Passively mode-locking operation of infrared solid-state lasers with a nickel-cobalt layered double hydroxide nanosheets saturable absorber

Abstract

Due to the advantages of ultra-broad bandwidth absorption and easy fabrication, passively mode-locked ultrashort lasers using two-dimensional (2D) materials as saturable absorbers (SA) have attracted extensive attention in recent years. In this experiment, the structure and light absorption properties of 2D nickel-cobalt layered double metal hydroxide (NiCo-LDH) nanosheets are characterized. The nonlinear absorption coefficient of NiCo-LDH are measured by Z-scan method to be -1.1 cm/GW. Using the NiCo-LDH SA, passively mode-locking is realized in a Nd:YVO₄ bulk laser near 1 μm, a Nd:Y_0.15V_0.85O₄ bulk laser near 1.3 μm and a Tm:YAG ceramic bulk laser near 2 μm. In the 1 μm passively mode-locking experiment, a continuous wave mode-locking (CWML) laser is obtained at 1065.92 nm with a repetition rate of 69 MHz and a pulse width of 18.0 ps. To our knowledge, this is the first time a CWML laser has been obtained using a layered double hydroxides (LDHs) SA. In addition, Q-switched mode-locking (QML) lasers are obtained based on NiCo-LDH SA at 1.3 μm and 2 μm. The experiments demonstrate that NiCo-LDH mode locking is a very promising practical technique for directly generating ultrashort pulsed laser from a laser oscillator.