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Thomas Erneux

Publications and source records attributed to Thomas Erneux.

7 recordsLinked to original sources
PubMed2006

Square-wave self-modulation in diode lasers with polarization-rotated optical feedback.

The square-wave response of edge-emitting diode lasers subject to a delayed polarization-rotated optical feedback is studied in detail. Specifically, the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. Square-wave self-modulated polarization intensities oscillating in antiphase are observed experimentally. We find numerically that these oscillations naturally appear for a broad range of values of parameters, provided that the feedback is sufficiently strong and the differential losses in the normally unsupported polarization mode are small. We then investigate the laser equations analytically and find that the square-wave oscillations are the result of a bifurcation phenomenon.

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PubMed2006

Fast self-pulsing through nonlinear incoherent feedback.

We consider a double-pass ring cavity with nonlinear incoherent optical feedback and analyze its response when it is driven by a continuous laser beam. This particular cavity is equivalent, in the temporal domain, to a simple spatial-pattern-generating system made from a Kerr slice and a feedback mirror. After formulating the evolution equations, we investigate the behavior of small-amplitude solutions and obtain an expression for the round-trip gains. We then explore the important effect of dispersion in the nonlinear medium. Finally, we show that stable modes are possible by solving numerically the full nonlinear equations.

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PubMed2006

Spatio-temporal behaviors of a clock reaction in an open gel reactor.

The concentration profiles along the feeding direction of a one side fed gel reactor are analyzed for the iodate-arsenous acid reaction. Multiplicity of inhomogeneous stationary solutions is derived. It is also shown that such profiles may undergo oscillatory bifurcations under long range activation conditions. The bifurcation diagram is analyzed using a Galerkin approximation, the asymptotic validity of which is discussed.

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PubMed2005

Bifurcation to large period oscillations in physical systems controlled by delay.

An unusual bifurcation to time-periodic oscillations of a class of delay differential equations is investigated. As we approach the bifurcation point, both the amplitude and the frequency of the oscillations go to zero. The class of delay differential equations is a nonlinear extension of a nonevasive control method and is motivated by a recent study of the foreign exchange rate oscillations. By using asymptotic methods, we determine the bifurcation scaling laws for the amplitude and the period of the oscillations.

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PubMed2004

Waveguiding effects in self-pulsing vertical-cavity surface-emitting lasers.

Self-pulsing in semiconductor lasers containing a saturable absorber is well documented. We propose an alternative mechanism leading to self-pulsing in vertical-cavity surface-emitting lasers. We specifically consider waveguiding effects and determine the conditions for self-pulsing. Our theoretical and numerical results agree with experimental observations reported by Willemsen et al. [Appl. Phys. Lett. 77, 3514 (2000)].

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PubMed2003

External cavity modes of semiconductor lasers with phase-conjugate feedback.

External cavity modes (ECMs) of a semiconductor laser with phase-conjugate feedback are defined as time-periodic pulsating intensity solutions exhibiting a frequency close to an integer multiple of the external cavity frequency. As the feedback rate progressively increases from zero, they sequentially appear as stable attractors in the bifurcation diagram. We construct a simple analytical approximation of these pulsating intensity solutions and determine their frequencies. We show that branches of ECMs are isolated. Finally, the validity of our approximation is tested by comparing numerical bifurcation diagrams obtained by simulation and continuation techniques with our analytical results.

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