▎ 摘　　要

In recent years, graphene and its compounds (e. g., oxides) have been used as saturable absorbers in passive Q-switched and mode-locked lasers, leading to the fabrication of compact pulsed fiber lasers. In this article, we study the operation of a Q-switched ytterbium-doped fiber ring laser based on a composite saturable absorber made of graphene oxide and chromium. We show that the addition of a thin layer of chromium can lead to pulse durations ranging from 3.5 to 9.4 mu s and subsequently increasing the laser peak power. (C) 2014 Optical Society of America