François Sanchez

Measurement of the elliptical birefringence of single-mode optical fibers

The polarization properties of single-mode optical fibers are theoretically modeled with use of the Jones formalism. The fiber is described as an elliptical birefringent plate. The properties predicted by this model are discussed and lead to the development of a simple experimental method to extract the parameters that describe a real fiber. A magneto-optic method that measures the beat length of the fiber is also presented and gives a more complete description of the fiber. The validity of the model is then clearly established. Finally, the wavelength dependence of the parameters characteristic of the fiber is experimentally investigated.

Experimental and theoretical study of higher-order nonlinearities in chalcogenide glasses

Abstract We investigate experimentally and theoretically the nonlinear properties of two distinct chalcogenide glasses. Nonlinearities are measured through a spatially resolved Mach–Zehnder interferometer. It is shown that the resulting nonlinear index coefficient cannot be correctly described with the usual cubic model. A more convenient theory is developed assuming a medium with two-photon nonlinear absorption and both cubic ( n 2 ) and quintic ( n 4 ) nonlinear index variations. The resulting closed-form expression for the effective nonlinear index coefficient allows to extract the cubic and quintic index coefficients.

Passively mode-locked erbium-doped double-clad fiber laser operating at the 322nd harmonic

We report passive mode locking of a soliton erbium-doped double-clad fiber laser operating at the 322nd harmonic of the fundamental cavity frequency. Repetition rates up to 3 GHz have been obtained with pulses of 1 ps duration and 18 pJ of energy. The supermode suppression at the 322nd harmonic is better than 25 dB. In addition, the transition dynamics from a bunched state of pulses to stable harmonic mode locking is presented, revealing a very long time scale.

EVIDENCE OF A SATURABLE-ABSORPTION EFFECT IN HEAVILY ERBIUM-DOPED FIBERS

A new configuration for erbium-doped fiber lasers in which two different connected fibers are used is studied: one is heavily and the other weakly doped. It is demonstrated that the dynamics of such a system depends on the fiber into which the pump is injected. The experimental results are interpreted in the framework of an ion-pair interaction model.

Evidence of Brillouin scattering in an ytterbium-doped double-clad fiber laser.

We have designed and performed an experiment that permitted direct observation of Brillouin backscattering in an Yb-doped double-clad fiber laser. Fifteen Brillouin-shifted frequencies were observed for the first time to our knowledge. We clearly demonstrate that stimulated Brillouin scattering is directly responsible for both fast transient dynamics of the laser and reduction of the lasers pulse width.

Mode-lock, Q-switch and CW operation of an Yb-doped double-clad fiber ring laser

We investigate the dynamics of a high power unidirectional Yb-doped fiber ring laser with an intracavity polarizer placed between two halfwave plates. We show that, depending on the respective orientation of the phase plates, the laser operates in different regimes: CW, Q-switched, mode locked, or unstable. The passive method exposed here allows us to choose the operating regime of the laser by a simple rotation of a halfwave plate.

Universal soliton pattern formations in passively mode-locked fiber lasers

We investigate multiple-soliton pattern formations in a figure-of-eight passively mode-locked fiber laser. Operation in the anomalous dispersion regime with a double-clad fiber amplifier allows generation of up to several hundreds of solitons per round trip. We report the observation of remarkable soliton distributions: soliton gas, soliton liquid, soliton polycrystal, and soliton crystal, thus indicating the universality of such complexes.

Antiphase dynamics and chaos in self-pulsing erbium-doped fiber lasers

We present experimental evidence of antiphase dynamics in self-pulsing erbium-doped fiber lasers operating simultaneously at 1.536- and 1.55-microm wavelengths. Autonomous chaos is also observed for several ranges of pumping rates. The fractal dimension of the chaotic attractor, calculated from experimental data by use of the Procaccia method, is found to depend on the pumping ratio but always remains smaller than 4.1, regardless of the chaotic regime considered.

Influence of ion pairs on the dynamical behaviour of Er3+-doped fibre lasers

We demonstrate experimentally the influence of ion-pair concentration on the dynamical behaviour of erbium-doped fibre lasers. At low pair densities, the laser has a CW output, while at higher densities it exhibits a self-pulsing behaviour. For intermediate pair concentrations, the output intensity evolves continuously from an infinite train of pulses to a CW steady state as the pumping ratio is increased.

Generation of bound states of three ultrashort pulses with a passively mode-locked high-power Yb-doped double-clad fiber laser

We report the generation of high-power ultrashort bound states of three pulses in an ytterbium-doped double-clad fiber laser. The laser is mode-locked through nonlinear polarization rotation technique in a unidirectional cavity configuration. A pair of diffraction grating is incorporated in the cavity to compensate for the normal dispersion of the fiber. The laser generates chirped bound states of three pulses with either equal or different time separations, with more than 500-pJ energy per pulse. These pulses are subsequently compressed to 100 fs with a compression factor of more than 40.