CN111504947A

CN111504947A - Surface plasmon refractive index sensor based on MIM annular grid point array

Info

Publication number: CN111504947A
Application number: CN202010287312.0A
Authority: CN
Inventors: 杨宏艳; 陈昱澎; 刘孟银
Original assignee: Guilin University of Electronic Technology
Current assignee: Guilin University of Electronic Technology
Priority date: 2020-04-14
Filing date: 2020-04-14
Publication date: 2020-08-07

Abstract

The invention discloses a surface plasmon refractive index sensor based on an MIM annular lattice point array. In an example of the invention, the sensor is comprised of a dielectric substrate and an array of annular MIM nanoparticles having a periodicity. The electric field of the incident light is polarized along the X axis of the coordinate, and the wave loss K of the incident light forms an included angle theta with the incident surface. By regulating and controlling the geometric parameters and the incident angle of the MIM lattice point array, the surface plasmon lattice point is excited to resonate, and the corresponding shift of the reflection spectrum formant along with the change of the refractive index is realized. Compared with refractive index sensors with other structures, the structure has smaller size and higher sensitivity, and has excellent application prospect in the field of micro-nano-scale photoelectric detectors.

Description

Surface plasmon refractive index sensor based on MIM annular grid point array

(I) technical field

The invention relates to the technical field of micro-nano photoelectron, in particular to a surface plasmon refractive index sensor based on an MIM annular lattice point array.

(II) background of the invention

Surface plasmons (SPPs) are evanescent waves formed by coupling free electrons and photons on a metal Surface to each other and propagating along the medium-metal Surface. Is a collective oscillation produced by the interaction between light waves having the same resonant frequency and free electrons in the metal. With the gradual maturity of nanotechnology and the gradual improvement of surface plasmon theory, surface plasmon photonics becomes an important subject of nano photonics, which has entered the period of high-speed development and raises the attention of people to the preparation of nano-sized optical devices by using surface plasmon polariton. With the development of the research, scientists will subdivide the optoelectronic devices into a plurality of branch points, and the classification of the optoelectronic devices on performance devices, such as sensors, optical amplifiers, modulators, filters, etc., plays an increasingly important role in various fields.

Conventional localized surface plasmon resonances supported by a single metal nanoparticle (L SPR) and propagating surface plasmon resonances supported by a metal-dielectric interface (SPR) both have problems of limited field strength enhancement and low quality factor, resulting in less than ideal performance in applications, many people are concerned with conventional localized surface plasmon resonances (L SPRs) which, when they are conducted, exhibit a low quality factor q despite the fact that conventional localized surface plasmons are mutually coupled in neighboring particles, but strong radiation damping is severely broadened, thus L SPRs exhibit a low quality factor q.

The surface plasmon refractive index sensor based on the annular lattice point array provided by the invention has excellent performances of small volume, high detection precision, easy integration and the like, and is particularly suitable for the research field of micro-nano sensing due to the sharp asymmetric spectral line shape, the reflectivity of the spectrum of the sensor can be sharply reduced from a peak to a trough, and the wavelength change can provide an ultra-narrow transmission peak and is easy to identify and track.

At present, the optical functional device based on the MIM structure surface lattice point has made a breakthrough in the aspect of theoretical research. For example, the rectangular lattice point array optical device of MIM on polymer substrate of the leeward et al (CN201910749239.1) design has the advantages of simplicity, preference for asymmetric dielectric point environment, etc. But is not specifically related to the specific application in refractive index sensing, such that its application may be somewhat limited. The invention provides a surface plasmon refractive index sensor based on an MIM annular lattice point array.

Disclosure of the invention

The invention aims to design a surface plasmon refractive index sensor based on an MIM annular lattice point array, further research on the structure of the nano lattice point array on a glass medium substrate, and by changing the size of the MIM nanoparticle array, the incident angle of incident light, the external refractive index and other parameters, the structure can be found to be capable of effectively regulating and controlling the properties of the surface plasmon refractive index sensor, such as reflectivity, resonance bandwidth, resonance wavelength and the like.

In order to solve the problems, the invention is realized by the following technical scheme:

the invention aims to design a surface plasmon refractive index sensor based on an MIM annular lattice point array, which mainly comprises a BK-7 glass medium substrate and a periodic MIM annular nano-column array, wherein a nano-column consists of an upper annular gold column and a lower annular gold column with the same size and an annular dielectric silicon column between the upper annular gold column and the lower annular gold column, and the medium substrate is positioned below the MIM annular column. The structures are distributed in the same period along the X and Y axes to form the MIM annular nano-pillar array, and the height of each period unit is the same. The whole structure is placed in a medium environment with the refractive index n, incident light is X polarized light, and reflected light is emitted from the upper side of the metal nanoparticle array.

In the above scheme, the annular metal column is made of gold.

In the above scheme, the height of the annular metal column only needs to meet the working conditions, and in order to obtain a good filtering effect, the height of the annular metal column is 120nm to 160 nm.

In the scheme, the annular medium column is made of silicon, and the height of the annular medium column meets the working condition.

In the scheme, the outer ring diameter W of the annular metal column and the annular medium column is 180nm, and the inner ring diameter d is 30 nm-60 nm.

In the scheme, the substrate material is BK-7 glass material with the refractive index of 1.52, the thickness P of the BK-7 glass material is 300nm, and the width T of the BK-7 glass material is 500 nm.

In the above scheme, the incident light is X polarized light, and the incident angle theta is 0-5 degrees.

In the scheme, the variation range of the external refractive index n is 1-1.5.

(IV) description of the drawings

Fig. 1 is a two-dimensional structure diagram of a single cell structure of the present invention.

FIG. 2 is a schematic three-dimensional structure of a plurality of periodic array structures according to the present invention.

Fig. 3 is a graph showing the reflectance when the incident angle θ is changed according to the present invention.

Fig. 4 is a graph of reflectivity for varying inner ring diameter d of the present invention.

FIG. 5 shows the thickness h of the metal block according to the present invention_mReflectance profile with change.

Fig. 6 is a graph showing the reflectance when the external refractive index n is changed according to the present invention.

(V) detailed description of the preferred embodiments

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings in conjunction with specific examples. It should be noted that directional terms such as "upper", "lower", "middle", "left", "right", "front", "rear", and the like, referred to in the examples, refer only to the direction of the drawings. Accordingly, the directions used are for illustration only and are not intended to limit the scope of the present invention.

A two-dimensional plan view of a single periodic unit structure of the surface plasmon refractive index sensor based on the MIM annular lattice point array is shown in figure 1 and comprises annular metal nano columns (1, 3), annular dielectric silicon nano columns (2) and a BK-7 glass substrate (4) which are symmetrical up and down.

The metal nano-pillars can be made of noble metal materials, such as gold, silver, copper and other metal materials, but in order to obtain better sensing performance, the metal film of the invention is made of gold.

The material of the metal film of the present invention is silicon.

The outer ring diameter W of all the annular metal columns and the annular dielectric columns is 180 nm.

Fig. 3 shows the relationship between the reflectance at the incident angle of 0 ° to 5 °. It can be seen that the reflection spectrum has only one asymmetric extremely narrow bandwidth formant at incident angles less than 2. When the incident angle is larger than 2 degrees, the formants are split to form a left formant and a right formant, wherein the right formant is obviously represented as a Fano line type with extremely high quality factors, and the bandwidth of the left formant is not obviously changed along with the increase of the angle, and the bandwidth of the right formant is gradually widened.

Fig. 4 shows reflection spectra when the ring-shaped outer diameter W is maintained at 180nm and the inner diameter d is maintained at 30nm, 40nm, 50nm, and 60nm, respectively. From fig. 4 we can see that the formant intensity becomes significantly lower with increasing d and the reflectivity becomes flat.

FIG. 5 shows that the height h of the annular metal nano-pillar is changed while the outer diameter W of the annular nano-pillar is kept 180nm and the inner diameter d of the annular nano-pillar is kept 30nm_mReflection spectra at 120nm, 130nm, 140nm, 150nm and 160nm, respectively. As can be seen from fig. 5, as the height of the circular metal nano-pillars increases, the lattice resonance effect between the circular metal pillars is gradually enhanced, which finally results in that the resonance peak is gradually enhanced, the bandwidth is narrowed, and the quality factor is gradually increased.

FIG. 6 shows the nano-pillars W held in a ring shape of 180nm, d 30nm, and h_mThe refractive index of the material is 1, 1.1, 1.2, 1.3, 1.4 and 1.5 with the external medium, which is not changed at 160 nm. From the change of the reflection line of fig. 6, we can see that there are left and right two resonance peaks, and as the refractive index increases, the intensity of the left resonance peak gradually increases and the bandwidth becomes narrower. The intensity of the right-side formant gradually decreases and the bandwidth becomes wider. It is important that both sets of formants are red-shifted in a linear relationship. Thus, a refractive index sensor capable of measuring a change in refractive index with high sensitivity between 1 and 1.5 is provided.

The refractive index sensor with the MIM annular structure works in visible light and near infrared frequency bands, has extremely high sensing sensitivity and has the characteristic of extremely high quality factor.

It should be noted that, although the above-mentioned embodiments of the present invention are illustrative, the present invention is not limited thereto, and thus the present invention is not limited to the above-mentioned embodiments. Other embodiments, which can be made by those skilled in the art in light of the teachings of the present invention, are considered to be within the scope of the present invention without departing from its principles.

Claims

1. Surface plasmon refractive index sensor based on MIM annular lattice point array, its characterized in that: the refractive index sensor is composed of upper and lower annular metal blocks (1, 3), an annular dielectric silicon layer (2) between the annular metal blocks and a BK-7 glass dielectric substrate (4). The structures are distributed in the same period along the X and Y axes to form the MIM annular nano-pillar array, and the height of each period unit is the same.

2. The MIM annular grid array based surface plasmon refractive index sensor according to claim 1, wherein: the annular metal blocks (1, 3) are made of gold.

3. The MIM annular grid array based surface plasmon refractive index sensor according to claim 1, wherein: the annular dielectric column (2) is made of silicon.

4. The MIM annular grid array based surface plasmon refractive index sensor according to claim 1, wherein: the diameter W of the outer ring of the MIM annular column is 180nm, and the diameter d of the inner ring is 30 nm.

5. The MIM annular grid array based surface plasmon refractive index sensor according to claim 1, wherein: in the periodic unit, the heights of the upper annular metal column and the lower annular metal column are consistent and adjustable.

6. The MIM annular grid array based surface plasmon refractive index sensor according to claim 1, wherein: the substrate material (4) is BK-7 glass material with the refractive index of 1.52, the thickness of the glass material is 300nm, and the width of the glass material is 500 nm.

7. The MIM annular grid array based surface plasmon refractive index sensor according to claim 1, wherein: the refractive index sensor works in the visible light and near infrared wave bands.