CN111552014B - A Transverse MIM Lattice Plasmon Absorber - Google Patents

Abstract

The invention relates to a transverse MIM grid lattice plasmon absorber which is composed of a dielectric substrate and a periodic metal nanoparticle array, wherein each group of metal nanoparticles is composed of two opposite gold cuboid blocks and a dielectric layer sandwiched between the two gold cuboid blocks. Incident light is TM plane wave with a magnetic field direction parallel to the plane of the medium substrate, and a certain included angle is formed between a wave vector k and the vertical direction, so that OLP-type lattice point array plasmons can be excited in the metal nanoparticle array, strong resonance coupling can be generated between adjacent nanometer metal units, and a specific absorption peak can be generated on the incident light under specific structural parameters and an incident angle. Compared with other array-based plasmon absorbers, the transverse MIM grid point array plasmon absorber has high quality factor and good tuning performance, and has good application prospect in the field of micro-nano optical integrated devices.

Description

A Transverse MIM Lattice Plasmon Absorber

(1) Technical field

The invention belongs to the technical field of micro-nano optics, and relates to the excitation of lattice plasmons in metal nanoparticle arrays by obliquely incident TM light waves, in particular to a transverse MIM lattice plasmon absorber.

(2) Background technology

Plasmonic nanostructures have received increasing attention due to their ability to concentrate light in a small area, thereby greatly enhancing the light-matter interaction, and a single metal nanoparticle can support localized surface plasmon resonance (LSPR). ), with a large local field enhancement. However, the short plasma duration and low quality factor of LSPR limit the enhancement of local field strength and light-matter interaction. However, due to the strong coupling between adjacent nanoparticles, lattice plasmons supported by metal nanoparticle arrays combine ideal photonic and plasmonic properties, while suppressing radiation loss, high quality factor, and large volume. It has very obvious advantages in terms of significant field enhancement. At present, plasmon-based absorbers have great potential in anti-reflection and solar energy utilization, and have become the research object of many research groups. They also have the advantages of small package size, low power consumption, and easy integration. Thermoelectric products have very high application potential.

With the continuous progress and development of social science and technology, people's requirements for the development and utilization of high-tech products and green new energy continue to increase. At the same time, with the progress of nanotechnology, the mutual conversion and application of photon energy, electricity, and thermal radiation energy is optoelectronics. The main content of the research field, the plasmon-based absorber provides a new way for this conversion and localization of photon energy, and has become an important research field of micro-nano optics.

In recent years, plasmonic absorbers have been proposed and studied, and their many obvious advantages attract more and more researchers to explore. The patent of the present invention proposes a new lateral MIM lattice lattice plasmon absorber. Compared with other plasmon-based absorbers, the transverse MIM lattice lattice plasmon absorber has higher quality factor, static tuning can be achieved relatively easily. When working, it only acts on the plane light wave in a specific incident direction, and can be dynamically tuned with the incident direction of the incident light. In addition, the transverse MIM lattice plasmon absorber has a single material, strong periodicity, and simple processing.

(3) Contents of the invention

The purpose of the present invention is to design a transverse MIM lattice plasmon absorber, further study the structure of the nano lattice array on the original dielectric substrate, by changing the period of the metal nano particle array, the According to the parameters such as the size and the incident angle of the oblique incident light, it can be found that this structure can effectively adjust the absorption rate, bandwidth, resonance wavelength and other properties of the transverse MIM lattice plasmon absorber.

The purpose of the present invention is to design a transverse MIM lattice lattice plasmon absorber, which is mainly composed of a dielectric substrate and an array of metal nanoparticles with periodicity, each group of metal nanoparticles is composed of two opposite gold cuboid blocks, A layer of medium is sandwiched between the two opposite gold cuboid blocks. The geometric parameters of each gold cuboid block are exactly the same, and are vertically erected on the upper surface of the medium base. The vertical X axis and Y axis are distributed in a certain period to form a metal nanoparticle array. The entire structure is placed in a vacuum or air. The incident light is a plane wave. Angle, the direction of the magnetic field of the incident light is parallel to the width of the two gold cuboid blocks in each group of metal nanoparticles, the electric field direction of the incident light has a certain angle with the upper surface of the dielectric substrate, and the incident direction, that is, the wave vector k, must be at a specific angle. oblique incidence direction. The transmitted light emerges from below the metal nanoparticle array, and the reflected light emerges from above the metal nanoparticle array.

The height of the gold cuboid block in each group of metal nanoparticles can be arbitrarily in line with the working conditions of the transverse MIM lattice plasmon absorber. In order to obtain the best characteristics of the absorber, the height of the gold cuboid block is 260 nm.

The length of the gold cuboid block in each group of metal nanoparticles can be arbitrarily in line with the working conditions of the transverse MIM lattice plasmon absorber. In order to obtain the best characteristics of the absorber, the length of the gold cuboid block is 180 nm.

The width of the gold cuboid block in each group of metal nanoparticles can be arbitrarily in line with the working conditions of the transverse MIM lattice plasmon absorber. In order to obtain the best characteristics of the absorber, the width of the gold cuboid block is 80 nm.

The spacing between the two gold cuboid blocks in each group of metal nanoparticles can be arbitrarily in line with the working conditions of the transverse MIM lattice plasmon absorber. In order to obtain the best characteristics of the absorber, two gold cuboid blocks are used. The pitch is 50nm.

The period of the metal nanoparticle array can be arbitrarily in line with the period of the working conditions of the transverse MIM lattice plasmon absorber. The period of each gold cuboid block is 450 nm in both the length direction and the width direction.

The material of the dielectric substrate can be any material that conforms to the working conditions of the transverse MIM lattice plasmon absorber. In order to obtain the best characteristics of the absorber, a dielectric substrate material with a refractive index of n=1.52 is used.

The angle θ between the wave vector k of the incident plane light of the metal nanoparticle array in the YZ plane and the Z axis can be any angle that conforms to the working conditions of the transverse MIM lattice plasmon absorber. To achieve the best characteristics, the angle θ between the wave vector k of the incident plane light in the YZ plane and the Z axis is 15°.

The dielectric layer between the two gold cuboid blocks in each metal nanoparticle can be any dielectric material that meets the working conditions of the transverse MIM lattice plasmon absorber. In order to obtain the best characteristics of the absorber, air is used as the medium. Material.

Compared with the existing plasmonic absorber, the advantages of the present invention are: 1. The incident direction of the plane light wave has a certain angle with the upper surface of the dielectric substrate, and the magnetic field direction of the incident light is parallel to the two in each group of metal nanoparticles; The width of a gold cuboid block, the electric field direction of the incident light has an included angle with the upper surface of the dielectric substrate, that is, the incident plane light wave is a TM wave, which makes the metal nanoparticle array not only have a laterally polarized electric field, but also exist The vertically polarized electric field perpendicular to the upper surface of the dielectric substrate produces stronger local electric field enhancement on the surface of the dielectric and metal in each group of metal nanoparticles, and there is a strong The coupling effect, so as to achieve stronger plasmon resonance and obtain higher quality factor and absorption coefficient. 2. The resonance wavelength, bandwidth, absorption rate and quality factor can be changed statically by changing the structural parameters of the gold cuboid block and the period of the metal nanoparticle array. 3. By changing the electric field direction (incidence angle) of incident plane light, the resonance wavelength, bandwidth, absorption rate and quality factor can be dynamically changed. 4. Compared with other plasmonic absorbers, the transverse MIM lattice plasmonic absorber has the characteristic that the resonance wavelength can be flexibly adjusted in the visible light to the near-infrared band. 5. Because there is a certain periodicity in the X-axis and Y-axis directions, and the structure of each group of metal nanoparticles is simple, and also has the characteristics of easy processing.

(4) Description of drawings

FIG. 1 is a schematic diagram of a three-dimensional structure of a transverse MIM lattice plasmon absorber.

FIG. 2 is a schematic diagram of the XZ plane of the two-dimensional structure of each group of metal nanoparticles of the transverse MIM lattice plasmon absorber.

FIG. 3 is a schematic diagram of the YZ plane of the two-dimensional structure of each group of metal nanoparticles of the transverse MIM lattice plasmon absorber.

FIG. 4 is a schematic XY plane of the two-dimensional structure of each group of metal nanoparticles of the present transverse MIM lattice plasmon absorber.

Figure 5 is the reflection, transmission and absorption spectra obtained when the transverse MIM lattice plasmon absorber works optimally.

FIG. 6 is an absorption spectrum diagram of the present transverse MIM lattice plasmon absorber obtained when the height h of each group of metal nanoparticles is changed in the range of 230 nm to 260 nm.

Fig. 7 is the absorption spectrum of the transverse MIM lattice plasmon absorber obtained when the angle θ of the incident plane light k in the YZ plane and the Z axis is adjusted in the range of 10° to 25°.

Fig. 8 is the transverse MIM lattice plasmon obtained when the metal nanoparticle array is parallel to the two gold cuboid blocks in each group of metal nanoparticles in the length direction and the width direction of the period D=430nm～460nm Absorption spectrum of the absorber.

(5) Specific implementation manner

The present invention will be further explained below with reference to the accompanying drawings and this embodiment.

FIG. 1 is a schematic diagram of the three-dimensional structure of the transverse MIM lattice plasmon absorber. Including a dielectric substrate 2 with a refractive index of n=1.52, two gold cuboid blocks facing each other and sandwiching a layer of medium (air) in the middle of each group of metal nanoparticles 1, the length of the two gold cuboid blocks is parallel to the Y axis, and the width is parallel to the Y axis. X axis. Each group of metal nanoparticles is distributed periodically along the X axis and the Y axis on the dielectric substrate to form a metal nanoparticle array, and the thickness of the dielectric substrate in the present invention only needs to meet the working conditions. The incident light is a plane wave, the wave vector k is in the YZ plane and the angle between the incident direction and the Z axis is θ, and the polarization direction (electric field direction) of the incident light is perpendicular to the wave vector k in the YZ plane, and the magnetic field direction is parallel to the X axis.

Figure 2 is a schematic diagram of the XZ plane of the two-dimensional structure of each group of metal nanoparticles in the transverse MIM lattice plasmon absorber. When working at the optimum, the width W of the two gold cuboid blocks in each group of metal nanoparticles =80nm, the relative distance between the two gold cuboid blocks is m=50nm, the dielectric layer sandwiched between the two gold cuboid blocks is air, and the period of each group of metal nanoparticles arranged along the X-axis direction above the dielectric substrate is D = 450nm, the whole structure is vertically arranged on the upper surface of the dielectric substrate.

Fig. 3 is a schematic diagram of the YZ plane of the two-dimensional structure of each group of metal nanoparticles in the transverse MIM lattice plasmon absorber. When working optimally, each group of metal nanoparticles is above the dielectric substrate along the Y-axis direction The period of the arrangement is T=D=450nm, and the height of the two gold cuboid blocks in each group of metal nanoparticles is h=260nm.

Fig. 4 is a schematic diagram of the XY plane of the two-dimensional structure of each group of metal nanoparticles in the transverse MIM lattice plasmon absorber. When working optimally, the length a of the two gold cuboid blocks in each group of metal nanoparticles =180nm.

When the present invention works: the polarization direction (electric field direction) of the incident plane light wave is in the YZ plane, the magnetic field direction is parallel to the X axis, and the angle between the incident direction and the Z axis is θ, and the optimal degree of θ is 15°, so that An electric field parallel to the Z axis will be generated in the metal nanoparticle array, so that lattice plasmons in the form of OLP can be excited in the metal nanoparticle array, and strong coupling will be generated between adjacent metal nanoparticles. Resonance produces a specific absorption peak for incident light under specific structural parameters and incident angles, and has a high quality factor compared to other periodic array-based plasmonic absorbers. Changing the structural parameters of the gold cuboid block and the period of the metal nanoparticle array can change the shift of the absorption peak to achieve static tuning, and changing the incident angle of the plane light wave can also change the shift of the absorption peak to achieve dynamic tuning. Figure 5 shows the spectrogram when the transverse MIM lattice plasmon absorber works optimally. The abscissa in the figure represents the incident wavelength of the plane light, and the ordinate represents the reflection coefficient, transmission coefficient, Absorption coefficient, the three curves represent the reflection line (Reflectance), transmission line (Transmittance), and absorption line (Absorbance) of the transverse MIM lattice plasmon absorber to the incident plane light wave respectively, and the relationship between the three is A=1-T-R. It can be seen from the absorption spectrum that the absorption peak of the transverse MIM lattice plasmon absorber has a very narrow bandwidth, and the absorption coefficient of the highest peak is as high as 0.88, so it has a high quality factor.

The working idea of the present invention is to carry out the work under the conditions of fixed structural parameters and initial values. ①When the height h=230nm～260nm of the gold cuboid block of each group of metal nanoparticles changes, the absorption spectrum results obtained are shown in Figure 6; ②When the incident plane light wave is the clip between the wave vector k and the Z axis When the angle θ=10°～25° is adjusted, the obtained absorption spectrum results are shown in Fig. 7; ③ When the period of the metal nanoparticle array along the X axis and the Y axis is D=T=430nm～460nm When changed, the resulting absorption spectrum results are shown in Figure 8.

The following results are obtained through the simulation and verification of the transverse MIM lattice plasmon absorber in combination with the implementation of this example:

FIG. 6 is an absorption spectrum diagram when the height of the gold cuboid block in each group of metal nanoparticles varies in the range of h=230 nm to 260 nm. The abscissa in the figure represents the incident wavelength of the plane light, and the ordinate represents the absorption coefficient of the incident plane light wave, also known as the absorptivity. It can be seen in the figure that four different absorption spectrum curves are the gold in each group of metal nanoparticles. The simulation results of different heights of the cuboid block, the heights h are 230nm, 240nm, 250nm and 260nm respectively. It can be seen from the results in the figure that with the increase of the height h, the absorption peak of the transverse MIM lattice plasmon absorber will gradually increase, the absorption peak will gradually red-shift, and the absorption coefficient in the absorption passband will gradually decrease. Therefore, as the height of the two gold cuboid blocks increases in the range of 230nm to 260nm, the performance of the transverse MIM lattice plasmon absorber gradually increases, and the peak absorption coefficient gradually increases from 0.76 to 0.88, and the resonance peak wavelength Gradually increased from 684nm to 693nm, with good static tuning characteristics.

Figure 7 shows the absorption spectrum of the transverse MIM lattice plasmon absorber obtained when the angle θ between the wave vector k of the incident plane light wave in the YZ plane and the Z axis is adjusted in the range of 10° to 25°. The representations of the abscissa and the ordinate in the figure are the same as in FIG. 6 . It can be found that the absorption peak of the transverse MIM lattice plasmon absorber gradually increases with the increase of the incident angle θ from the four absorption lines obtained by the simulation of the four different angles between the wave vector k and the Z axis. blue-shift, and with the increase of the incident angle θ, the absorption peak of this transverse MIM lattice plasmonic absorber gradually increases and then decreases, reaching a maximum value around 15°, and with the incident angle With the increase of θ, the absorption peak of this transverse MIM lattice plasmonic absorber gradually narrows and then widens, reaching the narrowest at about 15°, so it has a very high incidence angle θ=15°. When the angle θ between the wave vector k of the incident plane light wave and the Z-axis changes in the range of 10° to 25°, the resonance peak wavelength gradually decreases from 702 nm to 673 nm, so the absorption peak can be adjusted very flexibly offset, with non-superior dynamic tuning characteristics.

8 is an absorption spectrum diagram of the present transverse MIM lattice plasmonic absorber obtained when the period of the metal nanoparticle array along the X-axis and the Y-axis is changed in the range of D=T=430nm-460nm. The representations of the abscissa and the ordinate in the figure are the same as in FIG. 6 . The results of the four absorption lines of the transverse MIM lattice plasmon absorber obtained by adjusting the period of the metal nanoparticle array can be found that in the range of D=T=430nm～460nm, with the increase of the period, the The absorption peak of the transverse MIM lattice plasmonic absorber gradually shifted to red, and the resonance peak wavelength gradually increased from 664 nm to 708 nm, indicating that the resonance wavelength can also be flexibly tuned statically by changing the period of the metal nanoparticle array. And with the increase of the period, the absorption peak of the transverse MIM lattice plasmon absorber gradually increases, and the peaks are basically the same when the period D and T are 450 nm and 460 nm, but when the period D = T = 450 nm At the same time, the absorption coefficient in the absorption passband is better suppressed and reduced, so the performance of the transverse MIM lattice plasmon absorber is the best when the period D=T=450nm.

The above-mentioned embodiments are only further specific explanations of the technical solutions and purposes of the present invention, and are not intended to limit the present invention. For those skilled in the art, any Modifications, equivalent replacements, improvements, etc., should all be included within the protection scope of the present invention.

Claims (2)

1. A transverse MIM lattice lattice plasmon absorber, which is composed of a dielectric substrate and a periodic metal nanoparticle array, wherein the metal nanoparticles are composed of two opposite gold cuboid blocks, which are perpendicular to the dielectric substrate. A layer of medium is sandwiched between two opposite gold cuboid blocks, and each group of metal nanoparticles is periodically distributed along the horizontal X-axis and Y-axis perpendicular to each other on the upper surface of the substrate to form a metal nanoparticle array, The incident light is a plane wave, the light source is directly above the entire structure and obliquely incident on the upper plane of the medium substrate, the incident light wave is a TM wave with the magnetic field direction parallel to the upper plane of the medium substrate, the transmitted light is emitted from the bottom of the metal nanoparticle array, and the reflected light is emitted from the metal nanoparticle array. The nanoparticle array is ejected from above, and the whole structure works in a vacuum or air medium environment; each group of metal nanoparticles is composed of two opposite gold cuboid blocks and a dielectric layer sandwiched between them. The geometric dimensions of the two opposite gold cuboid blocks are exactly the same. ; The arrangement period D of each group of metal nanoparticles vertically erected on the upper surface of the dielectric substrate along the length direction of the gold cuboid block is between 300nm and 700nm, and the arrangement period T along the width direction of the gold cuboid block is between 300nm and 300nm. Between 700 nm; the height h of the gold cuboid blocks in each group of metal nanoparticles is between 150 nm and 300 nm, the width W is between 20 nm and 100 nm, and the length a is between 100 nm and 300 nm. The spacing m is between 20nm and 150nm. 2. a kind of transverse MIM lattice plasmon absorber according to claim 1, is characterized in that: incident light is TM plane light wave, and the magnetic field direction of incident light is parallel to two gold in each group of metal nanoparticles In the width direction of the cuboid block, the angle θ between the wave vector k of the incident plane light wave in the YZ plane and the Z axis is between 1° and 60°.

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