Strong cooperative effects between plasmonic nanoantennas mediated by whispering gallery modes of wavelength-scale dielectric resonators

Abstract

Here we theoretically investigate the cooperative effects between plasmonic nanoantennas mediated by whispering gallery modes (WGMs) of wavelength-scale dielectric resonators. Strong constructive cooperative effects can be obtained which lead to significantly enhanced optical responses of the antennas. This is represented by the enhanced absorption peaks or the broadened spectra of the antennas. An important feature in producing the strong cooperative effects is that the energies transfer constructively or destructively from different antennas to a WGM first. This requires the simultaneous excitation of the plasmonic modes of the antennas by a source. Otherwise, the cooperative effect between the antennas becomes much weaker. The spectral behaviors related to the cooperative effects are also highly dependent on the relative spectral overlapping between the antennas and WGM, the antenna-WGM coupling strength and the number of antennas. Specifically, the integrated absorption of each antenna in a four-antenna case can be about 4 times larger than that of the one-antenna case. The enhanced optical responses of the plasmonic antennas are important for enhancing light-matter interactions.