Synthesis of core-shell polyhedron ZIF-8@ZIF-67 as saturable absorber for passive Q-switching operation in Tm:YAP laser at 3H4????????3H5 transition

In this paper, we synthesized a novel core-shell polyhedron ZIF-8@ZIF-67 nanocomposites with a size of around 150 nm. Then the core-shell structure ZIF-8@ZIF-67 as a saturable absorber to passively Q-switch the Tm:YAP laser was demonstrated for the first time at 2.3 mu m based on the Tm3+ H-3(4) -> H-3(5) transition. ZIF-8@ZIF-67 possessed the excellent nonlinear optical absorption features with a large modulation depth of 6.7% at 2.3 mu m. The obtained stable shortest pulse width was 208 ns with a repetition rate of 128 kHz. Moreover, to fully understand the nonlinear optical properties of the core-shell ZIF-8@ZIF-67 nanocomposites, the coupled rate equations were setup to simulate the H-3(4) -> H-3(5) Q-switching operation. The numerical simulation results agreed well with the experimental results. It demonstrated that the ZIF-8@ZIF-67 core-shell nanocomposites feature great potential as saturable absorber candidate for the mid-infrared pulse generation.