▎ 摘　　要

The use of a graphene oxide (GO)-deposited D-shaped fiber as a saturable absorber for mode locking of a thulium-doped fiber laser is experimentally demonstrated. By using the evanescent field interaction of an oscillating beam with GO, a passive mode locking operation at a wavelength of similar to 1.91 mu m is shown to be achievable from a ring cavity. Stable picosecond pulses are readily obtained at a repetition rate of 15.9 MHz. This demonstration confirms that GO is a cost-effective saturable absorber applicable for similar to 2 mu m ultrafast pulse generation. (C) 2012 The Japan Society of Applied Physics