based dual tuned absorber of claim 1, wherein: the initial temperature T of the interlayer dielectric layer is between 250K and 400K, and the thickness is
Figure 462361DEST_PATH_IMAGE005
(ii) a The conductivity of the bottom gold grounding layer is
Figure 645080DEST_PATH_IMAGE006
A thickness of
Figure 595456DEST_PATH_IMAGE007
。
4. The dirac semimetal and strontium titanate-based double tuned absorber of claim 1, wherein: the double-tuned wave absorber equivalent circuit is as follows:
the bottom gold film layer is equivalent to a short-circuit device; when incident light is X polarized light, only the nanorods in the X direction can interact with incident waves, the nanorods in the Y direction cannot interact with the incident light because the polarization direction is vertical to the long axis of the nanorods, and the top cross BDS nanorods can be represented by a RLC series circuit connected in parallel; RLC series circuit route R 1 ,L 1 ,C 1 The RLC is connected in series and then connected with the short-circuit device in parallel;
the input impedance of the double tuned absorber can be expressed as:
Figure 787403DEST_PATH_IMAGE008
wherein, in the step (A),
Figure 742721DEST_PATH_IMAGE009
to represent
Figure 361921DEST_PATH_IMAGE010
A series circuit equivalent impedance;
Figure 35479DEST_PATH_IMAGE011
representing the characteristic impedance of the short-circuited transmission line;
Figure 499959DEST_PATH_IMAGE012
which represents the impedance of the wave in free space,
Figure 575362DEST_PATH_IMAGE013
respectively representing the relative dielectric constant and thickness of the STO layer,
Figure 365463DEST_PATH_IMAGE014
representing the free space wavenumber; thus, the reflection coefficient of the double tuned absorber
Figure 759273DEST_PATH_IMAGE015
Can be expressed as:
Figure 293023DEST_PATH_IMAGE016
(ii) a The equivalent impedance of the absorber can be expressed as:
Figure 222933DEST_PATH_IMAGE017
(ii) a According to the impedance matching theory, when the equivalent impedance of the absorber
Figure 918356DEST_PATH_IMAGE018
The absorber reflectivity will be equal to 0 and the absorption will be close to 1.
5. The dirac semimetal and strontium titanate-based double tuned absorber of claim 1, wherein: the absorptivity of the double-tuned wave absorber is more than 99%.
6. The dirac semimetal and strontium titanate-based double tuned absorber of claim 1, wherein: BDS Fermi energy
Figure 566506DEST_PATH_IMAGE019
Is selected at
Figure 779313DEST_PATH_IMAGE020
The resonance frequency and the absorption rate at the absorption peak can be dynamically adjusted.
7. The dirac semimetal and strontium titanate-based double tuned absorber of claim 1, wherein: the STO temperature T is selected to be
Figure 688363DEST_PATH_IMAGE021
In the meantime, the resonance frequency and the absorption rate at the absorption peak can be dynamically adjusted.
CN202211474008.2A 2022-11-23 2022-11-23 Dual-tuned absorber based on dirac semimetal and strontium titanate Pending CN115548690A (en)

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