阅读说明：本技术 一种mim格点阵等离激元吸收器 (MIM grid lattice plasmon absorber ) 是由 杨宏艳 刘雅洁 陈昱澎 刘梦银 于 2020-06-05 设计创作，主要内容包括：本发明公开一种MIM格点阵等离激元吸收器,其包括介质基底和周期性条状纳米阵列组成,每个周期单元结构为在基底上以两个三层等大长方体块组成,一块为两个金属层夹介质层,另一块为两个介质层夹金属层。本发明在入射光为电场方向沿X轴极化的情况下,其在金属纳米颗粒阵列中可以激发非平面格点阵等离激元,使相邻的纳米金属单元之间产生较强的耦合共振,在特定的结构参数下就会对入射光产生特定的吸收峰。本发明相比于与其它基于阵列的等离激元吸收器具有较高的品质因数,MIM格点阵等离激元吸收器在微纳光学集成器件领域具有着潜在的应用前景。(The invention discloses an MIM grid lattice plasmon absorber which comprises a dielectric substrate and periodic strip-shaped nano arrays, wherein each periodic unit structure is formed by two three layers of equal-length rectangular blocks on the substrate, one is formed by two metal layers sandwiching a dielectric layer, and the other is formed by two dielectric layers sandwiching a metal layer. Under the condition that incident light is polarized along an X axis in the direction of an electric field, the metal nanoparticle array can excite non-planar lattice point array plasmons in the metal nanoparticle array, so that stronger coupling resonance is generated between adjacent nanometer metal units, and a specific absorption peak can be generated on the incident light under specific structural parameters. Compared with other array-based plasmon absorbers, the invention has higher quality factor, and the MIM lattice point array plasmon absorber has potential application prospect in the field of micro-nano optical integrated devices.)

1. An MIM grid lattice plasmon absorber. The periodic unit structure is composed of a medium substrate (1) and a periodic strip-shaped nano array (2), wherein each periodic unit structure is formed by two three layers of equal-length square blocks on the substrate, one is formed by clamping a medium layer between two metal layers, and the other is formed by vertically placing the two medium layers above the medium substrate relative to the medium substrate by clamping the metal layers between the two medium layers. Each group of metal nano-particles are arranged on the substrate in a matrix form, incident light is polarized along an X-axis in an electric field direction, transmitted light is emitted from the lower part of the metal nano-particle array, and reflected light is emitted from the upper part of the metal nano-particle array.

2. The MIM lattice plasmonic absorber of claim 1, wherein: each group of nanoparticles is composed of two opposite equal-size cuboid blocks, one metal layer and the other metal layer are sandwiched by a medium layer and a metal layer.

3. The MIM lattice plasmonic absorber of claim 1, wherein: the incident light is polarized along the X-axis in the direction of the electric field.

4. A MIM lattice plasmonic absorber according to claim 1 or 2, wherein: the height h of two cuboid blocks in each group of nano-particles is 450nm, the width of the substrate is 1000nm, the thickness a of the metal layer is between 60nm and 180nm, and the distance between two opposite cuboid blocks is equal to the distance m between the cuboid blocks and the edge of the substrate and is between 70nm and 190 nm.

5. The MIM lattice plasmonic absorber of claim 1, wherein: the refractive index n of the working environment is between 1.00 and 1.10.

(I) technical field

The invention relates to the technical field of micro-nano photonics, in particular to an MIM grid lattice plasmon absorber.

(II) background of the invention

Surface Plasmon Resonance (SPR) is an optical phenomenon. Since the 90 s of the 20 th century, a novel biosensor analysis technology based on the SPR principle detects the interaction between a ligand and an analyte on a biosensor chip (biosensor chip), and can be used for tracking the interaction between biomolecules in a natural state in real time due to the advantages of no need of labeling, no need of purifying various biological components, no damage to the biomolecules and the like. The surface plasmon resonance greatly enhances the intensity of a local optical field and improves the interaction between light and substances, and is widely applied to the fields of sensing, imaging, nano laser, nonlinear optics, modulation, detection and the like. Based on this, plasmon absorbers have been proposed and studied, and many obvious advantages thereof have attracted increasing researchers to explore.

Surface Plasmon Polaritons (SPPs) are collective oscillations of electrons generated when the oscillation frequency of free electrons in a metal Surface region coincides with the frequency of incident light waves, and are charge density waves propagating along the metal Surface. The optical field amplitude is exponentially attenuated in the direction perpendicular to the interface, and the photonic device based on the SPPs can break through the traditional optical diffraction limit and can bind light in a sub-wavelength structure for propagation. Therefore, the photonic device based on the SPPs has smaller mode size, is beneficial to the integration development of the photonic device, and realizes the light manipulation in the micro-nano level.

Metal-dielectric-Metal (MIM) has the advantages of strong local light capability, enhanced field-space local area, simple structure, easy realization of high-density integration, and the like, and is widely applied to the research of various photonic devices, such as filters, biochemical sensors, and optical switches. With the development of high-sensitivity detection technology in the field of sensors, optical phenomena such as MIM waveguide structures based on SPPs and Fano resonance become hot spots in the field of micro-nano optics. The Fano resonance is quantum interference between a resonance process and a non-resonance process in condensed state physics, and a resonance line of the Fano resonance has obvious asymmetry and abnormal sensitivity to structural parameters and the surrounding environment. Compared with other plasmon-based absorbers, the MIM lattice point array plasmon absorber has higher quality factor, only acts on planar light waves in a specific incidence direction during work, can dynamically tune along with the incidence direction of incident light, is single in material and strong in periodicity, and has the advantage of simple processing.

Disclosure of the invention

The invention aims to design an MIM grid point array plasmon absorber to overcome the problems in the prior art.

An MIM lattice point array plasmon absorber is composed of a medium substrate and a periodic strip-shaped nano array, wherein each periodic unit structure is composed of two three-layer equal-length square blocks on the substrate, one is that a medium layer is clamped between two metal layers, the other is that the two medium layers are vertically arranged above the medium substrate relative to the medium substrate by clamping the metal layers, and all periodic units are arranged on the substrate in a matrix form. Incident light is polarized along an X axis in the direction of an electric field, transmitted light is emitted from the lower part of the metal nanoparticle array, and reflected light is emitted from the upper part of the metal nanoparticle array. The structure of the nano-grid point array is further researched on an original medium substrate, and the structure can be found to be capable of effectively adjusting the performances of the MIM grid point array plasmon absorber, such as the absorption rate, the resonance wavelength and the like, by changing parameters, such as the thickness of a metal layer of a unit nano-array, the spacing of nano-blocks, the refractive index of a working environment medium and the like.

The thickness of the cuboid block metal layer in the unit structure in each period can be arbitrarily in accordance with the thickness of the working condition of the MIM grid lattice plasmon absorber, and in order to obtain the optimal characteristic of the absorber, the metal layer thickness is 100 nm.

The interval between two cuboid blocks in the unit structure per period and the distance between the cuboid blocks and the edge can be in any interval according with the working condition of the MIM lattice plasmon absorber, and in order to obtain the optimal characteristic of the absorber, the interval is 90 nm.

The refractive index of the unit structure working environment in each period can be any according with the environmental refractive index of the MIM grid lattice plasmon absorber working condition, and in order to obtain the optimal characteristic of the absorber, the refractive index is 1.00.

The base dielectric material can be any material which meets the working conditions of the transverse MIM grid lattice plasmon absorber, and in order to obtain the optimal characteristics of the absorber, a medium with the refractive index n being 1.52 is used as the base material.

The dielectric layer between the two cuboid blocks in each group of nano-particles can be any dielectric material meeting the working conditions of the transverse MIM grid lattice plasmon absorber, and in order to obtain the optimal characteristics of the absorber, silicon dioxide is used as the dielectric layer material.

The metal layer in the middle of the two cuboid blocks in each group of nanoparticles can be made of any metal material meeting the working conditions of the transverse MIM grid lattice plasmon absorber, and gold is used as the metal layer material in order to obtain the optimal characteristics of the absorber.

Compared with the prior art, the invention has the following advantages:

1. the resonance wavelength, the absorption rate and the quality factor can be statically changed by changing the structural parameters of the cuboid block.

2. Compared with other plasmon absorbers, the transverse MIM grid lattice plasmon absorber has the characteristic that the resonance wavelength can be flexibly adjusted from visible light to near-infrared wave bands.

3. The structure is kept unchanged in the Y-axis direction, and the unit structure is simple in each period, and meanwhile, the processing is easy.

(IV) description of the drawings

Fig. 1 is a schematic three-dimensional structure diagram of the MIM grid lattice plasmon absorber.

Fig. 2 is a schematic diagram of a three-dimensional structure of each group of metal nanoparticles of the MIM lattice plasmon absorber.

Fig. 3 is an absorption spectrum of the MIM lattice plasmon absorber obtained when each group of nanoparticle metal layers a varies within a range of 60nm to 180 nm.

Fig. 4 is an absorption spectrum of the MIM lattice plasmon absorber obtained when the distance m between two nanoparticles varies in the range of 70nm to 190 nm.

Fig. 5 is an absorption spectrum of the MIM lattice plasmon absorber obtained when the environment medium n in which the MIM lattice plasmon absorber operates varies within a range of 1.00 to 1.10.

Reference numbers in the figures: 1. a dielectric substrate; 2. a strip-shaped nano array; 3. a periodic nano-array metal layer; 4. a periodic nanoarray dielectric layer.

(V) detailed description of the preferred embodiments

For a better understanding of the present invention, the present invention will be further explained with reference to the following examples and the accompanying drawings, which are illustrative only and not limiting of the present invention.

Fig. 1 is a schematic three-dimensional structure diagram of the MIM grid lattice plasmon absorber. The refractive index of a substrate 1 is 1.52, a plurality of groups of nano arrays are vertically arranged on the substrate, each group of metal nano particles is composed of two cuboid blocks with the same size, one group is a dielectric layer with the refractive index of 1.43 sandwiched between two metal gold layers, the other group is a metal layer sandwiched between two dielectric layers of the same kind, and the thicknesses of the three metal layers are all a.

Fig. 2 is a schematic diagram showing a three-dimensional structure of each group of metal nanoparticles of the MIM lattice plasmon absorber. The height of the two cuboids is fixed at 450 nm. When working best, the metal layer thickness a of each group of nanoparticles is 120nm, the spacing m is 150nm, and the whole structure works in an environment where n is 1.

When the invention works: the polarization direction (electric field direction) of incident plane light waves is in an XZ plane, the electric field direction is polarized along an X axis, so that non-planar lattice point array plasmons can be excited in a metal nanoparticle array, strong coupling resonance can be generated between adjacent nanometer metal units, a specific absorption peak can be generated on incident light under specific structural parameters and incidence angles, and the high-quality factor is achieved compared with other periodic array-based plasmon absorbers. Changing the structural parameters of the metal cuboid blocks and the period of the metal nanoparticle array can change the shift of the absorption peak.

The working idea of the invention is as follows: the unfolding operation is carried out under the condition that the structural parameters are fixed and initial values. The width of the unit structure substrate is fixed to be 1000nm per period, and the height of the cuboid block is fixed to be h-450 nm. The results of absorption spectra obtained when the thickness a of the metal layer in each nano array was varied in the range of 60nm to 180nm are shown in fig. 3; ② when the interval m between two cuboid blocks in each nano array is changed in the range of 70 nm-190 nm, the obtained absorption spectrum result is shown in figure 4; and thirdly, when the refractive index of the whole structure working environment is changed within n being 1.00-1.10, the obtained absorption spectrum result is shown in fig. 5.

Fig. 3 is an absorption spectrum obtained when the spacing between two cuboids is fixed to be m 130nm and the thickness a of the metal layer is changed within the range of 60nm to 180nm in each group of nano-arrays. The abscissa in the figure represents the incident wavelength of the plane light, and the ordinate represents the absorption coefficient, also called absorptivity, of the incident plane light wave, and it can be seen that seven different absorption spectrum curves are obtained by simulation when the thicknesses a of the unit structure metal layers per period are respectively 60nm, 80nm, 100nm, 120nm, 140nm, 160nm and 180 nm. As can be seen from the results in the figure, the absorption peak of the present MIM lattice plasmon absorber gradually red-shifts with increasing height a, and the absorption coefficient increases first and then decreases, and is maximum when a is 100 nm. Therefore, the performance of the MIM lattice plasmon absorber is firstly enhanced and then weakened when the thickness of the nano-array metal layer is increased in the range of 60nm to 180nm, when a is 100nm, the absorption coefficients of two peaks are 0.72 and 0.68 respectively, and the wavelengths of two resonance peaks are 926nm and 1504nm respectively.

Fig. 4 is an absorption spectrum obtained when the thickness of the metal layer in each set of nanoarrays was fixed at a value of 100nm, and the interval between two rectangular parallelepiped blocks and the distance m from the edge were varied within a range of 70nm to 190 nm. The abscissa in the figure represents the incident wavelength of plane light, and the ordinate represents the absorption rate, and it can be seen in the figure that seven different absorption spectrum curves are obtained by simulation when the interval m between two cuboid blocks of the unit structure per period is 70nm, 90nm, 110nm, 130nm, 150nm, 170nm and 190nm respectively. As can be seen from the results in the figure, the absorption peak of the present MIM lattice plasmon absorber gradually shifts blue with increasing height a, and the absorption coefficient increases first and then decreases, and is maximum when m is 150 nm. Therefore, the performance of the MIM lattice plasmon absorber is firstly enhanced and then weakened when the thickness of the nano-array metal layer is increased in the range of 70nm to 190nm, when m is 90nm, the absorption coefficients of two peaks are 0.75 and 0.84 respectively, and the wavelengths of two resonance peaks are 958nm and 1534nm respectively.

FIG. 5 is an absorption spectrum obtained when the refractive index of the whole structure working environment is changed within a range of n being 1.00-1.10. In the figure, the abscissa represents the incident wavelength of the plane light, the ordinate represents the absorption rate, and six different absorption spectrum curves are obtained by simulation when the refractive indexes are respectively 1.00, 1.02, 1,04, 1.06, 1.08 and 1.10. From the results in the figure, it can be seen that when the ambient refractive index n increases, the absorption peak of the MIM lattice plasmon absorber gradually red-shifts, and the absorption coefficient gradually decreases. Therefore, when the refractive index of the whole structure working environment is increased within the range of n 1.00-1.10, the performance of the MIM lattice point array plasmon absorber is gradually weakened.

The above embodiments are only intended to illustrate the present invention, and not to limit the scope of the present invention, and all equivalent modifications or improvements made by those skilled in the art without departing from the principle of the present invention are considered to be within the protection scope of the present invention.