Evolution Of Optical Response Research Articles

Probing role of shell thickness in the optical response of core-shell nanorods

Plasmonic nanostructures made from Earth abundant and low-cost metals have recently emerged as a potential alternative to typical noble plasmonic metals. Here we report a quantum mechanical study of the optical response evolution of bi-metallic core-shell nanorods made of simple-metals Mg, Al and Na atoms. We base our calculations on the computationally efficient time-dependent density-functional theory. We find that core-shell nanorods show rich and enhanced optical properties in comparison to pristine nanorods as a result of the interface formed between the core and the shell regions. Perhaps the most interesting result from our calculation is the dramatic spectral intensity enhancements in the case of core-shell nanorods. We believe that our findings will be helpful in the design of plasmonic devices based on core-shell nanorods made of simple metals.

Morphology dependent optical response tuning in planar square-shaped array of sodium nanoparticles.

Among the plasmonic nanostructures, ordered arrangement of metal nanoparticles with inter-particle gap distances in the nanometer scale is becoming increasingly important due to their ability to confine huge electromagnetic fields and tunable optical properties. Using time dependent density functional theory calculations, we study the optical response evolution in a planar square-shaped array of Sodium nanoparticles via morphology deformation. To this aim, we vary the inter-particle gap distance in the range of 2 to 30 Å separately along one and two directions. We compare and cross-examine the optical response evolution for both deformation process, and we find that the interaction between sodium nanoparticles in an ordered arrangement can be controlled to a large extent by simple deformation process. We believe that our theoretical results will be useful for designing ultra-small and tunable plasmonic devices that utilize quantum effects.

Nanoparticle heterodimers: The role of size and interparticle gap distance on the optical response

Composite plasmonic nanostructures with controlled size, shape and relative arrangement is a subject of significant current research interest. Much of this is stimulated by the prospects by generating enormous near-field enhancements of the surface and interparticle gap regions for potential applications in surface-enhanced spectroscopies. In this manuscript, using time-dependent density functional theory (TDDFT) calculations, we investigate how the optical response in size matched homodimers and size mismatched heterodimers composed of Aluminum modify while varying the size and interparticle gap distances in the sub-nanometer range. Both systems show interesting optical response evolution. In particular, the size mismatched heterodimers show even more complex optical response evolution due to a symmetry-breaking in the system.

A quantum mechanical study of the optical response evolution in nanorod dimers

Using the time dependent density functional theory calculations, we investigate how the optical response in Aluminium nanorod dimers evolve as a function of different tuning parameters such as gap distances (3–14 Å), structural configurations (compact, hollow and a combination of both) and relative spatial orientations (parallel and axial linkages). We found that the position and amplitude of the gap plasmons are continuously modified with decreasing gap distances in the case of nanorod dimer composed of compact structures, and below 6 Å, the electron tunnelling emerges in agreement with recent experiments. We have also investigated the gap plasmon modifications by placing a conducting molecule in the inter-particle gap region and found the molecule short circuits the junction and decreases the optical enhancement.

Optical response tuning in nanorod-on-semicontinous film systems: A computational study

Strongly confined and intense optical fields within the plasmonic metal nanocavities show outstanding potential for a wide range of functionalities in nanophotonics. Using time dependent density functional theory calculations, we investigate the optical response evolution as a function of the gap separation distances in nanorod-on-film systems comprised of a nanorod (NR) made of Al or Na on top of an Al film. Huge optical field modulations emerged in the chemically distinct Na NR – Al film system in comparison to the Al NR – Al film system, indicating the vital role of metals involved. We further study the optical response modifications by placing a conducting molecule in the gap region, finding strong spectral modulations via through-molecule electron tunneling.

Fabrication and Optical Properties of Three-Dimensional Magnetophotonic Heterostructures

The vertical deposition technique and the RF-magnetron sputtering method were employed for fabrication of three-dimensional (3-D) magnetophotonic crystals, in which a bismuth-substituted yttrium-iron-garnet planar defect layer was sandwiched in between two opal thin films. Optical properties and structure of constitutive elements (opal thin films) were studied in detail. An evolution of optical response of a magnetophotonic heterostructure under preparation is presented

Evolution of optical response in the series [formula omitted

Optical measurements from the far infrared to ultraviolet and at low temperature are used to study the evolution of Kondo lattice behaviors within the series YbCu 5 - x Au x . Heavy fermion (Kondo lattice) features have been observed in the low energy part of the spectrum of YbCu 5 , resembling the data of the isostructural YbCu 4 Ag , but for a shift towards the lowest frequencies of the free carrier behavior (consistent with a lower T K value). By moving to samples with an increasing amount of Au atoms substituting the Cu atoms, three effects can be observed: the closing of the hybridization gap signed by the red shift of a typical structure in the optical conductivity; the increasing amount of broadening effects, possibly related to stoichiometric disorder; the disappearing of a vibrational structure at about 3.5 meV, which could be due or to disordering effects, or to a change in the Yb–Cu (Yb–Au) bonds.

Femtosecond spectroscopic study of ultrafast carrier relaxation in hydrogenated amorphous silicon a-Si:H

We present a study of spectral- and time-resolved reflectivity and transmission measurements on hydrogenated amorphous silicon (a-Si:H) with 50 fs time resolution. Electron-hole pairs are photoexcited into the extended states of a-Si:H by an ultrashort pump pulse at ℏω=2 eV. The temporal evolution of the photoinduced optical response is studied for a broad range of excitation densities from 1018 up to 1020 cm−3, and on a timescale of up to 200 ps. The temporal evolution of the optical response is discussed in terms of recombination and trapping mechanisms for carriers in the extended states of a-Si:H.