CN202949024U - Electromagnetic resonance unit structures for realizing terahertz metamaterial - Google Patents

Abstract

The utility model relates to an electromagnetic resonance unit structure which can be used to realize a terahertz special medium. It is characterized in that the first electromagnetic resonance unit structure is composed of a "I"-shaped closed metal ring; the second electromagnetic resonance unit structure is to add two "T" between two nested closed metal rings The third type of electromagnetic resonance unit structure is to connect two open metal rings with metal strips, and the inner ring is connected to the outer ring of the adjacent unit. When the terahertz electromagnetic wave is vertically incident, the medium exhibits a negative permittivity or magnetic permeability, thus obtaining three kinds of electromagnetic resonance unit structures, which can realize the special medium in the terahertz band, with simple structure, low manufacturing cost, and wide frequency band The advantages can be effectively applied to the design of terahertz functional devices.

Description

Electromagnetic resonance unit structure that can be used to realize terahertz metamaterials

technical field

The utility model relates to a structure of an electromagnetic resonant unit which can be used to realize a special medium in the terahertz band. More precisely, the structure of the electromagnetic resonant unit is divided into three sub-wavelength structures of the electromagnetic resonant unit. the

Background technique

According to the internationally accepted definition: the particularity of a metamaterial lies in that its properties are not determined by its chemical composition, but by its subwavelength structure (Metamaterials are materials which owe their properties to sub-wavelength details of structure rather than to their chemical composition.) The subwavelength structure referred to here is usually a periodically arranged resonant structure. Metamedium has three important characteristics: it has a novel artificial structure; it has extraordinary physical properties (negative permittivity, negative magnetic permeability, negative refractive index, etc.); its properties are determined by the artificial structure and the intrinsic properties of the material irrelevant. the

It can be seen from this that the metamedia is a special man-made structure that does not exist in nature. Also because of the particularity of the special medium, it shows many special properties different from the usual medium. Generally, the dielectric constant ε and magnetic permeability μ of the medium are both greater than or equal to 1, but the dielectric constant ε and magnetic permeability μ of the metamaterial can be less than 1 or even less than 0. According to the interval of ε and μ, the specific medium can be further divided into invisible medium (ε or μ is less than 1) and chiral medium (ε or μ is less than 0). the

Through the orderly design of the structure on the key scale of the material, the limitation of some apparent natural laws can be broken through, so as to obtain the supernormal material function beyond the ordinary nature inherent in nature. Because the permittivity and permeability can be negative, metamaterials have many unusual properties, such as negative refractive index effect, inverse Doppler effect, and inverse Cerenkov effect, which can be used to make super lenses, invisibility cloaks, radomes and various Microwave and millimeter wave functional devices. the

As early as 1968, the Russian scientist Veselago had proposed the hypothesis of negative permittivity and negative magnetic permeability, and theoretically demonstrated the existence of special media. However, due to the lack of natural specific mediators, Veselago's work did not attract people's attention at that time. Until 1996, Pendry et al. proposed the idea of using the periodic structure of metal lines to obtain negative dielectric constant materials. The equivalent dielectric characteristic of the structure is similar to plasma, and its equivalent plasma frequency is in the GHz range, and when it is lower than the plasma frequency, the equivalent dielectric constant of the metal line array is a negative value. In 1999, British physicist Pendry and others proposed that negative magnetic permeability can be achieved by using split resonant ring arrays (SRRs). In 2000, Smith et al. made a split resonator ring and a metal wire composite structure to form a left-handed material (both dielectric constant and magnetic permeability are negative) in the microwave frequency band. the

In recent years, in the microwave and millimeter wave frequency bands, the designs of various metamaterials have emerged in an endless stream. For a long time, in the terahertz band, natural materials have shown weak electromagnetic responses, and the design of some functional devices (such as filters, modulators, phase shifters, and smart switches, etc.) has encountered great difficulties. In terms of microwave and millimeter waves, where active and passive devices are well developed, the technology in the terahertz field is relatively backward. Due to the special properties of metamedia, the realization and application of terahertz metamedia have attracted people's attention in recent years. In 2004, it was reported in Science magazine that T.J.Yen et al. realized for the first time a special medium in the terahertz band consisting of two split resonant rings arranged periodically. the

Based on the above description, the utility model intends to propose a structure of three kinds of electromagnetic resonance units that can realize terahertz meta-media, which has the advantages of simple structure, low manufacturing cost and wide frequency range. It can be used to realize the design of various functional devices (filters, phase shifters, modulators, smart switches, etc.) in the terahertz band. the

Contents of utility models

The purpose of the utility model is to provide three kinds of electromagnetic resonant unit structures that can be used to realize the terahertz special medium. the

The three kinds of electromagnetic resonance unit structures provided by the utility model are shown in Figure 1, wherein the first electromagnetic resonance unit structure is composed of a closed metal ring in the shape of "I", and the rectangular structures on both sides can show inductance characteristics. Parallel metals connecting two rectangular structures can exhibit capacitance characteristics; the second electromagnetic resonance unit structure is composed of two "T"-shaped metal strips between two nested closed metal rings, and the two closed metal rings can express One end of the "T"-shaped metal strip and one side of the inner closed metal ring can exhibit capacitance characteristics; the third electromagnetic resonance unit structure is to connect two open metal rings with metal strips, and the inner ring is connected to the adjacent unit. The outer ring of the split ring is connected, the gap of the split ring can be characterized as capacitive, and the other parts can be characterized as inductive, and the connection between the inner ring and the outer ring of the adjacent unit can enhance the electromagnetic interaction. When interacting with terahertz waves, a current is induced on the characteristic metal unit structure, and LC resonance occurs in the equivalent inductance and capacitance. the

The utility model adopts metal gold with a thickness of 200-400nm to realize three kinds of electromagnetic resonance units with different structures, which are respectively arranged periodically on the gallium arsenide substrate with a thickness of 50-600 μm, and the contact between the metal gold and the substrate adopts Schottky contact , achieved through titanium/platinum/gold (thicknesses are 5-30nm, 5-30nm and 200-400nm, respectively), three electromagnetic resonance unit structures. the

When the characteristic size of the resonant unit structure is equal to or smaller than the operating wavelength, the resonant unit can interact strongly with the electromagnetic wave through proper structural design. By changing the size of the electromagnetic resonance unit, the resonance frequency and resonance type (electric resonance and magnetic resonance) can be changed. The size of the three electromagnetic resonance units is between 60 μm and 120 μm, and the size of the sample obtained after periodic arrangement is 2mm×2mm. (figure 2)

The electromagnetic simulation software Ansoft HFSS was used to simulate, and the samples were tested on the terahertz time-domain spectroscopy (THz-TDS) experimental device, and three kinds of special media in the single-frequency terahertz band were realized and verified. the

The beneficial effect of the utility model is that: adopting the three kinds of electromagnetic resonance structural units proposed by the utility model can successfully realize the special medium in the THz band, and has the advantages of simple structure, low cost, wide frequency band, etc., and can be effectively applied to THz Design of functional devices. the

Description of drawings

Fig. 1 is three kinds of electromagnetic resonance unit structures that the utility model provides; Wherein, Fig. 1 (a) is the first kind of electromagnetic resonance unit structure; Fig. 1 (b) is the second kind of electromagnetic resonance unit structure; Fig. 1 (c) is the third electromagnetic resonance unit structure;

Fig. 2 is three kinds of structures that the utility model provides and realizes sample partial diagram; Wherein, Fig. 2 (a) is the first kind of electromagnetic resonance unit structure; Fig. 2 (b) is the second kind of electromagnetic resonance unit structure; Fig. 2 (c ) is the third electromagnetic resonance unit structure;

Fig. 3 provides (a), (b) and (c) three kinds of structure single frequency band samples that the utility model provides to the transmissivity schematic diagram of terahertz wave;

Fig. 4 (a) to Fig. 4 (c) are (a), (b) and (c) three kinds of structure single-frequency sample permittivity diagrams provided by the utility model, curve 1 represents the real part of permittivity, curve 2 represents the imaginary part of the permittivity. the

Detailed ways

The specific embodiment of the utility model will be further described in detail below in conjunction with the accompanying drawings. the

Fig. 1 is a structural schematic diagram of three kinds of electromagnetic resonance units provided by the present invention. the

According to Fig. 1, attached Fig. 2 is a partial picture of the sample with periodic arrangement of electromagnetic resonance units taken by scanning electron microscope. The size of the three electromagnetic resonance units is between 60 μm and 120 μm, and the actual sample size obtained after periodic arrangement is 2 mm. ×2mm. Using the terahertz time-domain spectroscopy (THz-TDS) experimental device, the samples realized on the gallium arsenide process line were tested to verify their physical properties. the

Figure 3 is a schematic diagram of the transmittance of single-band samples to THz waves, respectively. It can be seen that the first structure, the second structure and the third structure each have a transmission gap for THz waves. The transmission forbidden band of the first structure is around 0.73THz; the transmission forbidden band of the second structure is around 0.53; the transmission forbidden band of the third structure has a narrow-band transmission forbidden zone around 0.55THz and 0.8THz respectively. the

The propagation of electromagnetic waves should satisfy the dispersion equation:

k ² =ω ² εμ

电磁波将指数衰减而不能传播。表现出特异介质特性的频段，将会出现电磁波传输禁带，因此可通过实验得到传输禁带，验证特异介质特性。根据Smith等人的研究，均质介质中S参数与阻抗z，折射系数n关系式可用下式表示：  Where k is the wave vector, ω is the angular frequency, ε and μ represent the relative permittivity and relative permeability, respectively. When εμ<0,

Electromagnetic waves will decay exponentially and cannot propagate. In the frequency band exhibiting the characteristics of the special medium, there will be a forbidden band for electromagnetic wave transmission, so the transmission forbidden band can be obtained through experiments to verify the characteristics of the special medium. According to the research of Smith et al., the relationship between S parameter, impedance z and refractive index n in a homogeneous medium can be expressed by the following formula:

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nkd</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nkd</span>}<span\; class="notranslate">\; )</span>}$

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nkd</span>}<span\; class="notranslate">\; )</span>$

From the above two formulas, we can get:

$\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; kd</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

$\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; =</span>\sqrt{\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{{\mathrm{<span\; class="notranslate">\; S</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; S</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}}}$

So you can get:

$\mathrm{\&epsiv;}=\frac{\mathrm{no}}{z}={\mathrm{\&epsiv;}}^{\&prime;}+i{\mathrm{\&epsiv;}}^{\&prime;\&prime;},$ μ=nz=μ'+iμ"

Among them, S ₂₁ and S ₁₂ represent the projection between the two ports, S ₁₁ and S ₂₂ represent the reflection of the two ports, ε' is the real part of the permittivity, ε'' is the imaginary part of the permittivity, and μ' is the permeability The real part of the rate, μ'' is the imaginary part of the magnetic permeability, and d is the size of the metamedium in the direction of electromagnetic wave propagation.

The time-domain signal of the terahertz wave passing through the sample can be obtained by using the THz-TDS experimental device, and the time-domain signal can be converted into a frequency-domain signal by Fourier transform, and the effective permittivity and magnetic permeability can be obtained by using the Matlab tool to calculate according to the formula Rate. the

Figure 4 shows the relevant effective medium parameters of each sample, and the real part of the negative permittivity is realized in the respective resonant frequency bands, corresponding to the corresponding transmission forbidden bands shown in Figure 3, thus verifying and realizing the special medium in the THz band (Metamaterials). The first electromagnetic resonance unit structure (Fig. 4(a)) has a strong magnetic resonance with THz waves around 0.73THz, and achieves a negative dielectric constant (ε'<0) in the frequency range of 0.715THz-0.835THz. The second electromagnetic resonance unit structure (Fig. 4(b)) has a strong electrical resonance with THz waves near 0.5THz, and achieves a negative dielectric constant (ε'<0) in the frequency range of 0.522THz-0.61THz. The third electromagnetic resonance unit structure (Figure 4(c)) has strong electrical resonance with THz waves around 0.55THz and 0.8THz, and has achieved negative dielectric constant in the frequency range of 0.529THz～0.745THz and 0.788～0.88THz (ε'<0). the

It can be seen that by adopting the three kinds of electromagnetic resonance structural units proposed by the utility model, a special medium in the THz band can be realized, and has the advantages of simple structure, low cost, and wide frequency band. the

Claims (9)

1. can be used for realizing the electromagnetic resonance cellular construction of the special medium of Terahertz, it is characterized in that described electromagnetic resonance unit is comprised of the becket of " work " font sealing.

2. by cellular construction claimed in claim 1, it is characterized in that described electromagnetic resonance cell size is between 60-120 μ m.

3. by the described cellular construction of claim 1 or 2, it is characterized in that the sample size of described electromagnetic resonance unit after periodic arrangement is 2mm * 2mm.

4. can be used for realizing the electromagnetic resonance cellular construction of the special medium of Terahertz, it is characterized in that described volume electromagnetic resonance cellular construction is to add two "T"-shaped bonding jumpers between two nested closed beckets.

5. by cellular construction claimed in claim 4, it is characterized in that described electromagnetic resonance unit is comprised of the becket of " work " font sealing.

6. by the described cellular construction of claim 4 or 5, it is characterized in that the sample size of described electromagnetic resonance unit after periodic arrangement is 2mm * 2mm.

7. can be used for realizing the electromagnetic resonance cellular construction of the special medium of Terahertz, it is characterized in that described electromagnetic resonance unit is that two open metal rings are connected with bonding jumper, interior ring is connected with the outer shroud of adjacent cells.

8. by cellular construction claimed in claim 7, it is characterized in that described electromagnetic resonance unit is comprised of the becket of " work " font sealing.

9. by the described cellular construction of claim 7 or 8, it is characterized in that the sample size of described electromagnetic resonance unit after periodic arrangement is 2mm * 2mm.

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