Session D55: Invited Session: Isakson/ Bouchet/ Apker2 Prize Session

Frank Isakson Prize: Coherent Plasmonics

Metallic nanostructures generally give rise to both bright and dark plasmon modes, and through these modes and their interactions can support a variety of coherent phenomena more typically associated with atomic systems. The coupling between superradiant and subradiant plasmons can give rise to Fano resonances and electromagnetically induced transparency, for example. In plasmonic nanostructures, these properties can be systematically controlled through geometry, providing strategies for designing and engineering resonant lineshapes based on these interactions. Fano resonances can also selectively enhance the coupling between coherent optical sources, giving rise to a new class of nonlinear optical media tailored to enhance specific processes such as four-wave mixing and coherent anti-Stokes Raman scattering. Coherent interactions can be extended to the coupling of plasmon resonances to the vibronic states of molecules and extended disordered media. Spontaneous emission rates of molecules can also be manipulated by resonant and near-resonant proximal coherent plasmonic nanostructures.   

Frank Isakson Prize: Quantum Plasmonics and Plexcitonics

Plasmon energies can be tuned across the spectrum by simply changing the geometrical shape of a nanostructure. Plasmons can efficiently capture incident light and focus it to nanometer sized hotspots which can enhance electronic and vibrational excitations in nearby structures. The plasmon energies and induced electric field enhancements can be strongly influenced by quantum mechanical effects such as electron tunneling across narrow junctions and non-local screening of the electromagnetic fields near the surfaces of the nanostructures. Large molecules can exhibit molecular plasmon resonances that exhibit classical-like behavior but have a quantum mechanical origin. The coupling of plasmonic and excitonic systems can lead to hybrid states referred to as ``plexcitons'' which can exhibit quantum mechanical effects and nonlinear optical properties. Another important but still relatively unexplored quantum mechanical property of plasmons, is that they can be efficient sources of hot energetic electrons which can transfer into nearby structures and induce a variety of processes. In the talk, I will discuss various quantum mechanical effects in plasmonic systems and how they can be exploited in applications: such as to induce chemical reactions in molecules physisorbed on a nanoparticle surface; to inject electrons directly into the conduction band of a nearby substrate; to dramatically enhance the light harvesting efficiency of photonic devices; to induce local doping of a nearby graphene sheet; and to induce phase transition in adjacent media.   

Edward A. Bouchet Award: Liquid Crystal Nanocomposites: Bulk and Local Structure Due to the Presence of Nanoparticles

We investigate how liquid crystals order in the presence of diverse nanoparticles. These nanocomposites consisting of liquid crystals and nanoparticles have been studied for their applications in devices, such as photovoltaics and to model biological devices. In particular, we study nanocomposites formed by the smectic phases of calamitic liquid crystals in contact with nanoparticles between 2 and 5 nm in size. We have investigated the structural properties of the liquid crystal both far away from the nanoparticles (in the bulk of the sample) as well as in the vicinity of the nanoparticles. We find that the order of the bulk liquid crystal increases up to a certain weight percent concentration of the nanoparticles. The order is reflected in the current versus voltage curve of the different nanocomposites, but does not fully explain how this charge is transmitted from the liquid crystal to the nanoparticle. The liquid crystal in the immediate vicinity of the nanoparticles is fairly disordered, and the disorder depends on the functionalization of the nanoparticle, or lack of it. This disordered structure seems to reflect the faceting, or the arrangement of the nanoparticle into a faceted structure. Understanding the structure the liquid crystal assumes in the vicinity of the nanoparticles, and how it compares to the bulk structure of the liquid crystals gives us an idea of how electrons, or light are transmitted from the liquid crystal to the nanoparticle and viceversa, and how strong this transmission is. A simple model for the transmission of the electric charge is shown.   

Spinning Photons and Twisting Oscillators

Optomechanics is the study of the interaction between electromagnetic radiation and mechanical motion. A typical optomechanical system involves an optical resonator coupled to a mechanical degree of freedom. Some of the most striking experimental achievements include preparation of macroscopic mechanical oscillators in their quantum ground states, the detection of optomechanical quantum back-action, and generation of optomechanically induced transparency and slow light. Most optomechanical systems rely on linear coupling between the radiation and the displacement of the mechanical oscillator. I will begin this talk instead by discussing the basic quantum mechanics of a generic quadratically coupled optomechanical system. I will also mention our efforts in extending optomechanics to torsional and rotational systems. Specifically, I will describe our theoretical proposal to couple a windmill-shaped dielectric to cavity Laguerre Gaussian modes. Subsequently, I will suggest a method for coupling LG modes to surface acoustic waves on a cavity mirror as a new platform for storage of photons carrying orbital angular momentum. Finally, I will discuss our most recent study of the prospects of cooling full rotational motion to the quantum regime.   

Nanoscale Photon Management for Solar Energy Harvesting

Nanophotonics is an exciting new field of science and technology that is directed towards making the smallest possible structures and devices that can manipulate light. In this presentation, I will start by showing how semiconductor and metallic nanostructures can mold the flow of light in unexpected ways and well below the diffraction limit. I will then continue by illustrating how such nanostructures can be used to enhance our ability to harvest solar energy with solar cells and photoelectrochemical cells for generating solar fuel. In this part of the talk, it will become obvious how very different ways of photon management can be achieved by controlling the size and spacing (wavelength-scale/subwavelength-scale), shape, and spatial arrangement (periodic/aperiodic) of the nanostructures.