Study On Gold Nanoparticles Enhanced Dye Random Laser

Enhanced random laser,based on metal nano-structures,has important research significance based on its unique properties and potential application values,leading many potentials in surface enhanced fluorescence,optical switching devices,surface plasmon laser and other areas.A fast and effective method for the preparation of nanoparticles was proposed in the thesis,and the random laser phenomena and rules in the coating of dye-doped polymer films based on the structure of the nanoparticles were analyzed.The Au nanoparticles with different size distribution and spectral characteristics were obtained by metal sputtering deposition and high temperature heat treatment.The lasing system was constructed by coating PMMA polymer film doped with organic fluorescent dye DCJTB to obtain the random laser under the excited beams.Then the change rule characteristics of the light intensity and threshold were both studied.The main contents of the following three parts were included in this thesis:?.Different Au nanoparticles with regular shapes and adjustable sizes on quartz were prepared by ion sputtering deposition and high temperature heat treatment.The morphology and spectral properties of different nanoparticles were characterized by scanning electron microscopy(SEM),particle size statistics and spectral analysis.The method used here is very convenient and high efficiency.?.The influence of experimental conditions on Au nanoparticles was explored.By changing sputtering time,annealing temperature and annealing time,the size and morphology of Au nanoparticles were changed controllably.With longer the sputtering time,we obtained much thicker Au films,and larger size of gold nanoparticles after heat treatment.The critical heat treatment temperature to form regular Au nanoparticles is about 550 ?.The proper time of high temperature heat treatment should be controlled within 40min-1.5h as far as possible.?.The influence of Au nanoparticles with different morphologies on the laser results was studied by coating dye-doped polymer film onto Au nanoparticles which generate a photo-induced laser system.When the size of the Au nanoparticles is larger and the shape of Au nanoparticles is more uniform,strong photon scattering effect will occur to enhance the generation of lasing.While the absorption peak of Au nanoparticles is exactly matched with the fluorescence peak of the dye,the fluorescence efficiency of the dye will be significantly enhanced.At this condition,more dye molecules will be stimulated to undergo energy level transition,and the photon state density will be increased,leading to a lasing phenomenon with higher peak value and lower threshold.The laser can be obtained by exiting repeatedly when the pumping light does not destroy dye molecules.Although the luminous efficiency of the dye molecules decreases slightly with repeated excitation,it still plays an important role in the research and random laser devices development for multi-exciting of random lasing.The experimental results are good to match the theoretical analysis,which indicates that the random laser emission coming from scattering of Au nanoparticles to photons and plasmon resonance enhancement to light absorption.The strong scattering of Au nanostructures on photons is taken as the gain,and the random laser is obtained through theoretical analysis and experimental measurement.This study could provide a convenient technical method for a random laser with high efficiency and low threshold,and is expected to promote the development and application of random laser devices.