A tunable wavelength Q-switched fiber laser at C-band region by using CuPc as a saturable absorber

We utilized a Copper Phthalocyanines (CuPc) thin film as a saturable absorber (SA) to generate Q-switched pulses at 1560.6 nm. This CuPc SA exhibited a modulation depth of approximately 1.5% in nonlinear optical transmission at 1572 nm, alongside a linear absorption of about 3.2 dB across the full gain bandwidth of the erbium-doped fiber. As the input power increased, the pulse width decreased and the repetition rate rose from 9.8 mu s and 35 kHz to 4.64 mu s and 54 kHz, respectively. We then introduced a tunable band pass filter (TBPF) into the laser cavity. By adjusting the TBPF, we varied the central wavelength across the C-band region, from 1520.2 to 1560.2 nm, while maintaining stable Q-switched operation. The CuPc SA was fabricated affordably and easily, delivering consistent performance with a high signal-to-noise ratio exceeding 61 dB. The ability to achieve tunable and stable Q-switching with an organic SA could lead to significant advancements in fiber laser technology.