Abstract

We propose a Watt-level, ultrafast Er/Yb-codoped double-clad fiber laser mode-locked by reduced graphene oxide (rGO) interacting with an ultraweak evanescent field of photonic crystal fiber (PCF). The rGO solution is filled into the cladding holes of PCF, and after evaporation, the rGO flakes, which contribute saturable absorption and high nonlinearity coefficient, interacting with a light intensity only 1/10⁷ of that in the center of PCF. This ultraweakly-interacting structure enhances the thermal damage threshold and decreases the accumulated nonlinearity. We obtain a stable soliton laser with femtosecond duration, and harmonic mode-locking is formed when increasing pump strength. A maximum average power of 1.14 W is obtained for pump power at 7 W.

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