Muralidhar Ambati

Observation of Stimulated Emission of Surface Plasmon Polaritons

We report a direct experimental evidence of stimulated emission of surface plasmon polaritons (SPPs) at telecom wavelengths (1532 nm) with erbium doped glass as a gain medium. We observe an increase in the propagation length of signal surface plasmons when erbium ions are excited optically using pump SPP. The design, fabrication, and characterization of SPP waveguides, thin gold metal strips, embedded in erbium (Er) doped phosphate glass is presented. Such systems can be suitable as integrated devices coupling electronic and photonic data transmissions as well as SPP amplifiers and SPP lasers.

Surface Plasmon Amplification in Planar Metal Films

The propagation and amplification of surface plasmon polaritons (SPPs) is studied at the interfaces between metals and active media. A permittivity renormalization technique is proposed and developed to obtain an explicit analytic expression for the critical gain required to achieve infinite SPP propagation length. A specific multiple quantum-well (MQW) system is identified as a prospective medium for demonstrating efficient SPP amplification at telecommunication frequencies. The proposed system may have a strong impact on a variety of photonic devices ranging from plasmonic nanocircuits, subwavelength transmission lines and plasmonic cavities to nanosized transducers.

Active Plasmonics: Surface Plasmon Interaction With Optical Emitters

The interaction between surface plasmons and optical emitters is fundamentally important for engineering applications, especially surface plasmon amplification and controlled spontaneous emission. We investigate these phenomena in an active planar metal-film system comprising InGaN/GaN quantum wells and a silver film. First, we present a detailed study of the propagation and amplification of surface plasmon polaritons (SPPs) at visible frequencies. In doing so, we propose a multiple quantum well structure and present quantum well gain coefficient calculations accounting for SPP polarization, line broadening due to exciton damping, and particularly, the effects of finite temperature. Second, we show that the emission of an optical emitter into various channels (surface plasmons, lossy surface waves, and free radiation) can be precisely controlled by strategically positioning the emitters. Together, these could provide a range of photonic devices (for example, surface plasmon amplifiers, nanolasers, nanoemitters, plasmonic cavities) and a foundation for the study of cavity quantum electrodynamics associated with surface plasmons.

Determination of effective properties and effective thickness of resonant acoustic metamaterial

Multiple scattering in periodic structures with strong modulation of elastic constants leads to phononic band structures. According to the Bragg’s theory, the spatial modulation of the periodic structure must be of the same order as the wavelength of considered elastic waves. A resonant acoustic metamaterial’s respective wavelength is about two orders of magnitude larger than the lattice constant. Each unit cell consists of a locally resonant structural unit in contrast to simple acoustic scatterers in phononic crystals. In this report, we will address the design of locally resonant sonic materials. These materials may offer dynamic effective negative material properties around resonance frequency. Locally resonant sonic crystals, such as an array of Helmholtz resonators and cylinders or spheres coated with acoustically soft material, were analyzed in the literature. However, existing literature lacks a systematic study of the dependence of effective properties for a finite slab of these metamaterials bot...