Conversion of light into direct current is important for applications ranging from energy conversion to photodetection, yet often challenging over broad photon frequencies. Here we show a new architecture based on surface plasmon excitation within a metal–insulator–metal device that produces power based on spatial confinement of electron excitation through plasmon absorption. Plasmons excited in the upper metal are absorbed, creating a high concentration of hot electrons which can inject above or tunnel through the thin insulating barrier, producing current. The theoretical power conversion efficiency enhancement achieved can be almost 40 times larger than that of direct illumination while utilizing a broad spectrum of IR to visible wavelengths. Here we present both theoretical estimates of the power conversion efficiency and experimental device measurements, which show clear rectification and power conversion behavior.

Plasmonic Energy Collection through Hot Carrier Extraction

New trends in instrumental design for surface plasmon resonance-based biosensors

We present detailed analysis of the optical properties of a structure called a nanosheet plasmon cavity. It is a metal-insulator-metal (MIM) waveguide with a finite length. First, propagation of the lowest-energy surface-plasmon mode of a MIM waveguide, which is the fundamental structure of our cavity, is analytically investigated. In addition to the dispersion relation, localization and dissipation of the electromagnetic energy are discussed. Next, the optical properties of the nanosheet plasmon cavity are numerically examined with the boundary element method. The nanosheet plasmon cavity is found to inherit various natures of the original MIM waveguide. The resonance in this cavity can be understood as a Fabry-Perot-like resonance caused by the reflection of the guided mode at the entrance and the exit surfaces. This enables easy design of a cavity on the basis of the analytical dispersion relation of a MIM waveguide. The fields in a MIM waveguide are localized around the dielectric core, and the wavelength of the surface plasmon becomes shorter with decreasing the thickness of the core. Therefore the electromagnetic energy can be confined in a volume as small as $0.001\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}{\mathrm{m}}^{3}$ in a nanosheet plasmon cavity. Another feature of this cavity is that the electric field is maximized at the core entrance. By only letting molecules be adsorbed on the surface of the core, the molecules are exposed to the maximum field. This exhibits great potential of the nanosheet plasmon cavity for enhanced Raman spectroscopy.

Metal-insulator-metal plasmon nanocavities: Analysis of optical properties

Introduction General historical perspective The concept of metamaterials Modeling the material response Phase velocity and group velocity Metamaterials and homogenization procedure Metamaterials and Homogenization of Composites The homogenization hypothesis Limitations and consistency conditions Forward problem Inverse problems: retrieval and constitutive parameters Homogenization from averaging the internal fields Generalization to anisotropic and bianisotropic media Designing Metamaterials with Negative Material Parameters Negative dielectric materials Metamaterials with negative magnetic permeability Metamaterials with negative refractive index Chiral metamaterials Bianisotropic metamaterials Active and nonlinear metamaterials Negative Refraction and Photonic Bandgap Materials Photonic crystals and bandgap materials Band diagrams and iso-frequency contours Negative refraction and flat lenses with photonic crystals Negative refraction versus collimation or streaming Media with e < 0 and < 0: Theory and Properties Origins of negative refraction Choice of the wave-vector and its consequences Anisotropic and chiral media Energy and Momentum in Negative Refractive Index Materials Causality and energy density in frequency dispersive media Electromagnetic energy in left-handed media Momentum density, momentum flow, and transfer in media with negative material parameters Limit of plane waves and small losses Traversal of pulses in materials with negative material parameters Plasmonics of Media with Negative Material Parameters Surface electromagnetic modes in negative refractive materials Waveguides made of negative index materials Negative refraction of surface plasmons Plasmonic properties of structured metallic surfaces Surface waves at the interfaces of nonlinear media Veselago's Lens Is a Perfect Lens Near-field information and diffraction limit Mathematical demonstration of the perfect lens Limitations due to real materials and imperfect NRMs Issues with numerical simulations and time evolution Negative stream of energy with a perfect lens configuration Effects of spatial dispersion Designing Super Lenses Overcoming the limitations of real materials Generalized perfect lens theorem The perfect lens in other geometries Brief Report on Electromagnetic Invisibility Concept of electromagnetic invisibility Excluding electromagnetic fields Cloaking with localized resonances Appendix A: The Fresnel Coefficients for Reflection and Refraction Appendix B: The Dispersion and Fresnel Coefficients for a Bianisotropic Medium Appendix C: The Reflection and Refraction of Light across a Material Slab References Index

Physics and Applications of Negative Refractive Index Materials

A sensitivity comparison of optical biosensors based on four different surface plasmon resonance modes.

The method of frustrated total reflection is used to optically excite electromagnetic surface plasma waves (SPW) in two different layered structures. The first system studied has two films (Mg${\mathrm{F}}_{2}$-Ag) between glass and air, and the second has three films (Ag-Mg${\mathrm{F}}_{2}$-Ag) between glass and air. Surface roughness of the evaporated Mg${\mathrm{F}}_{2}$ films is found to increase with film thickness and this roughness has a pronounced effect on the SPW resonances. A cermet is imagined to form at the Mg${\mathrm{F}}_{2}$-Ag interface, and its effective optical constants can be evaluated using the Maxwell Garnett theory. If this cermet is treated as a separate layer in the structure, then good agreement is found with the experimentally observed resonances. A calculation of the Poynting vector field, current distributions, and surface charge densities, resulting from an incident monochromatic plane wave, shows the different modes of oscillation corresponding to each resonance.

G. D. Scott

Papers

Optical excitation of surface plasma waves in layered media