Accurately capturing the spatiotemporal information of surface plasmon polaritons (SPPs) is the basis for expanding SPPs applications. We record time-resolved nonlinear photoemission electron microscopy (TR-PEEM) images of weakly excited femtosecond SPPs launched from a rectangular trench milled into a flat silver film. Experimental results show that the overall photoelectron yield is greatly enhanced (typically 6-fold enhancement with the comparison of that without 400nm pulse) in this configuration. The spatiotemporal evolution of SPP can be easily investigated with its carrier wavelength, group velocityand phase velocity. The improvement of photoemission yield is interpreted by the quantum pathway for two-color with changing the nonlinear for photoemission. It is found that the contrast between bright and dark fringes of SPPs is significantly improved compared to the single-color scheme due to the improvement of quantum pathway channels for photoemission. These findings complete the underlying physics of two-color PEEM optimized SPP spatiotemporal imaging.
The remote excitation based on the propagating surface plasmons (PSP) is becoming increasingly extensive. Here, we study the dynamics of the localized surface plasmons (LSP) remotely excited by PSP on the gold film using the finitedifference time-domain numerical simulations method. The results show that the spectra of LSP excited by PSP change along with its excitation location, showing a unique phenomenon that the spectra exhibit a redshift tendency compared to the LSP excited by the traditional laser source. By comparing with the dynamics of LSP excited by a laser source, the unique near-field characteristics of that excited by PSP can be obtained. Furthermore, we find that the dephasing time of LSP excited by the PSP is longer than by the traditional laser source. We believe the results of this study can be used to improve the efficiency of remote catalytic reactions and provide new ways to prolong the dephasing time.
Accurately grasping and controlling the plasmon dynamics and dephasing time is a prerequisite for the application of plasmons. Here, we report on the investigation of dynamics and dephasing time of different plasmonic hot spots in a single bowtie structure under varied light polarization using time-resolved photoemission electron microscopy (PEEM). In contrast to those previous global-parameter descriptions, we here report the experimental observation of apparently spatially diverse plasmon dynamic characteristics and spatially different dephasing time within a plasmonic bowtie. We experimentally obtain different plasmon dynamics in the tips of the bowtie nanostructure with different light polarization and actively control dephasing time by changing the light polarization which transforms the plasmon mode. Experimental results got the minimum dephasing time of 8.5fs and the maximum dephasing time of 17fs, which has a large adjustment range. In addition, we found that structural defects can prolong the dephasing time, and we analyzed its role in the influence of plasmon dynamics and dephasing time.
The plasmon effect is of great significance for photoemission in metallic nanostructure. We introduced the photoemission electron microscope (PEEM) in detail, and used it to study the effects of polarization on the far-field and near-field of the plasmon. We further investigate the photoelectron energy spectrum obtained by PEEM and demonstrated the spatial distribution of photoelectrons with different energies. These experimental results help us to further understand the mechanism of photoemission and laid the foundation for the future development of plasmon device and technology.
The precise understanding of the spatiotemporal characteristics of ultrafast surface plasmons is a prerequisite for applications of plasmonics. Here, we report on the investigation of near-field imaging and dynamics of propagating and localized surface plasmons (PSPs and LSPs) using photoemission electron microscopy (PEEM) of the trench on the silver film and gold bowtie nanostructure. The actual propagation direction of PSPs is directly obtained by reading PEEM images via the non-collinear exciting method by the trench. The results have demonstrated that the trench structure is potential as a 2D plasmonic dispersion element. Moreover, we experimentally obtain different LSPs dephasing times in the tips of the bowtie nanostructure by interferometric time-resolved PEEM. Experimental result reveals the dynamics of the LSP field initially oscillate at the laser field frequency and finally develop into its eigenfrequency after experiencing a few periods of frequency fluctuation.
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