Generation of Q-switched and mode-locked pulses using neodymium oxide as saturable absorber

Generations of Q-switched and mode-locked pulses were successfully demonstrated in an erbium-doped fiber laser (EDFL) cavity using Neodymium oxide (Nd₂O₃) as saturable absorber (SA). Nd₂O₃ nano-powder was mixed with aqueous solution of polyvinyl alcohol (PVA) to form a thin film after a drying process. The thin film was used to form a SA device. A stable Q-switched EDFL pulses operating at a wavelength of 1558.5 nm were successfully obtained by incorporating the device into the laser cavity. The pulse's repetition rate rose from 89.45 to 104 kHz while the pulse width shrunk from 2.56 to 2.19 µs as the pump power was varied from the threshold of 91.17 to 142.08 mW. The output power steadily increased from 9.57 to 13.94 mW with a slope efficiency of 8.42% as the pump power was raised in the same range. Meanwhile, a stable mode-locked laser operating in soliton regime was also realized as the additional 100 m SMF was incorporated into the laser cavity. The laser operated at a central wavelength of 1559 nm with visible Kelly sidebands. The soliton pulses operated at a fixed repetition rate of 1.809 MHz with a pulse width of 4.62 ps as the pump power was varied within 25.03 to 75.92 mW. The peak power of the mode-locked laser increased from 0.37 kW to 1.26 kW as the pump power was varied within the pump power range. The finding reveals the outstanding optical nonlinearity of Nd₂O₃, which can open new potential in pulsed laser development for various applications including, optical communication, material processing, biomedical diagnostic etc.