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Q-Switched and Mode-Locked Pulse Generation with Titanium Oxide Based Saturable Absorber Film
N. Ahmed, N. F. Zulkipli, B. Musa, M. I. M. Ali, Z. Jusoh, M. Yasin and S. W. Harun

Q-switched and mode-locked Erbium-doped fiber lasers (EDFLs) were demonstrated using Titanium dioxide (TiO2) film as a saturable absorber (SA). The prepared SA film is cut into small piece and sandwiched between two ferrules in EDFL (EDFL) cavity to generate a stable and compact Q-switched and mode-locked pulses. By increasing the 980 nm pump power from 104.6 mW to 145.8 mW, the repetition frequency of the Q-switched EDFL increases from 81.04 kHz to 90.58 kHz while the pulse width reduces from 5.08 µs to 4.12 µs. The maximum pulse energy of 22.63 nJ is generated at the pump power of 145.8 mW. Meanwhile, self-starting mode-locked EDFL arises as 100 m long single-mode fiber is added into the laser cavity to balance the nonlinearity and the cavity dispersion. As the pump power was raised from 145.8 to 187 mW, the repetition rate and pulse width of the pulses are almost constant of 1.86 MHz and 3.34 ps, respectively. This experiment shows that TiO2 SA can be used to generate stable Q-switched and mode-locked pulsed lasers.

Keywords: saturable absorber, titanium oxide, Q-switching
PACS: 42.60.Gd, 42.55.Wd, 42.70.Nq