CN110707409A - A High Quality Factor Hybrid Plasmon Resonator - Google Patents

Abstract

The invention discloses a hybrid plasmon resonator with high quality factor. The resonator is a layered structure, wherein the uppermost layer is a sensing area layer, the lowermost layer is a large-area metal ground, and the large-area metal ground is The upper layer is a dielectric substrate, and the lower layer of the sensing area layer is the resonator body and the transmission layer where the microstrip line is located; the resonator body is formed by superimposing an artificial localized surface plasmon resonance structure and a fan-shaped resonance structure; the microstrip line and the microstrip line are superimposed. There are gaps between the resonator bodies. The resonator has the advantages of high quality factor and high resonance strength through the interference between multiple resonance modes.

Description

A High Quality Factor Hybrid Plasmon Resonator

technical field

The invention belongs to the technical field of resonators and transmission lines, and in particular relates to a microwave millimeter wave resonator with high quality factor and resonance strength.

Background technique

The quality factor (Q-factor) is an important indicator to measure the electromagnetic resonator, and its value represents the lifetime of the resonance mode, that is, the time for the electromagnetic field mode to interact with the surrounding environment. The quality factor is determined by the loss of the structure, including material loss, scattering loss, radiation loss. The material loss and scattering loss are determined by the properties of the material itself and the roughness of the structure, while the radiation loss is closely related to the electrical size of the resonator. In general, a large electrical size means that the electromagnetic wave resonance experiences less tortuosity and thus a higher Q value.

For microwave resonators, due to the long wavelength of microwaves, considering the size problem, the resonators are usually in the sub-wavelength order, such as microstrip ring resonator, split ring resonator, etc., so the radiation loss is large, The figure of merit is low. Although resonators with higher quality factors can be achieved through some special designs, such as dark mode, Fano resonance, etc., the excitation of sub-wavelength high quality factor resonators is more difficult, and the resonance peaks or valleys are shallow, and the excitation efficiency not tall. Large-scale resonator arrays or placing resonators in waveguides are often required to achieve high resonance strengths.

An artificial localized surface plasmon is a resonator based on an artificial subwavelength structure, usually a cylinder or disk with a periodic sawtooth structure. Artificial localized surface plasmons have similar properties to optical-frequency localized surface plasmons, such as high field enhancement, deep subwavelength field locality, etc. It has great application potential in terms of device size and enhanced sensing sensitivity. But like other microwave resonators, artificial localized surface plasmons also have the problem of difficult to achieve both quality factor and resonance strength.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a hybrid plasmon resonator, which has the advantages of high quality factor and high resonance strength through interference between multiple resonance modes .

Technical scheme: the present invention adopts the following technical scheme:

A hybrid plasmon resonator with high quality factor, the resonator is a layered structure, wherein the uppermost layer is the sensing area layer 1, the lowermost layer is a large-area metal ground 2, and the upper layer of the large-area metal ground is The dielectric substrate 3, the lower layer of the sensing area layer is the transmission layer 6 where the resonator body 4 and the microstrip line 5 are located;

The resonator body 4 is formed by superimposing an artificial localized surface plasmon resonance structure 7 and a fan-shaped resonance structure 8; a gap is provided between the microstrip line 5 and the resonator body 4, and the gap is a part of the sensing area. part.

The sensing area (1) covers only the resonator body (4), or covers the entire resonator body (4) and part and the microstrip line (5), or covers the entire resonator body (4) and all the microstrip line ( 5).

The sensing area (1) is a closed area or an open space covered by an outer wall, and the refractive index of the material of the sensing area is in the range of (1, 3).

Preferably, the refractive index of the material of the sensing region (1) is in the range of (1, 1.8).

The artificial localized surface plasmon resonance structure 7 is a circle with periodic sawtooth on the outer periphery, the inner diameter of the circle is r, and the radius of the annular sawtooth structure 9 is R; In each cycle, the metal strip is fan-shaped, its arc length is a, and the width of a single cycle is d, where d=2πR/N, a<d.

The sector-shaped resonant structure 8 is a sector with a periodic sawtooth structure 10 on the outer side of the circular arc, the inner diameter of the sector is R ₁ , and the radius of the fan-shaped sawtooth structure 10 is R ₂ .

The period width of a single sawtooth of the fan-shaped sawtooth structure (10) is d, and the width of the sawtooth is a.

The dielectric substrate 3 is FR4, F4B, RO4003, 3003, 4350, RT5880, 5870, 6002, 6006, 6010, 6035, 6202 produced by Rogers, printed circuits of N4000-13, N4000-13 EPSI produced by Nelco, or The dielectric substrate of the microwave circuit is either a semiconductor or dielectric material of Si, SiO ₂ , Al ₂ O ₃ , GaAs, GaN, or a flexible organic dielectric material.

The thickness of the dielectric substrate 3 is between 1 μm and 10 mm.

The large-area metal ground 2, the resonator body 4 and the microstrip line 5 are a single material of copper, tin, gold, silver, chromium, lead, platinum, zinc, aluminum, magnesium or titanium or a composite material thereof.

The thicknesses of the large-area metal ground 2 , the resonator body 4 and the microstrip line 5 are between 50 nm and 1 mm.

Beneficial effects: The hybrid plasmon resonator disclosed in the present invention utilizes the mutual interference between multiple electromagnetic resonance modes to form a single sharp resonance peak, which can enhance the quality factor and resonance strength of the resonance peak at the same time, thereby realizing the High Sensitivity Sensing of Dielectric Environments. The hybrid exciton resonator has considerable application prospects in integrated circuits, sensing chips, microwave millimeter wave and terahertz sensing.

The working principle of the present invention is as follows:

The resonator can be analyzed by Coupled Mode Theory (CMT) in the time domain. For the case of only one excitation port, any resonant mode nth, its amplitude an, the intrinsic resonance frequency ωn, the intrinsic decay time τn0, and the decay time caused by port coupling is τn1. Then the pattern follows the following equation:

where Sn,1+ is the energy flowing from port 1 (S1+) into the nth resonant mode

是由S1+到Sn,1+的耦合相位.耦合系数Kn1由耦合时间τn1和相位系数θn1决定：Except for special cases, most of the resonance modes γn1≈1.

is the coupling phase from S1+ to Sn,1+. The coupling coefficient Kn1 is determined by the coupling time τn1 and the phase coefficient θn1:

When there are multiple resonance modes in the structure, the resonance of the whole structure is determined by the mutual interference of multiple modes, and the reflected energy is:

Then the reflection coefficient of the whole structure is:

The superposition term of multiple resonant modes can be seen from equation (5).

In the first embodiment, we will illustrate the coupled mode theory with specific cases.

Description of drawings

1 is a schematic structural diagram of a resonator disclosed in the present invention;

2 is a schematic structural diagram of a resonator body in the resonator disclosed in the present invention;

3 is a schematic diagram of the geometric parameters of the resonator body in the resonator disclosed in the present invention;

Fig. 4 is the S ₁₁ curve comparison diagram of SLSP resonator, sector resonator and hybrid plasmon resonator;

Fig. 5 is the field distribution and radiation pattern of the two resonance modes of the SLSP resonance structure, the PR resonance structure and the hybrid plasmon resonator at the resonance peak;

Fig. 6 is the S ₁₁ spectrum diagram of each resonance mode under the coupled mode theory;

Fig. 7 is the S ₁₁ curve diagram of the resonator disclosed in the present invention under the change of refractive index in different dielectric environments;

FIG. 8 is a graph showing the sensing _S11 curve of the resonator disclosed in the present invention to different thicknesses of the F4B dielectric plate covered on the surface.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, specific implementation cases of the present invention are described below with reference to the accompanying drawings.

The present invention discloses a hybrid plasmon resonator with high quality factor. As shown in Figure 1, the resonator has a layered structure, Figure 1-(a) is a front view, and Figure 1-(b) is a side view. The uppermost layer is the sensing area layer 1, the lowermost layer is the large-area metal ground 2, the upper layer of the large-area metal ground is the dielectric substrate 3, and the lower layer of the sensing area layer is the transmission where the resonator body 4 and the microstrip line 5 are located. layer 6;

As shown in FIG. 2 , the resonator body 4 is formed by superposing an artificial localized surface plasmon (SLSP) resonant structure 7 and a fan-shaped resonator (Perturb Resonator, PR) 8 . FIG. 3 is a schematic diagram of the geometric parameters of the resonator body. The artificial localized surface plasmon resonance structure 7 is a circle with periodic sawtooth on the outer periphery, the inner diameter of the circle is r, and the radius of the annular sawtooth structure 9 is R; there are N sawtooth periods in one cycle, and each period , the metal strip is fan-shaped, its arc length is a, and the width of a single period is d, where d=2πR/N, a<d.

The sector-shaped resonant structure 8 is a sector with periodic sawtooth structures 10 on the outside of the circular arc, the inner diameter of the sector is R ₁ , the angle is θ, and the radius of the sector-ring saw-tooth structure 10 is R ₂ . The centers of the artificial localized surface plasmon resonance structure 7 and the fan-shaped resonance structure 8 overlap, and a gap is provided between the microstrip line 5 and the resonator body 4 , and the gap is a part of the sensing area. The slot spacing is S, and the width of the microstrip line is w. The period width of a single sawtooth structure 10 is d, and the width of the sawtooth is a, which are consistent with the period d and the width a of the circular sawtooth structure 9 in the artificial localized surface plasmon resonance structure 7, so that the two can overlap. ; Its radius R ₁ and R ₂ and the number of sawtooth cycles, that is, the angle θ, can be adjusted.

The dielectric substrate 3 can be FR4, F4B, RO4003, 3003, 4350, RT5880, 5870, 6002, 6006, 6010, 6035, 6202 produced by Rogers, printed circuits or microwaves of N4000-13 and N4000-13 EPSI produced by Nelco The dielectric substrate of the circuit is either a semiconductor or dielectric material of Si, SiO ₂ , Al ₂ O ₃ , GaAs, GaN, or a flexible organic dielectric material. The thickness of the dielectric substrate 3 is between 1 μm and 10 mm. The large-area metal ground 2, the resonator body 4 and the microstrip line 5 are a single material of copper, tin, gold, silver, chromium, lead, platinum, zinc, aluminum, magnesium or titanium or a composite material thereof. The thicknesses of the large-area metal ground 2, the resonator body 4 and the microstrip line 5 are between 50 nm and 1 mm.

Example 1:

The structure of the hybrid plasmon resonator in this embodiment is shown in Figures 1-3. The geometric parameters are: R=12mm, r=2.5mm, d=2.09mm, a=0.6*d=1.26mm, R1 ₌ 9mm, θ=86°. The structure is excited by a 50Ω microstrip line, the dielectric substrate 3 is a 0.5mm thick F4B plate, its dielectric constant is 2.65, the loss tangent is 0.001, the microstrip line width w=1.34mm, and the microstrip line to the resonator gap s =0.2mm.

The simulated _S11 curves of artificial localized surface plasmon resonator (SLSP), sector resonator (PR) and hybrid plasmon resonator (Hybrid) (resonator body) disclosed in the present invention are shown in Fig. 4 Show. The resonance peak of the hybrid plasmon resonator is at 9.16 GHz, S ₁₁ =0.04 (-22.8 dB), and the quality factor Q=142. The artificial localized surface plasmon resonator (SLSP) is a magnetic plasmon mode at 8.96 GHz with Q=44.8. Due to the superposition of the two resonators, the artificial localized surface plasmon resonator (SLSP) has a resonance peak at 8.96GHz, and the sector resonator (PR) has resonance peaks at 8.9GHz and 9.29GHz, and the three modes exist simultaneously in the stray The plasmonic resonator Hybrid (resonator body), the three modes are superimposed on each other, achieving a 3.4-fold enhancement of the Q value.

To measure the Q value and resonance strength, we define Figure of MeritFoM=Q×δI, where δI is the amplitude of the S ₁₁ resonance peak. The hybrid plasmon resonator has FoM=143.8, and the artificial localized surface plasmon resonator has FoM=1.8. Compared with the visible resonance peak, the FoM enhancement is 79.8 times.

The field distribution and radiation pattern of artificial localized surface plasmon resonator (SLSP), sector resonator (PR) and hybrid plasmon resonator (Hybrid, resonator body) at the resonance peak are shown in Fig. 5 shown. From the field distribution, it can be seen that the resonance mode of the hybrid plasmon resonator is formed by the superposition of the resonance of the SLSP and the resonance of the PR. From the perspective of radiation efficiency (RE), although the Q value of the hybrid plasmon resonator is very high, its radiation efficiency is still as high as 0.47. It can be seen that the high Q of the hybrid plasmon is not due to the low radiation, but is due to the superposition interference between multiple modes. The high radiation efficiency also makes the hybrid plasmon resonator here easy to be excited by space waves, which can be used for both wired and wireless detection.

For the specific structural parameters in the first embodiment, the coupled mode theory is applied, and the parameters of the three modes of the SLSP and the PR resonator are shown in Table 1. Since the microstrip excitation is weak here, the intrinsic resonance frequencies of the three modes are taken as the resonance frequencies of the S ₁₁ spectrum, and other parameters are obtained by fitting the S ₁₁ spectrum. The structure of the coupled mode theory and simulation comparison is shown in Figure 6, where the discrete points of the three shapes are the results of the coupled mode theory, and the black solid line is the simulation data. It can be seen that from the superposition of the single resonance of SLSP and the two resonances of PR, the resonance curve of the hybrid plasmon resonator (Hybrid, resonator body) obtained from the coupled mode theory is in good agreement with the simulation data, thus confirming that feasibility of our theory.

Table 1. Parameters of the three resonances in coupled mode theory.

Embodiment 2

The sensing area 1 is a closed area or an open space covered by an outer wall, and its material can be gas, liquid, solid or a mixture of the three; the refractive index of the sensing area material is in the range of (1, 3).

This embodiment adopts the same geometric structure as that of the first embodiment, which is the application of the resonator in the sensing of different dielectric environments (refractive index range 1-1.8). The electromagnetic simulation results are shown in Fig. 7 . Figure 7 shows the reflectance (S ₁₁ ) spectrum of the resonator body when the refractive index of the sensing area is different; the solid black line is the reflectance S ₁₁ when the refractive index of the sensing area is equal to 1 (air). When the refractive index of the sensing region 1 is gradually increased, we can see a red shift of the resonance frequency of the S ₁₁ spectrum, and the sensitivity of the frequency to the change of the refractive index is 1.1 GHz.RIU ^-1 . And the sensitivity of artificial surface plasmon resonator is 0.27GHz.RIU ^-1 . Therefore, the hybrid plasmon resonator achieves a 4.1-fold enhancement of the sensing sensitivity of the dielectric environment.

Embodiment 3

This embodiment adopts the same geometric structure as the first embodiment, which is used to detect the thickness of the F4B dielectric plate. The experimental test results are shown in Figure 8. In the figure, the hollow circle, solid circle, hollow triangle and solid triangle are the F4B dielectric substrate respectively. The S ₁₁ curves of the thickness of 0.5mm, 1mm, 1.5mm and 2mm, the black solid line is the S ₁₁ spectrum of the resonator body when the dielectric substrate is not covered. It can be seen that with the increase of the thickness of the surface dielectric material, the resonance peak exhibits an obvious red shift.

Claims (10)

1. A hybrid plasmon resonator of high quality factor, characterized in that the resonator is a layered structure, wherein the uppermost layer is a sensing region layer (1), and the lowermost layer is a large-area metal ground (1). 2), the upper layer of the large-area metal ground is the dielectric substrate (3), and the lower layer of the sensing area layer is the transmission layer (6) where the resonator body (4) and the microstrip line (5) are located; The resonator body (4) is formed by superimposing an artificial localized surface plasmon resonance structure (7) and a fan-shaped resonance structure (8); between the microstrip line (5) and the resonator body (4), a A gap, the gap being a part of the sensing area. 2 . The hybrid plasmon resonator with high quality factor according to claim 1 , wherein the artificial localized surface plasmon resonance structure ( 7 ) is a circle with periodic sawtooth on the periphery. 3 . The inner diameter of the circle is r, and the radius of the ring-shaped sawtooth structure (9) is R; there are N sawtooth periods in one cycle, and in each period, the metal sawtooth is fan-shaped, with a width of a, and the width of a single period is d, where d=2πR/N, a<d. 3. The hybrid plasmon resonator with high quality factor according to claim 2, wherein the fan-shaped resonance structure (8) is a fan-shaped with a periodic sawtooth structure (10) provided on the outside of the circular arc, The inner diameter of the sector is R ₁ , and the radius of the fan-shaped sawtooth structure (10) is R ₂ ; the single sawtooth period width of the fan-shaped sawtooth structure (10) is d, and the sawtooth width is a. 4. The hybrid plasmon resonator with high quality factor according to claim 1, wherein the dielectric substrate (3) is FR4, F4B, RO4003, 3003, 4350, RT5880 produced by Rogers Company , 5870, 6002, 6006, 6010, 6035, 6202, N4000-13, N4000-13 EPSI printed circuits or dielectric substrates for microwave circuits produced by Nelco, or Si, SiO ₂ , Al ₂ O ₃ , GaAs, GaN Semiconductor or dielectric material, or flexible organic dielectric material. 5 . The hybrid plasmon resonator with high quality factor according to claim 1 , wherein the thickness of the dielectric substrate ( 3 ) is between 1 μm and 10 mm. 6 . 6 . The hybrid plasmon resonator with high quality factor according to claim 1 , wherein the large-area metal ground ( 2 ), the resonator body ( 4 ) and the microstrip line ( 5 ) are 6 . Copper, tin, gold, silver, chromium, lead, platinum, zinc, aluminum, magnesium, or titanium, alone or in composites. 7. The hybrid plasmon resonator with high quality factor according to claim 1, characterized in that, the large-area metal ground (2), the resonator body (4) and the microstrip line (5) are The thickness is between 50nm and 1mm. 8. The hybrid plasmon resonator with high quality factor according to claim 1, wherein the sensing region (1) is: covering only the resonator body (4), or covering all the resonators The body (4) and part of the microstrip line (5), or cover the entire resonator body (4) and the entire microstrip line (5). 9 . The hybrid plasmon resonator with high quality factor according to claim 1 , wherein the sensing area ( 1 ) is a closed area or an open space covered by an outer wall, and the sensing area ( 1 ) is a closed area or an open space. 10 . The index of refraction of the domain material is in the range (1,3). 10 . The hybrid plasmon resonator with high quality factor according to claim 9 , wherein the refractive index of the material of the sensing region ( 1 ) is in the range of (1, 1.8). 11 .

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