Passively Q-switched erbium-doped fiber laser based on nickel ferrite (Ni-FeO) nanoparticles' saturable absorber: synthesis and experimental demonstration.

In this study, detailed experimental investigations of the passively -switched (PQS) erbium-doped fiber laser (EDFL) were reported based on nickel ferrite (-) thin-film saturable absorber (SA). The - nanoparticles (NPs) were synthesized using a sol-gel autocombustion mechanism, and its thin film was prepared in polyvinyl alcohol (PVA) via the solution casting method. The crystallographic structure, surface morphology, and particle size of - NPs were characterized using the X-ray diffraction (XRD) technique, high-resolution transmission electron microscopy (HR-TEM), and scanning electron microscopy (SEM). The obtained findings indicate that the prepared - SA yielded a 12.6% modulation depth (), the saturation intensity () of 34.04/, and nonsaturable losses () of 48.2%. The prepared SA upon integration within the laser cavity resulted in an emission wavelength of 1563.87 nm at an input pump power () of 104.6 mW. With increased , a stable passively -switched pulse operation, initiated by incorporating a - thin film as an SA in the EDFL ring cavity, yielded a repetition rate (RR) ranges from 34.18 to 69.44 kHz, and pulse width (PW) varied from 10.94 to 4.74 µs upon tuning a to 284 mW. Additionally, the pulse energy (PE), peak power, and average output power () were 167.33 nJ, 35.30 mW, and 11. 62 mW, respectively. Finally, the stability of EDFLs with - SA was thoroughly examined by operating the SA continuously for 1 h at a of 104.6 mW, which maintained a constant PW of 8.43±0.08µ and an RR of 43.89±0.10. This study shows that ferrite composites serve as highly effective SAs in EDFLs, enabling stable and controllable generation of ultrashort pulses due to their high-damage threshold and nonlinear optical properties that are critical for a variety of uses in photonics.