In Situ Synthesis of Graphene with Telecommunication Lasers for Nonlinear Optical Devices

Despite auspicious optical properties of graphene, particularly its ability to absorb light over a broad wavelength range, incorporating presynthesized graphene in optical system by recognized transfer methods has critical drawbacks of introducing impurities and damaging the graphene film which can affect the performance of optical system. Here a transfer-free, in situ synthesis of multilayered graphene is demonstrated directly onto single-mode optical fiber end facet and polished surface of D-shaped fiber by interfacial growth process in ambient condition. Conventional telecommunication lasers operating at ≈1550 nm band are employed to provide the activation energy for carbon atoms to diffuse, precipitate through Ni-catalyst layer, and form the graphene crystals at the interface of metal catalyst and optical fiber. The in situ grown graphene on optical fiber acts as saturable absorber in the fiber laser ring cavity to generate ultrafast optical pulses by mode-locking technique. The formation and the quality of the resulting multilayered graphene are confirmed by precision analysis tools. The synthesized graphene has the sp²-bond shares of 75.8% and it shows nonlinear optical absorption property with the modulation depth of 7%, guaranteeing passive mode-locking of fiber laser operating in femtosecond scale. Graphene is synthesized directly onto optical fiber end facets in ambient conditions via irradiation with a continuous wave laser operating at conventional telecommunication band. A nickel layer deposited onto the optical fiber acts both as catalyst and carbon host for the interfacial growth of graphene. The entire fiber-graphene device is used as passive mode-locker in a fiber laser ring cavity to generate ultrashort laser pulses.