Design And Research Of Plasmonic Nanosensor

Plasmonic sensing was named one of the top 10 emerging technologies of 2018 by Scientific American.Plasmonic sensors have been widely used for refractive index measurement in chemical,biomedical and food processing industries.SPPs can overcome the diffraction limit of light and control light in the sub-wavelength structure.With the continuous development of nano-processing technology,it has important advantages in replacing traditional optoelectronic devices to realize micro-nano optical devices and highly integrated photonic circuits.Among them,sensing has been identified as one of the most promising applications of SPPs.Due to the special distribution of the resonant field,the plasmonic sensor has high sensitivity to the change of refractive index in the environment,and the quality factor(FOM)is the most important parameter to evaluate the performance of the sensor.At the same time,the sensitivity and sensing performance of the plasmonic sensor depend on the material and structure of the sensor.Based on this,the main work and innovation of this paper are as follows:1.The research background,research significance,research status and many applications of SPPs are introduced.Then its applications in micro-nano optical devices such as nanosensors,optical switches and filters are introduced in detail.Based on the periodic staggered double-side trapezoidal plasmonic structure,a high-performance band-stop filter with ultra-wide bandwidth and good tunability is designed creatively in this paper.Finally,the main research methods of plasmononic nanosensors based on Fano resonance and the research progress at home and abroad are introduced.2.The basic concept and physical model of SPPs are introduced.The dispersion relation of SPPs on metal-dielectric interface and in metal-dielectric-metal waveguide(MIM)is derived by Maxwell equations,and the conditions for producing SPPs are obtained.Then it focuses on the Drude model used in this paper,and also introduces the finite element method(FEM)and the simulation software COMSOL Multiphysics.And taking the MIM waveguide structure as an example,the numerical simulation process is introduced.Finally,the coupled mode(CMT)formulas of two commonly used examples are given.3.The transmission response of the coupling structure between stub cavity and micro-ring cavity is studied by CMT and FEM.The innovation is mainly reflected in two aspects.On the one hand,the physical explanation is detailed,and the simulation results are highly consistent with the theoretical results.Specifically,the proposed CMT model can well fit the Fano resonance and EIT-like effect.According to the standing wave theory,the dispersion model of the TM mode and the Drude model of the metal,the order of the high-order resonance modes in the micro-ring cavity is derived,which is consistent with the numerical simulation results.On the other hand,the complex plasmonic structure proposed at last as a refractive index sensor has a high sensitivity of 1600nm/RIU and an ultra-high FOM value of 1.2 × 106,which is better than most related studies[15,16,22,28-30,55,61,63,64,67,70,93,94,109,111,119].In addition,the maximum group delay and group index of the system are 1.49ps and 221,respectively,which are better than the related researches[29,54'57,119].It has a good application prospect of on-chip slow-light devices.It is worth mentioning that it can also be designed as an optical switch with a high extinction ratio of about 43 dB,which is better than the related research[16,59,110].4.A simple plasmonic structure of MIM waveguide with metal baffle coupled with triangular cavity is proposed.The innovation is mainly reflected in three aspects.To begin with,the structure has independent tunability and flexible expansibility,which is shown as follows:the triple Fano resonance in the system can be tuned independently by adjusting the structural parameters to make the design more flexible;through the introduction of ring resonator,the structure can be easily extended to a quintuple Fano system.Next,the structure can be designed as a high-performance nanosensor with good sensitivity of 1200nm/RIU and ultra-high FOM of 3.0×106,which is obviously better than the current researches[15,16,22,28-30,55,61,63,64,67,70,93.94,95,109,111,119-122].Finally,the simulation results are consistent with the theoretical results.On the one hand,the proposed multimode interference coupled mode theory(MICMT)model can well fit the generated Fano resonance.On the other hand,the resonance order is calculated according to the standing wave theory,which is consistent with the simulation results.To sum up,two new types of plasmonic nanosensors are designed in this paper,and their FOM is up to 106 orders of magnitude,which is about an order of magnitude higher than the current research level,and the simulation results are the same as those deduced by CMT,MICMT and standing wave theory.Therefore,the research results of this paper provide a theoretical basis for the design of high-performance plasmonic sensors,and have a certain reference value for the design and research of micro-nano optical devices,and also have positive significance for the realization of highly integrated photonic circuits.