Experimental investigation of Q-switched and mode-locked fiber lasers using tin phthalocyanine absorber

We present an experimental investigation of a Q-switched and mode-locked erbium-doped fiber laser (EDFL) utilizing tin phthalocyanine (SnPc) as a saturable absorber (SA). The SnPc solution, deposited on the end face of a fiber ferrule connector, exhibits a notable modulation depth of 19.4 %. This passive SA device was incorporated into the EDFL cavity to generate Q-switched pulses at a center wavelength of 1561.8 nm. With pump powers ranging from 12.13 to 67.52 mW, the repetition rate and pulse width varied from 21.85 kHz / 12.16 µs to 58.34 kHz / 6.32 µs. The Q-switched laser demonstrated an efficiency of up to 9.16 %, with a peak output power of 5.9 mW. A signal-to-noise ratio (SNR) of 57.02 dB confirmed stable Q-switching operation. Upon extending the EDFL cavity to 162 m, stable mode-locked pulses of 5.05 ps were achieved with pump powers exceeding 85.99 mW. At 210.62 mW pump power, the mode-locked output exhibited a repetition rate of 1.28 MHz, a maximum pulse energy of 1.63 nJ, and a peak power of 0.28 kW. The frequency spectrum demonstrated a high SNR of 66.70 dB, verifying stable mode-locking performance. Operating at 1559.8 nm, this picosecond pulse train holds significant potential for applications such as frequency comb generation, high-precision optical metrology, and broadband absorption spectroscopy. These results highlight the promise of SnPc organic materials as efficient saturable absorbers for future photonic applications.