Near-Field-Mediated Photon–Electron Interactions by Nahid Talebi

Author:Nahid Talebi
Language: eng
Format: epub
ISBN: 9783030338169
Publisher: Springer International Publishing

However, this situation changes drastically when the gold fibre has a larger radius, which increases the effective “interaction length”. In Fig. 6.8, the calculated MREELS map is shown for a fibre of radius R = 400 nm. Somewhat surprisingly, it is the radiative modes—characterized by , where is the vacuum wavenumber of light—that dominate the total EELS signal. Significant contributions due to the bulk plasmon are observed again for energies above 2.0 eV, and the evanescent contributions (for ) are negligible in comparison, with only faint hints of fibre eigenmode resonances for lower values of . The EEL spectra for individual angular momentum orders, as shown in Fig. 6.8, elucidate the physics behind the experimentally observed resonances in the EEL spectra. In fact, the radiative part of the EEL spectra at each momentum contribution exhibits a clear peak versus energy, the position of which depends on m. The spectral width of these resonances of a few hundred meV is well in accord with that of the experimentally observed resonances. Consequently, for such larger radii, the EELS signal is mostly influenced by the spatial phase matching along the electron trajectory and much less by resonances due to excitation of fiber eigenmodes.

Fig. 6.8Interaction of a swift electron with a 400 nm infinitely long gold fibre. a Calculated MREELS maps versus the linear momentum along the axis of a gold fibre. b Summed over all the angular momentum contributions. c For the individual excited angular momentum orders m = 0 to m = 8. The straight dashed lines indicate the light line . The colour scale was normalized individually for each panel

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