Plasmonic Optical Fiber Perfect Absorber Of And Its Sensing Characteristics

Plasmonic nano-arrays is a kind of periodic nanostructure,which is formed using patterned metal or dielectric films made by nanofabrication technology.By designing the shape,size,period and material of array,plasmonic nano-arrays irradiated by incident light can excited various coupling optical phenomena.In these optical phenomena,some can enhance the interaction between light and matter,some can reduce the radiation loss.All of these have a significant improment for localized surface plasmon resonance(LSPR)sensors with high radiation loss and low absorptivity.Thus,in this thesis,optical fiber sensor based on surface lattice resonance(SLR)and perfect absorber is studied and the sensing structure is plasmonic nano-arrays.Finally,the optical fiber sensor with ultra-narrow linewidth and perfect absorption is achievement.(1)The current researches of sensors based on plasmonic nano-arrays or metal-insulatormetal(MIM)perfect absorber are summarized.Aiming at the problems of wide resonance spectrum and low absorptivity of LSPR,the idea of perfect absorber of SLR is proposed.(2)The basic principle and spectral linewidth of LSPR and SLR are analyzed by coupled dipole approximation(CDA)and finite element method(FEM).Then,finite element simulation model is established and the feasibility of FEM is proved by comparison between CDA and FEM.Meanwhile,the principles of perfect absorbion based on films and arrays are analyzed respectively.(3)The numerical model of Au-triangle array is established by FEM and the influences of PS diameter and thichness of Au film on absorption spectrum and sensing performances are analyzed.So the figure of merit is up to 125.71(the corresponding sensitivity is 440 nm/RIU with 3.5 nm of FWHM).(4)The numerical model of crescent nano-array is established by FEM and the influences of every parameter on absorption spectrum and sensing performance are analyzed.Futher,the coupled principles of two kinds of SLR are clarified by electric and charge distribution of nanostructure.Finally,the sensing structure with high FOM is achieved.The results show that crescent nano-array proposed in this thesis excite two coupled situation(coincidence coupling and non-coincidence coupling),which is different from traditional SLR.In the case of coincidence coupling,the FOM is 125(the sensitivity is 1000 nm/RIU and the FWHM is 8 nm);in the case of non-coincidence coupling,the FOM is 803.57 which is 400 times higher than traditional LSPR sensor(the sensitivity is 562.5 nm/RIU with 0.7 nm of FWHM).(5)First,optical fiber perfect absorber based on MIM nanohole array is established and the pseudo perfect absorption in reflectivity sense is achieved.Second,the sensing characteristic of coexistence of ultra-narrow linewidth and perfect absorption is achieved by establishing MIM crescent nano-array.Meanwhile,the characteristic electric and loss of LSPR and SLR are analyzed by electric and total power loss intensity distribution.The results show that the highest FOM is 86.67 with 12 nm of FWHM when the absorptivity is above 0.9;the highest FOM is 104 with 10 nm of FWHM when the absorptivity is above 0.8;the highest FOM is 114.44 with 9 nm of FWHM when the absorptivity is above 0.7.In general,FWHM can be controlled to about 10 nm in the case of near perfect absorption.In this thesis,the principle of perfect absorber of SLR,the numerical simulation and the analysis of sensing characteristics are studied on the basis of summarizing the application status in sensing field of plasmonic nano-arrays and perfect absorber.Finally,the high resolution optical fiber sensor with coexistence of ultra-narrow linewidth and perfect absorption is achieved.And this research will provide an idea for improving the performance of LSPR.