Nonlinear Dynamics in Optoelectronics Structures with Quantum Well

The author presents some results on nonlinear dynamics in optoelectronics nanostructures as lasers with quantum wells and quantum well solar cells using mathematical modeling and numerical simulations of the phenomena which take place in such kinds of structures. The nonlinear dynamics takes the complexity of the phenomena into account, which govern the field-substance interaction. Computational software was elaborated to study the nonlinear phenomena in such quantum devices, which put into evidence their complex nonlinear dynamics, characterized by bifurcation points and chaos, and the critical values of the parameters being determined. The mathematical modeling and numerical simulations for the quantum well solar cells for optimizing the values of their optical parameters (refraction index, reflectance, and absorption) were also analyzed, so that the conversion efficiency of the devices can be improved. Although in our study we have considered only rectangular quantum wells, the hybrid model allows computing the optimum values of the parameters whatsoever the form of the quantum wells. The developed numerical models and the obtained results are consistent with the existing data in the literature for the optoelectronics of quantum well structures, having important implications in the applications

Design Study of an Underground Detector for Measurements of the Differential Muon Flux

Since 2006 an underground laboratory is in operation in Unirea salt mine from Slanic Prahova Romania. A new rotatable detector for measurements of the directional variation of the muon flux has been designed and will be put in operation at the end of 2013. The detector will be used to investigate the possible presence of unknown cavities in the salt ore. Preliminary muon flux measurements performed in the underground of Slanic Prahova salt mine show an important variation of the flux with the thickness of the rock but indicate also that more precise data are necessary. Based on that, a modern detector using 4 layers of plastic scintillators bars has been designed. The detector is installed on a rotatable and mobile frame which allows precise directional measurements of the muon flux on different locations in the mine. In order to investigate the performances of the detector, detailed Monte Carlo simulations have been performed using several codes available on the market. The simulations show that the detector can be used for measurements of the differential flux of cosmic ray muons and for the detection of hidden cavities in the ore

Intitulé Etude et simulation d’un laser à semiconducteur à puits quantique (Study and simulation of a semiconductor single quantum well laser)

Nowadays, the development of short wavelength lasers which can emit coherent light in green, blue, violet, and ultraviolet (UV) regimes become one of the most important challenges in the field of optoelectronics, and in particular, those made by III-nitride wide bandgap materials. During this thesis, a modelling of a wurtzite compressive strain quantum well nanostructure laser based on III-nitride GaN/AlxGa1-xN was achieved by the use of ATLAS of SILVACO TCAD simulation software. The main focus of this research work was to study the effect of the quantum well (QW) width, carrier density, and Aluminum (Al) concentration in the barrier layers on the optical (optical gain, spontaneous emission and the power spectral density) and electrical characteristics of a gallium nitride (GaN)-based QW laser diode, which is investigated by means of a careful modelling analysis in a wide range of temperature, all by using two different approaches for the calculation of energy band edges and effective masses, where in the first we assume the conduction and valence bands are parabolic, however, the second model consider the non-parabolicity of the bands and computed via 6×6 band k.p formalism. The results allow us to say that, by the use k.p method, we can get more accurate results that are expressed as a more significant optical gain with low threshold current density operating at high temperatures and emitting in the ultraviolet (UV) regime

Advances in Optical Amplifiers

Optical amplifiers play a central role in all categories of fibre communications systems and networks. By compensating for the losses exerted by the transmission medium and the components through which the signals pass, they reduce the need for expensive and slow optical-electrical-optical conversion. The photonic gain media, which are normally based on glass- or semiconductor-based waveguides, can amplify many high speed wavelength division multiplexed channels simultaneously. Recent research has also concentrated on wavelength conversion, switching, demultiplexing in the time domain and other enhanced functions. Advances in Optical Amplifiers presents up to date results on amplifier performance, along with explanations of their relevance, from leading researchers in the field. Its chapters cover amplifiers based on rare earth doped fibres and waveguides, stimulated Raman scattering, nonlinear parametric processes and semiconductor media. Wavelength conversion and other enhanced signal processing functions are also considered in depth. This book is targeted at research, development and design engineers from teams in manufacturing industry, academia and telecommunications service operators