| Entering the 5G era,everything is connected and communication technology is developing rapidly.With the development of microelectronics processing,the optoelectronics integration technology represented by silicon-based optoelectronics has made great progress.The application of integrated photonic devices in transportation is also very extensive,the temperature sensor is used in vehicle transportation to detect the temperature of the vehicle engine,and the biosensor measuring the human body can monitor the driver’s physical condition in real time to avoid the occurrence of dangerous situations.In transportation,it is not limited to the monitoring of drivers and cars,ethanol concentration sensors can also help traffic police check the occurrence of drunk driving and other behaviors.In order to develop more integrated,lower power consumption,faster processing speed of optoelectronic devices,researchers have put forward a number of approaches,of which surface plasmon polaritons plays a very important role.Surface plasmon polaritons（SPPs）are a kind of hybrid excited state formed by the coupling of free electrons and photons localized on the metal surface.Since SPPs can break the diffraction limit of conventional optics and have the ability to confine the light field energy to the nanometer scale range,they have great potential for applications in silicon-based optoelectronics integration technology,integrated optics and devices.Among them,metal-insulator-metal（MIM）waveguide structures are gradually becoming important structures for transmission and control of SPPs due to their structural simplicity,high reliability,and subwavelength size magnitude,and are being studied by scholars at home and abroad.In this paper,three micro-nano refractive index sensor structures are designed,the Fano resonance generated in the structures is investigated,and the influence of structural geometric parameters on the sensing performance is explored.The designed structures were also applied to biosensing and temperature sensing,and good transmission characteristics were obtained.The details of the study are as follows.1.A refractive index sensing structure coupled by a MIM waveguide with two symmetric rectangular stubs and a connected concentric double-ring resonant cavity is designed.The maximum sensitivity of the refractive index sensor is 2260 nm/RIU and the figure of merit（FOM）is 56.5.The mechanism of Fano resonance generation in the system is analyzed,and the influence of the structure geometric parameters on the sensing performance is also investigated.In addition,the designed structure was used for ethanol-filled temperature sensor with a sensitivity of 1.48 nm/°C.2.A refractive index sensor structure consisting of a MIM waveguide with a short rectangular bar coupled to a bearing circular resonant cavity is proposed.Numerical analysis based on finite element analysis was carried out.The Fano resonance effect and sensing performance of different derived structures are compared.The effects of each geometrical parameter of the structure on the sensing performance were investigated.It is shown that different geometrical parameters have different effects on the wavelength and linearity of the Fano resonance.The maximum sensitivity of the refractive index sensor was 3220 nm/RIU and the FOM was 57.5.The sensitivities were 0.542 nm/mgd L-1,0.688 nm/mgd L-1,and 7.081nm/mgd L-1 for the detection of electrolytes（sodium and potassium ions）and glucose concentrations in human blood samples,respectively.3.A tunable nano refractive index sensor structure was designed,which consists of a metal-dielectric-metal waveguide coupled to a protractor semi-annular cavity with the MIM waveguide cut off in the middle by a metal baffle.Numerical analysis was carried out using multimode interference coupled mode theory and the finite element method.Four asymmetric Fano resonance peaks were found in the transmission spectra of the structure,and the effect of the structure geometry parameters on the four resonance peaks was investigated.It was found that the tuning of the resonance peaks could be achieved by adjusting the parameters.The maximum sensitivities were 2.45 nm/g L-1,3.00 nm/g L-1and 3.05 nm/g L-1 for the detection of hemoglobin concentration for type A,type B and type O blood,respectively,and 1.1 nm/°C for the detection of PDMS temperature.In summary,the three structures designed in this paper provide a new cavity choice for the research and application of medical detection,temperature sensing,transportation and other fields. |
