Sol-Gel growth of zinc oxide particles on graphene sheets for mode-locking in Thulium/Holmium-doped fiber laser

Abstract

In this work, Graphene/Zinc Oxide (G/ZnO) nanocomposite was used to generate mode-locked pulses in Thulium/Holmium-doped fiber (THDF). The sol-gel method was used to synthesize the ZnO particles decorated graphene sheets. The G/ZnO nanocomposite solution was deposited onto the arc-shaped fiber that had been fabricated to act as the saturable absorber (SA) device. The nonlinear optical response of G/ZnO-based SA was investigated via the twin detection approach, in which it exhibits a modulation depth of 15.62 % and a saturation intensity of 0.031 MW/cm2. After incorporating the fabricated SA into the THDF laser cavity, mode-locked pulses were produced at a threshold pump power of 274.3 mW with a centre wavelength of 1895 nm, fundamental frequency of 11.82 MHz, and a pulse duration of 1.7 ps. The maximum average output power and single pulse energy were determined to be 1.39 mW and 117 pJ, respectively. The mode-locked pulses generated were exceptionally stable giving a signal-to-noise ratio (SNR) of 58.2 dB. According to the findings of the current research, it is anticipated that the G/ZnO-arc-shaped fiber-based SA has the potential to produce stable mode-locked lasers in the region of 2.0 µm which can many applications.