▎ 摘　　要

Employing graphene oxide (GO)-COOH film as a new saturable absorber (SA), we demonstrate a high-efficiency, high-energy Q-switched ytterbium-doped fiber (YDF) laser operating at a wavelength of 1.03 mu m for the first time. GO-COOH film was prepared using a liquid-phase exfoliation method. Stable Q-switched pulses ranging from 4.5 mu s to 1.35 mu s with repetition rate in the range of 25 kHz-135kHz were achieved. The maximum total output power was 82 mW, slope efficiency was 61.1% and the highest single pulse energy was 685 nJ at the repetition rate of 74 kHz-which is, to the best of our knowledge, the highest slope efficiency and largest pulse energy yet obtained from a Q-switched single-mode YDF laser with SA. The Q-switched YDF laser demonstrated in this paper confirms that GO-COOH is a cost-effective SA suitable for practical application in similar to 1.0 mu m Q-switched YDF lasers.