Numerical modeling of extreme events observed in the all-solid-state laser with a saturable absorber

Abstract

Extreme events (pulses of high intensity) are observed to appear spontaneously in some chaotic regimes of the self-pulsing all-solid-state laser with a saturable absorber (diode-pumped Nd:YVO4 + Cr:YAG). Until now, the mechanism of build-up of these pulses has remained unknown. Besides the practical interest in this device of widespread use, the laser with a saturable absorber is homologous to the Bénard–Rayleigh system with a solute. Experimental observations show the events to appear even if a few different transverse modes oscillate. This leads to a description in terms of a few ordinary differential equations, instead of the more usual description with an equation in partial derivatives. A minimum of five transverse modes and hole burning in the absorber are found necessary elements of the description. On the other hand, phases among the spatial Fourier components do not need to be taken into consideration. The demonstration that, in some systems at least, the formation of extreme events can be explained with a few interacting degrees of freedom has a broad impact.