Opto-Electronic Advances, 2019, 2 (4): 180030, Published Online: Apr. 28, 2019
Revealing the plasmon coupling in gold nanochains directly from the near field
Abstract
We studied the near-field properties of localized surface plasmon resonances in finite linear gold nanochains using photoemission electron microscopy (PEEM). The localization of the electromagnetic field in the near-field region was mapped at high spatial resolution. By tuning the excitation laser wavelength, we can obtain the near-field spectra, from which the energy splitting between longitudinal (L) and transverse (T) plasmon modes can be revealed. In particular, the L-mode red shifts and the T-mode blue shifts with increasing chain length. The red shift of the L-mode is highly dependent on the gap distance. In contrast, the T-mode almost remains constant within the range of gap distance we investigated. This energy splitting between the L-mode and the T-mode of metallic chains is in agreement with previous far-field measurements, where it was explained by dipole-dipole near-field coupling. Here, we provide direct proof of this near-field plasmon coupling in nanochains via the above-described near-field measurements using PEEM. In addition, we explore the energy transport along the gold nanochains under excitation at oblique illumination via PEEM measurements together with numerical simulations.
Quan Sun, Han Yu, Kosei Ueno, Shuai Zu, Yasutaka Matsuo, Hiroaki Misawa. Revealing the plasmon coupling in gold nanochains directly from the near field[J]. Opto-Electronic Advances, 2019, 2(4): 180030.