Various pulse nonlinear evolution and dynamics employing CuCrO2 nanocrystals as a promising saturable absorber

Considering that fiber lasers are a far richer nonlinear optical system, a systematical study on various pulse nonlinear evolution and dynamics by one SA has great significance. However, investigating these important pulse nonlinear dynamic evolution processes of CuCrO₂ nanocrystals as new SAs applied in ultrafast fiber lasers has never been explored. Herein, we demonstrate the excellent nonlinear optical properties of CuCrO₂ nanocrystals and investigate the potential of CuCrO₂ nanocrystals for generating various pulse nonlinear dynamic evolution processes. Firstly, the output characteristics of the passively Q-switching pulsed fiber lasers have been regulated by using CuCrO₂ nanocrystals-polyimide film and a tapered fiber. The pulse duration and repetition rate were simultaneously compressed by 10 and 222 times, the pulse energy and peak power were increased by 79 and 827 times, respectively. Secondly, we are able to generate chaotic multi-pulse wave packets and optical rogue waves by the polarization mode dispersion of single-mode fiber together with the non-instantaneous relaxation of CuCrO₂ nanocrystals. Finally, the transition from chaotic multi-pulse wave packet to giant chirped mode-locked pulse is realized by introducing high nonlinear fibers. Our results show that CuCrO₂ nanocrystals are an efficient nonlinear material for studying various nonlinear phenomena, and give a new impetus to the development of nonlinear optics and ultrafast photonics.