Incoherent Interaction Research Articles

Incoherent interaction between bright–bright photovoltaic soliton in an unbiased series two-photon photorefractive crystal circuit

We have investigated incoherent interaction between photovoltaic bright–bright soliton pairs in photorefractive crystals under steady-state condition in an unbiased series two-photon photorefractive crystal circuit in one dimension. The numerical scheme according to the Crank-Nicholson and Runge-kutta methods are applied to simulate the propagation of incoherent interaction for different normalized separation distances and different E0. Results show that in the case of one-dimensional interaction between these photovoltaic solitons, attraction occurs and width of beams decreases with increasing biased field E0 and two soliton interact in longer distance for smaller E0. The result can be used for design optical switches that controlled by biased field.

Discrete soliton interaction in quasi one-dimensional optically induced photonic lattice

The coherent and the incoherent interactions of discreet solitons in quasi one-dimensional optically induced photonic lattice are theoretically and numerically analyzed. It is found that in-phase solitons attract each other and out-of-phase solitons repel one other. Due to the anisotropy of the nonlinearity, two initially attractive incoherent solitons will repel each other as their interval waveguide number increasing. Moreover, the pendulum-like intertwist of discrete solitons is observed during the incoherent interaction due to the interplay between soliton transverse motions resulting from the soliton interaction and the Bragg reflection of the lattice structure. These results help us to understand how the anisotropy of the nonlinearity response plays a role in discrete soliton interaction and offers the theoretical support for the experimental investigation.

Optical Modeling and Analysis of Organic Solar Cells with Coherent Multilayers and Incoherent Glass Substrate Using Generalized Transfer Matrix Method

We present optical modeling and physical analysis results of thin-film organic solar cells (OSCs) based on a generalized transfer matrix method, which can calculate, with a simple matrix form, the mixed coherent and incoherent interaction of an incoherent glass substrate with other coherent layers. The spatial distribution of the electric field intensity, power density, and power dissipation are calculated in both coherent and incoherent layers with respect to the optical spacer thickness. By decomposing the power density and power dissipation into forward-propagating, backward-propagating, and their interference components, we demonstrate that the dependence of the spacer thickness on the total device reflectance plays an important role in determining the light absorption efficiency of the OSC.

Optical Modeling and Analysis of Organic Solar Cells with Coherent Multilayers and Incoherent Glass Substrate Using Generalized Transfer Matrix Method

We present optical modeling and physical analysis results of thin-film organic solar cells (OSCs) based on a generalized transfer matrix method, which can calculate, with a simple matrix form, the mixed coherent and incoherent interaction of an incoherent glass substrate with other coherent layers. The spatial distribution of the electric field intensity, power density, and power dissipation are calculated in both coherent and incoherent layers with respect to the optical spacer thickness. By decomposing the power density and power dissipation into forward-propagating, backward-propagating, and their interference components, we demonstrate that the dependence of the spacer thickness on the total device reflectance plays an important role in determining the light absorption efficiency of the OSC.

Interactions of dark solitons in photovoltaic photorefractive crystals with diffusion nonlinearity

We investigate the interaction of spatial dark optical soliton pair in open-circuit photovoltaic photorefractive crystals by considering the effect of background light and diffusion nonlinearity. We show that the spatial dark solitons repel each other and travel along different trajectories for the coherent interactions that one undergoes reflection and the other one deflects significantly when they are closely overlapped, and the dark solitons attract and deflect simultaneously along a parabolic trajectory for the case of incoherent interactions. The deflection distance depends on the intensities and the initial separation between the dark solitons.

Generation of optical and matter-wave solitons in binary systems with a periodically modulated coupling

We consider a quasi-one-dimensional two-component systm, described by a pair of Nonlinear Schr\"{o}dinger/Gross-Pitaevskii Equations (NLSEs/GPEs), which are coupled by the linear mixing, with local strength $\Omega $, and by the nonlinear incoherent interaction. We assume the self-repulsive nonlinearity in both components, and include effects of a harmonic trapping potential. The model may be realized in terms of periodically modulated slab waveguides in nonlinear optics, and in Bose-Einstein condensates too. Depending on the strengths of the linear and nonlinear couplings between the components, the ground states (GSs) in such binary systems may be symmetric or asymmetric. In this work, we introduce a periodic spatial modulation of the linear coupling, making $\Omega $ an odd, or even function of the coordinate. The sign flips of $\Omega (x)$ strongly modify the structure of the GS in the binary system, as the relative sign of its components tends to lock to the local sign of $\Omega $. Using a systematic numerical analysis, and an analytical approximation, we demonstrate that the GS of the trapped system contains one or several kinks (dark solitons) in one component, while the other component does not change its sign. Final results are presented in the form of maps showing the number of kinks in the GS as a function of the system's parameters, with the odd/even modulation function giving rise to the odd/even number of the kinks. The modulation of $\Omega (x)$ also produces a strong effect on the transition between states with nearly equal and strongly unequal amplitudes of the two components.

One-dimensional optical dark screening photovoltaic–photorefractive solitons, soliton pairs and incoherent interaction between them in BaTiO 3 crystal

We studied the theory of the optical solitons and introduced the nonlinear equations governed by the screening photovoltaic–photorefractive dark solitons. By the use of the numerical methods, the intensity profile, refractive index change of the media and also stability under propagation are investigated. Also, we investigated incoherent coupled dark–dark soliton pairs and incoherent interaction between them.

Incoherent interaction between one- and two-dimensional solitons in noncentrosymmetric photorefractive media

The incoherent interaction between solitons with different transverse dimensions in a noncentrosymmetric photorefractive crystal is studied both in theory and in experiment. An anomalous incoherent interaction between one- and two-dimensional solitons, whose attractive and repulsive effects depend on the soliton separation, is numerically demonstrated by employing an anisotropic model. By launching a one-dimensional green beam and a two-dimensional red beam into a biased SBN:60 crystal, the hybrid-dimensional soliton interaction is performed. The experimental results are in good agreement with the numerical ones.

Incoherent interaction of propagating spin waves with precessing magnetic moments

The magnetization dynamics of the magnetic vortex state occurring in response to subnanosecond transitions of the externally applied magnetic field was investigated in ${\text{Ni}}_{80}{\text{Fe}}_{20}(12\text{ }\text{nm})/{\text{Ir}}_{80}{\text{Mn}}_{20}(5\text{ }\text{nm})$ square elements by exploiting time-resolved scanning Kerr microscope and micromagnetic modeling. Upon application of a magnetic field pulse the magnetization undergoes a precessional oscillation of $\ensuremath{\sim}2\text{ }\text{GHz}$ while the magnetic vortex core moves from the equilibrium position. Along the pathway of the moving core, strong bursts of spin waves are generated by the creation and subsequent annihilation of a vortex-antivortex pair. An abrupt suppression of magnetization precession occurs subsequently after a vortex-antivortex core annihilates. The observed suppression is attributed to the incoherent interaction of precessing magnetic moments with propagating spin waves. The experimental observations are qualitatively well reproduced by micromagnetic modeling.

Deflection characteristics of incoherent coupled bright and dark photovoltaic spatial soliton pairs

We numerically investigate the deflection characteristics of incoherent coupled bright and dark photovoltaic spatial soliton pairs in a photovoltaic photorefractive crystal with diffusion effect. The numerical results show that, owing to the incoherent interaction, a bright soliton and a dark soliton in the crystal trap each other and the centers of the two solitons move along the same trajectory. It is found that, the deflection of the bright soliton can be controlled by adjusting the input background intensity of the dark soliton when the input peak intensity of the bright soliton is fixed; and the deflection of the bright soliton is suppressed when the input background intensity of the dark soliton is at a special value, while the bright soliton undergoes a deflection when the input background intensity of the dark soliton deviates from this special value. Also, the deflection of the dark soliton can be controlled by adjusting the input peak intensity of the bright soliton when the input background intensity of the dark soliton is fixed.

THEORETICAL BACKGROUNDS OF NONLINEAR THz SPECTROSCOPY OF SEMICONDUCTOR SUPERLATTICES

We consider terahertz absorption and gain in a single miniband of semiconductor superlattice subject to a bichromatic electric field in the most general case of commensurate frequencies of the probe and pump fields. Using an exact solution of Boltzmann transport equation, we show that in the small-signal limit the formulas for absorption always contain two distinct terms related to the parametric and incoherent interactions of miniband electrons with the alternating pump field. It provides a theoretical background for a control of THz gain without switching to the negative differential conductivity state. For pedagogical reasons we present derivations of formulas in detail.

Kinetics of double resonant coherent excitation of relativistic multicharged ions in crystals beyond the channeling conditions

The latest experiments carried out by the Tokyo group on the double resonant coherent excitation of Ar16+ and Ar17+ ions in thin silicon targets beyond the channeling conditions have been theoretically analyzed using the density matrix method for the joint description of coherent and incoherent (relaxation) interactions of relativistic multicharged ions in crystals. The calculation results are compared in detail with the experimental data.

Polarization bremsstrahlung of a hydrogen-like ion in a single crystal

Polarization bremsstrahlung (PB) that arises when a fast hydrogen-like ion is scattered in a single crystal is investigated theoretically. Four types of the process are analyzed that are caused by virtual excitation of electrons of the target and of the incident particle (IP), as well as by a coherent and incoherent interaction between the IP and the single crystal. The spectral, angular, and velocity (of the IP) characteristics of PB are calculated with regard to the spectral function of a photodetector. Optimal observation conditions and regions in which different types of PB are dominant are determined, and the dependence of these regions on the charge of the IP nucleus and of the target atoms is revealed.

Entanglement and parametric dynamics in quantum optics with interacting polaritons

AbstractWe report on a microscopic investigation of the polariton parametric emission in the presence of coherent and incoherent interaction processes by means of a full quantum description based on a nonequilibrium quantum Langevin approach for open systems applied to interacting‐electron complexes described within the dynamics controlled truncation scheme. It provides an easy recipe to calculate multi‐time correlation functions which are key‐quantities in quantum optics. In particular we report on calculations of polariton intensities (i.e. single time correlators) and spectra (i.e. two times correlators). We apply our scheme to a two‐pumps set‐up in microcavity recently proposed showing a quantitative analysis of the quantum correlation properties of the emitted photons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

One-dimensional optical bright screening photovoltaic photorefractive solitons, soliton pairs and incoherent interaction between them in BaTiO 3 crystal

By the use of theory of optical solitons, nonlinear equations governed by screening photorefractive photovoltaic solitons are introduced. By means of numerical methods, intensity profile, refractive index change of the media and also stability under propagation are investigated. Self-bending of solitons under first-order diffusion is also studied. Besides, incoherent coupled bright–bright soliton pairs and incoherent interaction are studied.

An Analytical Scatter Correction for Singles-Mode Transmission Data in PET

We present an analytical scatter correction, based upon the Klein-Nishina formula, for singles-mode transmission data in positron emission tomography (PET) and its implementation as part of an iterative image reconstruction algorithm. We compared our analytically-calculated scatter sinogram data with previously validated simulation data for a small animal PET scanner with 68 Ge (a positron emitter) and 57 Co (approximately 122-keV photon emitter) transmission sources using four different phantom configurations (three uniform water cylinders with radii of 25, 30, and 45 mm and a nonuniform phantom consisting of water, Teflon, and air). Our scatter calculation correctly predicts the contribution from single-scattered (one incoherent scatter interaction) photons to the simulated sinogram data and provides good agreement for the percent scatter fraction (SF) per sinogram for all phantoms and both transmission sources. We then applied our scatter correction as part of an iterative reconstruction algorithm for PET transmission data for simulated and experimental data using uniform and nonuniform phantoms. For both simulated and experimental data, the reconstructed linear attenuation coefficients (mu-values-values) agreed with expected values to within 4% when scatter corrections were applied, for both the 68 Ge and 57 Co transmission sources. We also tested our reconstruction and scatter correction procedure for two experimental rodent studies (a mouse and rat). For the rodent studies, we found that the average mu-values for soft-tissue regions of interest agreed with expected values to within 4%. Using a 2.2-GHz processor, each scatter correction iteration required between 6-27 min of CPU time (without any code optimization) depending on the phantom size and source used. This extra calculation time does not seem unreasonable considering that, without scatter corrections, errors in the reconstructed mu-values were between 18%-45% depending on the phantom size and transmission source used.

Nonequilibrium Langevin approach to quantum optics in semiconductor microcavities

Recently, the possibility of generating nonclassical polariton states by means of parametric scattering has been demonstrated. Excitonic polaritons propagate in a complex interacting environment and contain real electronic excitations subject to scattering events and noise affecting quantum coherence and entanglement. Here, we present a general theoretical framework for the realistic investigation of polariton quantum correlations in the presence of coherent and incoherent interaction processes. The proposed theoretical approach is based on the nonequilibrium quantum Langevin approach for open systems applied to interacting-electron complexes described within the dynamics controlled truncation scheme. It provides an easy recipe to calculate multitime correlation functions which are key quantities in quantum optics. As a first application, we analyze the buildup of polariton parametric emission in semiconductor microcavities including the influence of noise originating from phonon-induced scattering.

Incoherent interaction of Gaussian beams in photorefractive optically active crystals

The incoherent interaction of (1+1)-dimensional Gaussian beams in cubic photorefractive optically active crystals is theoretically considered. The effect of optical activity on the interaction process is discussed. The obtained results are compared with those for the case of the coherent interaction. It is shown that during of the interaction between orthogonally polarized Gaussian beams one of them is deflected under the action of the other. This phenomenon is promising for the realization of optical address positioning of light beams.

Coherent and Incoherent Interactions between Discrete-Soliton Trains in Two-Dimensional Light-Induced Photonic Lattices

The coherent and incoherent interactions between discrete-soliton trains are numerically investigated in light-induced two-dimensional photonic lattices. The solutions of discrete-soliton trains for diamond and square lattices are obtained by Petviashvili iteration method. It is found that for both the kinds of lattices, two in-phase (out-of-phase) discrete-soliton trains attract (repel) each other, and the intermediates are always accompanied with energy transfer. While the interaction forces between two incoherent discrete-soliton trains are always attractive.

Spectroscopic Studies of Band Edge Electronic and Defect States in Elemental High-k Oxide Dielectrics and Si Oxynitride Alloys onto Si(100) Substrates

This paper applies near edge X-ray absorption spectroscopy (NEXAS) and soft-X-ray photoelectron spectroscopy (SXPS) to identity different length scales of nano-crystallinity in transition metal (TM) elemental oxides. Jahn-Teller (J-T) splittings in band edge HfO2 Eg states in O K1 NEXAS spectra requires nano-crystalline grain-sizes >3 to 4 nm and coherent p-bonding interactions. The spectroscopic studies provide an unambiguous way to distinguish between two regimes of nano-crystalline order with coherent and incoherent p-bonding interactions, yielding significant information on band edge electronic structure, and electronically active defects as well. Finally, defects in non-crystalline Hf Si oxynitride alloys are shown to be qualitatively different than those in either the nano-crystalline scale regimes.