(color online) Graphene mode-locked mid-infrared pulsed fiber laser. (a) Er³⁺-doped ZBLAN fiber laser incorporating a multi-layer graphene mirror as a saturable absorber. (b) Measured autocorrelation trace showing a FWHM (full-width-half-maximum) pulse width of ∼ 65 ps. Assuming a sech² profile, this yields a pulse duration of ∼ 42 ps. (c) Optical spectrum of the mode-locked laser, showing a mid-IR center wavelength of ∼2.78 μm.^[58]