Stable C-Band Q-Switched EDFL Using a D-Shaped Fiber Coated with Zn(II) Schiff-Base Complex

Abstract

Schiff-base zinc(II) complexes have recently attracted interest as nonlinear optical materials owing to their tunable molecular structure, strong electronic delocalization, and high optical stability. In this work, a D-shaped fiber coated with a Zn(II) Schiff-base complex was developed as a novel saturable absorber (DSF-Zn SA) for Q-switched operation in a C-band erbium-doped fiber laser (EDFL). The Zn(II) complex was synthesized via a two-step condensation and coordination process, producing a material with a measured modulation depth of 8.0%. Integration of the DSF-Zn SA into the EDFL cavity enabled stable Q-switched lasing within a pump range of 35.21–76.75 mW. The laser emitted at 1558.6 nm with a pulse width of 5.63 µs, a repetition rate of 45.56 kHz, and a maximum pulse energy of 110.40 nJ. The device exhibited strong nonlinear absorption and excellent operational stability, demonstrating the Zn(II) Schiff-base complex’s suitability for compact and efficient ultrafast photonic applications