Research On The Influence Of Ultrafast Laser Pulse Parameters On The Characteristics Of Plasmon Excitons

Ultrafast plasmons on the metallic nanostructure excited by ultrafast laser pulse is of importance for applications such as opto-logic devices,ultrafast opto-modulation device,ultrafast electron source and coherent X-ray generations due to the ultrafast response velocity,ultrahigh spatiotemporal localization and strong field enhancement.The modulation of spatial and intensity of localized surface plasmonic localized spots on the nanostructure mainly affects the characteristics and perspective for plasmonic device.As a result,coherent control of surface plasmons is becoming one of the hottest topics on the research of nanophotonics.Asymmetric nanostructure is paid more and more attention due to its ability for supporting surface plasmon multi-resonant modes with great degrees of freedom for all optical modulation among all the sorts of metallic nanostructure.Asymmetric gold nanocross excited with ultrafast laser pulse is employed for revealing the characteristics of surface plasmon dynamics in this thesis,and the coherent control of near field dynamics in the nanostructure is achieved via a variety of methods.The main part of this thesis is as follow:1.The influence of wavelength and polarization of ultrafast pulse on the characteristic of collective oscillation of surface plasmon is revealed in the asymmetric gold nano-cross.Two plasmonic resonant modes is supported by asymmetric gold nano-cross with different resonant wavelength and spatial distribution,moreover,the spatial and near field enhancement can be modulated by tuning the incident wavelength.The response of near field oscillation can also be modulated by rotating the polarization of incident laser pulse.2.The influence of carrier envelope phase of ultrashort laser pulse on the localized field dynamics is revealed in the asymmetric gold nano-cross.The temporal evolution of localized field from plasmonic hot spot is simulated with tuning the carrier envelope phase of ultrashort pulse asymmetric gold nano-cross.Under the irradiation of two laser pulses,the dynamics and enhancement factor of near field is coherently controlled with tuning the difference of carrier envelope phase between the two incident laser pulses.The maximum near field amplitude is achieved with zero difference of carrier envelope phase between two laser pulse.3.The coherent control of dynamics of near field is revealed in the nanostructure with chirped laser pulse.Two plasmonic resonant modes can be simultaneously excited with Fourier transform limited broadband laser pulse.Sequent excitation of these two plasmonic modes can be achieved with chirped laser pulses.The delay and sequence of two plasmonic modes can be controlled by tuning the amount and sign of chirp of incident laser pulse,which can be employed for actively controlling the near field dynamics at arbitrary spatial and temporal region.4.The influence of pulse chirp is revealed on the multiphoton photoelectron yield.The introduction of chirp could affect the near field dynamics of nanostructure.The center wavelength and chirp of laser pulse are tuning for revealing the influence of these with multiphoton photoemission yield.The conclusion of these parameters with laser with photoemission yield is summarized.These results provide the new methodology for actively controlling the dynamics response of near field from nanostructure,which is of great importance for expanding the regime and perspective of applications based on surface plasmons.