Disclosure of Invention
The present invention aims to solve at least one of the above technical problems to a certain extent.
Therefore, the invention aims to provide an ultra-thin ultra-wideband perfect absorber independent of polarization direction of incidence angle, which has simple structure, ultra-thin thickness and high absorptivity in the whole visible light range.
The ultra-thin ultra-wideband perfect absorber with the independent incidence angle and the independent polarization direction comprises the following components: at least one perfect absorber unit, the perfect absorber unit comprising: a substrate; the annular insulating layer is arranged on the substrate; the first reflecting layer is arranged on the insulating layer, and the insulating layer, the first reflecting layer and the substrate enclose a cavity with an opening at the upper end; the high-refractive-index material layer is a visible light waveband high-refractive-index material, is arranged on the substrate and is positioned in the cavity, and is of a central symmetrical structure; and the second reflecting layer is arranged on the high-refractive-index material layer.
According to the ultra-thin ultra-wide band perfect absorber irrelevant to the incident angle and the polarization direction, the ultra-thin ultra-wide band perfect absorber irrelevant to the polarization direction is realized by the combination structure of the high-refractive-index material layer, the insulating layer, the first reflecting layer and the second reflecting layer, so that the ultra-thin ultra-wide band perfect absorber has good optical performance in the whole visible light wave band, not only can the defects of low efficiency, narrow bandwidth, small incident angle range, polarization correlation and the like in the traditional absorption optical element be effectively avoided, but also the perfect absorption irrelevant to the polarization direction in the whole visible light wave band (400nm to 760nm) is realized, and the ultra-thin ultra-wide band perfect absorber has the advantages of simple structure, ultra.
In addition, the ultra-thin ultra-wideband perfect absorber with independent incidence angle and independent polarization direction according to the embodiment of the invention can also have the following additional technical characteristics:
according to one embodiment of the invention, the substrate is SiO2And (3) a layer.
According to one embodiment of the invention, the insulating layer is SiO2And (3) a layer.
According to one embodiment of the present invention, the high refractive index material layer is a GaN layer.
According to one embodiment of the invention, the first reflective layer and/or the second reflective layer is a Pt reflective layer.
According to one embodiment of the invention, the cavity is substantially square-shaped, and the high refractive index material layer is shaped to fit the shape of the cavity.
According to one embodiment of the invention, the second reflective layer conforms to the shape of the cross-section of the layer of high refractive index material.
According to one embodiment of the present invention, a sum of a height of the insulating layer and a height of the first reflective layer is equal to a height of the high refractive index material layer.
According to one embodiment of the invention, the height of the second reflective layer is equal to the height of the first reflective layer.
According to one embodiment of the invention, a plurality of the perfect absorber units are positioned on the same plane and connected with each other, a plurality of the high refractive index material layers are arranged at equal intervals, and the vertexes of two adjacent high refractive index material layers are oppositely arranged.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic diagram of the structure of an ultra-thin incident angle independent polarization direction independent ultra-wideband perfect absorber according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view of a perfect absorber unit of an ultra-thin incident angle independent polarization direction independent ultra-wideband perfect absorber according to an embodiment of the present invention;
FIG. 3 is a side view of FIG. 2;
FIG. 4 is a top view of a perfect absorber unit of an ultra-thin incident angle independent polarization direction independent ultra-wideband perfect absorber according to an embodiment of the present invention;
FIG. 5 is a simulation of an ultra-thin incident angle independent polarization direction independent ultra-wideband perfect absorber according to an embodiment of the present invention;
FIG. 6a is a test result of an ultra-thin incident angle independent polarization direction independent ultra-wideband perfect absorber according to an embodiment of the present invention under incident light conditions of different incident angles;
FIG. 6b is a test result of an ultra-thin incident angle independent polarization direction independent ultra-wideband perfect absorber according to an embodiment of the present invention under different angle incidence conditions at a wavelength of 658 nm;
FIG. 7 illustrates a sample optical path and a test optical path of an ultra-thin incident angle independent polarization independent ultra-wideband perfect absorber according to an embodiment of the present invention;
FIGS. 8a to 8d are x-y cross-sectional electric field distributions of the interface of the first reflective layer and the insulating layer at wavelengths of 400nm, 500nm, 600nm and 700nm for an ultra-thin incident angle independent polarization independent ultra-wideband perfect absorber according to an embodiment of the present invention;
figures 8e through 8h are x-z cross-sectional electric field distributions for ultra-thin, incident angle-independent polarization direction-independent ultra-wideband perfect absorbers according to embodiments of the present invention at the electric field maxima at wavelengths of 400nm, 500nm, 600nm, and 700nm, respectively.
Reference numerals:
an ultra-thin ultra-wideband perfect absorber 1000 with an incident angle independent of polarization direction;
a perfect absorber unit 100;
a substrate 10; an insulating layer 20; a first reflective layer 30; a high refractive index material layer 40; a second reflective layer 50;
a substrate width P; a second reflective layer width A; an absorption rate B; a reflectance C; a refractive index D; an absorption rate E; a reflectance F; a refractive index G; a polarization direction a; an incident direction b; the distance d between two adjacent second reflective layers.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations or positional relationships based on those shown in the drawings, are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
An ultra-thin, incident angle-independent polarization direction-independent ultra-wideband perfect absorber 1000 in accordance with an embodiment of the present invention is described in detail below with reference to the accompanying drawings.
As shown in fig. 1 to 4, the ultra-thin incident angle-independent polarization direction-independent ultra-wideband perfect absorber 1000 according to an embodiment of the present invention includes a perfect absorber unit 100, the perfect absorber unit 100 including a substrate 10, an insulating layer 20, a first reflective layer 30, a high refractive index material layer 40, and a second reflective layer 50.
Specifically, the number of the perfect absorber units 100 is at least one, and the perfect absorber unit 100 includes: the reflective film comprises a substrate 10, an annular insulating layer 20 arranged on the substrate 10, a first reflecting layer 30 arranged on the insulating layer 20, a cavity with an open upper end formed by the insulating layer 20, the first reflecting layer 30 and the substrate 10, a high-refractive-index material layer 40 which is a visible light waveband high-refractive-index material and is arranged on the substrate 10 and located in the cavity, the high-refractive-index material layer 40 which is a centrosymmetric structure, and a second reflecting layer 50 arranged on the high-refractive-index material layer 40.
In other words, the ultra-thin ultra-wideband perfect absorber 1000 with independent incidence angle and independent polarization direction comprises at least one perfect absorber unit 100, the perfect absorber unit 100 comprises a substrate 10, an annular insulating layer 20 is arranged on the substrate 10, the insulating layer 20 can be an insulating medium with low refractive index, low real part and no imaginary part, an annular first reflecting layer 30 can be arranged on the insulating layer 20, the shape of the first reflecting layer 30 can be matched with the shape of the insulating layer 20, the first reflecting layer 30 and the substrate 10 enclose a cavity with an open upper end, a high refractive index material layer 40 is arranged in the cavity, the high refractive index material layer 40 is a high refractive index material in the visible light band and has high refractive index, high real part and zero imaginary part, the lower end face of the high refractive index material layer 40 is connected with the substrate 10, the side walls are respectively connected with the insulating layer 20 and the first reflecting layer 30, the high refractive index material, a second reflective layer 50 may be disposed on the high refractive index material layer 40, and an upper end surface of the high refractive index material layer 40 is connected to the second reflective layer 50.
It should be noted that the ultra-surface material (MSM) is an ultra-thin planar material, which is a general term for a series of small-sized optical materials, and the two-dimensional or quasi-two-dimensional material makes it possible to control the light propagation by using an ultra-thin material element. The perfect absorber 1000 of the embodiment of the invention is an ultrathin super-surface perfect absorber (MSMPA), and has an important significance in converting the heat or electric field of light into energy for perfect absorption of light. Its absorption is as high as above 0.933 in the whole visible range (400nm to 760 nm). Unlike the conventional MMPA, which has a very high height, the msmspa according to the embodiment of the present invention has a height of only one sixth to one quarter wavelength, and has advantages of a thin thickness and a high absorption rate in the entire visible light range.
Therefore, according to the ultra-thin ultra-wideband perfect absorber 1000 with an incident angle independent of polarization direction, the structure of combining the insulating layer 20, the high refractive index material layer 40, the first reflective layer 30 and the second reflective layer 50 is adopted, the high refractive index material layer 40 with a centrosymmetric structure is adopted, good optical performance in the whole visible light band is achieved, the defects of low efficiency, narrow bandwidth, small incident angle range, polarization correlation and the like in the traditional absorption optical element can be effectively avoided, perfect absorption independent of polarization direction in the whole visible light band (400nm to 760nm) is achieved, and the ultra-thin ultra-wideband perfect absorber has the advantages of being simple in structure, ultra-thin, high in absorption rate in the whole visible light range and the like.
According to one embodiment of the invention, the substrate 10 may be SiO2And (3) a layer.
Alternatively, the insulating layer 20 may be SiO2The insulating layer 20 may be formed by etching, and the insulating layer 20 may also be air.
Preferably, the high refractive index material layer 40 may be a GaN layer.
Alternatively, the first reflective layer 30 and/or the second reflective layer 50 may be a Pt reflective layer.
In some embodiments of the present invention, the cavity may be substantially square shaped and the shape of the high refractive index material layer 40 may be adapted to the shape of the cavity. It should be noted that other geometries symmetrical about the horizontal and vertical axes can achieve similar performance, achieving polarization independent absorption.
Further, the second reflective layer 50 conforms to the shape of the cross-section of the high refractive index material layer 40.
According to one embodiment of the present invention, the sum of the height of the insulating layer 20 and the height of the first reflective layer 30 is equal to the height of the high refractive index material layer 40. That is, the high refractive index material layer 40 has a height H and is composed of the insulating layer 20 (SiO)2) And a first reflective layer 30(Pt), wherein the insulating layer 20 is at a lower height H1, and the first reflective layer 30 is at an upper height H2, H1+ H2.
Further, the height of the second reflective layer 50 is equal to the height of the first reflective layer 30, i.e., the height of the second reflective layer 50 above the high refractive index material layer 40 is H2.
In some embodiments of the present invention, the number of the perfect absorber units 100 may be plural and connected to each other, and the plural perfect absorber units 100 may be located on the same plane, wherein the plural high refractive index material layers 40 are disposed at equal intervals and the vertexes of two adjacent high refractive index material layers 40 are disposed opposite to each other.
In other words, the substrate 10 may have a square cross-section, the width of the substrate 10 may be set to P, the adjacent substrates 10 are connected to each other, the apexes of the high refractive index material layers 40 on the adjacent substrates 10 are disposed to face each other, the apexes of the second reflective layers 50 on the adjacent substrates 10 are also disposed to face each other, and the width of the second reflective layers 50 may be set to a.
The optical performance of the perfect absorber 1000 according to the embodiment of the present invention can be simulated by using Finite Difference Time Domain (FDTD) (Finite difference time Domain) Solution), since the structure of the perfect absorber unit 100 is the same in two vertical directions, and thus it is completely independent of the polarization direction of the incident light during operation, so that the complete absorption performance of the perfect absorber 1000 can be known only by considering the case that the polarized light is incident on the msmspa, in the simulation test, as shown in fig. 7, a beam of light is incident on the structure of the perfect absorber unit 100 from the bottom of the substrate 10 along the Z direction, the incident angle is initially set to 0, and the optimized structure parameters are: fig. 5 shows simulation results of H1 ═ H2 ═ 59nm, H ═ 118nm, P ═ 220nm, and a ═ 149nm, and the dotted line below line B in fig. 5 is 0.9 as a reference line. The light absorption can be calculated from 1-R-T, where T is the transmittance and R is the reflectance, and can be directly obtained from the simulation results. As can be seen from FIG. 5, the average absorption rate in the visible wavelength band (400nm to 760nm) was as high as 0.9785, showing excellent absorption properties.
In addition, the perfect absorber unit 100 also has excellent absorption performance at wide angle incidence, and the influence of the incidence angle on the absorption performance is shown in fig. 6a, it should be noted that the absorption curves in the range of 0 to 60 ° have approximately the same trend, approximately approximate curves, and the adjacent curves have overlapping regions, when the incidence angle is increased to 70 °, the absorption of the perfect absorber unit 100 in the whole visible light band range is still high, and when the incidence angle is increased to 80 °, the perfect absorber unit 100 also has excellent absorption performance in the visible light wavelength range except for the very short wavelength range. As shown in fig. 6b, at some wavelengths (e.g., 658 nm), the absorption remains around 0.9 when the angle of incidence is increased to 80 °, thus showing the excellent angular properties of the perfect absorber 1000.
When the ultra-thin ultra-wideband perfect absorber 1000 with independent incidence angle and independent polarization direction according to the embodiment of the present invention is used, the insulating layer 20 and the first reflective layer 30 form a double-layer structure, i.e., a silicon dioxide/platinum double-layer structure, and the silicon dioxide/platinum double-layer structure can be used as an attached nonmagnetic layer consisting of a layer of metal and a layer of medium, and the dielectric constant of the attached nonmagnetic layer is negative, so that the attached nonmagnetic layer can be regarded as a metamaterial with a negative dielectric constant. Such a two-layer material structure is shaped by a rectangular block of another dielectric material, namely a layer 40 of high refractive index material (gallium nitride). The composite structure can completely localize light therein, and when the light beam propagates in the double-layer structure, the light beam will experience a slight displacement parallel to the boundary each time the light beam reaches the boundary of the double-layer structure and the rectangular block of the medium, and the displacement can be made to be equal to and opposite to the component parallel to the boundary of the displacement during the propagation of the light beam from one interface to the other interface by properly setting the structural parameters. Thus, the beam, although always propagating, is not stopped in the direction parallel to the boundary and cannot escape from the composite structure. However, for a single structural parameter, only a single wavelength of light beam can be confined therein. The distance between two adjacent second reflection layers 50 in the ultra-thin ultra-wide band perfect absorber 1000 with the independent incidence angle and the independent polarization direction corresponds to the width of a double-layer material structure, so that the wavelength of a light beam which can be localized is directly determined, and the smaller the width is, the shorter the wavelength of the light beam which is localized is. When two layers of material are included in the structure with different widths (e.g., different widths of different regions between two adjacent second reflective layers 50), multiple wavelengths or even a continuous length of light beam can be successfully confined in the structure.
As shown in fig. 7, light of different wavelengths is localized at different positions, light is incident from below the double-layer structure in a direction of the z-axis, a distance between two adjacent second reflective layers 50 is equal to d, and light of different wavelengths is localized at different positions of d. Wherein, the short wavelength light is localized in the region with smaller d, and the long wavelength light is located in the region with longer d. As shown in fig. 8a to 8h, the electric field patterns inside the structure can further explain the operation principle of the MSPA, fig. 8a, 8b, 8c and 8d are x-y sections (just at the interface between the insulating layer 20 and the first reflective layer 30) at wavelengths of z 59nm at 400nm, 500nm, 600nm and 700nm, respectively, and fig. 8e, 8f, 8g and 8h are x-z sections at which the electric field is strongest at wavelengths of 400nm, 500nm, 600nm and 700nm, respectively, where y is 0 in fig. 8e, y is 20nm in fig. 8f, y is 40nm in 8g and y is 70nm in 8h, respectively, and thus it can be seen that light with shorter wavelength is localized in a region where d is smaller.
In summary, the ultra-thin ultra-wideband perfect absorber 1000 with independent incidence angle and independent polarization direction according to the embodiment of the present invention is a perfect absorbing optical element based on the negative goos-hanchen shift theory, which can effectively avoid the disadvantages of low efficiency, narrow bandwidth, small incidence angle range, polarization correlation, etc. in the conventional absorbing optical element, the optical material has good optical performance in the whole visible light wave band, the absorption rate in the whole visible light wave band is over 0.933, the highest absorption rate is as high as 0.98, the perfect absorption of the whole visible light wave band (400nm to 760nm) independent of the polarization direction is realized, the ultra-thin incident angle independent polarization direction independent ultra-wideband perfect absorber 1000 according to the embodiment of the present invention has a simple structure, is ultra-thin, has a high absorption rate in the whole visible light range, and has potential applications in optical communication, solar cell, thin film industry, and the like.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.