Epsilon-near-zero indium tin oxide nanocolumns array as a saturable absorber for a Nd:BGO laser

Indium tin oxide nanocolumns array (ITO-NCs-A), a typical epsilon-near-zero material, was prepared by chemical vapor deposition method. Due to the strong third-order optical nonlinearity and large refractive index change of the ITO-NCs-A at ∼1.06 μm, we used it as a passively Q-switched device and obtained a stable 1.06 μm Nd:BGO pulsed laser for the first time, to the best of our knowledge. The maximum average output power is 152 mW, the maximum repetition rate is 126.1 kHz, the shortest pulse width is 579.6 ns, and the corresponding single pulse energy and pulse peak power are 1.21 μJ and 2.08 W, respectively. This work indicates that ITO-NCs-A has promising applications in ultrafast photonics and is expected to provide a more reliable solution for optical modulators in pulsed lasers. (paper)