Dynamic modelling of electrooptically modulated vertical compound cavity surface emitting semiconductor lasers

A generalized rate equation model is used to simulate the interrelated amplitude and frequency modulation properties of Electrooptically Modulated Vertical Compound Cavity Surface Emitting Semiconductor Lasers in both large and small signal modulation regimes. It is shown that the photon lifetime in the modulator subcavity provides the ultimate limit for the 3 dB modulation cutoff frequency. It is shown that there is an optimum design (number of periods) of both the intermediate and top multistack reflectors to maximise the large-signal modulation quality

Digital data transmission using electro-optically modulated vertical-cavity surface-emitting laser with saturable absorber

An electro-optically (EO) modulated oxide-confined vertical-cavity surface-emitting laser (VCSEL) containing a saturable absorber in the VCSEL cavity is studied. The device contains an EO modulator section that is resonant with the VCSEL cavity. A type-II EO superlattice medium is employed in the modulator section and shown to result in a strong negative EO effect in weak electric fields. Applying the reverse bias voltages to the EO section allows triggering of short pulses in the device. Digital data transmission (return-to-zero pseudo-random bit sequence, 27-1) at 10Gb/s at bit-error-rates well below 10-9 is demonstrated. © 2014 AIP Publishing LLC

Systems of conservation laws: A challenge for the XXIst century

ory began in the 1950's, with the works by E. Hopf, O. Oleinik, I. Gelfand and P. Lax. Several important steps have been done since then, but obstacles have limited the theory to mainly weakly nonlinear problems and/or the single space dimension. The challenge for the XXIth century is therefore to solve large data and multi-d questions. The beauty of the field presented here lies in the variety of problems to be considered and the broad set of relevant mathematical techniques : functional analysis, dynamical systems, numerical analysis, pseudo-differential operators, differential geometry, etc... Besides, physical intuition is of great help in this kind of research. In this review, we first present the origin of conservation laws. We next describe their basic features with a non-exhaustive state-of-the-art. We conclude with a short list of open problems which we hope to be tractable in the next few decades. UMPA, CNRS # 5669, Ecole Normale Sup'erieure de Lyon