Paul E. Sterian

Solitons propagation in optical fibers computer experiments for students training

This paper aims to present a numerical simulation of soliton propagation, based on Korteweg-de Vries equation, using a powerful PC program (Maple 10) who permits to perform numerical calculations, plot or animate functions and manage analytical expressions. We discuss a model of one soliton propagation in a nonlinear medium and the interaction between two solitons, taking account both of fiber dispersion and nonlinearity. Numerical simulations show how soliton propagate in optical fibers and how two solitons interact, passing one through another, with only a phase change. These simulations are thought to be useful for both the designers working in digital data transmission and students performing numerical simulation on soliton propagation as computer experiments in Optoelectronics laboratory.

Study on the fermion systems coupled by electric dipol interaction with the free electromagnetic field

We established a master equation for a system of fermions coupled by electric dipol interaction with the free electromagnetic field. This equation has a Lindblad equation form, with a hamiltonian part corresponding to the shell model and a dissipative part with microscopic coefficients depending on physical constants, matrix elements, and temperature. The dependence on the transition energy of the dissipative coefficients satisfies asymptothycal conditions for the energy transfer in full agreement with the principle of the detailed balance.

Mathematical Models of Dissipative Systems in Quantum Engineering

The paper shows the results of theoretical research concerning the modeling and characterization of the dissipative structures generally, the dissipation being an essential property of the system with self-organization which include the laser-type systems also. The most important results presented are new formulae which relate the coupling parameters 𝑎𝑖𝑛 from Lindblad equation with environment operators Γ𝑖; microscopic quantitative expressions for the dissipative coefficients of the master equations; explicit expressions which describe the changes of the environment density operator during the system evolution for fermion systems coupled with free electromagnetic field; the generalized Bloch-Feynman equations for 𝑁-level systems with microscopic coefficients in agreement with generally accepted physical interpretations. Based on Maxwell-Bloch equations with consideration of the interactions between nearing atomic dipoles, for the dense optical media we have shown that in the presence of the short optical pulses, the population inversion oscillates between two extreme values, depending on the strength of the interaction and the optical pulse energy.

Modeling Quantum Well Lasers

In semiconductor laser modeling, a good mathematical model gives near-reality results. Three methods of modeling solutions from the rate equations are presented and analyzed. A method based on the rate equations modeled in Simulink to describe quantum well lasers was presented. For different signal types like step function, saw tooth and sinus used as input, a good response of the used equations is obtained. Circuit model resulting from one of the rate equations models is presented and simulated in SPICE. Results show a good modeling behavior. Numerical simulation in MathCad gives satisfactory results for the study of the transitory and dynamic operation at small level of the injection current. The obtained numerical results show the specific limits of each model, according to theoretical analysis. Based on these results, software can be built that integrates circuit simulation and other modeling methods for quantum well lasers to have a tool that model and analysis these devices from all points of view.

New Results in Optical Modelling of Quantum Well Solar Cells

This project brought further advancements to the quantum well solar cell concept proposed by Keith Barnham. In this paper, the optical modelling of MQW solar cells was analyzed and we focussed on the following topics: (i) simulation of the refraction index and the reflectance, (ii) simulation of the absorption coefficient, (iii) simulation of the quantum efficiency for the absorption process, (iv) discussion and modelling of the quantum confinement effect, and (v) evaluation of datasheet parameters of the MQW cell.

Dynamics of a two-mode erbium-doped fiber laser

The dynamics of a two-mode model of the erbium-doped fiber laser is analytically and numerically investigated. Apart from the intrinsic nonlinearity of a two-mode laser, the existence of erbium ion pairs introduces a supplementary nonlinearity with a saturable absorber action. The laser is described through six coupled differential equations. Steady states are analyzed, their dependence on the laser parameters, and the onset of the self-pulsing and chaotic states is pursued.

Charge Coupled Devices as Particle Detectors

As it is well known, while the most important advantages of the charge coupled devices, as high energy particle detectors are related to their (a) extremely high sensitivity (very important for the underground laboratories, also) and (b) huge number of very small independent components (pixels) of the magnitude order of , which allow the separate impressions of many different “signatures” of (silicon lattice defects produced by) these particles, their main disadvantages refer to the (a) difficulty to distinguish between the capture traps (of free electrons and holes, resp.) produced by the radiation particles and the numerous types of traps due to the contamination or dopants and (b) huge number of types of lattice defects due to the irradiation. For these reasons, this work achieves a state of art of the (i) main experimental methods and (ii) physical parameters intended to the characterization of the main types of traps embedded in the silicon lattice of CCDs. There were identified also some new physical parameters useful in this aim, as the polarization degree of capture cross-sections and the state character, as well as some new useful notions, as the trans-Fermi level capture states.

Exact quantum master equations for Markoffian systems

We show that the general quantum master equation used in quantum optics can be put in the form of Lindblad’s master equation obtained in the frame of the general theory of the dynamical semigroups. In this case, the dissipative interaction is described in the most general form by a system of openness parameters. We find the expressions of these parameters as functions of the operators of the dissipative environment.

New results in forecasting of photovoltaic systems output based on solar radiation forecasting

Accurate short term forecasting of photovoltaic (PV) systems output has a great significance for fast development of PV parks in South-East Europe, as well as in the case of Romania. Our approach on solar radiation forecast is based on two methods: autoregressive integrated moving average and artificial neural network. We have analyzed the daily solar irradiation variability and defined four synoptic situations to include the influence of cloudiness changes. Decadal variations of global solar radiation were also considered for long term forecast. The results were obtained using a database from Bucharest/Afumati Meteorological Station. We have developed an accurate forecasting model for a PV systems power output based on solar radiation forecasting results. By using complete datasets and including meteorological parameters such as cloudiness, relative humidity, air temperature, atmospheric pressure, and sunshine duration, as input for our model, we have managed to minimize forecasting errors and to obtain a more accurate forecast of the power output for the analyzed demo PV system.

Perspectives on Entangled Nuclear Particle Pairs Generation and Manipulation in Quantum Communication and Cryptography Systems

Entanglement between two quantum elements is a phenomenon which presents a broad application spectrum, being used largely in quantum cryptography schemes and in physical characterisation of the universe. Commonly known entangled states have been obtained with photons and electrons, but other quantum elements such as quarks, leptons, and neutrinos have shown their informational potential. In this paper, we present the perspective of exploiting the phenomenon of entanglement that appears in nuclear particle interactions as a resource for quantum key distribution protocols.