Abstract
The application of atto-second streaking spectroscopy (ASS) to direct time-domain studies of the plasmonic excitations in metallic nano-objects is addressed theoretically. The streaking spectrograms for a rectangular gold nano-antenna and spherical gold clusters are obtained within strong field approximation using classical electron trajectory calculations. The results reported here for spherical clusters are also representative of spherical nano-shells. This study demonstrates that ASS allows for detailed characterization of plasmonic modes, including near-field enhancement, frequency and decay rate. The role of the inhomogeneity of the induced electric fields is also demonstrated.
Highlights
The application of atto-second streaking spectroscopy (ASS) to direct time-domain studies of the plasmonic excitations in metallic nanoobjects is addressed theoretically
We show that the external IR field enhancement near the nano-object reveals itself in a large amplitude of the streaking oscillations
With examples of a gold rectangular nano-antenna and spherical gold clusters we have shown that ASS allows direct observation of the time evolution of the induced field, and allows a rather complete characterization of the plasmonic mode excited by the external IR field
Summary
The ‘streaking camera’ scheme was invented for the investigation of the reaction of atoms on the atto-second pulse and for the control of the characteristics of this pulse [40]. Averaging the result of computations with equation (6) over the energy distribution of the emitted electrons, one obtains the streaking spectrogram for the free-atom case shown in figure 1. The energy sampling is performed with the distribution function given by equation (7), where the effective spectral width δ is computed not with the field of the incident IR pulse FL(td), but with the total electric field FIR(r0, td) at the point and the moment of the electron emission. When the spectrum of the incident IR pulse overlaps the nano-particle plasmon, the latter can be efficiently excited, leading to a strong near-field enhancement In this case, FIR(r, t) is dominated by the induced plasmonic field which reveals itself in the streaking spectrograms. Our study shows that ASS offers a time-domain insight into plasmonic dynamics
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