Broadband Terahertz Absorber Based on Patterned Slotted Vanadium Dioxide

Abstract

The present invention discloses a broadband terahertz absorber based on patterned slotted vanadium dioxide, which includes M×N tunable broadband terahertz absorption units of patterned vanadium dioxide. The M×N tunable broadband terahertz absorption units of patterned vanadium dioxide are distributed in an M×N two-dimensional pattern, where both M and N are positive integers. Each tunable broadband terahertz absorption unit of patterned vanadium dioxide includes a vanadium dioxide resonant layer, a dielectric layer, and a metal reflection layer arranged in sequence from top to bottom, and the three layers are bonded to each other. The shapes of the dielectric layer and the metal reflection layer are both square. The vanadium dioxide resonant layer is formed by a patch with "concave"-shaped slots symmetrically opened on two opposite sides of a square patch and two rectangular slots symmetrically opened at the center of the square patch. This terahertz absorber achieves high absorption, dynamic tunability, and a simple structure simultaneously in a relatively wide frequency range.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz waves, and particularly to a broadband terahertz absorber based on patterned slotted vanadium dioxide. Background Art

[0002] Terahertz (THz) waves generally refer to electromagnetic waves with frequencies ranging from 0.1 to 10 THz. Due to their low energy, strong penetrability, and unique frequency and wavelength, the application of terahertz waves and related technologies has become a research hotspot in various fields. As a basic functional device for terahertz applications, terahertz absorbers are widely used in detectors, spectral imaging, stealth, and other fields.

[0003] A terahertz absorber based on metamaterials is a device that can efficiently absorb incident terahertz waves. The main principle is to use different loss mechanisms to convert terahertz waves into heat energy or other forms of energy, ultimately achieving the effect of absorbing terahertz waves. Among various absorbers, absorbers based on metamaterial structures have received extensive attention from domestic and foreign scholars in recent years. Compared with traditional absorbers, metamaterial absorbers have the characteristics of small volume, high absorption rate, and easy integration. The current absorbers achieve broadband absorption by adopting a stacked multi-layer structure or using multiple resonant structures with different sizes in the same plane. The structure is complex, the manufacturing and processing are difficult, and once the device is determined, its absorption function cannot be adjusted, which restricts the application of the absorber. Therefore, there is an urgent need to develop a terahertz broadband absorber with a simple structure, easy fabrication, and flexible tunability to meet the actual needs of terahertz applications. Summary of the Invention

[0004] The object of the present invention is to propose a broadband terahertz absorber based on patterned slotted vanadium dioxide, which can achieve high absorption, dynamic tunability, and a simple structure simultaneously within a relatively wide frequency range.

[0005] The technical solution adopted by the present invention is that a broadband terahertz absorber based on patterned slotted vanadium dioxide includes M*N tunable broadband terahertz absorption units of patterned vanadium dioxide. The M*N tunable broadband terahertz absorption units of patterned vanadium dioxide are distributed in an M*N two-dimensional manner, where M and N are both positive integers; each tunable broadband terahertz absorption unit of patterned vanadium dioxide includes a vanadium dioxide resonant layer, a dielectric layer, and a metal reflection layer arranged in sequence from top to bottom, and the three layers are attached to each other;

[0006] The shapes of the dielectric layer and the metal reflection layer are both square; the vanadium dioxide resonant layer is formed by a patch with "concave"-shaped slots symmetrically opened on two opposite sides of the square patch and two rectangular slots symmetrically opened at the center of the square patch.

[0007] The features of the present invention further lie in:

[0008] The side length w of the resonant layer of the vanadium dioxide resonant layer is 38 μm - 46 μm, the slot width f is 3 μm - 7 μm, the thickness h3 of the vanadium dioxide resonant layer is 0.09 μm, and the geometric parameters of the slotted vanadium dioxide resonant cavity are as follows: the distance d between the outer sides of the two rectangular slots is 24 μm, the inner length e in the vertical direction of the "concave" - shaped slot is 27 μm, the outer length g in the horizontal direction of the "concave" - shaped slot is 12 μm, the distance t between the inner sides of the two rectangular slots is 6 μm, and the period p of the designed absorber is 50 μm.

[0009] The conductivity of the vanadium dioxide resonant layer in the insulating phase is 200 S / m, and in the metallic phase is 200000 S / m.

[0010] The material of the dielectric layer is Topas, and the relative dielectric constant is 2.35; the side length of the dielectric layer is 50 μm, and the thickness is 15.5 μm - 17.5 μm.

[0011] The material of the metal reflective layer is gold, and the conductivity is 4.56×10 7 S / m, the side length of the metal reflective layer is 50 μm, and the thickness is 0.1 μm - 0.4 μm.

[0012] The beneficial effects of the present invention are:

[0013] (1) The broadband terahertz absorber based on patterned slotted vanadium dioxide of the present invention patterns the vanadium dioxide resonant layer to improve impedance matching in order to broaden the absorption bandwidth. It consists of a vanadium dioxide resonant layer, a middle Topas dielectric layer, and a bottom metal reflective layer. Under normal incidence, the absorption rate reaches more than 95% in the frequency range of 1.5 - 4.2 THz, the absorption bandwidth is 2.7 THz, the center frequency is 2.85 THz, and the corresponding relative bandwidth is 94.7%. This terahertz absorber realizes high absorption, dynamic tunability, and a simple structure in a relatively wide frequency range.

[0014] (2) The broadband terahertz absorber based on patterned slotted vanadium dioxide of the present invention can adjust the conductivity of vanadium dioxide from 200 S / m to 200000 S / m by changing the temperature, and realize amplitude tuning of the absorption peak from 2.5% - 99% within the corresponding bandwidth.

[0015] (3) The broadband terahertz absorber based on patterned slotted vanadium dioxide of the present invention has polarization insensitivity and maintains excellent absorption performance at different polarization angles and wide incident angles. Description of the Drawings

[0016] Figure 1 is the periodic structure of the broadband terahertz absorption unit of patterned slotted vanadium dioxide provided in Embodiment 1 of the present invention;

[0017] Figure 2 Schematic diagram of the unit structure of the broadband terahertz absorber based on patterned slotted vanadium dioxide provided in Embodiment 1 of the present invention;

[0018] Figure 3 Top view of the unit structure of the broadband terahertz absorber based on patterned slotted vanadium dioxide provided in Embodiment 1 of the present invention;

[0019] Figure 4 Absorption spectrum of the patterned slotted vanadium dioxide broadband terahertz absorber when vanadium dioxide is in the metallic phase provided in Embodiment 1 of the present invention;

[0020] Figure 5 Absorption spectra of the patterned slotted vanadium dioxide broadband terahertz absorber with vanadium dioxide at different conductivities provided in Embodiment 1 of the present invention;

[0021] Figure 6 Electric field distribution of the patterned slotted vanadium dioxide broadband terahertz absorber with vanadium dioxide at a conductivity of 200 S / m provided in Embodiment 1 of the present invention;

[0022] Figure 7 Electric field distribution of the patterned slotted vanadium dioxide broadband terahertz absorber with vanadium dioxide at a conductivity of 200000 S / m provided in Embodiment 1 of the present invention;

[0023] Figure 8 Absorption characteristics of the broadband terahertz absorber based on patterned slotted vanadium dioxide at different polarization angles when the electromagnetic wave is normally incident provided in Embodiment 1 of the present invention;

[0024] Figure 9 Absorption spectra of the broadband terahertz absorber based on patterned slotted vanadium dioxide at different incident angles under TE wave provided in Embodiment 1 of the present invention;

[0025] Figure 10 Absorption spectra of the broadband terahertz absorber based on patterned slotted vanadium dioxide at different incident angles under TM wave provided in Embodiment 1 of the present invention.

[0026] In the figure, 1. Vanadium dioxide resonant layer, 2. Dielectric layer, 3. Metal reflection layer. Detailed implementation manners

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific implementation manners.

[0028] The present invention provides a broadband terahertz absorber based on patterned slotted vanadium dioxide, as Figure 1-3As shown in the figure, it includes M*N tunable broadband terahertz absorption units with patterned vanadium dioxide. The M*N tunable broadband terahertz absorption units are distributed in a two-dimensional M*N pattern, where both M and N are positive integers. Each tunable broadband terahertz absorption unit with patterned vanadium dioxide includes a vanadium dioxide resonant layer 1, a dielectric layer 2, and a metal reflective layer 3 arranged in sequence from top to bottom, and the three layers are bonded to each other.

[0029] The shapes of the dielectric layer 2 and the metal reflective layer 3 are both square. The vanadium dioxide resonant layer 1 is formed by a patch with "concave"-shaped grooves symmetrically opened on two opposite sides of a square patch and two rectangular grooves symmetrically opened at the center of the square patch.

[0030] The side length w of the resonant layer of the vanadium dioxide resonant layer 1 is 38μm - 46μm, the slot width f is 3μm - 7μm, the thickness h3 of the vanadium dioxide resonant layer is 0.09μm, and the geometric parameters of the slotted VO2 resonant cavity are as follows: the distance d between the outer sides of the two rectangular grooves is 24μm, the vertical inner length e of the "concave"-shaped groove is 27μm, the horizontal outer length g of the "concave"-shaped groove is 12μm, the distance t between the inner sides of the two rectangular grooves is 6μm, and the period p of the designed absorber is 50μm.

[0031] The conductivity of the vanadium dioxide resonant layer 1 in the insulating phase is 200S / m, and in the metallic phase is 200000S / m.

[0032] The material of the dielectric layer 2 is Topas, and the relative dielectric constant is 2.35. The side length of the dielectric layer 2 is 50μm, and the thickness is 15.5μm - 17.5μm.

[0033] The material of the metal reflective layer 3 is gold, and the conductivity is 4.56×10 7 S / m. The side length of the metal reflective layer 3 is 50μm, and the thickness is 0.1μm - 0.4μm.

[0034] Example 1:

[0035] As Figure 1-3 shown in the figure, the broadband terahertz absorber based on patterned slotted vanadium dioxide includes 3*3 broadband terahertz absorption units with patterned slotted vanadium dioxide. The number of broadband terahertz absorption units with patterned slotted vanadium dioxide does not affect the overall absorption performance. Each broadband terahertz absorption unit with patterned slotted vanadium dioxide includes a patterned slotted vanadium dioxide resonant layer 1, a dielectric layer 2, and a metal reflective layer 3 arranged in sequence from top to bottom.

[0036] The shapes of both the dielectric layer 2 and the metal reflective layer 3 are square; the vanadium dioxide resonant layer 1 is formed by a patch with "concave"-shaped grooves symmetrically opened on two opposite sides of a square patch and two rectangular grooves symmetrically opened at the center of the square patch.

[0037] The top layer is the patterned slotted vanadium dioxide resonant layer 1 with a thickness h3 of 0.09 μm, the side length w of the resonant layer is 42 μm, the slot width f is 5 μm, the period p of the absorber is 50 μm, and the other structural parameters are as follows: d = 24 μm, e = 27 μm, g = 12 μm, t = 6 μm. The conductivity of the vanadium dioxide resonant layer in the insulating phase is 200 S / m and it is in a total reflection state. The conductivity in the metallic phase is 200000 S / m, and an absorption performance with an absorption rate higher than 90% is obtained in the frequency band of 1.5 - 4.2 THz. The absorption bandwidth is 2.7 THz, the central frequency is 2.85 THz, and the corresponding relative bandwidth is 94.7%. By changing the conductivity of vanadium dioxide, the absorption peak can be approximately tuned from 2.5% to 99%. The middle layer is the dielectric layer 2 made of Topas dielectric with a relative dielectric constant of 2.35, a thickness of 16.5 μm, and a side length of 50 μm. The bottom layer is the metal reflective layer 3 made of lossy material gold with a conductivity of 4.56×10 7 S / m, a thickness of 0.2 μm, and a side length of 50 μm, which is much larger than the skin depth of the metal in the terahertz band, ensuring that the transmittance T of the absorber is 0.

[0038] The periodic structure of the absorber in this embodiment is as Figure 1 shown, and the schematic diagram of the unit structure is as Figure 2 shown, including three-layer structure, from top to bottom are the patterned vanadium dioxide resonant layer 1, the Topas dielectric layer 2, and the bottom metal reflective layer 3. The top view of the vanadium dioxide resonant layer on the top layer is as Figure 3 shown. The period p of the absorption unit is 50 μm, the thickness h3 is 0.09 μm, the side length w of the resonant layer is 42 μm, the slot width f is 5 μm, and the other structural parameters are as follows: d = 24 μm, e = 27 μm, g = 12 μm, t = 6 μm. The absorption spectrum is as Figure 4 shown. In the frequency range of 1.5 - 4.2 THz, the absorption bandwidth with an absorption rate exceeding 90% can reach 2.7 THz, achieving good absorption performance. The absorption spectra of vanadium dioxide with different conductivities are as Figure 5 shown. When vanadium dioxide is in the insulating phase with a conductivity of 200 S / m, it is in a total reflection state; when vanadium dioxide is in the metallic phase with a conductivity of 200000 S / m, an absorption performance with an absorption rate higher than 90% is obtained in the 1.5 - 4.2 THz frequency band and it is in a total absorption state, achieving tunable performance. The electric field distribution diagrams with different conductivities are as Figures 6-7As shown, at a conductivity of 200 S / m, there is almost no electric field distribution in the resonant layer, indicating that VO2 is in the insulating phase at this time. This is because when electromagnetic waves are incident on the metamaterial structure, they can almost completely penetrate the resonant layer, and the reflective layer and the insulating-phase VO2 have little effect on THz waves, so a low absorption rate appears. When the conductivity is high, since VO2 gradually transforms into metallic properties, it can be seen that the charges are mainly distributed at the outer edges of the patterned VO2. When the conductivity is 200000 S / m, the position of the electric field distribution remains unchanged, and the electric field intensity increases significantly, generating local surface plasmon resonance at the Topas dielectric / VO2 interface. The influence of the resonant layer and the reflective layer on THz waves is enhanced, further improving the absorption performance and increasing the absorption rate. The polarization behavior of different polarization angles under TE waves is as Figure 8 shown. The proposed absorber has polarization-insensitive characteristics due to its symmetric structure. The absorption performance at different incident angles under TE waves and TM waves is as Figure 9 and Figure 10 shown. For TE waves, as the incident angle increases, the absorption bandwidth increases and the absorption rate decreases slightly. This is because the low resonant frequency remains stable while the high resonant frequency undergoes a blue shift. In the range of 0 - 60° of the incident angle, the broadband absorption performance is relatively stable. When the incident angle is greater than 60°, the absorption performance drops sharply, which is related to the resonance of the top-layer patterned VO2, resulting in the disruption of resonance. For TM waves, additional absorption peaks appear as the incident angle increases. Therefore, the proposed absorber can maintain excellent absorption performance at different polarization angles and wide incident angles.

[0039] Example 2

[0040] The broadband terahertz absorber based on patterned slotted vanadium dioxide includes 3×3 broadband terahertz absorption units of patterned slotted vanadium dioxide. The number of broadband terahertz absorption units of patterned slotted vanadium dioxide does not affect the overall absorption performance. Each broadband terahertz absorption unit of patterned slotted vanadium dioxide includes a patterned slotted vanadium dioxide resonant layer 1, a dielectric layer 2, and a metal reflective layer 3 arranged in sequence from top to bottom.

[0041] The shapes of the dielectric layer 2 and the metal reflective layer 3 are both square; the vanadium oxide resonant layer 1 is formed by a patch with "concave"-shaped slots symmetrically opened on two opposite sides of the square patch and two rectangular slots symmetrically opened at the center of the square patch.

[0042] The top layer is the patterned slotted vanadium dioxide resonant layer 1 with a thickness h3 of 0.08 μm, the side length w of the resonant layer is 38 μm, the slot width f is 7 μm, the period p of the absorber is 52 μm, and the other structural parameters are as follows: d = 25 μm, e = 28 μm, g = 14 μm, t = 8 μm. The material of the resonant layer is vanadium dioxide with a conductivity of 200000 S / m. The middle layer uses Topas medium with a relative permittivity of 2.35, a thickness of 16 μm, and a side length of 52 μm. The bottom metal plate uses lossy material gold with a conductivity of 4.56×10 7 S / m, a thickness of 0.2 μm, and a side length of 52 μm, which is much larger than the skin depth of the metal in the terahertz band, ensuring that the transmittance T of the absorber is 0.

[0043] Example 3

[0044] The broadband terahertz absorber based on patterned slotted vanadium dioxide includes 3*3 broadband terahertz absorption units of patterned slotted vanadium dioxide. The number of broadband terahertz absorption units of patterned slotted vanadium dioxide does not affect the overall absorption performance. Each broadband terahertz absorption unit of patterned slotted vanadium dioxide includes a patterned slotted vanadium dioxide resonant layer 1, a dielectric layer 2, and a metal reflection layer 3 arranged in sequence from top to bottom.

[0045] The shapes of the dielectric layer 2 and the metal reflection layer 3 are both square; the vanadium oxide resonant layer 1 is formed by a patch with "concave"-shaped slots symmetrically opened on two opposite sides of the square patch and two rectangular slots symmetrically opened at the center of the square patch.

[0046] The top layer is the patterned slotted vanadium dioxide resonant layer 1 with a thickness h3 of 0.1 μm, the side length w of the resonant layer is 40 μm, the slot width f is 6 μm, the period p of the absorber is 55 μm, and the other structural parameters are as follows: d = 22 μm, e = 26 μm, g = 8 μm, t = 8 μm. The material of the resonant layer is vanadium dioxide with a conductivity of 200000 S / m. The middle layer uses Topas medium with a relative permittivity of 2.35, a thickness of 15.5 μm, and a side length of 55 μm. The bottom metal plate uses lossy material gold with a conductivity of 4.56×10 7 S / m, a thickness of 0.2 μm, and a side length of 55 μm, which is much larger than the skin depth of the metal in the terahertz band, ensuring that the transmittance T of the absorber is 0.

[0047] Example 4

[0048] The broadband terahertz absorber based on patterned slotted vanadium dioxide includes 3*3 broadband terahertz absorption units of patterned slotted vanadium dioxide. The number of broadband terahertz absorption units of patterned slotted vanadium dioxide does not affect the overall absorption performance. Each broadband terahertz absorption unit of patterned slotted vanadium dioxide includes a patterned slotted vanadium dioxide resonant layer 1, a dielectric layer 2, and a metal reflective layer 3 arranged in sequence from top to bottom.

[0049] The shapes of the dielectric layer 2 and the metal reflective layer 3 are both square; the vanadium oxide resonant layer 1 is formed by a patch with "concave"-shaped slots symmetrically opened on two opposite sides of the square patch and two rectangular slots symmetrically opened at the center of the square patch.

[0050] The top layer is the patterned slotted vanadium dioxide resonant layer 1 with a thickness h3 of 0.09 μm, a side length w of the resonant layer of 44 μm, a slot width f of 4 μm, and a period p of the absorber of 48 μm. Other structural parameters are as follows: d = 20 μm, e = 25 μm, g = 10 μm, t = 6 μm. The material of the resonant layer is vanadium dioxide with a conductivity of 200000 S / m. The middle layer uses Topas dielectric with a relative dielectric constant of 2.35, a thickness of 17 μm, and a side length of 48 μm. The bottom metal plate uses lossy material gold with a conductivity of 4.56×10 7 S / m, a thickness of 0.4 μm, and a side length of 48 μm, which is much larger than the skin depth of the metal in the terahertz frequency band, ensuring that the transmittance T of the absorber is 0.

[0051] Example 5

[0052] The broadband terahertz absorber based on patterned slotted vanadium dioxide includes 3*3 broadband terahertz absorption units of patterned slotted vanadium dioxide. The number of broadband terahertz absorption units of patterned slotted vanadium dioxide does not affect the overall absorption performance. Each broadband terahertz absorption unit of patterned slotted vanadium dioxide includes a patterned slotted vanadium dioxide resonant layer 1, a dielectric layer 2, and a metal reflective layer 3 arranged in sequence from top to bottom.

[0053] The shapes of the dielectric layer 2 and the metal reflective layer 3 are both square; the vanadium oxide resonant layer 1 is formed by a patch with "concave"-shaped slots symmetrically opened on two opposite sides of the square patch and two rectangular slots symmetrically opened at the center of the square patch.

[0054] The top layer is the patterned slotted vanadium dioxide resonant layer 1 with a thickness h3 of 0.11 μm, the side length w of the resonant layer is 46 μm, the slotted width f is 3 μm, the period p of the absorber is 45 μm, and the other structural parameters are as follows: d = 28 μm, e = 25 μm, g = 16 μm, t = 6 μm. The material of the resonant layer is vanadium dioxide with a conductivity of 200000 S / m. The middle layer uses Topas medium with a relative permittivity of 2.35, a thickness of 17.5 μm, and a side length of 45 μm. The bottom metal plate uses lossy material gold with a conductivity of 4.56×10 7 S / m, a thickness of 0.1 μm, and a side length of 45 μm, which is much larger than the skin depth of the metal in the terahertz band, ensuring that the transmittance T of the absorber is 0.

[0055] The broadband terahertz absorber of the present invention based on patterned slotted vanadium dioxide obtains good absorption performance in the wide frequency band range of 1.5 - 4.2 THz by optimizing the structural parameters, and can achieve the adjustment between full absorption and total reflection. The broadband terahertz absorber of the present invention with patterned slotted vanadium dioxide has a simple structure and good absorption performance, and has potential application value.

Claims

1. A broadband terahertz absorber based on patterned slotted vanadium dioxide, characterized in that, An adjustable broadband terahertz absorption unit including M*N patterned vanadium dioxides, and the M*N adjustable broadband terahertz absorption units of patterned vanadium dioxides are distributed in a two-dimensional M*N pattern, where both M and N are positive integers; each adjustable broadband terahertz absorption unit of patterned vanadium dioxide includes a vanadium dioxide resonance layer (1), a dielectric layer (2), and a metal reflection layer (3) arranged in sequence from top to bottom, and the three layers are bonded to each other; The shapes of the dielectric layer (2) and the metal reflection layer (3) are both square; the vanadium dioxide resonance layer (1) is formed by a patch with "concave"-shaped grooves symmetrically opened on the left and right opposite sides of a square patch and two rectangular grooves symmetrically opened at the center of the square patch; among them, the notches of the two "concave"-shaped grooves are arranged opposite to each other; The side length w of the resonance layer of the vanadium dioxide resonance layer (1) is 38 µm - 46 µm, the grooving width f of the protrusion of the notch of the "concave"-shaped groove is 3 µm - 7 µm, the thickness h3 of the vanadium dioxide resonance layer is 0.09 µm, and the geometric parameters of the grooved vanadium dioxide resonance cavity are as follows: the distance d between the outer sides of the two rectangular grooves is 24 µm, the length e in the vertical direction between the two protrusions of the notch of the "concave"-shaped groove is 27 µm, the outer length g in the horizontal direction of the "concave"-shaped groove is 12 µm, the distance t between the inner sides of the two rectangular grooves is 6 µm, and the period p of the designed absorber is 50 µm; The material of the dielectric layer (2) is Topas, and the relative dielectric constant is 2.35; the side length of the dielectric layer (2) is 50 µm, and the thickness is 15.5 µm - 17.5 µm.

2. The broadband terahertz absorber based on patterned slotted vanadium dioxide according to claim 1, wherein The conductivity of the vanadium dioxide resonance layer (1) is 200 S / m in the insulating phase and 200000 S / m in the metallic phase.

3. The broadband terahertz absorber based on patterned slotted vanadium dioxide according to claim 1, wherein The material of the metal reflective layer (3) is gold, and its conductivity is 4.56×10 7 S / m. The side length of the metal reflective layer (3) is 50 µm, and its thickness is 0.1 µm - 0.4 µm.

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