Nonlinear Optical Dynamics and Pulse Generation in Cu/CuO Saturable Absorber-based Passively Q-Switched Erbium-doped Fiber Laser

This study investigates the performance of a passively Q-switched (PQS) erbium-doped fiber laser (EDFL) incorporating copper (Cu) and copper oxide (CuO) material as a saturable absorber (SA). The structural and surface properties of the Cu and CuO-SA were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Energy dispersive X-ray spectroscopy (EDS), along with elemental mapping, was utilized to ensure the elemental composition, and Raman spectroscopy was used to investigate the structural properties of CuO material. The modulation depth of the Cu and CuO-SA was systematically investigated using a twin-detector method and was found to be 15.08 % for CuO-SA and 8.25 % for Cu-SA. The integration of Cu-SA material inside a laser cavity generated a stable pulse operation with a minimum pulse width of 2.4 μs, a maximum repetition rate of 116 kHz, and an average output power of 2.87 mW. In contrast, the EDFL based on CuO-SA yielded a minimum pulse width of 1.93 μs, a repetition rate of 129.9 kHz, and an output power of 4.58 mW, underscoring the superior efficacy of CuO as an SA material. The long-term stability of Cu/CuO-SA-based EDFL was measured by continuously monitoring the pulse width for a period of 4 hours. Finally, the band structure and optical characteristics of CuO were thoroughly examined by DFT computations that confirmed the CuO-SA’s potential as an efficient SA in EDFL. These findings demonstrate that CuO-based SAs significantly outperform Cu-based counterparts, establishing CuO as an efficient material for enhancing the performance of PQSEDFL, making it a promising candidate for high-power fiber laser applications.