CN209727774U - A plasmon-induced transparent metamaterial sensor - Google Patents

Abstract

The utility model discloses a plasma-induced transparent metamaterial sensor, which belongs to a graphene material sensor device in the mid-infrared band, and utilizes the graphene surface plasma characteristics and the plasma-induced transparency theory. The sensor device is a three-dimensional periodic structure, and its structure is composed of: the top layer is a graphene split resonator ring and graphene double nanoribbon structure, the middle layer is a silicon dioxide medium, and the bottom layer is a doped silicon substrate layer, stacked from top to bottom A three-layer structure formed. The utility model mainly calculates and simulates the resonance spectrum of the plasma-induced transparent metamaterial sensor through the finite element method, optimizes the sensor structure, has the ability to excite the plasma-induced transparent resonance in the mid-infrared frequency band, and can effectively tune the plasma-induced The line shape and resonant frequency of the transparent resonance. The utility model is simple in structure, compact and reasonable, and is convenient for processing.

Description

A plasmon-induced transparent metamaterial sensor

technical field

The utility model relates to a plasma-induced transparent metamaterial sensor, which belongs to the application field of graphene materials in mid-infrared band sensor devices.

Background technique

Electromagnetically induced transparency (EIT) is a phenomenon of absorption-transmission enhancement caused by quantum interference, which enables the control of the optical response of materials with electromagnetic fields. This phenomenon was first observed in atomic systems, and it can be realized in three-level systems. The atomic EIT effect has been widely used in slow light, nonlinear optics and other fields. However, the realization of the atomic EIT effect is very difficult and requires very harsh environmental and operating conditions, which greatly limits the application and development of traditional atomic EIT. In order to overcome these problems, a new system similar to the atomic EIT system has been studied. Plasmon-induced transparency (PIT) is a kind of EIT-like effect, which has attracted widespread attention and has been applied in sensing, slow light, optical storage and other fields. The realization of the PIT effect usually uses the coupling of bright and dark modes, that is, it is generated by direct destructive interference between the bright state mode and the dark state mode.

The frequency of mid-infrared is mainly the spectrum in the range of 15-150THz (2μm-20μm). Mid-infrared spectroscopy has great potential in various fields such as environmental monitoring, sensing and astronomical detection, because the fingerprints of many materials fall in this spectral region. Especially in the field of sensing, many molecular fingerprints are distributed in the mid-infrared band, and these molecular fingerprints can be judged very accurately by sensors. This feature has made mid-infrared band sensors receive widespread attention in recent years. However, traditional sensors generally use metal and semiconductor materials, which have large ohmic and radiation losses, which will seriously degrade performance, and the quality factor and sensitivity are generally low. For reduced losses in the mid-infrared region, plasmon resonance (PFR) should exhibit a high quality factor. This feature has a strong effect on surface-enhanced infrared absorption (SEIRA), which can provide molecular information due to material-specific vibrational absorption in the region of the mid-infrared fingerprint. As a form of resonance in plasmons, plasmon-induced transparency exhibits an ultra-high quality factor and high sensitivity in the mid-infrared band, which indicates its great potential in sensing and other fields.

In recent years, with the research of graphene by researchers, the plasmon-induced transparency effect based on graphene has also attracted everyone's attention. As we all know, the plasmonic transparency effect based on the excitation of traditional metallic metamaterials has a serious disadvantage, that is, the operating wavelength of the transparent window is fixed once the structure is fabricated. The plasmon-induced transparency effect based on graphene can control the transparent window by adjusting the Fermi level of graphene, so it has shown great application potential in fields such as slow light devices and sensors. By biasing and adjusting the Fermi level of single-layer graphene, the sensor can realize dynamic tuning of the resonance spectrum, so that the optical resonance can overlap with the molecular vibration fingerprint. As a new type of graphene material, its processing technology has also been studied by a large number of scientific researchers and has become increasingly mature. The most commonly used processing technology is the CVD method. Therefore, the utility model has important scientific significance and practical application value, and also has a certain prospect in the practical application in the field of mid-infrared resonance. In addition, the utility model can also provide important theoretical and technical support for the design and development of mid-infrared band sensors.

Contents of the invention

The technical problem to be solved by the utility model is to provide a metamaterial sensor with simple structure, which can conveniently excite high-performance plasma and induce transparency in the mid-infrared band.

Considering the requirements such as the difficulty of the structure, the utility model proposes a plasma-induced transparent metamaterial sensor, which provides important help for the development of highly adjustable and high-sensitivity sensors based on graphene metamaterials.

In order to achieve the above purpose, the technical solution adopted by the utility model is: a plasma-induced transparent metamaterial sensor, the sensor is a three-dimensional periodic structure, and a graphene split resonator ring and a graphene double nanoribbon structure are used to excite the plasma Induced transparent resonance; characterized in that: the structural composition from bottom to top is a doped silicon base layer, a silicon dioxide dielectric layer, and the top layer is a graphene split resonator ring and a graphene double nanobelt structure.

The mid-infrared band plasma-induced transparent sensor in this technical solution is based on graphene material and can be produced by graphite oxide reduction method, and the processing of the device also includes photolithography and etching technology. The selected Fermi level of the graphene material described in the utility model can be between 0.5eV and 1.0eV, which can be easily realized by doping in experiments.

Effective gain described in the present invention is:

(1) The sensor has a simple and compact structure, and can excite high-performance plasmon-induced transparent resonance in the mid-infrared band.

(2) The transparent window of the plasmon-induced transparency excited by this sensor is very sharp, which proves that the resonance of the plasmon-induced transparency with excellent performance is excited.

(3) Using the destructive interference between the graphene double nanoribbons as the bright state mode and the graphene split resonator ring as the dark state mode, a high-performance plasmon-induced transparent resonance is excited.

(4) The plasmon-induced transparency resonance excited by the sensor can adjust the Fermi level of graphene by adding a polarization voltage, thereby changing the resonance frequency and resonance intensity of the plasmon-induced transparency to meet the different needs of the sensor .

Description of drawings

Fig. 1 is the structural schematic diagram of this sensor unit;

Fig. 2 is a schematic diagram of the top graphene structure of the sensor;

Fig. 3 is the transmission spectrum of the plasmon-induced transparent resonance of the sensor at different graphene Fermi levels;

Fig. 4 is the transmission spectrum of the sensor under different material refractive indices for plasmon-induced transparent resonance;

The above picture contains: px=py=200nm, R=80nm, G=20nm, W=20nm, L=80nm, S=20nm, P=30nm, d=30nm, h=30nm.

Explanation of reference numerals: 1-doped silicon base layer; 2-silicon dioxide dielectric layer; 3-graphene split resonator ring; 4-graphene double nanoribbons.

Detailed ways

The following is a specific embodiment of the utility model and in conjunction with the accompanying drawings, the technical solution of the utility model is further described, but the utility model is not limited to this embodiment.

Figure 1 is a schematic diagram of a unit structure of a plasmon-induced transparent metamaterial sensor. The length and width of the structural unit are px and py, the thickness of the doped silicon base layer is h, the thickness of the silicon dioxide dielectric layer is d, the thickness of the graphene split resonator ring and the graphene double nanoribbon is 1nm, and the graphene opening The radius length of the resonant ring is R, the gap width of the split resonant ring is G, the width of the split resonant ring is W, the length of the double nanoribbon is L, the width of the double nanoribbon is S, and the spacing between the double nanoribbons is P, The graphene split resonator ring-double nanoribbon structure is shown in Figure 2.

The working principle or working process of the sensor can be explained as follows. Since the graphene material has very high electron mobility characteristics, by adding a bias voltage to the graphene, the Fermi energy level of the graphene is adjusted, and the conductivity of the graphene layer is enhanced so that it presents the properties of a metal. Surface plasmon resonance is excited by the interaction of silicon medium and air medium. Here, a graphene thin film with a thickness of 1nm can be produced by the graphite oxide reduction method, and then transferred to the silicon dioxide dielectric layer, and the graphene split resonator ring-double nanobelt structure array can be obtained by mask photolithography. In order to tune the Fermi energy of graphene, an ion gel layer is spin-coated on top of the graphene layer, and a polarization voltage is added together with the doped silicon substrate layer. This top-gated method can conveniently adjust the Fermi energy of graphene. class. In the mid-infrared band, when the mid-infrared electromagnetic wave is vertically incident on the surface of the graphene split resonator ring-double nanoribbon, it can directly excite the surface plasmon polaritons (SPPs) in the graphene double nanoribbon, and generate dipoles near 29.2THz resonance. The graphene split resonator ring cannot directly excite resonance near 29.2 THz, but the sixth-order resonance of the graphene split resonator ring can be excited indirectly at this frequency point by using the dipole resonance of the graphene double nanoribbon. At this time, destructive interference occurs between the graphene double nanoribbons and the graphene split resonator ring, thus exciting the plasmon-induced transparency resonance. On the other hand, the transparent window with plasmon-induced transparent resonance is characterized by high sensitivity and quality factor, which can realize high-performance sensing applications. When different gases or liquids are injected above the sensor, due to the different refractive indices of these gases or liquids, the resonant excitation frequency of the sensor in the mid-infrared band will shift, so that these gases or liquids can be detected, and finally Realize the sensing application.

Accompanying drawing 3 is the transmission spectrum of the plasmon-induced transparent _metamaterial sensor under different graphene Fermi levels EF. The typical feature of the plasmon-induced transparency resonance is an asymmetric line shape, that is, the two resonance valleys and the transparent window in the middle in the figure indicate that the typical plasmon-induced transparency resonance is excited. In the transmission spectrum, the narrower the transparent window of the plasmon-induced transparent resonance, the better the excited resonance, so the sharp transparent window in the figure proves that the excellent plasmon-induced transparent resonance is excited. Tuning the Fermi level of graphene by adding a polarization voltage, the intensity of the plasmon-induced transparent resonance increases as the Fermi level of graphene increases from 0.5 eV (0.5 electron volts) to 0.9 eV (0.9 electron volts). , that is, the change of the transmittance at the resonance increases, and the resonance frequency gradually increases with the increase of the Fermi level, moving from 24-26THz to 33-34THz, which further increases the excitation frequency in the mid-infrared band.

Accompanying drawing 4 is when the graphene Fermi energy level is 0.7eV (0.7 electron volts), when the material above the sensor changes, the change of the sensor transmission curve caused by the material refractive index change, when the refractive index n changes from 1 to At 1.4, the position of the transparent window of plasma-induced transparent resonance shifts from 25.1THz to 29.6THz, so the material composition of the gas or liquid to be measured can be judged from the position change of the transparent window.

Claims (3)

1. a kind of plasma-induced transparent metamaterial sensor, it is characterised in that: structure composition is respectively one layer from bottom to top Silicon substrate layer, layer of silicon dioxide dielectric layer are adulterated, top layer is graphene split ring resonator and graphene double nano band structure.

2. a kind of plasma-induced transparent metamaterial sensor according to claim 1, it is characterised in that: doping silicon substrate Bottom thickness h is 30nm, and silica dioxide medium layer thickness d is 30nm.

3. a kind of plasma-induced transparent metamaterial sensor according to claim 1, it is characterised in that: graphene is opened Mouth resonant ring radius length is R=80nm, the gap width G=20nm of split ring resonator, the width W=of split ring resonator 20nm, the length L=80nm of double nano band, width S=20nm of double nano band, the spacing P=30nm between double nano band.