• 3D Nanophotonic device fabrication using discrete components

      Melzer, Jeffrey E.; McLeod, Euan; Univ Arizona, Coll Opt Sci; Univ Arizona, Dept Biomed Engn (WALTER DE GRUYTER GMBH, 2020-06-06)
      Three-dimensional structure fabrication using discrete building blocks provides a versatile pathway for the creation of complex nanophotonic devices. The processing of individual components can generally support high-resolution, multiple-material, and variegated structures that are not achievable in a single step using top-down or hybrid methods. In addition, these methods are additive in nature, using minimal reagent quantities and producing little to no material waste. In this article, we review the most promising technologies that build structures using the placement of discrete components, focusing on laser-induced transfer, light-directed assembly, and inkjet printing. We discuss the underlying principles and most recent advances for each technique, as well as existing and future applications. These methods serve as adaptable platforms for the next generation of functional three-dimensional nanophotonic structures.
    • Directing Cherenkov photons with spatial nonlocality

      Hu, Hao; Gao, Dongliang; Lin, Xiao; Hou, Songyan; Zhang, Baile; Wang, Qi Jie; Luo, Yu; Univ Arizona, James C Wyant Coll Opt Sci (WALTER DE GRUYTER GMBH, 2020-09)
      Cherenkov radiation in natural transparent materials is generally forward-propagating, owing to the positive group index of radiation modes. While negative-index metamaterials enable reversed Cherenkov radiation, the forward photon emission from a swift charged particle is prohibited. In this work, we theoretically investigate emission behaviours of a swift charged particle in the nanometallic layered structure. Our results show that Cherenkov photons are significantly enhanced by longitudinal plasmon modes resulting from the spatial nonlocality in metamaterials. More importantly, longitudinal Cherenkov photons can be directed either forward or backward, stringently depending on the particle velocity. The enhanced flexibility to route Cherenkov photons holds promise for many practical applications of Cherenkov radiation, such as novel free-electron radiation sources and new types of Cherenkov detectors.
    • Second harmonic generation in metasurfaces with multipole resonant coupling

      Han, Aoxue; Dineen, Colm; Babicheva, Viktoriia E.; Moloney, Jerome; Univ Arizona, Coll Opt Sci; Univ Arizona, Dept Math (WALTER DE GRUYTER GMBH, 2020-09)
      We report on the numerical demonstration of enhanced second harmonic generation (SHG) originating from collective resonances in plasmonic nanoparticle arrays. The nonlinear optical response of the metal nanoparticles is modeled by employing a hydrodynamic nonlinear Drude model implemented into Finite-Difference Time-Domain (FDTD) simulations, and effective polarizabilities of nanoparticle multipoles in the lattice are analytically calculated at the fundamental wavelength by using a coupled dipole-quadrupole approximation. Excitation of narrow collective resonances in nanoparticle arrays with electric quadrupole (EQ) and magnetic dipole (MD) resonant coupling leads to strong linear resonance enhancement. In this work, we analyze SHG in the vicinity of the lattice resonance corresponding to different nanoparticle multipoles and explore SHG efficiency by varying the lattice periods. Coupling of electric quadrupole and magnetic dipole in the nanoparticle lattice indicates symmetry breaking and the possibility of enhanced SHG under these conditions. By varying the structure parameters, we can change the strength of electric dipole (ED), EQ, and MD polarizabilities, which can be used to control the linewidth and magnitude of SHG emission in plasmonic lattices. Engineering of lattice resonances and associated magnetic dipole resonant excitations can be used for spectrally narrow nonlinear response as the SHG can be enhanced and controlled by higher multipole excitations and their lattice resonances. We show that both ED and EQ-MD lattice coupling contribute to SHG, but the presence of strong EQMD coupling is important for spectrally narrow SHG and, in our structure, excitation of narrow higher-order multipole lattice resonances results in five times enhancement.