CN113346248B - Terahertz wave beam scanning super-surface device, wave beam scanning antenna, system and method - Google Patents
Terahertz wave beam scanning super-surface device, wave beam scanning antenna, system and method Download PDFInfo
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- CN113346248B CN113346248B CN202110414023.7A CN202110414023A CN113346248B CN 113346248 B CN113346248 B CN 113346248B CN 202110414023 A CN202110414023 A CN 202110414023A CN 113346248 B CN113346248 B CN 113346248B
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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
- H01Q15/0086—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
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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
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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
- H01Q15/0026—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
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Abstract
The application relates to a terahertz wave beam scanning super-surface device, a wave beam scanning antenna, a system and a method, wherein the terahertz wave beam scanning super-surface device comprises two layers of super surfaces, and each layer of super surface is formed by periodically arranging a plurality of super periods; each supercycle consists of ten artificial atoms arranged in a line; each artificial atom is formed by sequentially and seamlessly laminating a top silicon column, a silicon substrate and a bottom silicon column; the cross sections of the top silicon column and the bottom silicon column are both square, and the silicon substrate is square; at the working frequency of 0.7THz, the phase difference of two adjacent artificial atoms is pi/5; the bottom silicon column of one super surface of the two cascaded super surfaces is close to the top silicon column of the other super surface; two far surfaces of the two cascaded super surfaces are respectively fixed with a rotating mechanism, and the rotating axes of the two cascaded super surfaces are superposed. The terahertz beam positioning device has the effects of realizing accurate control and positioning of the terahertz beam direction.
Description
Technical Field
The application relates to the technical field of terahertz beam dynamic regulation, in particular to a terahertz beam scanning super-surface device, a beam scanning antenna, a system and a method.
Background
The terahertz wave band is generally an electromagnetic wave in the frequency range of 0.1-10 THz, and the wave band is between the infrared and microwave wave bands. Due to the unique spectral characteristics, the terahertz waves are widely applied to the fields of astrophysics, communication, materials, chemistry, national defense safety, biomedicine and the like.
However, the terahertz band exceeds the cutoff frequency of semiconductor materials essential in electrical amplifiers and mixers, so that currently widely used radio frequency electronic components are no longer compatible with the terahertz band. Therefore, the terahertz wave front needs to be freely and dynamically controlled to realize accurate control and positioning of the terahertz beam direction.
Currently, due to the lack of suitable sub-micron sized tunable elements, existing beam scanning methods operating at microwave frequencies do not work well in the terahertz frequency band.
Disclosure of Invention
In order to realize accurate control and positioning of the terahertz light beam direction, the application provides a terahertz wave beam scanning super-surface device, a wave beam scanning antenna, a system and a method.
In a first aspect, the application provides a terahertz wave beam scanning super-surface device, which adopts the following technical scheme:
a terahertz wave beam scanning super-surface device comprises two cascaded super-surfaces, wherein each super-surface is formed by periodically arranging a plurality of super-periods;
each supercycle consists of ten artificial atoms arranged in a line; each artificial atom is formed by sequentially and seamlessly laminating a top silicon column, a silicon substrate and a bottom silicon column; the cross sections of the top silicon column and the bottom silicon column are both square, and the silicon substrate is square; the artificial atoms have a transmission phase of
At the working frequency of 0.7THz, the phase difference of two adjacent artificial atoms is pi/5;
the two cascaded super surfaces are arranged in parallel, and a bottom silicon column of one super surface of the two cascaded super surfaces is close to a top silicon column of the other super surface;
two surfaces, far away from each other, of the two cascaded super surfaces are respectively fixed with a rotating mechanism, the rotating mechanisms drive the corresponding super surfaces to rotate, and the rotating axes of the two cascaded super surfaces are overlapped.
Optionally, for the same supercycle, the cross-sectional dimensions of the top silicon pillars of the ten artificial atoms are increased or decreased in the order of arrangement, the heights of all the top silicon pillars are the same, and the geometric dimensions of all the bottom silicon pillars are the same.
Optionally, the rotating mechanism is a metal turntable, and the super surface is attached to the metal turntable.
Optionally, in
Polarized wave sum
Fixing the side length P and the thickness h of the silicon substrate under normal incidence of polarized waves 2 Simulating the artificial atoms with the bottom silicon by using a finite difference time domain methodSide length omega of cross section of column x And height h 3 Varying phase difference Δ Φ i And transmission coefficient amplitude
Determining the section side length omega of the bottom silicon column with high transmission performance and expected phase difference according to the phase diagram obtained by simulation x And height h 3 。
Optionally, the silicon substrate has a side length P of 130 μm and a height h 2 ＝110μm。
Optionally, in
Polarized wave sum
At normal incidence of the polarized wave, when Δ Φ i When the value is 0, the side length omega of the cross section of the bottom silicon column at the moment is fixed x And height h 3 And simulating and calculating the side length l and the height h of the artificial atom along with the section of the top silicon column by using a time domain finite difference method 1 Varying average phase
And transmission coefficient amplitude
Determining the phase with the expected average phase according to the phase diagram obtained by simulation
The side length l and the height h of the cross section of the top silicon column 1 。
Optionally, the expected average phase
The value of (d) may cover a range of 2 pi.
In a second aspect, the present application provides a beam scanning antenna applying the terahertz beam scanning super-surface device as described in the first aspect.
In a third aspect, the present application provides a beam scanning system for scanning a super-surface device by using a terahertz beam as described in the first aspect, and adopts the following technical solutions:
a beam scanning system comprising the terahertz beam scanning super-surface device and a terahertz time-domain spectroscopy system;
the terahertz time-domain spectroscopy system comprises a transmitter, a first lens, a quarter-wave plate, a second lens and a receiver which are sequentially arranged, wherein the terahertz wave beam scanning super-surface device is arranged between the quarter-wave plate and the second lens; the top silicon pillar of each super-surface layer is close to the second lens relative to the bottom silicon pillar, and the bottom silicon pillar of each super-surface layer is close to the quarter-wave plate relative to the top silicon pillar.
In a fourth aspect, the present application provides a beam scanning method based on the beam scanning system of the third aspect, which adopts the following technical solutions:
a method of beam scanning, comprising:
rotating each of the super surfaces at a different rotational speed;
the transmitter transmits a terahertz light beam, the terahertz light beam sequentially transmits the first lens, the quarter-wave plate, the terahertz wave beam scanning super-surface device and the second lens, and the terahertz light beam is received by the receiver;
and measuring to obtain the angular power distribution of the terahertz light beam incident to the terahertz beam scanning super-surface device at different moments, wherein the incident terahertz light beam is effectively redirected to a direction which is changed along with time and deviates from a normal line.
By adopting the technical scheme, the terahertz transmission super-surface device is composed of two all-silicon transmission super-surfaces which display different phase distributions, different layers (each showing specific stage) of the cascade super-surface are rotated at different speeds, the property of an effective Jones-matrix (Jones-matrix) of the whole device can be dynamically changed, a terahertz light beam incident along a normal line can be effectively redirected to a direction deviating from the normal line, and the terahertz light beam is scanned in a larger solid angle range, so that the terahertz light beam wavefront can be excellently modulated; in addition, the dynamic beam steering capability of the terahertz beam scanning super-surface device is verified through good consistency of experiment and simulation display, a road is paved for realizing dynamic regulation and control of terahertz beams, and the terahertz beam scanning super-surface device can be better applied to various fields such as terahertz radar, biochemical sensing and imaging.
Drawings
Fig. 1 is a schematic structural diagram of an xz plane of a terahertz beam scanning super-surface device according to an embodiment of the present application.
Fig. 2 is a schematic perspective structure diagram of a terahertz beam scanning super-surface device according to an embodiment of the present application.
Fig. 3(a) is a schematic plan view of a side surface of the super-surface where the top silicon pillar is disposed according to the embodiment of the present application.
Fig. 3(b) is a schematic plan view of a side surface of the super-surface where the bottom silicon pillar is disposed according to the embodiment of the present application.
Fig. 4 is a schematic structural diagram of an artificial atom according to an embodiment of the present application.
FIG. 5(a) is a phase difference Δ Φ of the bottom silicon pillar of the embodiment of the present application i Side length omega of cross section of bottom silicon column x And height h 3 A phase diagram of the relationship of (1).
FIG. 5(b) is the transmission coefficient amplitude of the bottom silicon pillar of the embodiment of the present application
Side length omega of cross section of bottom silicon column x And height h 3 A phase diagram of the relationship of (1).
FIG. 5(c) is the average phase of the top silicon pillar of the embodiment of the present application
Length l and height h of cross section of top silicon column 1 A relational phase diagram of (c).
FIG. 5(d) is the transmission coefficient amplitude of the top silicon pillar of the embodiment of the present application
Cut off from the top silicon pillarLength l and height h of face side 1 A phase diagram of the relationship of (1).
FIG. 6(a) shows a deflection angle θ and a rotation angle α in the embodiment of the present application 1 (t) and alpha 2 (t) a phase diagram.
FIG. 6(b) is an azimuth angle of an embodiment of the present application
Angle of rotation alpha 1 (t) and alpha 2 (t) a phase diagram.
FIG. 6(c) shows the deflection angle θ and the azimuth angle in the scanning path pathl according to the embodiment of the present application
Trend graph over time.
FIG. 6(d) is a schematic diagram of the deflection angle θ and the azimuth angle in the scanning path pathll according to the embodiment of the present application
Trend graph over time.
Fig. 7 is a schematic structural diagram of a beam scanning system according to an embodiment of the present application.
Fig. 8 is a flowchart illustrating a beam scanning method according to an embodiment of the present application.
Fig. 9 is a test light path diagram of an embodiment of the present application.
FIG. 10 shows an embodiment of the present application
Power profiles measured at different times on the surface.
Fig. 11 is a diagram of a simulated far-field scattered power distribution of a full wave at a corresponding time in an embodiment of the present application.
FIG. 12 is an illustration of pathl and pathll in k-space according to an embodiment of the present application; wherein, the solid line is the simulation result, the star is the experimental result, and the upper region is the spatial range of beam scanning.
Description of reference numerals: 10. scanning the super-surface device by a terahertz wave beam; 11. a super-surface; 110. overcycling; 111. artificial atoms; 1111. a top silicon pillar; 1112. a silicon substrate; 1113. a bottom silicon pillar; 12. a rotation mechanism; 20. a terahertz time-domain spectroscopy system; 201. a transmitter; 202. a first lens; 203. a quarter wave plate; 204. a second lens; 205. a receiver.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.
Fig. 1 is a schematic structural diagram of a terahertz beam scanning super-surface device 10 provided in this embodiment. As shown in fig. 1, the terahertz beam scanning super-surface device 10 is formed by cascading two identical super-surfaces 11. Two surfaces 11 far away from the two layers of super surfaces 11 are respectively fixedly connected with a rotating mechanism 12, the rotating mechanism 12 drives the corresponding super surfaces 11 to rotate at a certain rotating speed, and the rotating axes of the two layers of super surfaces 11 are overlapped.
Alternatively, the rotating mechanism 12 is a circular electric metal turntable. Fig. 2 shows a schematic perspective structure of a terahertz wave beam scanning super-surface device 10 applying an electric metal turntable, and fig. 2 is only for illustrating a positional relationship between a super-surface 11 and a rotating mechanism 12, so that a specific structure of the super-surface 11 is not shown and is only for illustration. The electric metal turntable comprises a turntable 121 and a fixing support (not shown in the figure) for fixing the position of the turntable 121, the super surface 11 is attached to one surface of the turntable 121, and the relative positions of the two super surfaces 11 can be adjusted and fixed through the corresponding positions of the turntable 121.
In this embodiment, the two super-surfaces 11 are arranged parallel to each other and at a distance h 4 ，h 4 ＝[200μm，1000μm]Preferably, h 4 ＝600μm。
Fig. 3(a) and 3(b) respectively show the structural schematic diagrams of the two side surfaces of each super surface 11. As shown in fig. 3(a) and 3(b), each layer of the super-surface 11 is formed by a plurality of super-periods 110 arranged periodically; each supercycle 110 is formed by ten artificial atoms 111 arranged in a line, the transmission phase of the artificial atoms 111 being
And at the working frequency of 0.7THz, the phase difference of two adjacent artificial atoms 111 is pi/5.
As shown in fig. 1 and 4, each artificial atom 111 includes a square silicon substrate 1112, and a top silicon pillar 1111 having a square cross-section is deposited on one side of the silicon substrate 1112, and a bottom silicon pillar 1113 having a square cross-section is deposited on the other side of the silicon substrate 1112.
As shown in fig. 3(a), for the same supercycle 110, the cross-sectional sizes of the top silicon pillars 1111 of the ten artificial atoms 111 increase or decrease in the order of arrangement, and the heights of the top silicon pillars 1111 are all the same; as shown in fig. 3(b), the bottom silicon pillars 1113 of the ten artificial atoms 111 are all identical in geometric size.
As shown in fig. 1, the bottom silicon pillar 1113 of one super-surface 11 of the two cascaded super-surfaces 11 is opposite to the top silicon pillar 1111 of the other super-surface 11, and does not contact each other.
The artificial atom 111 is an all-dielectric artificial atom with high transmission efficiency in the terahertz wave band, and can generate average phase in a wide range
And phase difference Δ Φ i May help to implement a super-surface device that controls the programmable function of the wavefront.
Since the top silicon pillar 1111 and the bottom silicon pillar 1113 used by the artificial atoms 111 are both square in cross section and are all isotropic in shape, there is no need to control the local polarization of the incident wave. At the same time, the top silicon pillars 1111 of these artificial atoms 111 vary significantly in lateral size, creating different transport phases for accumulating enough of the transmission phase to generate the desired average phase
The bottom silicon pillar 1111 is mainly responsible for generating the required phase difference Δ Φ i . The terahertz wave beam prepared by the artificial atoms 111 scans the super-surface device 10 when the two layers of super-surfaces 11 rotate at different speedsWhen rotated, the incident beam of terahertz waves can be redirected.
In order to make the terahertz beam scanning super-surface device 10 have high transmission performance and wide coverage beam steering capability, the geometric dimensions of the top silicon pillar 1111 and the bottom silicon pillar 1113 of the artificial atoms 111 need to be designed experimentally.
First, in
Polarized wave sum
Under normal incidence of polarized waves, the fixed silicon substrate 1112 has a side length P of 130 μm and a thickness h 2 110 mu m, simulating the side length omega of the artificial atom 111 along the cross section of the bottom silicon column 1113 by using a finite difference time domain method x And height h 3 Varying phase difference Δ Φ i And transmission coefficient amplitude
Wherein the content of the first and second substances,
from the simulation, two phase diagrams as shown in FIG. 5(a) and FIG. 5(b) were obtained, from which the side length ω of the cross section of the bottom silicon pillar 1113 having high transmission performance and expected phase difference was determined x And height h 3 。
Then, when Δ Φ i When the length of the cross-sectional side of the bottom silicon pillar 1113 is fixed to 0, the length ω of the cross-sectional side is fixed x And height h 3 Simulating and calculating the side length l and the height h of the section of the artificial atom 111 along with the top silicon column 1111 by using a time-domain finite difference method 1 Varying average phase
And transmission coefficient amplitude
From the simulation, two phase diagrams as shown in FIGS. 5(c) and 5(d) were obtained, which were found at h 1 At 240 μm, the average phase changes with l
Can cover a range of 2 pi.
To deflect a normally incident terahertz wave to a time-dependent off-normal direction, first, the present embodiment constructs two identical transmissive-type super-surfaces 11. The phase distribution of the super-surface 11 is set to be a linear gradient phase, and the propagation path of light can be changed by introducing a phase jump at the light incidence interface according to the generalized Snell's law of refraction. The phase mutation of the super surface is generated by unit structures in which phase differences are sequentially linearly superposed, so that the wave front can be regulated and controlled by changing phase gradients.
Each meta-surface 11 has the following linear gradient phase profile at both polarized wave incidences:
in the formula (I), the compound is shown in the specification,
is composed of
The phase of the polarized wave incident on the i-th layer meta-surface 11,
is composed of
The phase of the polarized wave incident on the i-th layer super surface 11; xi i Is the gradient of the i-th layer super-surface 11,
ξ 0 ＝0.33k 0 ，i＝1,2。
the two super-surfaces 11 are then cascaded as a super-surface device, assuming two super-surfacesThe corners of the surface 11 are each alpha 1 (t) and alpha 2 (t), calculating the Jones matrix of the whole super-surface device, wherein the formula is as follows:
further, a polarization manipulation operator M (r, t) ≡ L of the super-surface device is found, which means that the super-surface device can maintain local polarization of the terahertz transmitted wave, and also means that the super-surface device can work on terahertz incident waves with any polarization.
In addition, as further revealed by the formula (2), the transmitted wave obtains a tangential wave vector k which varies with time || (t)，
Means that a normal incident wave can be redirected to a time-dependent off-normal direction after passing through the super-surface device
From the formula (3), it can be seen that the deflection angle θ and the azimuth angle of the transmitted wave
Angle of rotation alpha to the super surface of each layer 1 And alpha 2 There is a special functional relationship, which is shown in fig. 6(a) and 6(b) by way of a phase diagram. As is apparent from fig. 6(a) and 6(b), the time function α is obtained by changing the two rotation angles i (t) the angle theta and the angle theta varying with time can be effectively controlled
So that the transmitted wave can be carried out in a specific solid angle rangeScanning, wherein the scanning range is as follows:
in the formula (4), the maximum value θ of the deflection angle max ＝2arc sin(2ξ 0 /k 0 )＝41.2°。
In order to show the beam scanning effect of the super-surface device, the rotating speed of the upper and lower super-surfaces is firstly considered to be { omega [ ] 1 ＝-π/(2T),ω 2 pi/(2T) }. Then, from the functional relationship in equation (3), the range of the deflection angle θ, which is varied in [0 °,41.2 ° ] with time t, can be calculated]Internal variation, angle of azimuth of outgoing wave at the time
Always equal to 0, this scan path is designated as pathl and is shown in fig. 6(a), 6 (b); FIG. 6(c) shows two angles θ and θ in pathl
Trend over time.
Then, the rotational speed of the super-surface of each layer is set to { ω 1 ＝π/(8T),ω 2 Re-analyzing the new scan path pathll, which is a more complex scan path than pathll, as shown in fig. 6(a), 6(b), and fig. 6(d) shows two angles θ and θ in pathll
Trend over time.
It follows that the super-surface device can be made to exhibit the required beam scanning function by setting a specific rotation speed for each layer of the super-surface 11.
The beam steering capability of the terahertz beam scanning super-surface device 10 when the two layers of super-surfaces 11 rotate at different speeds is verified through experiments.
Fig. 7 is a schematic structural diagram of a beam scanning system provided in this embodiment. As shown in fig. 7, the beam scanning system includes a terahertz beam scanning super-surface device 10 and a terahertz time-domain spectroscopy system 20.
The terahertz time-domain spectroscopy system 20 comprises a transmitter 201, a first lens 202, a quarter wave plate 203, a second lens 204 and a receiver 205 which are arranged in sequence, and the terahertz beam scanning super-surface device 10 is arranged between the quarter wave plate 203 and the second lens 204.
The top silicon pillar 1111 of each super-surface 11 is close to the second lens 204 relative to the bottom silicon pillar 1113, and the bottom silicon pillar 1113 of each super-surface 11 is close to the quarter-wave plate 203 relative to the top silicon pillar 1111, that is, the terahertz light beam emitted by the emitter 201 is transmitted through the bottom silicon pillar 1113 of each super-surface 11 and then through the top silicon pillar 1111 of the super-surface 11.
The terahertz time-domain spectroscopy system 20 is used for measuring the angular power distribution of the terahertz light beam scanning the super-surface device 10 through the terahertz wave beam at different moments.
Fig. 8 is a schematic flowchart of a beam scanning method based on the beam scanning system according to this embodiment. As shown in fig. 8, the main flow of the method is described as follows (steps S301 to S303):
step S301 of rotating each super surface 11 at a different rotation speed;
step S302, the transmitter 201 transmits a terahertz light beam, the terahertz light beam sequentially transmits the first lens 202, the quarter-wave plate 203, the terahertz light beam scanning super-surface device 10 and the second lens 204, and is received by the receiver 205;
step S303, the angular power distribution of the terahertz beam of the incident terahertz beam scanning super-surface device 10 at different times is measured, and the incident terahertz beam is effectively redirected to a direction deviating from the normal line, which changes with time.
In this embodiment, the two-layer super-surface 11 is rotated at a rotation speed { ω 1 ＝-π/(2T),ω 2 The rotation is performed by pi/(2T), and the scanning path of the emergent beam at this time is pathl shown in fig. 5 (c). When in test, the used test equipment is terahertzIn the far field portion of the time domain spectroscopy system 20, the incident terahertz wave is irradiated to the terahertz time domain spectroscopy system 20, and the test optical path is as shown in fig. 9.
Respectively at [ T ═ 0, (1/3) T, (2/3) T,1T]The angular power distribution of the transmitted wave was tested at these four moments. FIG. 10 shows that
The gradual change of the deflection angle theta from 41.2 degrees to 0 degree can be observed from the power distribution measured on the surface at different moments, which indicates that the terahertz wave beam scanning super-surface device 10 can effectively deflect the incident terahertz waves to the direction deviated from the normal line.
In addition, full-wave simulation is performed on the terahertz beam scanning super-surface device 10 to obtain far-field scattering power distribution at a moment corresponding to the measurement experiment of the terahertz time-domain spectroscopy system 20, and a simulation result is shown in fig. 11. With reference to fig. 10 and fig. 11, the simulation result is compared with the measurement result of the terahertz time-domain spectroscopy system 20 in conformity. From experimental and simulated scattering maps, the deflection angle θ and azimuth angle of the transmitted wave at different moments can be determined
The sum of θ over time t may then be
Labeled in k-space as pathl in fig. 12. Obviously, both the experimental value and the analog value are in good agreement with the theoretical predicted value (i.e. pathl in fig. 6 (c)), and good consistency is presented, which further verifies the expected beam scanning capability, i.e. beam steering effect, of the terahertz beam scanning super-surface device 10.
In order to further verify the beam steering effect of the terahertz beam scanning super-surface device 10, the terahertz beam scanning super-surface device 10 can be continuously tested at another set of rotation speeds { omega } 1 ＝π/(8T),ω 2 Beam scanning performance at 3 pi/(4T) }. At such a rotation speed, the terahertz wave beam scanning super-surface device 10 can be driven in along with the time changeThe beam is deflected onto pathll as shown in fig. 6 (d).
From the test and simulation results, it was possible to determine T, (1/4) T, (1/2) T, (3/4) T,1T at different times [ T ═ 0, (1/2) T]Scanning the direction of the transmitted wave of the super-surface device 10 (with θ and T) through the terahertz wave beam
Represented) and may be depicted on a k-space sphere in fig. 12, pathll. Both the test and simulation results show that the working efficiency of the terahertz wave beam scanning super-surface device 10 is about 50%, and thus, the good consistency among the theory, simulation and test results clearly proves the wave beam scanning function of the terahertz wave beam scanning super-surface device 10.
The embodiment also discloses a beam scanning antenna, which is constructed by the cascade super-surface structure with low loss, low cost and easy processing, and through proper phase distribution construction, the propagation direction of terahertz waves can be effectively changed, the coverage of a larger scanning range is realized, arbitrary, rapid and accurate wavefront modulation is realized in terahertz wave bands, the antenna volume is further reduced, and the production cost is reduced.
In addition, it is to be understood that relational terms such as first and second, and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present application shall fall within the protection scope of the present application.
Claims (10)
1. A terahertz wave beam scanning super-surface device is characterized by comprising two cascaded super-surfaces, wherein each super-surface is formed by periodically arranging a plurality of super-periods;
each supercycle consists of ten artificial atoms arranged in a line; each artificial atom is formed by sequentially and seamlessly laminating a top silicon column, a silicon substrate and a bottom silicon column; the cross sections of the top silicon pillar and the bottom silicon pillar are both square, and the silicon substrate is square; the transmission phase of the artificial atom is
Wherein the content of the first and second substances,
is composed of
The phase of the polarized wave incident on the meta-surface of the ith layer,
is composed of
The phase of the polarized wave incident on the meta-surface of the ith layer,
and
representing a unit vector in a local coordinate system,
polarized waveIs an electromagnetic wave with a polarization direction along the u-axis,
the polarized wave is an electromagnetic wave with the polarization direction along the v axis, and the phase difference of two adjacent artificial atoms is pi/5 at the working frequency of 0.7 THz;
the two cascaded super surfaces are arranged in parallel, and a bottom silicon column of one super surface of the two cascaded super surfaces is close to a top silicon column of the other super surface;
two surfaces, far away from each other, of the two cascaded super surfaces are respectively fixed with a rotating mechanism, the rotating mechanisms drive the corresponding super surfaces to rotate, and the rotating axes of the two cascaded super surfaces are overlapped.
2. The terahertz beam scanning super-surface device of claim 1, wherein for the same super-cycle, the cross-sectional dimensions of the top silicon pillars of the ten artificial atoms increase or decrease in the order of arrangement and the heights of all the top silicon pillars are the same, and the geometric dimensions of all the bottom silicon pillars are the same.
3. The terahertz beam scanning super-surface device of claim 1, wherein the rotating mechanism is a metal turntable, and the super-surface is attached to the metal turntable.
4. The terahertz beam scanning super-surface device of any one of claims 1 to 3, wherein the terahertz beam scanning super-surface device is arranged on
Polarized wave sum
Fixing the side length P and the thickness h of the silicon substrate under normal incidence of polarized waves 2 Simulating the section of the i-th super surface of the artificial atom along with the bottom silicon column by using a time-domain finite difference methodSide length omega of surface x And height h 3 Varying phase difference Δ Φ i And transmission coefficient amplitude
Determining the section side length omega of the bottom silicon column with high transmission performance and expected phase difference according to the phase diagram obtained by simulation x And height h 3 。
5. The terahertz beam scanning super-surface device of claim 4, wherein the silicon substrate has a side length P of 130 μm and a height h 2 ＝110μm。
6. The terahertz beam scanning super-surface device of claim 4, wherein the terahertz beam scanning super-surface device is arranged on
Polarized wave sum
At normal incidence of the polarized wave, when Δ Φ i When the value is 0, the side length omega of the cross section of the bottom silicon column at the moment is fixed x And height h 3 Simulating and calculating the side length l and the height h of the i-th layer super surface of the artificial atom along with the section of the top silicon column by using a time domain finite difference method 1 Varying average phase
And transmission coefficient amplitude
Determining the phase with the expected average phase according to the phase diagram obtained by simulation
The side length l and the height h of the cross section of the top silicon column 1 。
7. The terahertz beam scanning super-surface device of claim 6, wherein the expected average phase
The value of (d) may cover a range of 2 pi.
8. A beam scanning antenna applying the terahertz beam scanning super-surface device as claimed in any one of claims 1 to 7.
9. A beam scanning system for scanning a terahertz beam by applying the terahertz beam as claimed in any one of claims 1 to 7, comprising the terahertz beam scanning super-surface device and a terahertz time-domain spectroscopy system;
the terahertz time-domain spectroscopy system comprises a transmitter, a first lens, a quarter-wave plate, a second lens and a receiver which are sequentially arranged, wherein the terahertz wave beam scanning super-surface device is arranged between the quarter-wave plate and the second lens; the top silicon pillar of each layer of the super-surface is close to the second lens relative to the bottom silicon pillar, and the bottom silicon pillar of each layer of the super-surface is close to the quarter-wave plate relative to the top silicon pillar.
10. A beam scanning method based on the beam scanning system of claim 9, comprising:
rotating each of the super surfaces at a different rotational speed;
the transmitter transmits a terahertz light beam, the terahertz light beam sequentially transmits the first lens, the quarter-wave plate, the terahertz wave beam scanning super-surface device and the second lens, and the terahertz light beam is received by the receiver;
and measuring to obtain the angular power distribution of the terahertz light beam incident to the terahertz beam scanning super-surface device at different moments, wherein the incident terahertz light beam is effectively redirected to a direction which is changed along with time and deviates from the normal.
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