Enhanced saturable absorption of MoS_2 black phosphorus composite in 2 μm passively Q-switched Tm: YAP laser

We report the fabrication of an MoS_2 black phosphorus(BP) composite saturable absorber by liquid phase exfoliation and the spin-coating method and further exploitation to build a 2 μm passively Q-switched Tm:YAP laser. Such a composite based Q-switched laser with a duration of 488 ns and corresponding peak power of 85.9 W is obtained, which shows an improved saturable absorption effect than that of single MoS_2(616 ns,68.7 W) and BP(932 ns, 22.4 W). The results indicate that simple and reasonable fabrication of the vertical composite from two-dimensional atomic layer materials opens up the possibility to create an unprecedented saturable absorber with exciting properties.