Multi-spectral plasmon induced transparency based on three-dimensional metamaterials

We theoretically and numerically demonstrate multi-spectral plasmon induced transparency (PIT) in three-dimensional metamaterials comprising of parallel nanorods and a vertical nanorod. By moving the vertical middle nanorod to break the structural symmetry, the structure presents single-spectral or dual-spectral PIT windows, while it exhibits multi-spectral PIT windows at the laser wavelengths with He-Ne, ruby Cr3+ and Kr, via moving the bottom nanorod. The quasi-static interaction model reveals that the near-field coupling strength between nanorods increases with the movement of the nanorod. The coupling strength between nanorods is enhanced, which makes vertical middle nanorod support dipole and quadrupole modes and further results in multi-spectral PIT by bright-dark mode coupling. This work provides a way to obtain multi-spectral PIT in an easily fabricable nanostructure, and it may achieve potential applications in a variety of fields including filters, sensing, and some other nanoplasmonic functional devices.