Igor E. Protsenko

Enhanced Electron Photoemission by Collective Lattice Resonances in Plasmonic Nanoparticle-Array Photodetectors and Solar Cells

We propose to use collective lattice resonances in plasmonic nanoparticle arrays to enhance and tailor photoelectron emission in Schottky barrier photodetectors and solar cells. We show that the interaction between narrow-band lattice resonances (the Rayleigh anomaly) and broader-band individual-particle excitations (localized surface plasmon resonances) leads to stronger local field enhancement. In turn, this causes a significant increase of the photocurrent compared to the case when only individual-particle excitations are present. The results can be used to design new photodetectors with highly selective, tunable spectral response, which are able to detect photons with the energy below the semiconductor bandgap. The findings can also be used to develop solar cells with increased efficiency.

Photoemission from metal nanoparticles

The approach of A M Brodsky and Yu Ya Gurevich is generalized to photoemission from metal nanoparticles at the excitation of a localized plasmon resonance (LPR) in them. The cross section and the probability amplitude of photoemission from a nanoparticle are obtained analytically, taking into account the LPR excitation and the electromagnetic field and photoelectron mass changes at the metal-environment interface. An increase by two orders of magnitude in the photocurrent from a layer of Au nanoparticles to silicon compared to a bulk Au layer is predicted due to an increase in the electromagnetic field strength under the excitation of LPR and due to a significant part of the nanoparticle surface being nonparallel to the incident field polarization. Practicable applications of the results include improving the performance of photocells and photodetectors, and probably reducing the minimum photoeffect time.

Spontaneous Hot-Electron Light Emission from Electron-Fed Optical Antennas.

Nanoscale electronics and photonics are among the most promising research areas providing functional nanocomponents for data transfer and signal processing. By adopting metal-based optical antennas as a disruptive technological vehicle, we demonstrate that these two device-generating technologies can be interfaced to create an electronically driven self-emitting unit. This nanoscale plasmonic transmitter operates by injecting electrons in a contacted tunneling antenna feedgap. Under certain operating conditions, we show that the antenna enters a highly nonlinear regime in which the energy of the emitted photons exceeds the quantum limit imposed by the applied bias. We propose a model based upon the spontaneous emission of hot electrons that correctly reproduces the experimental findings. The electron-fed optical antennas described here are critical devices for interfacing electrons and photons, enabling thus the development of optical transceivers for on-chip wireless broadcasting of information at the nanoscale.

Broadening of Plasmonic Resonance Due to Electron Collisions with Nanoparticle Boundary: а Quantum Mechanical Consideration

We present a quantum mechanical approach to calculate broadening of plasmonic resonances in metallic nanostructures due to collisions of electrons with the surface of the structure. The approach is applicable if the characteristic size of the structure is much larger than the de Broglie electron wavelength in the metal. The approach can be used in studies of plasmonic properties of both single nanoparticles and arrays of nanoparticles. Energy conservation is insured by a self-consistent solution of Maxwells equations and our model for the photon absorption at the metal boundaries. Consequences of the model are illustrated for the case of spheroid nanoparticles, and results are in good agreement with earlier theories. In particular, we show that the boundary-collision broadening of the plasmonic resonance in spheroid nanoparticles can depend strongly on the polarization of the impinging light.

Internal photoemission from plasmonic nanoparticles: comparison between surface and volume photoelectric effects

We study the emission of photoelectrons from plasmonic nanoparticles into a surrounding matrix. We consider two mechanisms of electron emission from the nanoparticles--surface and volume ones--and use models for these two mechanisms which allow us to obtain analytical results for the photoelectron emission rate from a nanoparticle. Calculations have been carried out for a step potential at the surface of a spherical nanoparticle, and a simple model for the hot electron cooling has been used. We highlight the effect of the discontinuity of the dielectric permittivity at the nanoparticle boundary in the surface mechanism, which leads to a substantial (by ∼5 times) increase of the internal photoelectron emission rate from a nanoparticle compared to the case when such a discontinuity is absent. For a plasmonic nanoparticle, a comparison of the two photoeffect mechanisms was undertaken for the first time which showed that the surface photoeffect can in the general case be larger than the volume one, which agrees with the results obtained for a flat metal surface first formulated by Tamm and Schubin in their pioneering development of a quantum-mechanical theory of photoeffect in 1931. In accordance with our calculations, this possible predominance of the surface effect is based on two factors: (i) effective cooling of hot carriers during their propagation from the volume of the nanoparticle to its surface in the scenario of the volume mechanism and (ii) strengthening of the surface mechanism through the effect of the discontinuity of the dielectric permittivity at the nanoparticle boundary. The latter is stronger at relatively lower photon energies and correspondingly is more substantial for internal photoemission than for an external one. We show that in the general case, it is essential to take both mechanisms into account in the development of devices based on the photoelectric effect and when considering hot electron emission from a plasmonic nanoantenna.

Heterogeneous medium as a filter of electromagnetic radiation

The optical properties of a light filter consisting of a transparent dielectric matrix with inclusion of metallic nanoparticles of various shapes and sizes are investigated theoretically. By selecting distributions of nanoparticles, it is possible to achieve absorption of electromagnetic radiation in specified spectral regions of visible or near IR radiation. Such filters have narrow transition regions, high contrast and low fabrication temperature in comparison with well known absorption filters. A filter for absorption of optical radiation transparent in the infrared region and an infrared filter transmitting optical radiation are considered as examples.

Increasing the efficiency of organic solar cells using plasmonic nanoparticles

Numerical simulations show that the introduction of aluminum nanoparticles into one layer of a bulk-heterojunction organic solar cell leads to an increase in the rate of exciton generation in the active layer of the cell. According to calculations of the optical absorption in the cell, which have been performed in the effective refractive index approximation using the Maxwell-Garnet model, a maximum relative increase in the rate of exciton generation due to plasmonic nanoparticles is about 4%.

A Single-Emitter Gain Medium for Bright Coherent Radiation from a Plasmonic Nanoresonator

We theoretically demonstrate the generation and radiation of coherent nanoplasmons powered by a single three-level quantum emitter on a plasmonic nanoresonator. By pumping the three-level emitter in a Raman configuration, we show a pathway to achieve macroscopic accumulation of nanoplasmons due to stimulated emission in the nanoresonator despite their fast relaxation. Thanks to the antenna effect of the nanoresonator, the system acts as an efficient and bright nanoscopic coherent light source with a photon emission rate of hundreds of Terahertz and could be realized with solid-state emitters at room temperatures in pulse mode. We provide physical interpretations of the results and discuss their realization and implications for ultra-compact integration of optoelectronics.

Biased Nanoscale Contact as Active Element for Electrically Driven Plasmonic Nanoantenna

Electrically-driven optical antennas can serve as compact sources of electromagnetic radiation operating at optical frequencies. In the most widely explored configurations, the radiation is generated by electrons tunneling between metallic parts of the structure when a bias voltage is applied across the tunneling gap. Rather than relying on an inherently inefficient inelastic light emission in the gap, we suggest to use a ballistic nanoconstriction as the feed element of an optical antenna supporting plasmonic modes. We discuss the underlying mechanisms responsible for the optical emission, and show that with such a nanoscale contact, one can reach quantum efficiency orders of magnitude larger than with standard light-emitting tunneling structures.

Giant Photogalvanic Effect in Noncentrosymmetric Plasmonic Nanoparticles

Photoelectric properties of metamaterials containing non-centrosymmetric, similarly oriented metallic nanoparticles embedded in a homogeneous semiconductor matrix are theoretically studied. Due to the asymmetric shape of the nanoparticle boundary, photoelectron emission acquires a preferred direction, resulting in a photocurrent flow in that direction when nanoparticles are uniformly illuminated by a homogeneous plane wave. This effect is a direct analogy of the photogalvanic (or bulk photovoltaic) effect known to exist in media with non-centrosymmetric crystal structure, such as doped lithium niobate or bismuth ferrite, but is several orders of magnitude stronger. Termed the giant plasmonic photogalvanic effect, the reported phenomenon is valuable for characterizing photoemission and photoconductive properties of plasmonic nanostructures, and can find many uses for photodetection and photovoltaic applications.