Ameliorating the stability of a thulium-doped mode-locked fiber laser using a yttrium iron garnet nanoparticles-based saturable absorber

This study investigates the application of yttrium iron garnet nanoparticles (YIG-NPs) as a saturable absorber (SA) to improve the stability of mode-locked thulium-doped fiber lasers (TDFLs). The YIG-NPs were synthesized via a sol-gel technique and subsequently characterized using high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-VIS absorption, and Raman spectroscopy. These analyses confirmed the successful synthesis of YIG-NPs. Experimental results demonstrate that the modulation depth, non-saturable losses, and saturation intensity were measured to be 31%, 32%, and 28.30 MW/cm 2 , respectively. YIG-NPs, when integrated into the TDFL system, the laser achieved a central wavelength of 1958.77 nm, a 3 dB bandwidth of 7.41 nm. It delivered a maximum output power of 137.94 mW, with a pulse repetition and pulse width of 23.99 MHz and 1.31 ps, respectively. A lasing threshold was observed at 768 mW of pump power, stabilizing the TDFL and maintaining the stable wavelength between 1079 and 2250 mW of the pump. The enhanced stability was further confirmed through theoretical simulation by assessing the pulse energy consistency over 500 successive cavity round trips. These findings illustrate the potential of YIG-NPs for developing ultrastable mode-locked TDFLs for ultrafast pulse generation, positioning YIG-NPs as a viable SA in advanced photonic applications.