arXiv subjects

Alexander L. Burin

Publications and source records attributed to Alexander L. Burin.

41 records · Page 3Linked to original sources

arXiv2007

Investigation of Whispering Gallery Modes in Circular Arrays of Dielectric Spherical Particles using multisphere Mie Scattering formalism

quality factor depending on the material used. If these arrays consist of metal particles, then they cannot have a high quality factor because their light absorption restricts performance. In this paper we address the following question: can bound modes be formed in dielectric systems where the absorption of light is negligible? Our investigation of circular arrays of spherical particles within the framework of the multisphere Mie scattering theory using the simplest dipolarlike approach shows that (1) high quality modes in an array of 10 or more particles can be attained at least for a refractive index n > 2, so optical materials like TiO2 or GaAs can be used; (2) the most bound modes have nearly transverse polarization perpendicular to the circular plane; (3) in a particularly interesting case of TiO2 particles (rutile phase, n = 2.7), the quality factor of the most bound mode increases almost by an order of magnitude with the addition of 10 extra particles, while for particles made of GaAs the quality factor increases by almost two orders of magnitude with the addition of ten extra particles. The consideration of higher multipole contributions has demonstrated that the error of the dipolar approach does not exceed one percent if the refractive index nr is greater than 2. Minimum acceptable disordering not affecting the quality factor is studied.

physics.optics↗

arXiv2007

Optical modes in linear arrays of dielectric spherical particles: A numerical investigation

We have investigated bound modes in finite linear chains of dielectric particles of various lengths, interparticle spacing and particle materials. Through a unique application of the multisphere Mie scattering formalism, we have developed numerical methods to calculate eigen-optical modes for various arrays of particles. These numerical methods involve the use of the multisphere scattering formalism as the entries in NxN matrices where N represents the number of particles in the chain. Eigenmodes of these matrices correspond to the eigen-optical modes of interest. We identified the eigenmodes with the highest quality factor by the application of a modified version of the Newton-Raphson algorithm. We found that convergence is strong using this algorithm for linear chains of up to several hundreds of particles. By comparing the dipolar approach with the more complex approach which utilizes a combination of both dipolar and quadrupolar approaches, we demonstrated that the dipolar approach has an accuracy of approximately 99%. We found that the quality factor Q of the mode increases with the cubed value of the number of particles in chain in agreement with the previously developed theory, the effects of disordering of particle sizes and inter-particle distances will be discussed.

physics.optics↗

arXiv2006

Energy delocalization in strongly disordered systems induced by the long-range many-body interaction

Anderson localization1 in a random system is sensitive to a distance dependence of the excitation transfer amplitude V(r). If V(r) decreases with the distance r slower than 1/r^d in a d-dimensional system then all excitations are delocalized at arbitrarily strong disordering, due to the resonant interaction of far separated quantum states (Fig. 1). At finite temperature T>0 the density of excitations is finite and they can influence each other by means of their interaction. Many body excitations involving simultaneous transitions of several single particle excitations create additional channels for energy delocalization and transport. Here we show that if the interaction of excitations decreases with the distance slower than 1/R^(2d) then excitations are delocalized at finite temperature irrespectively to disordering. This delocalization results in the finite decoherence rate in the ensemble of interacting spins 1/2 representing the model of quantum computer, thus restricting the quantum hardware performance. It also leads to the energy and particle delocalization and transport at finite temperature in various physical systems including doped semiconductors, despite of the full localization of electrons at zero temperature.

cond-mat.dis-nn↗

arXiv2006

Bound whispering gallery modes in circular arrays of dielectric spherical particles

Low-dimensional ordered arrays of optical elements can possess bound modes having an extremely high quality factor. Typically, these arrays consist of metal elements which have significantly high light absorption thus restricting performance. In this paper we address the following question: can bound modes be formed in dielectric systems where the absorption of light is negligible? Our investigation of circular arrays of spherical particles shows that (1) high quality modes in an array of 10 or more particles can be attained at least for a refractive index $n_{r}>2$, so optical materials like TiO$_{2}$ or GaAs can be used; (2) the most bound modes have nearly transverse polarization perpendicular to the circular plane; (3) in a particularly interesting case of TiO$_{2}$ particles (rutile phase, $n_{r}=2.7$), the quality factor of the most bound mode increases almost by an order of magnitude with the addition of 10 extra particles, while for particles made of GaAs the quality factor increases by almost two orders of magnitude with the addition of ten extra particles. We hope that this preliminary study will stimulate experimental investigations of bound modes in low-dimensional arrays of dielectric particles.

physics.optics↗

arXiv2004

Physics of Proteins at Low Temperature

We present results of a hole burning study with thermal cycling and waiting time spectral diffusion experiments on a modified cytochrome - c protein in its native as well as in its denatured state. The experiments show features which seem to be characteristic for the protein state of matter and its associated dynamics at low temperature. The properties responsible for the observed patterns are organisation paired with randomness and, in addition, the finite size which gives rise to surface and solvent effects. We discuss some general model approaches which might serve as guide lines for understanding these features.

cond-mat.dis-nn↗