Passively Q-Switched 2.8-$\mu{\rm m}$ Nanosecond Fiber Laser

A diode-pumped erbium ion-doped single-mode ZBLAN fiber laser passively Q-switched by a Fe
²⁺
:ZnSe crystal is reported. Mid-infrared (MIR) pulses at 2.8 μm with a pulse energy of 2.0 μJ and pulse duration of 370 ns, corresponding to a peak power of 5.34 W, are achieved at a repetition rate of 161 kHz. Our experiment demonstrates that Fe
²⁺
: ZnSe crystal is a promising Q-switching element for high power pulsed MIR fiber lasers.