Nickel–cobalt layered double hydroxide saturable absorber for a mid-infrared 2 µm Tm:YAG ceramic mode-locked laser

The nickel–cobalt (NiCo) layered double hydroxide (LDH) prepared by the hydrothermal method is fabricated into a saturable absorber mirror using the ultrasonic liquid phase-assisted exfoliation method and results in achieving a 2 μm passively mode-locked laser operation. Using an X-type resonator based on Tm:YAG ceramic, a Q-switched mode-locked laser output with a maximum output power of 278 mW was achieved, with a repetition frequency of 146 MHz and a pulse width of 221 ps. To the best of our knowledge, this is the first report on the application of NiCo-LDH saturable absorber as an optical modulator in a mid-infrared mode-locked laser.