Generation and evolution of multiple operation states in passively mode-locked thulium-doped fiber laser by using a graphene-covered-microfiber Project supported by the National Natural Science Foundation of China (Grant Nos. 11304409 and 61705028), the Natural Science Foundation of Chongqing City, China (Grant Nos. csct2013jcyjA4004 and cstc2017jcyjA0893), the Scientific and Technological Research Program of Chongqing Municipal Education Commission, China (Grant No. KJ1500422), and the Postgraduate Research Innovation Foundation of Chongqing City, China (Grant No. CYS17240). |
(color online) Raman spectrum of the monolayer graphene film. |