Considerations of a classical model for spontaneous emission in a nonhomogeneous medium

1992 ◽  
Vol 70 (8) ◽  
pp. 631-636
Author(s):  
André Reid ◽  
Michel Piché
Keyword(s):  
General Solution ◽  
Frequency Shift ◽  
Spontaneous Emission ◽  
Transition Rate ◽  
Classical Model ◽  
Nonhomogeneous Medium ◽  
Effective Polarizability ◽  
Analytical Expressions

The classical model for spontaneous emission from a source embedded in a nonhomogeneous medium is examined in a new light. It is shown that the general solution may be expressed in terms of an effective polarizability associated with the transition being modeled. The case of a transition occurring in the vicinity of a perfect mirror is then studied as an illustration. Analytical expressions for the frequency shift and changes in the transition rate as a function of distance are found.

scholarly journals Molecular-Theory of High Frequency Dielectric Susceptibility of Nematic Nanocomposites

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 970
Author(s):  
Mikhail A. Osipov ◽  
Alexey S. Merekalov ◽  
Alexander A. Ezhov
Keyword(s):  
Plasmon Resonance ◽  
High Frequency ◽  
Volume Fraction ◽  
Simple Expression ◽  
Dielectric Anisotropy ◽  
Dielectric Susceptibility ◽  
Nanoparticle Volume Fraction ◽  
Effective Polarizability ◽  
Dielectric And Optical Properties ◽  
Analytical Expressions

A molecular-statistical theory of the high frequency dielectric susceptibility of the nematic nanocomposites has been developed and approximate analytical expressions for the susceptibility have been obtained in terms of the effective polarizability of a nanoparticle in the nematic host, volume fraction of the nanoparticles and the susceptibility of the pure nematic phase. A simple expression for the split of the plasmon resonance of the nanoparticles in the nematic host has been obtained and it has been shown that in the resonance frequency range the high frequency dielectric anisotropy of the nanocomposite may be significantly larger than that of the pure nematic host. As a result, all dielectric and optical properties of the nanocomposite related to the anisotropy are significantly enhanced which may be important for emerging applications. The components of the dielectric susceptibility have been calculated numerically for particular nematic nanocomposites with gold and silver nanoparicles as functions of the nanoparticle volume fraction and frequency. The splitting of the plasmon resonance has been observed together with the significant dependence on the nanoparticle volume fraction and the parameters of the nematic host phase.

Distortion of Polymer Matrix Composite Panels Under Transverse Thermal Gradients

2007 ◽  
Author(s):  
Pei Gu ◽  
R. J. Asaro
Keyword(s):  
General Solution ◽  
Polymer Matrix ◽  
Thermal Loading ◽  
Polymer Matrix Composites ◽  
Functionally Graded ◽  
Thermal Distortion ◽  
Matrix Composites ◽  
Graded Materials ◽  
Internal Forces ◽  
Analytical Expressions

This paper discusses the distortion of panels made by fiber reinforced polymer matrix composites under transverse thermal-loading conditions. We formulate thermal distortion from the bending theory of functionally graded materials. General solution for thermal distortion is derived in terms of material variation and temperature profile along the thickness of the panels. Using the general solution, analytical expressions of thermal distortion and associated internal forces for commonly used end supports are obtained. From these solutions, we discuss the failure mechanism induced by thermal distortion and design criteria that can be placed to prevent such failure. The roles of geometry, temperature and temperature gradients, and the competition among them in the process of structural failure are addressed.

General solution for the complex frequency shift in microwave measurements of thin films

2001 ◽  
Vol 64 (22) ◽  
Author(s):  
D.-N. Peligrad ◽  
B. Nebendahl ◽  
M. Mehring ◽  
A. Dulčić ◽  
M. Požek ◽  
...  
Keyword(s):  
Thin Films ◽  
General Solution ◽  
Frequency Shift ◽  
Microwave Measurements ◽  
Complex Frequency

An Analytical Poroelastic Model of a Nonhomogeneous Medium Under Creep Compression for Ultrasound Poroelastography Applications—Part II

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Md Tauhidul Islam ◽  
J. N. Reddy ◽  
Raffaella Righetti
Keyword(s):  
Normal Tissue ◽  
Soft Tissue Tumor ◽  
Fluid Pressure ◽  
Companion Paper ◽  
Finite Element Models ◽  
Nonhomogeneous Medium ◽  
Statistical Comparison ◽  
Poroelastic Model ◽  
The One ◽  
Analytical Expressions

An analytical theory for the unconfined creep behavior of a cylindrical inclusion (simulating a soft tissue tumor) embedded in a cylindrical background sample (simulating normal tissue) is presented and analyzed in this paper. Both the inclusion and the background are considered as fluid-filled, porous materials, each of them being characterized by a set of mechanical parameters. Specifically, in this derivation, the inclusion is assumed to have significantly higher interstitial permeability than the background. The formulations of the effective Poisson's ratio (EPR) and fluid pressure in the inclusion and in the background are derived for the case of a sample subjected to a creep compression. The developed analytical expressions are validated using finite element models (FEM). Statistical comparison between the results obtained from the developed model and the results from FEM demonstrates accuracy of the proposed theoretical model higher than 99.4%. The model presented in this paper complements the one reported in the companion paper (Part I), which refers to the case of an inclusion having less interstitial permeability than the background.

scholarly journals High-power amplified spontaneous emission pulses with tunable coherence for efficient non-linear processes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nicolas Valero ◽  
Denis Marion ◽  
Jerome Lhermite ◽  
Jean-Christophe Delagnes ◽  
William Renard ◽  
...  
Keyword(s):  
Spontaneous Emission ◽  
High Power ◽  
Second Harmonic ◽  
Classical Model ◽  
Linear Method ◽  
Amplified Spontaneous Emission ◽  
Linear Process ◽  
Fiber System ◽  
Linear Processes ◽  
Non Linear

AbstractWe report on a detailed study of an amplified spontaneous emission source operated in a pulsed regime with particular attention paid to the influence of high-intensity chaotic temporal events on the generation of nonlinear processes. To this aim, we have developed a monolithic high-power fiber system delivering partially coherent pulses of adjustable coherence. We also have demonstrated a non-linear method to characterize the stochastic properties of the source mitigating the bandwidth limitation of linear techniques. Measured parameters of the source for various configurations are presented. An enhanced classical model has been established to reproduce the statistical properties of the source and predict the behaviour when exciting non-linear processes. Finally, a non-linear process (second harmonic generation) is investigated comparing the efficiency when the process is pumped by a pulsed beam with maximal and low coherence.

scholarly journals Using high refractive index nanoparticles to inhibition of spontaneous emission

2021 ◽  
Vol 65 (5) ◽  
pp. 546-551
Author(s):  
D. V. Guzatov ◽  
S. V. Gaponenko
Keyword(s):  
Refractive Index ◽  
Spontaneous Emission ◽  
Spectral Range ◽  
Transition Rate ◽  
High Refractive Index ◽  
Visible Spectral Range ◽  
Optimal Size ◽  
Spherical Nanoparticles ◽  
Optimal Distance

 The article discusses the issues of inhibition of spontaneous emission of molecules by using silicon spherical nanoparticles and dimers made from them. It is shown that at different wavelengths of the visible spectral range, the value of the total spontaneous transitions rate in a molecule located at an optimal distance with respect to the structure with silicon nanospheres and at an optimal size of the structure can be up to 5–10 times lower than the transition rate in the case when the nanoparticles are absent.

scholarly journals Spontaneous Emission of an Atom Near an Oscillating Mirror

Symmetry ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1384 ◽  
Author(s):  
Alessandro Ferreri ◽  
Michelangelo Domina ◽  
Lucia Rizzuto ◽  
Roberto Passante
Keyword(s):  
Spontaneous Emission ◽  
Transition Rate ◽  
Modulation Frequency ◽  
Vacuum State ◽  
Central Peak ◽  
Time Dependent ◽  
Level System ◽  
Radiative Processes ◽  
Physical Features ◽  
Plate Distance

We investigate the spontaneous emission of one atom placed near an oscillating reflecting plate. We consider the atom modeled as a two-level system, interacting with the quantum electromagnetic field in the vacuum state, in the presence of the oscillating mirror. We suppose that the plate oscillates adiabatically, so that the time-dependence of the interaction Hamiltonian is entirely enclosed in the time-dependent mode functions, satisfying the boundary conditions at the plate surface, at any given time. Using time-dependent perturbation theory, we evaluate the transition rate to the ground-state of the atom, and show that it depends on the time-dependent atom–plate distance. We also show that the presence of the oscillating mirror significantly affects the physical features of the spontaneous emission of the atom, in particular the spectrum of the emitted radiation. Specifically, we find the appearance of two symmetric lateral peaks in the spectrum, not present in the case of a static mirror, due to the modulated environment. The two lateral peaks are separated from the central peak by the modulation frequency, and we discuss the possibility to observe them with actual experimental techniques of dynamical mirrors and atomic trapping. Our results indicate that a dynamical (i.e., time-modulated) environment can give new possibilities to control and manipulate also other radiative processes of two or more atoms or molecules nearby, for example their cooperative decay or the resonant energy transfer.

Nonlinear resonant wave motion of a radiating gas

1973 ◽  
Vol 60 (1) ◽  
pp. 161-186 ◽  
Author(s):  
James E. Eninger ◽  
Walter G. Vincenti
Keyword(s):  
Wave Equation ◽  
General Solution ◽  
Shock Waves ◽  
Resonant Frequency ◽  
Spontaneous Emission ◽  
Wave Motion ◽  
Black Body ◽  
Black Body Radiation ◽  
Relative Level ◽  
Resonant Wave

A method due to Chester is applied to the theoretical study of resonant wave motion of a radiatively active gas. The inviscid non-conducting grey gas is confined between two infinite parallel walls, and a one-dimensional wave motion is driven by a sinusoidally varying input of black-body radiation from one of the walls. For sufficiently weak driving radiation, the motion can be described by the general solution of the classical wave equation (with the functional form of the solution still undetermined) plus a particular solution due to the driving radiation. When the driving is done at or near a resonant frequency, however, nonlinearities and perturbations in spontaneous emission from the gas must be taken into account before application of the boundary conditions. Such application then leads to a nonlinear integral equation governing the undetermined function in the general solution of the wave equation. This equation is solved numerically by the method of parametric differentiation.In a frequency range around resonance and for a sufficiently weak relative level of spontaneous emission, the nonlinearities give rise to shock waves (numberingNat theNth resonant frequency) that are repeatedly reflected at the walls. The perturbations in spontaneous emission give rise to damping, however, and for sufficiently high levels of emission the shock waves disappear. Specific results for various values of optical thickness and various relative levels of spontaneous emission are presented at frequencies in a range around the first resonance.

The Role of VLBI in the Establishment of Coordinate Systems

1975 ◽  
Vol 26 ◽  
pp. 293-295 ◽  
Author(s):  
I. Zhongolovitch
Keyword(s):  
General Solution ◽  
Future Development ◽  
Rational Approach ◽  
Radio Telescopes ◽  
Coordinate Systems ◽  
Tectonic Plates ◽  
Astronomical Observations ◽  
Optical Instruments ◽  
Fundamental Polyhedron

Considering the future development and general solution of the problem under consideration and also the high precision attainable by astronomical observations, the following procedure may be the most rational approach:1. On the main tectonic plates of the Earth’s crust, powerful movable radio telescopes should be mounted at the same points where standard optical instruments are installed. There should be two stations separated by a distance of about 6 to 8000 kilometers on each plate. Thus, we obtain a fundamental polyhedron embracing the whole Earth with about 10 to 12 apexes, and with its sides represented by VLBI.

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