Esteban Moreno

Transmission of Light through a Single Rectangular Hole

We show that a single rectangular hole in a metallic film exhibits transmission resonances that appear near the cutoff wavelength of the hole waveguide. For light polarized with the electric field pointing along the holes short axis, it is shown that the normalized-to-area transmittance at resonance is proportional to the ratio between the long and short sides, and to the dielectric constant inside the hole. Importantly, this resonant transmission process is accompanied by a huge enhancement of the electric field at both entrance and exit interfaces of the hole.

Entanglement of Two Qubits Mediated by One-Dimensional Plasmonic Waveguides

We investigate qubit-qubit entanglement mediated by plasmons supported by one-dimensional waveguides. We explore both the situation of spontaneous formation of entanglement from an unentangled state and the emergence of driven steady-state entanglement under continuous pumping. In both cases, we show that large values for the concurrence are attainable for qubit-qubit distances larger than the operating wavelength by using plasmonic waveguides that are currently available.

Enhanced transmission and beaming of light via photonic crystal surface modes

Surface modes are generally believed to be an undesirable feature of finite photonic crystals (PC), unlike point or line defect modes. However, it is possible to make the surface mode radiate by appropriate corrugation of the PC interface. In this paper we show theoretically that the coherent action of these surface indentations can be engineered to collimate within a few degrees the light exiting a PC waveguide, or to funnel light coming from free space into the waveguide.

Domino plasmons for subwavelength terahertz circuitry.

A new approach for the spatial and temporal modulation of electromagnetic fields at terahertz frequencies is presented. The waveguiding elements are based on plasmonic and metamaterial notions and consist of an easy-to-manufacture periodic chain of metallic box-shaped elements protruding out of a metallic surface. It is shown that the dispersion relation of the corresponding electromagnetic modes is rather insensitive to the waveguide width, preserving tight confinement and reasonable absorption loss even when the waveguide transverse dimensions are well in the subwavelength regime. This property enables the simple implementation of key devices, such as tapers and power dividers. Additionally, directional couplers, waveguide bends, and ring resonators are characterized, demonstrating the flexibility of the proposed concept and the prospects for terahertz applications requiring high integration density.

Triangular metal wedges for subwavelength plasmon-polariton guiding at telecom wavelengths

We report on subwavelength plasmon-polariton guiding by triangular metal wedges at telecom wavelengths. A high-quality fabrication procedure for making gold wedge waveguides, which is also mass-production compatible offering large-scale parallel fabrication of plasmonic components, is developed. Using scanning near-field optical imaging at the wavelengths in the range of 1.43-1.52 microm, we demonstrate low-loss (propagation length approximately 120 microm) and well-confined (mode width congruent with 1.3 microm) wedge plasmon-polariton guiding along triangular 6-microm-high and 70.5 degree-angle gold wedges. Experimental observations are consistent with numerical simulations performed with the multiple multipole and finite difference time domain methods.

Resonance Energy Transfer and Superradiance Mediated by Plasmonic Nanowaveguides

We show how both the subwavelength confinement associated with surface plasmons and the one-dimensional character of plasmonic waveguides can be exploited to enhance the coupling between quantum emitters. Resonance energy transfer and the phenomenon of superradiance are investigated in three different waveguiding schemes (wires, wedges, and channels) by means of the Finite Element Method. We also develop a simplified model that is able to capture the main features of the numerical results.

Multiple multipole method with automatic multipole setting applied to the simulation of surface plasmons in metallic nanostructures

Highly accurate computations of surface plasmons in metallic nanostructures with various geometries are presented. Calculations for cylinders with irregular cross section, coupled structures, and periodic gratings are shown. These systems exhibit a resonant behavior with complex field distribution and strong field enhancement, and therefore their computation requires a very accurate numerical method. It is shown that the multiple multipole (MMP) method, together with an automatic multipole setting (AMS) procedure, is well suited for these computations. An AMS technique for the two-dimensional MMP method is presented. It relies on the global topology of each domain boundary to generate a distribution of numerically independent multipole expansions. This technique greatly facilitates the MMP modeling.

Extraordinary optical transmission without plasmons: the s-polarization case

It is shown that extraordinary optical transmission through perforated metallic films is possible for s-polarization. Although surface plasmons do not exist for this polarization, their role can be played by a wave sustained by a thin dielectric layer on top of the metallic film. The numerical simulations presented here confirm that the existence of a surface wave, whatever its nature, is responsible for the extraordinary optical transmission phenomenon.

Energy-Time Entanglement Preservation in Plasmon-Assisted Light Transmission

We report on experimental evidence of the preservation of the energy-time entanglement of a pair of photons after a photon-plasmon-photon conversion. This preservation is observed in two different plasmon conversion experiments, namely, extraordinary optical transmission through subwavelength metallic hole arrays and long range surface plasmon propagation in metallic waveguides. Plasmons are shown to coherently exist at two different times separated by much more than their lifetimes. This kind of entanglement involving light and matter is expected to be useful for future processing and storing of quantum information.

Terahertz wedge plasmon polaritons

We propose a metamaterial approach to route terahertz waves that features subwavelength confinement in the transverse plane. The guiding mechanism is based on geometrically induced electromagnetic modes sustained by corrugated metallic wedges, whose characteristics resemble those of wedge plasmon polaritons at telecom and optical frequencies. Additionally, frequency selective focusing and slowing down of terahertz radiation based on the proposed wedge waveguides are presented.