Black phosphorus mode-locked Er:ZBLAN fiber laser at 3.5 µm

In this paper, we demonstrate a all-fiber 3.5 μm mode-locked fiber laser based on Black phosphorus. The fiber laser delivered pulses with a central wavelength of 3468.4 nm, 3 dB spectral bandwidth of 2.1 nm, pulse repetition rate of 16.85 MHz, average output power of 46 mW, and signal-to-noise ratio of 65 dB. Due to the relative low output power and the low sensitivity of detectors in 3.5 μm regime, the pulse width had not hitherto been acquired using a commercial autocorrelation. The Fourier transform limit pulse width estimated by the hyperbolic secant curve is 8.4 ps. This work opens up new ideas for generating all-fiber mode-locking mid-infrared laser.