High intensity and frequency modulations based on infinite pulse trains and ultrashort pulses in a modified semiconductor laser system.

Abstract

We report on high intensity and frequency modulations (IM-FM) through various infinite pulse trains derived from the dynamics of a modified rate equations laser system endowed with an additional control parameter (γ), wherein a direct modulation of the injection current is performed. Analytical and numerical investigations showcase the significant impact of the additional control parameter on the enhancement of the relaxation frequency and a resizing of the modulation bandwidth through a full control of the modulation peak. In this way, linear stability of the new modulated laser system is carried out around the steady-state solutions by using the small-signal analysis method, wherefrom we demonstrate that the stability of equilibria can be governed by γ-variations. A route to a new infinite-scroll vibrational attractor through FM-to-IM conversion is investigated, leading to a linear phase-and-frequency-modulated link. Both scenarios based on the propagation of asymmetric horn-shaped pulse trains lead to high FM and exhibit various amplitude-squeezed states and phase-squeezed states by varying the α-factor and the frequency detuning parameter, respectively. Intricate phenomena such as the nonlinear generation and collapsing of ultrashort pulse trains resulting from the infinite pulse trains, internal crisis appearing as a ground for the amplitude-squeezed state of light, and the modulation instability of large amplitude of laser arising from unstable fixed points are also investigated in this work.