Abstract

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A new all-photonic switching of nonlinear optical materials with very low signal/noise background was presented. Fe and Mg were used to prepare doped and co-doped PbS/PVA freestanding nanocomposite; films were prepared by a simple chemical method with different doping concentrations. The X-ray diffraction patterns, scanning electron microscope images, and optical absorption spectrum of the prepared films were examined. The crystallinity and optical band gap of the prepared co-doped PbS/PVA were found to be affected by Fe and Mg, doping concentrations. The all prepared samples showed a blue shift in the absorption spectra and the optical band gap was increased when the doping concentration is increased. The all-optical switching effect performance of metal doped and (Fe, Mg) co-doped PbS/PVA with various Fe and Mg concentrations were investigated. The results showed that the (Fe, Mg) co-doped PbS/PVA at 1.2%M Fe and 0.8%M Mg doping concentration can  demonstrate an active all-photonic switching device and lead to the realization with maximum modulation depth of 86.5% and switching contrast of 8.8 dB at minimum switching time of 47 ms.

We present a random Raman fiber laser pumped by a continuous-wave 1480nm source where neither a visible saturable absorber nor a fiber Bragg grating were incorporated. The backward pumping feedback loop allows a single direction of 1584nm wave propagation under tighter focusing of a dispersion compensating fiber (DCF). This geometry that implies a stronger Kerr-lensing effect supports two types of nonlinear broadening that were achieved in the stable output power generation. The first that agrees well to wave kinetics theory favors 1.76 to 3.53nm spectral progress. Against this flow, another type of wider broadening begun at 4.88nm before reducing gradually to 4.05nm with the increase in pump power. The former corresponds to a maximum of 6.3 times broadening ratio with respect to the pump linewidth. To date, this is the best achievement in the world at just below 1.7 W pump power level especially without utilizing pump-pulse synchronization or any external mode-locking modulations. In contrast without the tighter confinement geometry, the initiation of 4.25nm bandwidth was realized in the unstable power zone. These ascertain the double roles of dispersion compensating fiber as a stabilizing factor as well as for dispersion management.