Nonlinear Dynamics in Directly Modulated Semiconductor Lasers with Optical Loop Mirror Feedback

Abstract

<p class="MsoNormal" style="text-align:justify;"> <span lang="EN-GB">The investigation of the nonlinear dynamics of a semiconductor laser based on nonlinear optical loop mirror (NOLM) feedback using Ge doped optical fiber was carried out experimentally. Animations of compilations of the output power as a function of time series and phase plane with effects of optical feedback level, carrier current and modulation signal strength are demonstrated as a tool to give insight into the laser dynamics. </span><span lang="EN-US">Different dynamic states, including </span><span lang="EN-GB">2</span><span lang="EN-US">×</span><span lang="EN-GB">, 4</span><span lang="EN-US">×</span><span lang="EN-US"> </span><span lang="EN-GB">multiplication and </span><span lang="EN-US">quasi-</span><span lang="EN-GB">periodic and periodic frequency-locked pulsing states extended to chaotic behaviour </span><span lang="EN-US">were observed by varying the parameters of modulated frequency and optical feedback strength. </span><span lang="EN-GB">The frequency-locked pulsing states were observed to exhibit a harmonic frequency-locking phenomenon and the pulsing frequency is locked to a harmonic nonlinearity in loop instead of the modulated frequency.</span> </p&gt