Dynamics of erbium-doped fibre ring laser under cavity-loss modulation

• Experimental work on cavity-loss modulated class B laser for its dynamics.
• Fine control demonstrated in the evolution of the laser from linear to nonlinear dynamical state.
• Experimental results provide the frequency and amplitude of modulating signal for chaotic laser action.
• Dynamical results at resonance relevant for understanding physiological systems that mimic forced damped harmonic oscillators.
• Experimental results supported by results based on simulations.

The time-domain response of an erbium doped fibre laser constructed with a uni-directional ring cavity is studied when the cavity loss is sinusoidally modulated in the frequency range of the relaxation oscillation frequency of the laser. Fourier transformed data are used to analyse the spectral features. The experimental demonstration of different periodic states and chaos thus reached under the period-doubling route at kHz frequencies are substantiated with numerical calculations using parameters appropriate to the experimental conditions. Bifurcation diagrams and reconstructed attractors are calculated to show the change of different dynamical regimes while varying the modulation frequency. The modulation of intra-cavity losses in a fibre laser enables the study of its nonlinear dynamical response in a highly controlled manner.