Hybrid organic small molecules as a saturable absorber for passive Q-switching in erbium-doped fiber laser

This work demonstrates a Q-switched fiber laser by utilizing hybrid organic small molecules (HOSM) based on Tris-(8-hydroxyquinoline) aluminum (Alq3) and N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) as a saturable absorber. The HOSM was embedded into poly(vinyl alcohol) and inserted into a fiber laser cavity to achieve pulsing at 1560.1 nm. The pulse repetition rate was tuned from 66.3 kHz to 109 kHz whereas the pulse width duration decreased from 6.3 µs to 2.2 µs as the laser diode power gradually increased from 56 to 262 mW. Then a tunable bandpass filter (TBF) was used to produce tunable wavelength operation. As the TBF was tuned, the wavelength of the Q-switched laser shifted continuously from 1519.6 nm to 1562.8 nm. The results show that HOSM could be an efficient, easy to fabricate, and inexpensive saturable absorber for generating single and tunable wavelength Q-switched fiber laser.