Passively Q-switched fiber lasers using a multi-walled carbon nanotube polymer composite based saturable absorber

Abstract

We demonstrate a simple, compact and low cost Q-switched fiber lasers based on Erbium-doped fiber (EDF) and Thulium-doped fiber (TDF) to operate at 1534.5nm and 1846.4nm, respectively by exploiting a multi-walled carbon nanotubes (MWCNTs) polymer composite film based saturable absorber (SA). The composite is prepared by mixing the MWCNTs homogeneous solution into a dilute polyvinyl alcohol polymer solution before it is left to dry at room temperature to produce thin film. Then the film is sandwiched between two FC/PC fiber connectors and integrated into the laser cavity for Q-switching pulse generation. The EDF laser generates a stable pulse train with repetition rates ranging from 38.11kHz to 48.22kHz by varying the 980nm pump power from 39.0mW to 65.3mW. At the 65.3mW pump power, the pulse width and pulse energy were 5.3μs and 99.75nJ, respectively. The TDF laser generates a stable pulse train with 10.38kHz repetition rate, 17.52μs pulse width and 11.34nJ pulse energy at 121.1mW 800nm pump power. A higher performance Q switching is expected to be achieved in both fiber lasers with the optimization of the SA and laser cavity.