Indium tin oxide nanocrystals as saturable absorbers for passively Q-switched erbium-doped fiber laser

A new type of saturable absorber (SA) based on indium tin oxide (ITO) nanocrystals for passively Q-switched erbium-doped fiber (EDF) laser has been demonstrated experimentally. High quality ITO nanocrystals were prepared by the coprecipitation method. As a degenerate oxide semiconductor, the ITO has a wide range of saturable absorption regions, strong plasmonic absorption peaks, and ultra-fast recovery time. The nonlinear absorption properties of ITO are investigated by a balanced twin-detector measurement system. The saturation intensity and modulation depths are 9.87 MW/cm(2) and 0.83%, respectively. We successfully fabricated ITO SAs by depositing the ITO dispersion solution at the end of a fiber connector. By inserting the ITO SAs into an EDF fiber cavity, stable passively Q-switched pulses with the minimum pulse width of 1.15 mu s under a repetition rate of 81.28 kHz were obtained. The maximum output power of 1722 mu W and pulse energy of 21.19 nJ were realized when the pump power was 480 mW at the wavelength of 1530.3 nm. The results suggest that ITO nanocrystals are expected to develop into another effective SA for ultrafast photonics. (C) 2017 Optical Society of America