  In this work we demonstrate comprehensive studies on graphene oxide (GO) and
reduced graphene oxide (rGO) based saturable absorbers (SA) for mode-locking of
Er-doped fiber lasers. The paper describes the fabrication process of both
saturable absorbers and detailed comparison of their parameters. Our results
show, that there is no significant difference in the laser performance between
the investigated SA. Both provided stable, mode-locked operation with sub-400
fs soliton pulses and more than 9 nm optical bandwidth at 1560 nm center
wavelength. It has been shown that GO might be successfully used as an
efficient SA without the need of its reduction to rGO. Taking into account
simpler manufacturing technology and the possibility of mass production, GO
seems to be a good candidate as a cost-effective material for saturable
absorbers for Er-doped fiber lasers.
