Direct laser writing of graphene oxide patterns using femtosecond laser pulses with different repetition rates

We studied the thermal effect in the photoreduction process for the sub-micrometer thin graphene oxide (GO) films using femtosecond laser direct writing (FsLDW). For efficient photoreduction of GO films, various laser parameters, especially the repetition rate, were examined to identify the photothermal effect with different pulse-to-pulse spacing using a femtosecond laser having a 515-nm central wavelength. The linewidths of photoreduction were measured and the photoreduction degrees were characterized by the optical transmittance of the films. The results show that the heat accumulation due to the time interval between pulses dominantly affects the reduction degree and the linewidth.