We report on a bifurcation scenario from which emerges oscillations at a frequency higher than the relaxationoscillation frequency in an edge-emitting laser diode subjected to polarized optical feedback; these oscillations appear in the square-wave regime. The study has been performed experimentally and numerically based on Lang-Kobayashi model. We unveil bifurcation diagrams showing a clear bifurcation point that marks the transition between sustained and damped oscillations on the plateaus of square-waves. We extend this first bifurcation study by providing additional analytical insight to characterize the main parametric dependence of the frequency of these undamped oscillations.
We study numerically and experimentally the transition from convective to absolute dynamical instabilities in an optical system composed of a bulk photorefractive crystal subjected to a single optical feedback. We demonstrate that the convective regime is directly related to the bistability area in which the homogeneous steady state coexists with a Turing pattern solution. Outside this domain, the system exhibits either a homogeneous steady state or an absolute dynamical regime. Moreover, an external background illumination applied onto the nonlinear medium is used as an external parameter for controlling the size of the bistability area. We question the role of this parameter and show how the background illumination makes the bistability area even larger.
We study both analytically and numerically the rate equations of a laser diode subject to a filtered phase-conjugate optical feedback (FPCF). We formulate dimensionless equations for the FPCF and determine the Hopf bifurcation conditions. The coalescence of different Hopf bifurcations as the filter width decreases suggests the disappearance of the external cavity modes for a narrow width. We confirm our analytical predictions with direct numerical simulations of the FPCF equations.
We analyze numerically and experimentally the pattern formation process in an optical system composed of a bulk photorefractive crystal subjected to a single optical feedback. In this configuration, the system admits an homogeneous solution for low coupling strength. Increasing the coupling strength leads to a sub-critical bifurcation which leads to a pattern state. Such a bifurcation gives access to a well-defined hysteresis. In this paper we demonstrate that the size of the bistable area can be adjusted by different system parameters such as the intensity of the input beam, the power of an external background illumination and more interestingly by the feedback mirror tilt angle.