Search

Abstract: We present experimental evidence of the in-phase and out-phase synchronization of the polarization in two coupled quasi-isotropic CO2 lasers. We also show, by means of numerical simulations, how it is possible to retrieve message encoded in the polarization of the master laser from the observation of the slave laser alone, due to the synchronization. [Copyright &y& Elsevier]

The dynamics of a semiconductor laser with AC-coupled nonlinear optoelectronic feedback has been experimentally studied. A period doubling sequence of small periodic and chaotic attractors is observed, each of them displaying excitable features. This scenario is found also in a simplified physical model of the system, thus extending the concept of excitability, usually associated to fixed points, also to the case of higher-dimensional attractors. [ABSTRACT FROM AUTHOR]

The effect of temperature variation on nonlinear refractive indices of several types of liquid crystals (LCs) compound has been reported. Birefringence and the temperature gradients of refractive indices of the LCs are determined. Five samples have been investigated; two of them are E7 and MLC 6241-000. The other three have been obtained by mixing the previous two LCs in different proportions. The measurements performed at 632 nm and 1550 nm wavelengths using wedged cell refractometer method. The variation in refractive indices and birefringence were fitted theoretically using the modified Vuks equation. Excellent agreement between the fitted values and experimentally is obtained. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the feedback control of a periodically driven FitzHugh–Nagumo circuit (FHN), which displays both spiking and non-spiking behaviors in chaotic or periodic regimes. The simple high pass filter (washout filter) is compared with an all pass filter which only affects the phase characteristics of the input signal. Experimental measurements performed on the electronic implementation of the FHN are in good agreement with numerical simulations. Apart a small difference in their amplitude corrections that remain in both cases within a few percent with respect to the unperturbed spiking signal, we prove the key role of the phase characteristics of the two filters in achieving control. [Copyright &y& Elsevier]

Chaotically spiking attractors in semiconductor lasers with optoelectronic feedback have been recently observed to be the result of canard phenomena in three-dimensional phase space (incomplete homoclinic scenarios). Since light-emitting diodes display the same dynamics and are much more easily controllable, we use one of these systems to complete the attractor analysis demonstrating experimentally and theoretically the occurrence of complex sequences of periodic mixed-mode oscillations. In particular, we investigate the transition between periodic and chaotic mixed-mode states and analyze the effects of the unavoidable experimental noise on these transitions. [ABSTRACT FROM AUTHOR]

Abstract: We report on the fabrication of optical Bragg type phase gratings in polymethyl methacrylate substrates by a femptosecond Ti: Sapphire laser. As for their optical characterization, a spatially resolved microscopy interferometric technique is used to investigate the two-dimensional distribution of the refractive index change produced by the irradiation process. The technique gives a direct and quantitative two-dimensional profile of the index of refraction in irradiated PMMA, providing information on how the fabrication process depends on the laser irradiation. [Copyright &y& Elsevier]

Abstract: We present experimental and numerical evidence of polarization selection in an isotropic CO2 laser achieved by means of an unpolarized optical feedback. This mechanism can be applied in situations where the direction of polarization plays a crucial role, including polarization coding. [Copyright &y& Elsevier]