All-Fiber Q-Switched Mid-Infrared Ring Cavity Laser

We demonstrate the first Q-switched all-fiber ring cavity laser operating in the mid-infrared. The laser comprises an erbium-doped ZBLAN fiber, a single-mode ZBLAN optical fiber coupler, carbon nanotubes as a saturable absorber, and an integrated inline polarization controller. Q-switched operation is enabled by a sandwiched single-wall carbon nanotube saturable absorber at pump powers exceeding 0.430 W, delivering pulses with a repetition rate of 87 kHz with a pulse duration of 1.2 μs at the maximum pump power.