CN102820512B - Electromagnetic resonance unit structures and method for realizing specific terahertz mediums - Google Patents

Abstract

The invention relates to three electromagnetic resonance unit structures and a method for realizing specific terahertz mediums. The unit structure is characterized by being any one of an SR1, an SR2 and an SR3, wherein the SR1 is formed by an I-shaped sealed metal ring; the SR2 is formed in a manner that two T-shaped metal strips are added between two embedded closed metal rings; and the SR3 is formed in a manner that two opened metal rings are connected with each other through a metal strip and each inner ring is connected with an outer ring of an adjacent unit. Three micron-grade electromagnetic resonance units which take metal gold as materials are periodically arrayed on a gallium arsenide substrate according to a certain size, and the metal gold is in Schottky contact with the substrate, so that the property of a substance is determined by the resonance units which are periodically arrayed; when a terahertz electromagnetic wave is vertically emitted, the medium has negative medium electric constant or magnetic conductivity, thereby obtaining the three specific mediums applicable to terahertz wave bands. Therefore, the specific terahertz mediums successfully obtained from the structures and the method have the advantages of simple structure, low manufacturing cost and wide wave band, and can be effectively applied to the design of a terahertz functional device.

Description

Can be used for the electromagnetic resonance cellular construction and the method that realize the special medium of Terahertz

Technical field

The present invention relates to sub-wavelength structure and the method for three kinds of electromagnetic resonance unit of the special medium that can be used for realizing terahertz wave band, belong to the special media application of Terahertz.

Background technology

Defining according to the current international practice: the particularity of special medium is just---its character is not determined by its chemical composition, but determines (Metamaterials are materials which owe their properties to sub-wavelength details of structure rather than to their chemical composition by its sub-wavelength structure.) described in the resonance structure of sub-wavelength structure normally periodic arrangement.Special medium has three key characters: have novel artificial structure; There is extraordinary physical property (negative permittivity, negative magnetoconductivity, negative index etc.); Its character is decided by artificial structure wherein and has nothing to do with the intrinsic properties of material.

Therefore, special medium is a kind of special man-made structures, is not present in occurring in nature.Also just because of the particularity of special medium, it shows the property being much different from usual medium.DIELECTRIC CONSTANT ε and the magnetic permeability μ of usual medium are more than or equal to 1, but the DIELECTRIC CONSTANT ε of special medium and magnetic permeability μ but can be less than 1 is even less than 0.According between ε and μ location, further special medium can be divided into stealthy medium (ε or μ is less than 1) and Chiral Media (ε or μ is less than 0).

By the structurally ordered design in the critical dimension of material, the restriction of some apparent natural law can be broken through, thus obtain the meta-materials function exceeding the intrinsic common character of nature.Because dielectric constant and magnetic permeability can be negative value, special medium has a lot of unusual peculiar performance, as negative index effect, inverse Doppler effect, inverse Cerenkov effect, can be used for making Superlens, invisible clothes, radome and various microwave and millimeter wave function element.

As far back as nineteen sixty-eight, Russian scientist Veselago just proposes the imagination of negative permittivity and negative magnetoconductivity, and demonstrates the existence of special medium theoretically.But there is natural special medium owing to lacking, Veselago is operated in the attention not causing people at that time.Until 1996, the people such as Pendry propose to utilize metal wire periodic structure to obtain the conception of negative permittivity material.The equivalent dielectric characterization of this structure is similar to plasma, and its equivalent plasma frequency is within the scope of GHz, and when lower than plasma frequency, the effective dielectric constant of array of metal lines is negative value.1999, the people such as English physicist Pendry proposed again to utilize split ring resonator array (SRRs) can realize the magnetic permeability born.2000, the people such as Smith produced split ring resonator and metal wire composite construction formation left-handed materials (dielectric constant and magnetic permeability are all negative value) at microwave frequency band.

In recent years, in microwave and millimeter wave frequency range, the design of various special medium emerges in an endless stream.And for a long time, at terahertz wave band, natural material shows more weak electromagnetic response, the design of some function elements (as filter, modulator, phase shifter and intelligent switch etc.) encounters very large difficulty, develop for good microwave and millimeter wave relative to various active and passive device, the technology backwardness relatively in Terahertz field.Due to the property of special medium, start to attract much attention about the realization of the special medium of Terahertz and application in recent years.Within 2004, Science magazine reports the special medium that the people such as T.J.Yen achieve the terahertz wave band be made up of two split ring resonator periodic arrangement first.

On the basis of existing technology, the present invention intends the three kinds of electromagnetic resonance cellular constructions and the method that propose to realize the special medium of Terahertz, three kinds of described special media of single-frequency point (SR1, SR2, SR3).Have that structure is simple, cost of manufacture is low, the advantage of bandwidth.Can be used for the design realizing the various function element of terahertz wave band (filter, phase shifter, modulator, intelligent switch etc.).

Summary of the invention

The object of the invention is to three kinds of electromagnetic resonance cellular constructions proposing to can be used for realizing the special medium of Terahertz and method.

The three kinds of electromagnetic resonance cellular constructions that can be used for realizing the special medium of Terahertz of the present invention as shown in Figure 1, the becket that the first cellular construction SR1 is closed by " work " font forms, the rectangle structure being positioned at both sides shows inductance characteristic, and the parallel metal connecting both sides rectangle structure can show capacitance characteristic; The second cellular construction SR2 adds two "T"-shaped bonding jumpers compositions between two nested closed beckets, and two closed beckets can show inductance characteristic, and what one end of "T"-shaped bonding jumper and inside closed becket can show capacitance characteristic; Two open metal ring bonding jumpers are connected by the third cellular construction SR3, inner ring is connected with the outer shroud of adjacent cells, the breach place of split ring can show as capacitance characteristic, and other parts can show as inductance characteristic, and inner ring is connected can strengthens electromagnetic interaction with the outer shroud of adjacent cells.When occurring interactional with THz wave, characteristic metal cellular construction inducing electric current, there is LC resonance in inductance, the electric capacity of equivalence.When the characteristic size of resonant element structure and operation wavelength quite or less time, by suitable structural design, can make resonant element and electromagnetic wave that strong interaction occurs.Frequency and resonant type (electric resonance and magnetic resonance) that resonance occurs can be changed by the size changing electromagnetic resonance cell size.Three electromagnetic resonance cell sizes are between 60 μm ~ 120 μm, and the sample size obtained after periodic arrangement is 2mm × 2mm.When terahertz electromagnetic wave vertical incidence, three kinds of cellular constructions show negative dielectric constant or negative magnetic permeability, thus obtain the special medium that three kinds can be used for terahertz wave band.

Cellular construction of the present invention is on GaAs (GaAs) substrate, be the micron order electromagnetic resonance unit of material with metal by certain size difference periodic arrangement SR1, SR2 and SR3 tri-kinds, specifically electromagnetic resonance unit is periodically arranged in thickness is on GaAs (GaAs) substrate of 50-600 μm, resonant element adopts titanium/platinum/layer gold gold to realize, and wherein layer of titanium metal thickness is 5-30nm, metal platinum layer thickness is 5-30nm, metallic gold layer thickness is 200-400nm.Electromagnetic resonance unit and substrate form Schottky contacts.

Emulated by electromagnetic simulation software Ansoft HFSS, and on terahertz time-domain spectroscopy (THz-TDS) experimental provision, sample is tested, realize and demonstrate the special medium of three kinds of single-frequency terahertz wave bands.

The invention has the advantages that: the three kinds of electromagnetic resonance construction units adopting the present invention to propose, successfully can realize the special medium of THz wave band, and have the advantages such as structure is simple, cost is low, bandwidth.

Accompanying drawing explanation

Fig. 1 is three kinds of electromagnetic resonance cellular construction schematic diagrames provided by the invention;

Fig. 2 realizes sample Local map for using process of the present invention;

Fig. 3 is that single band sample (SR1, SR2, SR3) of the present invention is to the transmissivity schematic diagram of THz wave;

Fig. 4 is the dielectric constant schematic diagram of single-frequency point sample of the present invention, and curve 1 represents real part of permittivity, and curve 2 represents imaginary part of dielectric constant.

Embodiment

The specific embodiment of the present invention is further described below in conjunction with accompanying drawing.

Fig. 1 is three kinds of electromagnetic resonance cellular construction schematic diagrames provided by the invention.

Fig. 2 is the sample Local map of each electromagnetic resonance unit periodic arrangement with ESEM shooting, and three electromagnetic resonance cell size are between 60 μm ~ 120 μm, and the actual sample size obtained after periodic arrangement is 2mm × 2mm.Utilize terahertz time-domain spectroscopy (THz-TDS) experimental provision to be tested by the sample realized on GaAs technology line, verify its physical characteristic.

Fig. 3 is respectively the transmissivity schematic diagram of single band sample to THz ripple.Can find out that SR1, SR2, SR3 respectively have a transmission forbidden band to THz ripple.Wherein SR1 transmission forbidden band is near 0.73THz; SR2 transmission forbidden band is near 0.53; Respectively there is transmission forbidden zone, an arrowband in SR3 transmission forbidden band near 0.55THz and 0.8THz.

Electromagnetic wave propagation should meet dispersion equation:

k ²=ω ²εμ

Wherein k is wave vector, and ω is angular frequency, ε and μ represents relative dielectric constant and relative permeability respectively.As ε μ <0, exponential damping can not be propagated by electromagnetic wave.Show the frequency range of special dielectric property, electromagnetic transmission forbidden band will be there will be, therefore obtain transmitting forbidden band by experiment, verify special dielectric property.According to the research of the people such as Smith, S parameter and impedance z in homogeneous medium, refraction coefficient n relational expression can be represented by the formula:

$S_{21}=S_{12}=\frac{1}{\cos \left(\mathrm{nkd}\right)-\frac{i}{2}(z+\frac{1}{z})\sin \left(\mathrm{nkd}\right)}$

$S_{11}=S_{22}=\frac{i}{2}(\frac{1}{z}-z)\sin \left(\mathrm{nkd}\right)$

By above two formulas, can obtain:

$n=\frac{1}{\mathrm{kd}}{\cos }^{-1}\left[\frac{1}{{2S}_{21}}(1-S_{11}^2+S_{21}^2)\right]$

$z=\sqrt{\frac{{(1+S_{11})}^2-{S^2}_{21}}{{(1-S_{11})}^2+{S^2}_{21}}}$

So can obtain:

$\mathrm{\&epsiv;}=\frac{n}{z}={\mathrm{\&epsiv;}}^{\&prime;}+i{\mathrm{\&epsiv;}}^{\&prime;\&prime;},$ μ=nz=μ′+iμ"

Wherein S ₂₁, S ₁₂represent the projection between two ports, S ₁₁and S ₂₂represent the reflection of two-port, ε is real part of permittivity, ε " for imaginary part of dielectric constant, μ ' are magnetic permeability real part, μ " is magnetic permeability imaginary part, and d is the size of special medium on Electromagnetic Wave Propagation direction.

Utilize THz-TDS experimental provision can obtain the time-domain signal of THz wave through sample, utilize Fourier transform to convert time-domain signal to frequency-region signal, utilize Matlab instrument can obtain effective dielectric constant and magnetic permeability by formulae discovery.

Fig. 4 shows the relevant Effective medium parameter of each sample, achieves negative permittivity real part in the frequency range of each self-resonance, corresponding to the corresponding transmission forbidden band shown in Fig. 3, thus verifies and achieve the special medium (Metamaterials) of THz wave band.There is strong magnetic resonance with THz ripple in SR1 cellular construction, realize negative permittivity (ε ' <0) at frequency range 0.715THz ~ 0.835THz near 0.73THz.There is strong electric resonance with THz ripple in SR2 cellular construction, achieve negative permittivity (ε ' <0) at frequency range 0.522THz ~ 0.61THz near 0.5THz.All there is strong electric resonance with THz ripple in SR3 cellular construction, achieve negative permittivity (ε ' <0) at frequency range 0.529THz ~ 0.745THz and 0.788 ~ 0.88THz near 0.55THz and 0.8THz.

As can be seen here, the three kinds of electromagnetic resonance construction units adopting the present invention to propose, can realize the special medium of THz wave band, and have the advantages such as structure is simple, cost is low, bandwidth.

Claims (2)

1. can be used for the electromagnetic resonance cellular construction realizing the special medium of Terahertz, described cellular construction is any one in SR1, SR2 and SR3; Wherein, the becket that SR1 is closed by " work " font forms; SR2 adds two "T"-shaped bonding jumpers compositions between two nested closed beckets; Two open metal ring bonding jumpers are connected by SR3, and inner ring is connected with the outer shroud of adjacent cells,

It is characterized in that SR1, SR2, SR3 cellular construction respectively has a transmission forbidden band to THz, wherein,

1. the transmission forbidden band of SR1 cellular construction is at 0.73THz; Be positioned at structure on two sides in SR1 cellular construction and show inductance characteristic, the parallel metal connecting structure on two sides shows capacitance characteristic;

2. the transmission forbidden band of SR2 cellular construction is at 0.53THz; In SR2 cellular construction, two closed metals change and show inductance characteristic, and what one section of "T"-shaped bonding jumper and inside closed becket shows capacitance characteristic;

3. respectively there is transmission forbidden zone, an arrowband in the transmission forbidden band of SR3 cellular construction at 0.55THz and 0.8THz place; The breach place of SR3 cellular construction split ring shows as capacitance characteristic, and other positions show as inductance;

Described SR1, SR2 and SR3 are respectively the first single-frequency structure, the second single-frequency structure and the 3rd single-frequency structure.

2., by cellular construction according to claim 1, it is characterized in that SR1 cellular construction, at 0.73THz place and THz ripple, strong magnetic resonance occurs, realize negative permittivity at frequency range 0.715THz ~ 0.835THz; There is strong electric resonance at 0.5THz place and THz ripple in SR2 cellular construction, achieves negative permittivity at frequency range 0.522THz ~ 0.61THz; There is strong electric resonance at 0.55THz and 0.8THz place and THz ripple in SR3 cellular construction, achieves negative permittivity at frequency range 0.529THz ~ 0.745THz and 0.788 ~ 0.88THz.