Passively Q-switched and mode-locked pulses in erbium-doped fiber laser based on Cr2Ge2Te6 saturable absorber

This paper reports the preparation of Cr2Ge2Te6 (CGT)-polyvinyl alcohol (PVA) by the liquid-phase exfoliation method. And the characterization of CGT nanosheets is carried out systematically. In our experiments, CGT-PVA was used as a nonlinear saturable absorber to achieve passively Q-switched erbium-doped fiber laser with wavelengths of 1531 nm and 1556 nm, respectively. The repetition frequency of the Q-switched fiber laser changes from 30.86 kHz to 70.81 kHz, with a tuning range of approximately 40 kHz. In addition, the mode-locked operation can be easily performed by controlling the polarization states in the cavity. A stable 471.2 fs soliton was obtained with a maximum pulse energy of 3.85 mW at a repetition frequency of 18.08 MHz. Our study shows that CGT nanosheets open up new opportunities for the development of future high-performance photonic devices.