摘要
飞秒传输表面等离激元(femtosecond propagating surface plasmon,fs-PSP)的近场成像表征和激发效率的主动控制是实现其应用的先决条件.本文利用光发射电子显微镜对银纳米薄膜上刻蚀的凹槽耦合结构处激发的fs-PSP进行近场成像.并系统测量了入射激光波长在720—900 nm范围内fs-PSP近电场与入射激光场干涉信号的周期和fs-PSP的波长.在此基础上,进一步利用飞秒双光束泵浦-探测实验证实了调节入射激光的偏振方向可实现对fs-PSP激发效率的调控.由实验结果可知,当入射激光偏振接近0°(P偏振)时,fs-PSP的激发效率最高,当入射光偏振接近90°(S偏振)时,fs-PSP的激发效率最低.相较于有限时域差分方法模拟,在飞秒双光束泵浦-探测实验中归一化光发射电子产额随入射激光偏振方向变化的曲线出现平台区,我们把这一现象归因于探测激光的背景噪声淹没了fs-PSP激发效率的变化.该研究为实现fs-PSP激发效率的工程性调控和优化等离激元器件的性能奠定了基础.
Near-field imaging and active control of excitation efficiency of femtosecond propagating surface plasmon(fs-PSP)are the prerequisites for its application.Here,we perform near-field imaging of fs-PSP excited at the trench etched on silver nano-film by using photoemission electron microscopy(PEEM).As an excellent nearfield microscopy technique of in situ imaging with a high spatial resolution(<20 nm),it needs neither molecular reporters nor scanning probes as required in nonlinear fluorescence microscopy in nonlinear fluorescence microscopy or scanning near-field optical microscopy,both of which may potentially bias PSP derived from such measurements.The period of the interference patterns induced by the incident femtosecond laser and the laser-induced fs-PSP and the wavelength of fs-PSP in a range of 720-900 nm of the incident laser wavelength are systematically measured.The fringe period of the interference pattern between fs-PSP and the incident laser is a range of 5.9-7.7μm,and the wavelength of fs-PSP is in a range of 700-879 nm.The experimental results are consistent with the theoretical simulation results.Furthermore,we demonstrate that the excitation efficiency of fs-PSP can be actively controlled by adjusting the polarization direction of the incident laser in the femtosecond pump-probe experiments.Specifically,it is found that when the incident laser is polarized to 0°(p-polarization light),the excitation efficiency of PSP reaches a maximum value,and when the incident light is polarized to 90°(s-polarization light),the excitation efficiency of fs-PSP is the lowest.Unlike the simulation result by the finite difference time domain(FDTD)method,a plateau area of the intensity of the photoemission signal with the polarization direction of the incident laser appears in the femtosecond pump-probe experiment.This phenomenon is attributed to the background noise of the detection laser that masks the change of the fs-PSP excitation efficiency.In a word,this research realizes the experimental measurement of the basic parameters of fs-PSP and the manipulation of fs-PSP excitation efficiency by adjusting the polarization angle of the incident laser.This research lays a foundation for realizing the engineering manipulation of fs-PSP excitation efficiency and optimizing the performance of plasmonic devices.
作者
赵翔宇
秦楡禄
季博宇
郎鹏
宋晓伟
林景全
Zhao Xiang-Yu;Qin Yu-Lu;Ji Bo-Yu;Lang Peng;Song Xiao-Wei;Lin Jing-Quan(School of Science,Changchun University of Science and Technology,Changchun 130022,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第10期253-259,共7页
Acta Physica Sinica
基金
国家自然科学基金(批准号:61775021,91850109,11474040,62005022,12004052)
吉林省教育厅基金(批准号:JJKH20190555KJ)
吉林省科技厅基金(批准号:20200201268JC,20200401052GX)
中国博士后科学基金(批准号:2019M661183)资助的课题.
关键词
光发射电子显微镜
飞秒传输表面等离激元
近场成像
激发效率的调控
photoemission electron microscopy
femtosecond propagating surface plasmon
near-field imaging
regulation of excitation efficiency
