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Optical Modes (optical + mode)

Distribution by Scientific Domains

Physics and Astronomy	50%

Selected Abstracts

Engineered Light Scattering in Colloidal Photonic Heterocrystals

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Boyang Ding
Abstract Photonic heterocrystals are prepared by sandwiching films of self-assembled opal and force-assembled Langmuir,Blodgett colloidal crystals. Anomalously strong light scattering in conjunction with low reflectivity is observed with increasing angle of incidence in the spectral range of photonic bandgaps. The occurrence of light scattering at the interface has been assigned to the optical mode mismatch between the two types of photonic crystals. Photonic bandgap-related mechanisms of trapping the decaying photonic crystal modes at the interface are suggested. [source]

Vibrational properties of single walled carbon nanotubes under pressure from Raman scattering experiments and molecular dynamics simulations

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2007
In-Hwan Choi
Abstract We have investigated theoretically and experimentally the pressure dependent structural and vibrational properties of single-walled carbon nanotubes (SWNT). Bundles of SWNTs are studied inside a diamond anvil high pressure cell with micro-Raman scattering. The tube diameter and size distribution are determined from the radial breathing modes (RBM) of the tubes. The pressure coefficient and linewidth of one of the high frequency C,C bond stretching modes was found to change suddenly at ,3 GPa which is well below the structural transformation pressure (Pc) for the tubes in our sample. Molecular dynamics simulations were used to calculate the vibrational density of states of SWNTs as a function of pressure. Our simulations suggest that the experimental results can be explained by a softening of a low-frequency optical mode of the SWNTs , the "squashing" mode , and the dynamical effect of this softening on other phonon modes. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

High Quality Factor Metallodielectric Hybrid Plasmonic,Photonic Crystals

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2010
Xindi Yu
Abstract A 2D polystyrene colloidal crystal self-assembled on a flat gold surface supports multiple photonic and plasmonic propagating resonance modes. For both classes of modes, the quality factors can exceed 100, higher than the quality factor of surface plasmons (SP) at a polymer,gold interface. The spatial energy distribution of those resonance modes are carefully studied by measuring the optical response of the hybrid plasmonic,photonic crystal after coating with dielectric materials under different coating profiles. Computer simulations with results closely matching those of experiments provide a clear picture of the field distribution of each resonance mode. For the SP modes, there is strong confinement of electromagnetic energy near the metal surface, while for optical modes, the field is confined inside the spherical particles, far away from the metal. Coating of dielectric material on the crystal results in a large shift in optical features. A surface sensor based on the hybrid plasmonic,photonic crystal is proposed, and it is shown to have atomic layer sensitivity. An example of ethanol vapor sensing based on physisorption of ethanol onto the sensor surface is demonstrated. [source]

Optically-Pumped Lasing in Hybrid Organic,Inorganic Light-Emitting Diodes

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009
Myoung Hoon Song
Abstract Here, the use of metal oxide layers both for charge transport and injection into an emissive semiconducting polymer and also for the control of the in-plane waveguided optical modes in light-emitting diodes (LEDs) is reported. The high refractive index of zinc oxide is used to confine these modes away from the absorbing electrodes, and include a nano-imprinted grating in the polymer layer to introduce distributed feedback and enhance optical out-coupling. These structures show a large increase in the luminescence efficiency over conventional devices, with photoluminescence efficiency increased by up to 45%. Furthermore, optically-pumped lasing in hybrid oxide polymer LEDs is demonstrated. A tuneable lasing emission is also obtained in a single device structure by employing a graduated thickness of a zinc oxide inter-layer. This demonstrates the scope for using such architectures to improve the external efficiency of organic semiconductor LEDs, and opens new possibilities for the realization of polymer injection lasers. [source]

Nonlinear Tamm states and surface effects in periodic photonic structures

LASER PHYSICS LETTERS, Issue 10 2008
Yu. S. KivsharArticle first published online: 10 JUL 200
Abstract We present a brief overview of the basic concepts and important experimental observations of the effect of light localization near the surfaces of truncated periodic photonic structures. In particular, we discuss the formation of nonlinear localized modes and discrete surface solitons near the edges of nonlinear optical waveguide arrays and two-dimensional photonic lattices. We draw an analogy between the nonlinear surface optical modes and the surface Tamm states known in the electronic theory. We discuss the crossover between discrete solitons in the array and surface solitons at the edge of the array by analyzing the families of even and odd nonlinear localized modes located at finite distances from the edge of a waveguide array. We discuss various generalization of this concept including surface solitons in chirped lattices, multi-gap vector surface solitons, polychromatic surface states generated by a supercontinuum source, surface modes in two-dimensional photonic lattices, and spatiotemporal surface solitons. Finally, we discuss briefly several other related concepts including the enhanced beaming of light from subwavelength waveguides in photonic crystals. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

On the way to InGaN quantum dots embedded into monolithic nitride cavities

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007
K. Sebald
Abstract We present photoluminescence measurements on single InGaN quantum dots (QDs) grown by metalorganic vapor phase epitaxy, and on monolithicly grown GaN-based quantum well airpost pillar microcavities. The observed sharp emission lines of the quantum dots are characterized by excitation density dependent measurements. The photoluminescence of individual quantum dots can easily be detected for temperatures up to 150 K. The micro-photoluminescence measurements on microcavities reveal three-dimensional confined optical modes which are not seen in the luminescence of the simply planar cavity. The realization of rather temperature stable QDs as well as of nitride based microcavity samples are promising with respect to the intended implementation of QD layers into microcavities. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]