Coherence and Stochastic Resonances in Chaotic Semiconductor Lasers

Abstract

In the last three decades a plethora of works has been devoted to study both stochastic coherence (SC) and stochastic resonances (SR) phenomena in chaotic dynamical systems. In this work we experimentally investigated the route to chaos in stable dynamical laser diode system via optoelectronic feedback, SC or CR and SR phenomena. Our work consists of three phases: Firstly: we report the experimental evidence the spiking generation in semiconductor laser with a closed loop ac-coupled optoelectronic feedback. The results show that when the feedback strength fixed in a certain value and fluctuating the values of the bias current, stability in chaotic regime decreases towards unstable behavior. At a given laser bias current value with changing in the feedback strength, the behavior of the stability laser diode regime displayed sequence gradation from stable, quasi-stable and chaotic states. The results declare that optoelectronic feedback is one of the important routes to the chaos, through the perturbations of bias current (δ) or feedback strength (ε) as control parameters. Secondly: we show that dynamical nonlinear chaotic laser diode (LD) system, can display the main feature of coherence resonance, in particular the presence of noise signal exhibits oscillations whose regularity is optimal for some intermediate value of the noise intensity (D). Finally: we observed that a dynamical chaotic system of (LD) driven to both periodic weak forcing (signal) and random perturbation (white noise) sequentially, shows a resonance (peak in the power spectrum) where that peak is absent whenever either the forcing or the perturbation is absent, this feature so call stochastic resonance (SR). The presence of the noise becomes beneficial to signal up to a point where an increase of the noise improves the performance for transmitting or detecting the signal. At the end of this work, we summarized all the results obtained from this work, and also we suggested some works for future in the field of semiconductor laser applications.