One-step deposition and in-situ reduction of graphene oxide in photonic crystal fiber for all-fiber laser mode locking

•A simple process to coat the capillaries of PCFs with graphene oxide presented.•Tens of centimeters of microcapillaries are continuously coated.•For the 1st time, specific PCF microcapillaries were selectively coated.•The coated fiber produced pulses as short as 356 fs in a fiber laser via mode locking.•These are the shortest pulses reported so far with a PCF coated with a 2D material.