CN111007036B

CN111007036B - Refractive index sensor based on flat plate symmetrical structure

Info

Publication number: CN111007036B
Application number: CN201911420040.0A
Authority: CN
Inventors: 王俊俏; 赵文涵; 李冉; 郜雅
Original assignee: Zhengzhou University
Current assignee: Zhengzhou University
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2022-03-25
Anticipated expiration: 2039-12-30
Also published as: CN111007036A

Abstract

The invention relates to a refractive index sensor based on a flat symmetric structure, which comprises a substrate, wherein a metal nano structure is arranged on the substrate, the metal nano structure comprises two metal nano wire units which are arranged at intervals transversely and symmetrically along the longitudinal direction, each metal nano wire unit comprises two transverse metal nano wires which are arranged at intervals along the longitudinal direction and a vertical metal nano wire connected between the two transverse metal nano wires, an I-shaped structure is formed between each vertical metal nano wire and the two transverse metal nano wires, a middle metal nano wire which is close to and extends towards the other metal nano wire unit is transversely arranged on each vertical metal nano wire, and the widths of the metal nano wires are equal. The refractive index sensor with the structure is immersed in a solution to be measured, a beam of vertically incident test light is projected above the structure, the refractive index of the solution can be detected and is expressed by the wavelength value of the appearance position of a scattering dark state, and the sensor is high in sensitivity, simple in structure and easy to process.

Description

Refractive index sensor based on flat plate symmetrical structure

Technical Field

The invention relates to the field of sensors, in particular to a refractive index sensor based on a flat plate symmetrical structure.

Background

With the development of microelectronic technology, the requirements of sensors on size, service life, sensitivity, stability, response time and the like are higher and higher, and the development of sensors with smaller volume, more sensitive reaction and more stable performance by adopting new materials has become an important direction for sensor research. The one-dimensional nano material has the advantages of large specific surface area, high surface activity and the like, and is very sensitive to the surrounding environment. The novel sensor developed by using the metal nano wire as the material has the advantages of small volume, simple structure, high sensitivity and the like, and draws wide attention.

Sanjida Akter and the like provide a refractive index sensor composed of a fused silica layer, a gold layer, a PML layer and a hole in a high purity sensitive open-channel doped silica biosensor in visible to near isolated wavelength.

Disclosure of Invention

The invention aims to provide a refractive index sensor based on a flat symmetric structure, which has a simple structure, is easy to process and has high sensitivity.

In order to achieve the purpose, the refractive index sensor based on the flat symmetric structure adopts the following technical scheme: the utility model provides a refracting index sensor based on dull and stereotyped symmetrical structure, which comprises a substrate, be provided with the metal nanometer structure of dimer structure on the basement, the metal nanometer structure includes two metal nanowire units that set up along horizontal interval and set up along vertical symmetry, each metal nanowire unit all includes two horizontal metal nanowires that set up along vertical interval and connects the vertical metal nanowire between two horizontal metal nanowires, form "worker" font structure between the vertical metal nanowire of each metal nanowire unit and two horizontal metal nanowires, transversely be provided with the middle metal nanowire that is close to and extends towards another metal nanowire unit on the vertical metal nanowire of each metal nanowire unit, the width homoenergetic of each metal nanowire equals.

The gap between two metal nanowire units on the substrate is 20 nm.

The width of each metal nanowire is 30 nm.

The thickness of the metal nanostructure is 10 nm.

The length of each transverse metal nanowire is 90-260 nm.

The length of each intermediate metal nanowire is 20-140 nm.

The length of each longitudinal metal nanowire is 90 nm.

The invention has the beneficial effects that: the refractive index sensor with the structure is immersed in a solution to be measured, a beam of vertically incident test light is applied to the upper side of the structure, a narrow descending interval called as a scattering dark state appears in the peak of a scattering spectral line, and along with the change of the solution refractive index (namely the solution concentration), the position where the scattering dark state appears is linearly changed along with the wavelength, namely the solution refractive index (namely the solution concentration) can be represented by the wavelength value of the position where the scattering dark state appears, and the sensitivity is high. The refractive index sensor with the structure is simple in structure and easy to process.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of a refractive index sensor based on a slab symmetry structure according to the present invention;

FIG. 2 is a front view of FIG. 1;

FIG. 3 is a bottom view of FIG. 2;

FIG. 4 is a plot of an extinction spectrum of a refractive index sensor of the present invention;

FIG. 5 is a graph of the position at which a scattering dark state appears as a function of the refractive index of the solution;

FIG. 6 is a schematic diagram of the quality factor of a refractive index sensor and its fitted straight line;

FIG. 7 is a graph showing the wavelength at which the scattering dark state occurs and its linear fit;

FIG. 8 is a graph showing the difference X₀A plot of the scattering spectra over length;

FIG. 9 is a graph of the scattering spectra at different X lengths.

Detailed Description

The embodiment of the refractive index sensor based on the flat symmetric structure comprises a substrate made of glass, wherein a metal nano structure with a dimer structure is arranged on the substrate, and is embedded in the substrate and made of metal silver, as shown in fig. 1-3. The metal nano structure comprises two metal nano wire units which are arranged at intervals along the transverse direction and are symmetrically arranged along the longitudinal direction, and the gap between the two metal nano wire units on the substrate is 20 nm. Each metal nanowire unit comprises two transverse metal nanowires which are arranged at intervals along the longitudinal direction, are equal in length and are aligned at the ends, and a vertical metal nanowire connected between the two transverse metal nanowires, and an I-shaped structure is formed between the vertical metal nanowire and the two transverse metal nanowires of each metal nanowire unit. And a middle metal nanowire which is close to and extends towards the other metal nanowire unit is transversely arranged on the vertical metal nanowire of each metal nanowire unit.

The widths of all the metal nanowires are equal and are all 30 nm. The thickness of each metal nanowire is 10nm, namely the thickness of the metal nanostructure is 10 nm. The length of each transverse metal nanowire is 176 nm. The lengths of all the middle metal nanowires are all 60 nm. The length of each longitudinal metal nanowire is 90 nm. And each end part of the longitudinal metal nanowire is positioned at the central line position of the corresponding transverse metal nanowire, and the middle metal nanowire is positioned at the middle position of the corresponding longitudinal metal nanowire.

The sensing performance of the sensor is simulated by using an FDTD method, a structural model is firstly constructed in software CST (MicroWave studio), then boundary conditions are set, open (add space) is adopted as the boundary conditions, the influence can be eliminated by constructing a perfect matching layer aiming at the boundary reflection condition, and finally the whole structure is simulated. The simulation is a common simulation method in the art, and the detailed process is not described in detail here. The calculated extinction spectrum plot for the refractive index sensor, as shown in fig. 4, where the dashed line represents the scattering curve and the solid line represents the absorption line, can be calculated to yield a quality factor of about 26.6. As can be seen from FIG. 4, the peak of the scattered light line decreases at a wavelength of about 1400nm and the absorbed light line exhibits an intensity of about 160000nm²Peak of (2). This indicates that at a wavelength of about 1400nm, the structure produces a scattering dark state with an EIT (electromagnetically induced transparency) like effect due to the coupling between the two modes, where the scattering suddenly disappears and the absorption increases. FIG. 5 is a graph of the refractive index of the solution as a function of the position of the scattering dark state, and it can be easily seen from the graph that the position of the scattering dark state shifts with the change of the refractive index of the solution, and this characteristic enables us to obtain the refractive index of the solution by detecting the position of the scattering dark state in the absorption line. FIG. 6 is a diagram illustrating a calculated value of the quality factor Q of the refractive index sensor and a straight line fitting the calculated value. FIG. 7 is a graph showing the wavelength at which the scattering dark state occurs and its linear fit, and it can be seen that it exhibits good linear characteristics and the sensor sensitivity is as high as 699nm/RIU, which shows that when the refractive index is slightly changed, the position at which the scattering dark state occurs is significantly changed. FIG. 8 shows a difference X₀The scattering spectrum under the length can be obtained according to X₀The position where the scattering dark state appears is shifted toward the long wavelength direction. The characteristics say thatBy changing X₀Can change the position where the scattering dark state appears, so that it is convenient for practical measurement. FIG. 9 is a scattering spectrum diagram under different X lengths, which can show that the position where the scattering dark state appears does not change with the increase of X, and proves that the change of X length is irrelevant to the position where the scattering dark state appears, and only influences the intensity of the scattering spectrum.

The metal nano structure is a dimer structure, and the structure is simple, the process difficulty is low, the preparation is easy, and the sensing performance is excellent. The refractive index sensor can obtain the refractive index of the solution by detecting the position where the scattering dark state appears. And the structure is capable of producing different spectral responses by varying the structural parameters of the nanostructure.

The preparation process of the refractive index sensor comprises the following steps:

step 1, cleaning a substrate made of glass: the substrate is firstly subjected to surface treatment, and then is subjected to prebaking to remove water vapor and chemicals brought by the surface treatment.

Step 2, rotary gluing: a spray gluing method is selected, and rotary gluing is carried out through several steps of glue dripping, low-speed rotation and high-speed rotation.

Step 3, exposure: and exposing the photoresist under the action of a mask plate to prepare the flat symmetric nano structure shown in figure 1.

And 4, electron beam evaporation: and evaporating metal into the nanowire holes of the flat-plate symmetrical nanostructure by using an electron beam evaporation system.

And step 5, developing: and carrying out corrosion development on the exposed photoresist by using a developing solution.

Step 6, cleaning: the photoresist is washed away to obtain the corresponding structure. As shown in fig. 1.

When the structure is used, the refractive index sensor of the structure is immersed in a solution to be measured, a beam of vertically incident test light is projected above the structure, a narrow descending interval called as a scattering dark state appears at the peak of a scattering spectral line, and along with the change of the solution refractive index (namely the solution concentration), the position where the scattering dark state appears is linearly changed along with the wavelength, namely the solution refractive index (namely the solution concentration) can be expressed by the wavelength value of the position where the scattering dark state appears, so that the sensitivity is high. The refractive index sensor with the structure is simple in structure and easy to process.

In other embodiments of the present invention, the length of each lateral metal nanowire may also be 90 nm; the length of each transverse metal nanowire can also be 260 nm; the length of each intermediate metal nanowire may be 20 nm; each intermediate metal nanowire may have a length of 140 nm.

Claims

1. The utility model provides a refractive index sensor based on dull and stereotyped symmetrical structure which characterized in that: the metal nano structure comprises a substrate, wherein a metal nano structure with a dimer structure is arranged on the substrate, the metal nano structure comprises two metal nano wire units which are arranged at intervals transversely and symmetrically along the longitudinal direction, each metal nano wire unit comprises two transverse metal nano wires which are arranged at intervals along the longitudinal direction and a vertical metal nano wire which is connected between the two transverse metal nano wires, an I-shaped structure is formed between the vertical metal nano wire and the two transverse metal nano wires of each metal nano wire unit, a middle metal nano wire which is close to and extends towards the other metal nano wire unit is transversely arranged on the vertical metal nano wire of each metal nano wire unit, and the widths of the metal nano wires are equal; the gap between two metal nanowire units on the substrate is 20nm, the width of each metal nanowire is 30nm, the thickness of the metal nanostructure is 10nm, the length of each transverse metal nanowire is 90-260nm, the length of each middle metal nanowire is 20-140nm, and the length of each longitudinal metal nanowire is 90 nm.