**3.1. Configuration of the proposed modelocked TYDFL**

Experimental setup for the Thulium-Ytterbium co-doped fiber laser (TYDFL) is shown in **Figure 13** [1]. It uses a double clad Thulium-Ytterbium co-doped fiber (TYDF) as the lasing medium in ring cavity configuration. The TYDF has an octagonal inner cladding to enhance the pump light interaction with the doped core. The core has 5.96-nm diameter with an NA of 0.23. The selected fiber length of 10 m provides more than 90% pump absorption. The fiber type SA

device was constructed by inserting graphene PVA film between two ferules. The length of total cavity is set at around 17 m, so that the net cavity dispersion is anomalous for facilitating self-starting mode locked laser.
