Hydrothermal-assisted synthesis of reduced graphene oxide/zinc oxide nanocomposite for ultrashort pulse generation in 1.5 µm and 2.0 µm spectral regions

Abstract

Our research focuses on synthesizing reduced graphene oxide/zinc oxide (rGO/ZnO) nanocomposite using hydrothermal techniques, which we then utilized as a saturable absorber (SA) to generate ultrashort pulses at wavelengths of 1.5 μm and 2.0 μm. A balanced twin detector approach investigated the nonlinear optical properties of rGO/ZnO nanocomposite, giving modulation depths of 4.06 % and 46.23 % at the 1.5 µm and 2.0 µm wavelength ranges, respectively. Stable mode-locked pulses with picosecond pulse widths and megahertz repetition rate were obtained after inserting the rGO/ZnO-coated arc-shaped fiber into an erbium-doped fiber laser (EDFL) and Thulium/Holmium-doped fiber laser (THDF) cavities. The pulse width and repetition rate differ between EDFL and THDFL, with EDFL generating an output soliton with a pulse width of 0.92 ps and a repetition rate of 18.19 MHz, and THDFL producing a pulse width of 1.36 ps and a repetition rate of 12.14 MHz. Upon assessment of their long-term stability, it was found that both generated lasers exhibited remarkable resilience, with signal-to-noise ratio (SNR) values surpassing 50 dB. Our study indicates the extraordinary broadband nonlinear features of rGO/ZnO nanocomposite. It presents a new opportunity to develop ultrashort nonlinear devices utilizing rGO/metal oxide-based nanocomposites.