Saturable absorption characteristics of Bi 2 Se 3 in a 2 µm Q-switching bulk laser

We investigate the saturable absorption properties of Bi Se in a bulk laser operating at 2 µm wavelength region. The Bi Se saturable absorber (SA) is prepared with the liquid-phase exfoliation method, which gives a saturable input flux of 4.3 mJ/cm , a modulation depth of ∼10%, and a non-saturable absorption of 10.2%. With the Bi Se saturable absorber, a passive Q-witching Tm:YAG ceramic laser is realized with a shortest pulse duration of 355 ns, a single pulse energy of 6.76 µJ and peak power of 19 W. We believe that this is the first report on Bi Se Q-switched 2 µm bulk laser.