Experimental investigation on Q-switching and Q-switched mode-locking operation in gold nanorods-based erbium-doped fiber laser

We report on the generation of Q-switched and Q-switched mode-locked(QML) pulses in an erbium-doped fiber ring laser by using a polyvinyl alcohol(PVA)-based gold nanorod(GNR) saturable absorber(SA). The PVAbased GNR SA has a modulation depth of ～4.8% and a non-saturable loss of ～26.9% at 1.5 μm. A Q-switched pulse train with a repetition rate varying from 18.70 to 39.85 k Hz and a QML pulse train with an envelope repetition rate tuning from 20.31 to 31.50 k Hz are obtained. Moreover, the lasing wavelengths of the Q-switched pulses can be flexibly tuned by introducing a narrow bandwidth, tunable filter into the laser cavity. The results demonstrate that the GNRs exhibit good optical performance and can find a wide range of applications in the field of laser technology.