3-μm passively Q-switched fiber laser using Au-nanocages as saturable absorber

摘要

Q-switched fiber lasers emitting at around 3μm have been widely applied in various scientific and industrial fields, suchas molecular spectroscopy, laser surgery, material processing, remote sensing, and mid-infrared (mid-IR)supercontinuum source generation. Au nanocages (Au-NCs) have attracted much attention recently due to theiroutstanding saturable absorption properties including broadband absorption, ultrafast optical response (a fewpicoseconds), and large third-order optical nonlinearity coefficient that caused by local surface plasmon resonance(LSPR). We propose and demonstrate a tunable Er~(3+) doped ZBLAN fiber laser using Au-NCs as a Q-switcher for thefirst time. Nonlinear absorption of the Au-NCs was measured by a home-made Ho~(3+)/Pr~(3+) co-doped mode-locked fiberlaser at 2850 nm. The measured modulation depth, saturation intensity and non-saturation loss are 10.73%, 0.11MW/cm~2 and 3.26%, respectively. The central wavelength of the Q-switched pulses could be tuned across 54.1 nm (from2753.0 to 2807.1 nm). The Q-switched fiber laser delivers a maximum average power of 253.7 mW with correspondingpulse energy of 4.06 μJ and pulse width of 1.30 μs at repetition rate of 62.5 kHz. Our work shows the Au-NCs arepromising saturable absorbers (Sas) for 3μm mid-infrared (mid-IR) pulse generation.