Mode-locked thulium doped fiber laser utilizing tungsten trioxide saturable absorber

Abstract

Stable mode-locked thulium-doped fiber laser (TDFL) is demonstrated using tungsten trioxide (WO3) deposited on a microfiber as a passive saturable absorber. The WO3 composite was prepared and deposited onto the microfiber before being integrated into the laser cavity. Owing to the interaction of WO3 nanoparticles with the evanescent field of the propagating light, a stable soliton mode-locked TDFL at 1955.3 nm with 3 dB bandwidth of 3.22 nm, repetition rate of 10.98 MHz, and pulse width of 1.26 ps was obtained. The pulse energy and peak power were then calculated to be 0.59 nJ and 419 W respectively, with a signal-to-noise ratio of 54.8 dB. The microfiber WO3 saturable absorber showed no sign of deterioration even though the laser cavity was pumped at 1.15 W power. The findings indicate that WO3 could be an excellent candidate as saturable absorber for mode-locking generation at mid-infrared fiber lasers.