Surface Plasmon Resonance Manipulated Upconversion Luminescence Of Single Rare Earth Doped Nanocrystal And Fano Resonance

The upconversion nanocrystal can generate high-energy upconversion luminescence when excited by low-energy excitation light.Compared with fluorescence emitted by quantum dots and fluorescent dyes,upconversion light emission has many advantages,such as multi-colored fluorescence and narrow line width,good photochemical stability,long fluorescence lifetime,and low toxicity.Therefore,upconversion nanomaterials can be applied in fluorescence imaging,biosensing,display technology,and solid state lighting.However,the efficiency of upconversion luminescence is usually limited.Surface plasmon resonance is an effective method to improve the upconversion efficiency.In addition,the polarization modification of the upconversion luminescence has great potential in applications and has shown significance in multi-information transmission,polarization-based 3D display,and high-resolution imaging technology.Besides generating the surface plasmon resonance,plasmonic nanostructures can produce Fano resonance that displays a sharp spectral line.It is highly sensitive to changes in plasmonic structure and environment,and can be applied to biosensor filters and nonlinear optical devices.In this dissertation,we first studied the upconversion enhancement and polarization modification of single NaYF4:Yb3+,Er3+ upconversion nanocrystals with rectangular slot nanoantenna arrays.The upconversion luminescence spectrum and its polarization state were measured by a scanning confocal microscope system.The innovation can be exhibited in two ways:firstly,the localized surface plasmon resonance enhances the fluorescence intensity of single NaYF4:Yb3+ and Er3+nanoparticles by 29 times when the polarization direction of the excitation light is perpendicular to the long axis of the rectangular slot.The power density dependence of the upconversion luminescence and the time-resolved lifetime measurement results indicate that the enhancement of the local field enhances the absorption of the excitation light and increases the quantum field.Secondly,the emission polarization sensitivity of the upconversion at 660 nm reached 80%when the nanocrystal was excited by a vertically polarized incident light,showing the linear polarization of high quality.Theoretical simulations well verify the experimental results.The dissertation also introduces the simulation of Au-Ag nanorods heterodimer Fano resonance.By altering the length of the gold or silver nanorods,the spacing between them and the surrounding environment,we measured the variation of the Fano resonance dip.