CN112859204A - Based on phase change material Ge2Sb2Te5Reconfigurable super-surface cloaking cloak - Google Patents
Based on phase change material Ge2Sb2Te5Reconfigurable super-surface cloaking cloak Download PDFInfo
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Abstract
The invention relates to a phase-change material Ge-based material2Sb2Te5The reconfigurable super-surface cloaking cloak of (1). The cloaking cloak consists of W rows and V columns of reconfigurable super-surface cloaking units which are fixedly covered on the surface of a cloaked object, and adjacent reconfigurable super-surface cloaking units are fixedly spliced in a seamless mode. The reconfigurable super-surface stealth unit comprises a lower layer with the side length ofpThe square metal substrate layer, the dielectric layer in the middle layer and the gold nano-antenna on the upper layer form a W-row X-V-column gold nano-antenna resonant array. The spatial distribution of the phase of the reflected wave is modulated by using the surface plasmon resonances of the gold nano resonant antennas with different sizes in the super-surface structure, so that the reconstruction of the wave front of the reflected wave can be realized, and the camouflage and stealth effect is achieved; using Ge2Sb2Te5The unique phase change characteristic of the film can tune the dielectric environment around the cloak and can be realizedContinuous tuning and "ON" and "OFF" of the stealth performance now. The super-surface stealth cloak disclosed by the invention realizes the perfect stealth effects of wider working bandwidth, larger incident angle range and dynamically tunable performance.
Description
Technical Field
The invention relates to the relevant technical field of electromagnetic wave stealth, in particular to a phase-change material Ge-based phase-change material2Sb2Te5The reconfigurable super-surface cloaking cloak of (1).
Background
With the development of science and technology, stealth gradually moves from a simple and naive means of visual 'cheating' to an accurate and systematic modern technical system. Through reasonable design of electromagnetic parameters, the stealth technology can flexibly regulate and control the transmission and scattering of electromagnetic waves and reduce the detectability of stealthed objects, so that the stealth technology is particularly important in the military field.
The traditional stealth technology mainly comprises wave-absorbing or directional scattering stealth, mimicry stealth, interference deception stealth and the like. However, wave-absorbing or directional scattering stealth is only suitable for single-base-station radar stealth; the mimicry stealth can only statically adjust the scattering of the material and cannot adapt to the changes brought by different background environments; the detector is deceived by the fact that the interference deception cloaking cannot adjust the scattering of the object to any specific non-zero value. Therefore, the above stealth techniques cannot achieve perfect stealth in the true sense.
The ideal stealth principle is not wave-absorbing but changes the propagation path of electromagnetic wave, namely the electromagnetic wave still propagates according to the original path after bypassing the stealth object. In this case, the electromagnetic wave is irradiated onto the object, which "seemingly does not exist", thereby realizing perfect stealth. At present, two methods for hiding electromagnetic waves mainly exist, one of which is based on the principle of scattering cancellation: the scattering of a basic mode of the scatterer is counteracted by wrapping a shell with relative dielectric constant less than 1 outside the spherical or cylindrical scatterer, so that the total scattering cross section of a covered object is obviously reduced, and the stealth effect is achieved. Although the structure is simple, the ultrathin stealth clothes designed by the scattering phase elimination method are only suitable for objects with sub-wavelength sizes, when the size of the object is larger than the wavelength, the influence of high-order mode components on a scattering field is increased, the complexity of design can be greatly increased, and the experiment is very difficult to realize. Another method is the transform optics method proposed by Pendry: a hole is created in a real space by utilizing a measurement invariance and a coordinate transformation method of a Maxwell equation set, so that light rays smoothly bypass the hole to achieve invisibility, but due to the fact that the requirements on constructed metamaterial are strict, short plates with large size, difficulty in preparation, narrow bandwidth and the like exist generally, and practical application is limited to a certain extent.
In recent years, with the continuous maturity of micro-nano processing technology, a novel wavefront regulation and control element, namely an optical ultrastructure surface, is proposed and rapidly developed. The super surface (Metasurfaces), also called two-dimensional super structure material, is essentially characterized in that a wave front is regulated and controlled by utilizing the phase space change generated by the coupling of a unit structure of the super structure surface and incident electromagnetic waves, and is a functional film layer device based on a sub-wavelength anisotropic structure. Due to the fact that abnormal phase mutation can be generated in the planar sub-wavelength structure, and the planar sub-wavelength structure has the advantages of being capable of randomly regulating and controlling sub-wavelength scale phase, amplitude and polarization, light, thin, easy to integrate, low in loss, capable of being designed in a conformal mode on the surface and the like, an effective means is provided for applications including large-aperture plane imaging, electromagnetic stealth, electromagnetic virtual shaping, large-view-field holographic display and the like.
Super surface cloaking is a new idea of designing a cloak or a cloak with new design proposed in recent years along with the development of super surface material research. The method not only retains the singular characteristics of the metamaterial, but also overcomes the difficulties of high loss, difficult processing, difficult integration and the like of the three-dimensional metamaterial. Compared with a three-dimensional metamaterial, the stealth coat realized by utilizing the super surface does not relate to complex material parameters in the design process, and has the advantages of light weight, small thickness, easiness in processing, easiness in conformal and the like, so that the stealth coat has wide attention of researchers. However, due to the influence of chromatic dispersion of the optical properties of materials and the limitation of a design principle, the performance of the existing super-surface stealth cloak is difficult to dynamically tune, the working bandwidth is limited, the incident angle domain is narrow, the excitation and polarization mode of incident waves is seriously depended on, and the requirements of modern military on wide-band, wide-angle domain, full-polarization and tunable stealth technologies cannot be met.
Disclosure of Invention
In view of the above, it is an object of the present invention to provide a phase change material G based on phase change materialse2Sb2Te5The reconfigurable super-surface cloaking cloak is used for solving the technical bottlenecks of narrow working bandwidth, narrow incident angle range, difficult dynamic tuning of performance and the like of the conventional super-surface cloak.
The technical scheme adopted by the invention for solving the technical problems is as follows: based on phase change material Ge2Sb2Te5The reconfigurable super-surface stealth cloak is characterized by comprising W rows and V columns of reconfigurable super-surface stealth units which are fixedly connected on the surface of a stealth object in a covering mode, wherein adjacent reconfigurable super-surface stealth units are fixedly spliced in a seamless mode;
the reconfigurable super-surface stealth unit comprises a lower square metal substrate layer with the side length of p, a middle dielectric layer and an upper gold nano antenna, wherein the metal substrate layer is fixedly connected to the surface of a stealth object in a covering mode, and the middle dielectric layer is made of Ge2Sb2Te5Film and MgF2Film composition of said Ge2Sb2Te5The film is covered and fixed on the upper surface of the metal basal layer, and the MgF2The film is arranged in Ge2Sb2Te5Upper end of film and MgF2Lower surface of film and Ge2Sb2Te5The upper surface of the film is tightly attached and the size of the film is completely matched, and the gold nano-antenna on the upper layer is fixed on the MgF2On the upper surface of the thin film layer, multiple groups of gold nano-antennas form a W-row multiplied by V-row gold nano-antenna resonant array, the geometric dimensions of the gold nano-antennas meet the requirement of identical rows, and the geometric dimension of each row of gold nano-antennas is determined by the reflection phase compensation quantity provided by the gold nano-antennas;
the calculation formula of the reflection phase compensation amount is as follows:
in the formula
Indicating the amount of reflected phase compensation, k 02 pi/lambda denotes the wave number of the incident electromagnetic wave, hi＝(i-1/2) psin theta represents the height of the geometric center of the ith (i is 1,2,3 … W) row gold nano-antenna in any column from the ground, theta is 15 degrees and represents the included angle between the stealth cloak and the horizontal ground, p represents the distance between the geometric centers of two adjacent gold nano-antennas, alpha represents the incident angle of electromagnetic waves, and pi represents the phase change quantity caused by specular reflection.
Preferably, the range of the incident angle alpha of the electromagnetic wave is-25 degrees.
Preferably, the wavelength λ of the infrared electromagnetic wave ranges from λ 6920nm to λ 8220 nm.
Preferably, the Ge of the middle layer2Sb2Te5The film has two phase states of a crystalline state and an amorphous state, the dielectric constants of the two phases are obviously different, the two phases can be mutually converted, and multi-stage phase change can be realized by controlling different proportions of the crystalline state and the amorphous state in the conversion process to generate various Ge2Sb2Te5An intermediate phase.
Preferably, to achieve continuous tuning of the stealth performance (center wavelength), Ge2Sb2Te5The crystallinity m of the film is controlled to 0,0.2,0.4,0.6,0.8,1, wherein m ═ 0 represents amorphous Ge2Sb2Te5And m ═ 1 represents a crystalline state Ge2Sb2Te5。
Preferably, Ge is used to achieve both "ON" and "OFF" stealth performance2Sb2Te5The film is set in an amorphous state and a crystalline state, respectively.
Preferably, to achieve the ultra-thin cloaking effect, the overall thickness of the cloak is 700nm, which is only 1/11 of the designed working wavelength.
Preferably, the material of the lower metal layer can be made of one of Au, Ag and Pt.
The invention has the beneficial effects that: the spatial distribution of the phase of the reflected wave is modulated by using the surface plasmon resonances of the gold nano resonant antennas with different sizes in the super-surface structure, so that the reconstruction of the wave front of the reflected wave can be realized, and the effect of camouflage and invisibility is achieved. Using Ge2Sb2Te5Unique phase change characteristic of filmThe sexual tuning stealth cloak surrounding dielectric environment can realize the continuous tuning and ON and OFF of stealth performance. The super-surface stealth cloak disclosed by the invention realizes the perfect stealth effects of wider working bandwidth, larger incident angle range and dynamically tunable performance.
Drawings
FIG. 1 is Ge2Sb2Te5A structural unit oblique view of the reconfigurable super surface;
FIG. 2 is Ge2Sb2Te5A structural unit front side view capable of reconstructing the super surface;
FIG. 3 is Ge2Sb2Te5A top view of a structural unit of the reconfigurable super surface;
FIG. 4 is based on Ge2Sb2Te5An oblique view of a triangular prismatic convex cloak structure constructed by a reconfigurable super surface;
FIG. 5 is based on Ge2Sb2Te5A front side view of a triangular prismatic raised cloak structure constructed by a reconfigurable super surface;
FIG. 6 is a diagram of the correspondence between the reflection phase of the super-surface structure unit and the geometric structure size of the gold nano-antenna;
FIG. 7 is a diagram of the correspondence between the amplitude of the reflected wave of the super-surface structure unit and the geometric structure size of the gold nano-antenna;
FIG. 8 is λ0When 7620nm infrared electromagnetic wave is vertically incident on the bare triangular prismatic convex inclined plane with the inclined plane inclination angle theta of 15 degrees, the reflection electric field distribution diagram of the y-z plane;
FIG. 9 is λ0When 7620nm infrared electromagnetic wave is vertically incident on the bare triangular prismatic convex inclined plane with the inclined plane inclination angle theta of 15 degrees, two-dimensional and three-dimensional far-field radiation directional diagrams of reflected waves are obtained;
FIG. 10 is λ07620nm infrared electromagnetic wave is perpendicularly incident to Ge with crystallinity m of 02Sb2Te5When the reconfigurable super-surface stealth cloak covers a triangular prismatic projection with an inclined plane inclination angle theta equal to 15 degrees, the reflection electric field distribution diagram of the y-z plane is formed;
FIG. 11 is λ07620nm infrared electromagneticThe wave is vertically incident to Ge with crystallinity m equal to 02Sb2Te5When the triangular prismatic projection covered by the super-surface stealth cloak is reconstructed and the inclined angle theta of the inclined plane is 15 degrees, the two-dimensional and three-dimensional far-field radiation directional diagrams of the reflected wave are constructed;
FIG. 12 is λ07620nm infrared electromagnetic wave is incident obliquely at an incident angle α of 15 ° to Ge having a crystallinity m of 02Sb2Te5When the reconfigurable super-surface stealth cloak covers a triangular prismatic projection with an inclined plane inclination angle theta equal to 15 degrees, the reflection electric field distribution diagram of the y-z plane is formed;
FIG. 13 is λ07620nm infrared electromagnetic wave is incident obliquely at an angle of incidence α -25 ° to Ge with a crystallinity m-02Sb2Te5When the reconfigurable super-surface stealth cloak covers a triangular prismatic projection with an inclined plane inclination angle theta equal to 15 degrees, the reflection electric field distribution diagram of the y-z plane is formed;
FIG. 14 shows the two-dimensional far-field radiation pattern of the reflected wave when the infrared electromagnetic wave with λ 6020nm to λ 9420nm range is vertically incident on the bare triangular prismatic convex slope with the slope angle θ of 15 °, in which λ0＝7620nm，λ1＝6920nm，λ2＝8220nm；
Fig. 15 shows that infrared electromagnetic waves ranging from λ 6020nm to λ 9420nm are perpendicularly incident on Ge having a crystallinity m of 02Sb2Te5When the reconfigurable super-surface stealth cloak is covered by the triangular prismatic projection with the inclined plane inclination angle theta equal to 15 degrees, the two-dimensional far-field radiation directional diagram of the reflected wave is shown in the figure by lambda0＝7620nm，λ1＝6920nm，λ2＝8220nm。
Fig. 16 shows that infrared electromagnetic waves with λ 6020nm to λ 9420nm range are incident perpendicularly/obliquely to Ge with crystallinity m of 02Sb2Te5And when the reconfigurable super-surface stealth cloak covers a triangular prismatic projection with an inclined plane inclination angle theta equal to 15 degrees, the total radar scattering cross section RCS is reduced.
Fig. 17 shows that an infrared electromagnetic wave with λ 7720nm is perpendicularly incident on Ge with a crystallinity m of 0.22Sb2Te5Triangular edge with inclined plane inclination angle theta of 15 degrees and capable of being covered by reconfigurable super-surface stealth cloakThe reflection electric field distribution diagram of the y-z plane when the convex is formed;
fig. 18 shows that an infrared electromagnetic wave with λ 7820nm is perpendicularly incident on Ge with a crystallinity m of 0.42Sb2Te5When the reconfigurable super-surface stealth cloak covers a triangular prismatic projection with an inclined plane inclination angle theta equal to 15 degrees, the reflection electric field distribution diagram of the y-z plane is formed;
fig. 19 shows normal incidence of an infrared electromagnetic wave with λ 7920nm to Ge with a crystallinity m of 0.62Sb2Te5When the reconfigurable super-surface stealth cloak covers a triangular prismatic projection with an inclined plane inclination angle theta equal to 15 degrees, the reflection electric field distribution diagram of the y-z plane is formed;
fig. 20 shows that λ 7920nm infrared electromagnetic wave is perpendicularly incident to Ge with crystallinity m 0.82Sb2Te5When the reconfigurable super-surface stealth cloak covers a triangular prismatic projection with an inclined plane inclination angle theta equal to 15 degrees, the reflection electric field distribution diagram of the y-z plane is formed;
fig. 21 shows that λ 7920nm infrared electromagnetic wave is perpendicularly incident on Ge with crystallinity m 12Sb2Te5When the reconfigurable super-surface stealth cloak covers a triangular prismatic projection with an inclined plane inclination angle theta equal to 15 degrees, the reflection electric field distribution diagram of the y-z plane is formed;
fig. 22 shows that infrared electromagnetic waves ranging from λ 6020nm to λ 9420nm are perpendicularly incident on Ge having a crystallinity m of 12Sb2Te5When the reconfigurable super-surface stealth cloak is covered by the triangular prismatic projection with the inclined plane inclination angle theta equal to 15 degrees, the two-dimensional far-field radiation directional diagram of the reflected wave is shown in the figure by lambda0＝7620nm，λ3＝7920nm，λ4＝8720nm。
FIG. 23 is a37920nm infrared electromagnetic wave is perpendicularly incident to Ge with crystallinity m equal to 12Sb2Te5When the triangular prismatic projection covered by the super-surface stealth cloak is reconstructed and the inclined angle theta of the inclined plane is 15 degrees, the two-dimensional and three-dimensional far-field radiation directional diagrams of the reflected wave are constructed;
FIG. 24 is a4An infrared electromagnetic wave with the wavelength of 8720nm is perpendicularly incident to Ge with the crystallinity m of 12Sb2Te5Reconfigurable super-surface cloaking cloak-covered, tiltWhen the surface inclination angle theta is 15 degrees of triangular prismatic projection, the two-dimensional and three-dimensional far-field radiation directional diagrams of reflected waves are formed;
FIG. 25 is a07620nm infrared electromagnetic wave is perpendicularly incident to Ge with crystallinity m 12Sb2Te5When the reconfigurable super-surface stealth cloak covers a triangular prismatic projection with an inclined plane inclination angle theta equal to 15 degrees, the two-dimensional and three-dimensional far-field radiation directional diagrams of reflected waves are obtained.
In the figure, 1 is a metal base layer, and 2 is Ge2Sb2Te5Dielectric layer, 3 is MgF2And the dielectric layer 4 is a gold nano antenna layer.
Detailed Description
The present invention will be described below by way of examples with reference to the accompanying fig. 1 to 25.
The invention provides a phase-change material Ge-based material2Sb2Te5The reconfigurable super-surface cloaking cloak comprises W rows and V columns of reconfigurable super-surface cloaking units which are fixedly covered on the surface of a cloaked object, adjacent reconfigurable super-surface cloaking units are fixedly spliced in a seamless way, a plurality of groups of cloaking units are spliced in a seamless way to form the reconfigurable super-surface cloaking cloak, and the reconfigurable super-surface cloaking units are regularly arranged in an array way, as shown in figures 1,2,3, 4 and 5;
the reconfigurable super-surface stealth unit comprises a lower square metal substrate layer 1 with the side length of p and an intermediate Ge layer2Sb2Te5Dielectric layer 2, MgF of the middle layer2A dielectric layer 3 and an upper layer gold nano-antenna 4, wherein the metal substrate layer is fixedly connected with the surface of the concealed object in a covering way, and the middle layer dielectric layer is made of Ge2Sb2Te5Film and MgF2Film composition of said Ge2Sb2Te5The film is covered and fixed on the upper surface of the metal basal layer, and the MgF2The film is arranged in Ge2Sb2Te5Upper end of film and MgF2Lower surface of film and Ge2Sb2Te5The upper surface of the film is tightly attached and the size of the film is completely matched, and the gold nano-antenna on the upper layer is fixed on the MgF2On the film layerOn the surface, multiple groups of gold nano-antennas form a W-row multiplied by V-row gold nano-antenna resonant array, the geometric dimensions of the gold nano-antennas meet the requirement of identical rows, and the geometric dimensions of each row of gold nano-antennas are determined by the reflection phase compensation quantity provided by the gold nano-antennas;
the calculation formula of the reflection phase compensation quantity is as follows:
in the formula
Indicating the amount of reflected phase compensation, k 02 pi/lambda denotes the wave number of the incident electromagnetic wave, hiThe height of the geometric center of the ith (i-1, 2,3 … W) gold nano-antenna in any column from the ground is represented by (i-1/2) psin theta, the included angle between the stealth cloak and the horizontal ground is represented by theta 15 degrees, and p represents the distance between the geometric centers of two adjacent gold nano-antennas. α represents an electromagnetic wave incident angle, and π represents a phase jump due to specular reflection. The value range of the incident angle alpha of the electromagnetic wave is-25 degrees, when the incident angle of the electromagnetic wave is in the range, the cloak has a stealth effect, and the wavelength range of the incident electromagnetic wave applicable to the cloak for stealth is 6920-8220 nm.
The length, the width and the height of the gold nano antenna are respectively a, b and d, wherein the values of a and b are selected according to the theoretically calculated reflection phase compensation quantity at the corresponding position. The distance between the geometric centers of every two adjacent gold nano antennas, namely the periods of the super-surface structure units are equal and are represented by p, wherein the metal layer at the lower layer and the dielectric layer at the middle layer of the reconfigurable super-surface stealth unit are also in a p-p square structure, and MgF2The thickness of the dielectric layer is t1，Ge2Sb2Te5The thickness of the dielectric layer is t2The thickness of the metal substrate layer is t3. The infrared electromagnetic plane wave is vertically incident downwards, the polarization direction is parallel to the long edge a of the gold nano-antenna, and the gold nano-antenna resonant array reflects part of the incident infrared electromagnetic plane wave and metalThe base layer acts as a total reflection mirror.
The dielectric layer material in the invention is Ge2Sb2Te5And MgF2，MgF2Lower surface of layer and Ge2Sb2Te5The upper surface of the layer is tightly attached and completely matched, and the side length of the dielectric layer in the reconfigurable super-surface stealth unit is also p. Phase change material Ge2Sb2Te5The layer acts as an active layer, MgF, which changes the local dielectric environment2A dielectric layer deposited on Ge2Sb2Te5The upper surface of the layer to prevent it from being oxidized in the atmosphere. The upper layer of the gold nano-antenna resonant array is obtained by etching by using techniques such as focused-ion-beam (FIB) or Electron Beam Lithography (EBL).
Phase change material Ge2Sb2Te5The wave front (phase and amplitude) of the reflected wave of the reconfigurable super surface depends on the geometric parameters of the gold nano antenna, the sizes of the gold nano antenna are different, and the phase and amplitude of the corresponding reflected wave are also different. The period of the super-surface structural unit adopted by the invention is 3 mu m, MgF2The thickness of the dielectric layer is t1＝100nm，Ge2Sb2Te5The thickness of the dielectric layer is t2400nm, thickness of the metal base layer t3The height d of the gold nano antenna is 100nm, the length a and the width b of the gold nano antenna are both 100 to 2900nm, and the wavelength lambda of the infrared electromagnetic plane wave vertically downwards incident 07620 nm; at this time, the correspondence between the phase and amplitude of the reflected wave of the super-surface structure unit and the geometric size of the gold nano-antenna is as shown in fig. 6 and 7, wherein the abscissa and the ordinate of the circular mark correspond to the geometric size of the W kinds of gold nano-antennas constituting the cloak, W is 24, that is, the number of rows of the gold nano-antenna resonant array in fig. 4 of the present invention is 24, and the number of columns V can be changed according to actual requirements.
The invention adds Ge2Sb2Te5The reconfigurable super-surface structure units are arranged along the inclined plane of the triangular prismatic protrusion to construct a cloak covered on the triangular prismatic protrusion, as shown in fig. 4 and 5. Several sheets are arranged along the x axis through the inclined plane of the triangular prismatic projectionThe gold nano antenna resonant arrays with the same geometric dimension and different geometric dimensions are arranged along the y axis, so that specific phase space compensation can be obtained, wave front modulation of reflected waves is realized, and the triangular prismatic bulge and the internal space thereof are invisible relative to incident infrared electromagnetic plane waves.
For the triangular prismatic projection with the inclined plane inclination angle theta, the calculation formula of the reflection phase compensation quantity is as follows:
in the formula
Indicating the amount of reflected phase compensation, k 02 pi/lambda denotes the wave number of the incident electromagnetic wave, hiThe height of the geometric center of the ith (i-1, 2,3 … W) gold nano-antenna in any column from the ground is represented by (i-1/2) psin theta, the included angle between the stealth cloak and the horizontal ground is represented by theta 15 degrees, and p represents the distance between the geometric centers of two adjacent gold nano-antennas. α represents an electromagnetic wave incident angle, and π represents a phase jump due to specular reflection.
Fig. 6 and 7 are contour diagrams of reflected wave phase and amplitude of the super-surface structure unit, which are drawn based on simulation results, when the geometric sizes a and b of the gold nano-antenna are different values. Therefore, the surface plasmon resonances of the gold nano-antennas with different sizes can realize different reflected wave phases, so that the gold nano-antennas with different sizes are arranged to modulate Ge2Sb2Te5The spatial distribution of the phase of the super-surface reflection wave can be reconstructed. The specific process is as follows: firstly, when the camouflage stealth is realized according to a calculation formula of the reflection phase compensation quantity, the super-surface structure unit is in hiThe phase of the reflection that needs to be provided. Further, according to the spatial distribution of the reflection phase obtained by the simulation calculation, the structure (geometric dimension) of the gold nano antenna which satisfies the distribution of the reflection phase and has a strong amplitude of the reflected wave is found out from the data sets corresponding to fig. 6 and 7. Finally, the gold nano-antennas with specific geometric dimensions are overruledThe surface structure units are arranged at corresponding positions (h)iAt (c).
As shown in fig. 8, is λ0When an infrared electromagnetic plane wave with the wavelength of 7620nm is vertically incident (namely alpha is 0 degrees) to a bare triangular prismatic convex inclined plane with an inclined plane inclination angle theta of 15 degrees, a reflected electric field distribution diagram of a y-z plane is formed; as shown in fig. 9, for the two-dimensional and three-dimensional far-field radiation patterns of the reflected wave, it can be clearly seen that the incident wave is reflected by the two inclined planes and then propagates in the obliquely upward directions along the two sides. As shown in fig. 10 and 11, Ge with a degree of crystallinity m of 0 is protruded in a triangular prism shape2Sb2Te5After the reconfigurable super-surface stealth cloak is covered, the distribution of a reflection electric field of a y-z plane and two-dimensional and three-dimensional far-field radiation patterns of reflection waves are constructed; compared with the naked situation, when the triangular prismatic convex surface covers the designed super-surface invisible cloak, reflected waves are reflected along the normal direction of the horizontal ground, the wave front is uniformly distributed in a plane, the wave front is similar to the reflection field of the horizontal ground (without the triangular prismatic convex) to the vertical incident waves, namely the invisible performance is ON, and the camouflage and the invisibility of the triangular prismatic convex and the internal space of the triangular prismatic convex are realized.
The stealth cloak is obliquely incident to test the stealth performance through the infrared electromagnetic plane wave. As shown in fig. 12 and 13, is λ0An infrared plane wave of 7620nm is obliquely incident on Ge with crystallinity m of 0 at incident angle alpha of 15 deg. and alpha of 25 deg.2Sb2Te5When the reconfigurable super-surface stealth cloak covers the triangular prismatic bulges with the inclined plane inclination angle theta equal to 15 degrees, the electric field distribution of the reflection field is similar to that of the reflection field of the incident wave by the horizontal ground, and the camouflage and stealth of the triangular prismatic bulges are realized, so that the super-surface stealth cloak has certain wide-angle-range stealth performance.
The stealth cloak is vertically incident to test the stealth performance through infrared plane waves with different wavelengths. As shown in fig. 15, when infrared electromagnetic waves in the range of λ 6020nm to λ 9420nm are perpendicularly incident, Ge having a crystallinity m of 0 covering the surface of triangular prismatic projection with a tilt angle θ of 15 ° is present2Sb2Te5And a reflected wave two-dimensional far field radiation directional diagram of the super-surface stealth cloak can be reconstructed. For comparison, FIG. 14And meanwhile, when infrared electromagnetic waves in the range of lambda 6020nm to lambda 9420nm are vertically incident on the bare triangular prismatic convex inclined plane, a two-dimensional far-field radiation directional diagram of reflected waves is given. At the designed operating wavelength λ0λ around 7620nm1～λ2Within the wave band range, reflected wave energy covered by triangular prismatic protrusions of the super-surface invisible cloak mainly propagates along the normal direction of a horizontal plane, and the reflected wave energy shows the distribution characteristic of the reflected field of the normal incident wave on the horizontal ground. Therefore, the super-surface cloaking cloak has better camouflage cloak performance in a wider wave band range. In the figure lambda1＝6920nm，λ2＝8220nm。
The invention quantitatively tests the stealth performance of the reduced total radar scattering cross section RCS by researching the RCS. As shown in fig. 16, when infrared electromagnetic waves are vertically incident in a range from λ 6020nm to λ 9420nm, Ge with a crystallinity m of 0 covered on the surface of triangular prism-shaped protrusions with a tilt angle θ of 15 ° is used2Sb2Te5The total radar scattering cross section diagram reduced by the reconfigurable super-surface stealth cloak has the maximum RCS reduction amount of-10 dB and the 3dB RCS reduction bandwidth of 35.43 percent of the total research waveband. Ge with crystallinity m equal to 0 at oblique incidence of infrared electromagnetic wave2Sb2Te5The reconfigurable super-surface stealth cloak can also obtain the RCS which is obviously reduced, but the RCS reduction degree is weakened because the initial structural design aims at the infrared electromagnetic wave vertical incidence condition.
The invention utilizes a wave optical module of finite element electromagnetic field simulation software Comsol Multiphysics to design a super-surface structure unit and carry out analog simulation verification on the stealth performance of the built stealth cloak. In the infrared electromagnetic wave band, the metal substrate layer is replaced by a perfect electric conductor boundary, the relative dielectric coefficient of the gold nano antenna adopts a Drude model, and amorphous/crystalline Ge is adopted2Sb2Te5And MgF2The relative permittivity of the dielectric layer was measured using related experiments. Ge (germanium) oxide2Sb2Te5In the process of mutual transformation of amorphous state and crystalline state, a plurality of intermediate phase states are experienced, and the relative dielectric constant epsilon of the intermediate states is determined according to the equivalent medium theory and the Lorentz equationeff(λ) is described by the following formula:
in the formula, epsilonc(lambda) represents a crystalline Ge2Sb2Te5Relative dielectric constant,. epsilona(λ) represents amorphous Ge2Sb2Te5Relative permittivity, m represents Ge2Sb2Te5The crystallinity ranges from 0 to 1, and m is 0 and represents Ge2Sb2Te5In the amorphous state, m ═ 1 represents Ge2Sb2Te5Is in a crystalline state; epsiloneff(λ)，εc(λ)，εaThe values of (λ) are all related to the incident wavelength. According to the above formula, Ge2Sb2Te5The change in crystallinity directly results in Ge2Sb2Te5The relative dielectric constant changes, which in turn affects the dielectric environment surrounding the device. Ge (germanium) oxide2Sb2Te5The crystallinity/phase state can be controlled by means of heating, bias voltage, optical modulation and the like.
The invention relates to a Ge vertical incidence method by infrared plane waves2Sb2Te5Stealth cloak with varying crystallinity/phase was tested for its continuous tuning stealth performance. As shown in fig. 17 to 21, Ge with a crystallinity of m of 0.2,0.4,0.6,0.8,1 is coated on the triangular prismatic convex surface with an inclination angle θ of 15 °2Sb2Te5The reconfigurable super-surface stealth cloak has the advantages that when an infrared plane wave with the lambda being 7720,7820,7920,8020,8120nm is vertically incident, the distribution of a reflection field is similar to that of a reflection field of a horizontal ground facing the incident wave, and Ge is illustrated2Sb2Te5Crystallinity change or Ge2Sb2Te5The perfect stealth can be realized at the proper wavelength when different phases are taken, namely Ge2Sb2Te5The reconfigurable super-surface stealth cloak can realize the stealth performance of continuously tuning the stealth center wavelength.
The invention also provides the infrared plane wave vertical incidence crystallinity m ═1, i.e. crystalline Ge2Sb2Te5The super-surface cloaking cloak can be reconfigured to test its cloaking performance. As shown in fig. 22, when infrared electromagnetic waves in the range of λ 6020nm to λ 9420nm are vertically incident, the wavelength λ is set to be equal to3～λ4In a waveband range, Ge with crystallinity m equal to 1 is covered2Sb2Te5The reflected wave energy of the triangular prismatic protrusions of the reconfigurable super-surface stealth cloak mainly propagates along the normal direction of a horizontal plane, and the reflected field distribution characteristic of the horizontal ground alignment incident wave is shown. FIGS. 23 and 24 show a wavelength of λ3And λ4When the plane wave is vertically incident, the triangular prismatic projection is crystallized by Ge with the crystallinity m equal to 12Sb2Te5The covering of the super-surface stealth cloak and the two-dimensional and three-dimensional far-field radiation directional diagrams of reflected waves can be reconstructed. Further, the super-surface cloaking cloak is determined to have better disguising cloak performance in the wave band range, so that Ge is widened2Sb2Te5The stealth bandwidth of the super-surface stealth cloak can be reconstructed; while at the initial design operating wavelength lambda07620nm, the reflected wave energy is mainly transmitted along the direction perpendicular to the inclined plane of the triangular prism-shaped protrusion, showing the distribution characteristics of the reflected field of the incident wave aligned with the inclined plane of the triangular prism-shaped protrusion, and fig. 25 shows the designed working wavelength λ0When plane wave is vertically incident at 7620nm, the triangular prismatic projection is crystallized by Ge with m equal to 12Sb2Te5The covering of the super-surface stealth cloak and the two-dimensional and three-dimensional far-field radiation directional diagrams of reflected waves are reconstructed, and the further verification is that the super-surface stealth cloak is covered at the designed working wavelength lambda0The camouflage stealth performance is lost, namely OFF of the camouflage stealth performance is realized. In the figure lambda0＝7620nm，λ3＝7920nm，λ4＝8720nm。
In summary, the present invention provides Ge2Sb2Te5The reconfigurable super-surface cloaking cloak can achieve a camouflage cloaking effect in a certain angular range in a wider wave band range. By regulating Ge2Sb2Te5The crystallinity/phase state of the dielectric layer can realize effective broadening of the working wave band of the invisible cloak, and the invisible central wavelength can realize continuous adjustmentHarmonic and at the initial design operating wavelength λ0The invisible performance can be realized ON and OFF.
The above-described embodiments are merely examples of the present invention and are not intended to limit the scope of the present invention, it should be understood that various equivalent modifications and substitutions can be made by those skilled in the art within the scope of the present invention, and the exposed bump shape, the shape of the nano-antenna, the laser wavelength, etc. can be changed. Such equivalent modifications and substitutions, as well as adjustments to the frequency range, should also be considered to be within the scope of the present invention.
Claims (7)
1. Based on phase change material Ge2Sb2Te5The reconfigurable super-surface stealth cloak is characterized by comprising W rows and V columns of reconfigurable super-surface stealth units which are fixedly connected on the surface of a stealth object in a covering mode, wherein adjacent reconfigurable super-surface stealth units are fixedly spliced in a seamless mode;
the reconfigurable super-surface stealth unit comprises a lower square metal substrate layer with the side length of p, a middle dielectric layer and an upper gold nano antenna, wherein the metal substrate layer is fixedly connected to the surface of a stealth object in a covering mode, and the middle dielectric layer is made of Ge2Sb2Te5Film and MgF2Film composition of said Ge2Sb2Te5The film is covered and fixed on the upper surface of the metal basal layer, and the MgF2The film is arranged in Ge2Sb2Te5Upper end of film and MgF2Lower surface of film and Ge2Sb2Te5The upper surface of the film is tightly attached and the size of the film is completely matched, and the gold nano-antenna on the upper layer is fixed on the MgF2On the upper surface of the thin film layer, multiple groups of gold nano-antennas form a W-row multiplied by V-row gold nano-antenna resonant array, the geometric dimensions of the gold nano-antennas meet the requirement of identical rows, and the geometric dimension of each row of gold nano-antennas is determined by the reflection phase compensation quantity provided by the gold nano-antennas;
the calculation formula of the reflection phase compensation amount is as follows:
in the formula
Indicating the amount of reflected phase compensation, k02 pi/lambda denotes the wave number of the incident electromagnetic wave, hiThe height of the geometric center of the ith (i-1, 2,3 … W) gold nano-antenna in any column from the ground is represented by (i-1/2) psin theta, the included angle between the stealth cloak and the horizontal ground is represented by theta 15 degrees, the distance between the geometric centers of two adjacent gold nano-antennas is represented by p, the incident angle of electromagnetic waves is represented by alpha, and the phase bump variable caused by mirror reflection is represented by pi.
2. The phase change material Ge-based of claim 12Sb2Te5The reconfigurable super-surface cloaking cloak is characterized in that the value range of the incident angle alpha of the electromagnetic wave is-25 degrees.
3. Phase change material Ge-based according to claim 1 or 22Sb2Te5The reconfigurable super-surface stealth cloak is characterized in that the wavelength lambda of the infrared electromagnetic wave ranges from 6920nm to 8220 nm.
4. The phase change material Ge-based of claim 12Sb2Te5The reconfigurable super-surface cloak is characterized in that Ge of the middle layer2Sb2Te5The film has two phase states of a crystalline state and an amorphous state, the dielectric constants of the two phases are obviously different, the two phases can be mutually converted, and multi-stage phase change can be realized by controlling different proportions of the crystalline state and the amorphous state in the conversion process to generate various Ge2Sb2Te5An intermediate phase.
5. The phase change material Ge-based of claim 42Sb2Te5Reconfigurable super-surface concealmentA body cape, characterized in that Ge2Sb2Te5The crystallinity m of the film is controlled to 0,0.2,0.4,0.6,0.8,1, wherein m ═ 0 represents amorphous Ge2Sb2Te5And m ═ 1 represents a crystalline state Ge2Sb2Te5。
6. The phase change material Ge-based of claim 12Sb2Te5The reconfigurable super-surface cloak is characterized in that the overall thickness of the cloak is 700nm, and is only 1/11 of the designed working wavelength.
7. The phase change material Ge-based of claim 12Sb2Te5The reconfigurable super-surface cloaking cloak is characterized in that the lower metal layer can be made of one of Au, Ag and Pt.
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| CN202110028835.8A CN112859204A (en) | 2021-01-11 | 2021-01-11 | Based on phase change material Ge2Sb2Te5Reconfigurable super-surface cloaking cloak |
| ZA2022/00437A ZA202200437B (en) | 2021-01-11 | 2022-01-10 | Reconfigurable meta-surface invisibility cloak based on phase change material ge2sb2te5 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114527521A (en) * | 2022-03-04 | 2022-05-24 | 郑州航空工业管理学院 | Polarization-insensitive active super-surface cloak |
| CN114721072A (en) * | 2022-05-05 | 2022-07-08 | 中国计量大学 | Oblique incidence super-surface stealth device based on achromatic multilayer frame structure |
| CN115542432A (en) * | 2022-09-23 | 2022-12-30 | 成都信息工程大学 | Metal-dielectric embedded super surface and preparation method thereof |
-
2021
- 2021-01-11 CN CN202110028835.8A patent/CN112859204A/en not_active Withdrawn
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114527521A (en) * | 2022-03-04 | 2022-05-24 | 郑州航空工业管理学院 | Polarization-insensitive active super-surface cloak |
| CN114527521B (en) * | 2022-03-04 | 2023-07-07 | 郑州航空工业管理学院 | Polarization insensitive active super-surface stealth cloak |
| CN114721072A (en) * | 2022-05-05 | 2022-07-08 | 中国计量大学 | Oblique incidence super-surface stealth device based on achromatic multilayer frame structure |
| CN114721072B (en) * | 2022-05-05 | 2024-01-02 | 中国计量大学 | Oblique incidence super-surface stealth device based on achromatic multi-layer frame structure |
| CN115542432A (en) * | 2022-09-23 | 2022-12-30 | 成都信息工程大学 | Metal-dielectric embedded super surface and preparation method thereof |
| CN115542432B (en) * | 2022-09-23 | 2023-06-30 | 成都信息工程大学 | Metal-dielectric embedded type super surface and preparation method thereof |
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