Ytterbium-doped fiber laser passively mode locked by evanescent field interaction with CH₃NH₃SnI₃ perovskite saturable absorber

Methylammonium tin triiodide (CH₃NH₃SnI₃) as a kind of lead-free perovskite semiconductor materials has emerged as a star material for photonic applications. Herein, for the first time, we demonstrate CH₃NH₃SnI₃ microcrystals grown directly on D-shaped fibers as saturable absorber for generating mode-locked pulses in fiber laser. The saturable absorber device shows a high nonlinear optical modulation depth of 15.2% and considerably low saturation absorption intensity of 76.5 MW cm^-2. By incorporating the CH₃NH₃SnI₃ saturable absorber into an ytterbium-doped (Yb-doped) fiber laser, stable mode-locking pulses were produced with a duration of 1.77 ns, maximum output power of 28.19 mW, 3 dB bandwidth of about 8.09 nm and a central wavelength at 1064 nm. The output pulses show representative characteristics of dissipative soliton with excellent long term stability and an energy efficiency of 5.6%. This study may facilitate the development of ultrafast photonic and optoelectronic functional devices based on lead-free perovskites.