Research On Optical Fiber Sensor Based On Metal Nanoparticles

The nanometer sensing technology has become one of hot researches in near years.This article makes a study on optical fiber sensor with metal nanostructure based on the properties of optical fiber sensing technology and the optical performances of metal nanoparticles.Theoretically,localized surface plasmons resonant(LSPR) and electric filed enhancement are simulated by Discrete Dipole Approximation method.In experiment,metal nanoshperes and metal nanorods are synthesized.With the different fiber structure,such as multimode silica fiber,silica fiber taper,polymer optical fiber(POF) taper,and solid core photonic crystal fiber optical fiber localized LSPR sensor,silica fiber surface enhanced Raman scattering (SERS) taper probe,POF SERS taper probe,and broad spectral PCF SERS sensor,are developed respectively.The main research works and conclusions are as following:1.Localized surface plasmons(LSPs) on metal nanospheres are simulated by the discrete dipole approximation(DDA) method.In the optical fiber LSPR sensor, substrate-nanaoparticle interaction and nanoparticle-nanoparticle interaction are considered.With chemical self assembly method,an optical fiber LSPR sensor is developed.The sensing sensitivity reaches 99+4nm/RIU by measuring the response of refractive index on environment dielectric.The experiment result indicates that the sensitivity of this sensor is influenced by fiber substrate and nanoparticles aggregation.2.The silica fiber SERS taper probe is prepared with fused taper method and self assembly way.The 4-MBA molecule with 10^-6M concentration is measured with this sensor.The 4-MBA molecule SERS spectrum is achieved successfully.To improve the flexibility of fiber SERS probe for application,a novelty polymer optical fiber SERS probe is presented based on gold nanorods.The transverse and longitudinal LSPs of gold nanorods are researched on electrnic field enhanment. To substitute the traditional fiber SERS configuration with TERS configuration, the background of POF self Raman scattering is avoided effectively,and an enhancement factor with 10⁹ is obtained in the R6G molecule SERS experiment. 3.The broad spectral solid core photonic crystal fiber SERS sensor is developed.In theory,except for evanescent wave mechanism,the leakage mode mechanism is presented in SERS exciting and collecting process in this sensor structure.In experiment,with the excitation of visible light 514.5nm and near infrared light 785nm respectively,the SERS spectrum of the 4-MBA molecule with 10^-6M is demonstrated,thus the broad spectral SERS property is validated.The result shows that the performance of this broad spectral PCF SERS sensor is dependent on the LSPR intensity of silver nanoparticles cluster,the SERS exciting and collecting efficiency of solid core PCF,and the self Raman scattering cross section of analyte molecule.Highlights of the dissertation are as following:1.A novelty polymer optical fiber SERS probe based on gold nanorods is presented. To substitute the traditional fiber SERS configuration with TERS configuration, the background of POF self Raman scattering is avoided effectively,and An SERS enhancement factor with 10⁹ is obtained.2.A new broad spectral solid core photonic crystal fiber SERS sensor is developed. In theory,the leakage mode mechanism is presented in SERS exciting and collecting process.The broad spectral SERS property is validated by the demonstration of SERS experiment in visible light 514.5nm and near infrared light 785nm.The important factors in the influence of the performance of this broad spectral PCF SERS sensor are analyzed.