Plasmonic internal-photoemission-based Si photodetector design suitable for optical communication.

We propose a high-performance plasmonic photodetector based on the internal photoemission (IPE) process for the C-band communication wavelength. This photodetector takes advantage of an embedded nanohole array in Schottky metal. Owing to localized surface plasmon resonance, the absorption of the active metal layer increases, which results in the generation of more hot carriers and subsequently compensates for the low efficiency of IPE-based photodetectors.

Directional optical absorption and scattering in conical plasmonic nanostructures.

Asymmetric plasmonic nanostructures can be exploited to realize directional optical absorption or scattering for oppositely propagating optical waves. Here we theoretically investigate the roles of asymmetry and interaction of nanoparticles in directional optical responses. It is shown that adding optical interaction to a single truncated nanocone by dividing it into interacting nanodisks without changing geometrical asymmetry causes significant enhancement of directionality.

Packed Yagi-Uda nano-antennas using a unidirectional feed at visible wavelengths.

Optical nano-antennas' capability for controlling the intensity and direction of freely propagating waves is a precursor to demanding on-chip optical communications. Here we present a novel and efficiently packed Yagi-Uda (P-YU) nano-antenna which is dramatically directive and shortened. This is due to the excitation of a pair of strong interacting Au nanorods as a feed in the form of conventional Yagi-Uda (YU).

Solar Transparent Radiators by Optical Nanoantennas.

Architectural windows are a major cause of thermal discomfort as the inner glazing during cold days can be several degrees colder than the indoor air. Mitigating this, the indoor temperature has to be increased, leading to unavoidable thermal losses. Here we present solar thermal surfaces based on complex nanoplasmonic antennas that can raise the temperature of window glazing by up to 8 K upon solar irradiation while transmitting light with a color rendering index of 98.

Optical absorbing origin of chiroptical activity in planar plasmonic metasurfaces.

As a significant characteristic of many biomolecules, chemical substances, and artificial nanostructures, chirality conduce different types of optical interactions with the spin angular momentum of the impinging light field. Although, chiral arrangement and spatial phase retardation are the key factors for obtaining chirality in three-dimensional (3D) structures, the origin of chirality in the feasible planar structures has not been thoroughly addressed. Here using an intuitive and simple analytical approach, called cross-hybridization model, the essence and properties of the optical chirality of individual planar nanostructures are unveiled.

Magnetoplasmonic design rules for active magneto-optics.

Light polarization rotators and nonreciprocal optical isolators are essential building blocks in photonics technology. These macroscopic passive devices are commonly based on magneto-optical Faraday and Kerr polarization rotation. Magnetoplasmonics, the combination of magnetism and plasmonics, is a promising route to bring these devices to the nanoscale.

Strong optical interaction of two adjacent rectangular nanoholes in a gold film.

The strong near-field optical interaction between two adjacent nanoholes milled in a gold film is investigated. A single nanohole is modeled as a magnetic dipole described by the simple relation between the magnetic- and electric-polarization in electromagnetic theory. To elucidate the role of the electric and magnetic fields in near-field characteristics of a nanohole illuminated by an optical plane-wave, the normalized electric and magnetic power amplitudes are accordingly introduced.

Highly directional bottom-up 3D nanoantenna for visible light.

Controlling light at the nanoscale is of fundamental importance and is essential for applications ranging from optical sensing and metrology to information processing, communications, and quantum optics. Considerable efforts are currently directed towards optical nanoantennas that directionally convert light into strongly localized energy and vice versa. Here we present highly directional 3D nanoantenna operating with visible light.

Fano interference in supported gold nanosandwiches with weakly coupled nanodisks.

We studied the far-field optical response of supported gold-silica-gold nanosandwiches using spectroscopic ellipsometry, reflectance and transmittance measurements. Although transmittance data clearly shows that the gold nanodisks in the sandwich structure interact very weakly, oblique reflectance spectra of s- and p-polarized light show clearly asymmetric line-shapes of the Fano type. However, all experimental results are very well described by modeling the gold nanodisks as oblate spheroids and by employing a 2 × 2 scattering matrix formulation of the Fresnel coefficients provided by an island film theory.

Selective-mode optical nanofilters based on plasmonic complementary split-ring resonators.

A nanoplasmonic optical filtering technique based on a complementary split-ring resonator structure is proposed. The basic and modal properties of the square-nanoring are studied using the group theory. Degeneracy and non-degeneracy of the possible TM odd- and even-modes are characterized based on the symmetry elements of the ring structure.

Designer magnetoplasmonics with nickel nanoferromagnets.

We introduce a new perspective on magnetoplasmonics in nickel nanoferromagnets by exploiting the phase tunability of the optical polarizability due to localized surface plasmons and simultaneous magneto-optical activity. We demonstrate how the concerted action of nanoplasmonics and magnetization can manipulate the sign of rotation of the reflected light's polarization (i.e.

Optical response of supported gold nanodisks.

It is shown that the ellipsometric spectra of short range ordered planar arrays of gold nanodisks supported on glass substrates can be described by modeling the nanostructured arrays as uniaxial homogeneous layers with dielectric functions of the Lorentz type. However, appreciable deviations from experimental data are observed in calculated spectra of irradiance measurements. A qualitative and quantitative description of all measured spectra is obtained with a uniaxial effective medium dielectric function in which the nanodisks are modeled as oblate spheroids.

Unidirectional ultracompact optical nanoantennas.

We report on a dramatic directionality effect in a simple and ultracompact optical nanoantenna consisting of a pair of interacting plasmonic nanoparticles. We found that the emission from a dipole source positioned close to one of the particles in the pair exhibits an essentially unidirectional radiation pattern for emission wavelengths close to the antiphase hybridized plasmon. We analyze this unique effect in terms of radiation, reception, and reciprocity concepts using electrodynamics simulations and dipole analysis.

Intrinsic Fano interference of localized plasmons in Pd nanoparticles.

Palladium (Pd) nanoparticles exhibit broad optical resonances that have been assigned to so-called localized surface plasmons (LSPs). The resonance's energy varies with particle shape in a similar fashion as is well known for LSPs in gold and silver nanoparticles, but the line-shape is always anomalously asymmetric. We here show that this effect is due to an intrinsic Fano interference caused by the coupling between the plasmon response and a structureless background originating from interband transitions.

Enhanced nanoplasmonic optical sensors with reduced substrate effect.

We present a straightforward method to double the refractive index sensitivity of surface-supported nanoplasmonic optical sensors by lifting the metal nanoparticles above the substrate by a dielectric nanopillar. The role of the pillar is to substantially decrease the spatial overlap between the substrate and the enhanced fields generated at plasmon resonance. Data presented for nanodisks and nanoellipsoids supported by pillars of varying heights are found to be in excellent agreement with electrodynamics simulations.

Magnetic-field enhancement in gold nanosandwiches.

Using dispersive finite-difference time-domain (D-FDTD) simulations, we show that a pair of gold nanodisks stacked in a 'sandwich'-like (end-fire) configuration produces a large enhancement of the magnetic field when irradiated with a plane optical wave, if the distance between the nanodisks is optically small. The effect, which can be rationalized in terms of a magnetic dipole resonance, is due the excitation of a hybridized asymmetric plasmon mode, in which the induced electrical dipoles in the two disks oscillate out-of-phase. The strong magnetic response, together with the simple morphology, suggests that Au nanosandwiches are suitable elementary building blocks for optical metamaterials that exhibit negative refraction.