Abstract
Real-time observation of the emergence of coherent structures from noise via instabilities is of particular interest across disciplines ranging from biology to astrophysics. In the context of photonics, ultrafast fibre lasers provide an ideal test-bed for experimental observation of dynamical instabilities and generation of coherent structures of ultrashort pulses. Here we present experimentally obtained switch-on dynamics of counter-propagating ultrashort pulses in a bidirectional mode-locked fibre laser with delayed pulse formation via Q-switched and modulation instabilities, pronounced central wavelength drift, with the multiple-pulse formation. We define a localisation parameter using the round-trip resolved autocorrelation function to quantify the extent of the pulse formation, indicating an energy interchange between coherent features and background radiation. Furthermore, we report the formation of synchronised and unsynchronised dispersion waves. Our results reveal the complexity of the establishment of coherent features and their interaction with background radiation, contributing further towards the understanding of nonlinear systems in general.
Highlights
Real-time observation of the emergence of coherent structures from noise via instabilities is of particular interest across disciplines ranging from biology to astrophysics
The direction with the highest energy was governed by adjustment of polarisation controllers (PCs) that highlight the influence of nonlinear polarisation rotation on pulse formation[33]
It should be mentioned that the repetition rates are slightly different during Q-switched instabilities than in a mode-locked generation owing to the effect of the nonlinear refractive index and a slight central wavelength offset of Q-switched instabilities
Summary
Real-time observation of the emergence of coherent structures from noise via instabilities is of particular interest across disciplines ranging from biology to astrophysics. The availability of real-time measurement techniques like spatiotemporal dynamics, time lenses[10], Dispersive Fourier Transform (DFT)[11] and others have enabled the observation of selforganisation of such coherent features[12] and their complexes[13], soliton interactions[14] and soliton explosions[15]. Such real-time approaches enable observation of build-up dynamics of various ultrashort pulses. The existence of myriad phenomena and events shows the potential of bidirectional ultrafast laser platform to serve as an efficient test-bed for the investigation of complex dynamics of nonlinear systems in general
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