Holmium Oxide Thin Film As A Saturable Absorber For Generating Q-Switched And Mode-Locked Erbium-Doped Fiber Lasers

We demonstrated a new type of transition metal oxide (TMO) material, Holmium oxide (Ho2O3) polymer film SA for compact passively Q-switched and mode-locked erbium-doped fiber laser (EDFL) generations. The film SA has a thickness of ~40 µm and modulation depth of ~45%. It was fabricated by embedding Ho2O3 nanoparticles into PVA polymer solution. The Q-switched laser operated stably at a center wavelength of 1563 nm within a pump power range of 45–97 mW. The maximum Q-switching pulse repetition rate and the narrowest attainable pulse width were 115.8 kHz and 0.64 µs, respectively; while, the maximum pulse energy was obtained as 129.36 nJ. On the other hand, the mode-locked EDFL emerged stably within a pump power range of 62–180 mW at a center wavelength of 1565.4 nm. The repetition rate was 17.1 MHz, while the pulse width was 650 fs. Additionally, the maximum output power was measured as 9.01 mW; while, the corresponding maximum pulse energy was obtained as 0.524 nJ. This Ho2O3 film SA offers simplicity and reliability in the design of compact and portable fiber pulsed laser generators particularly in the 1.55-µm regime