One-step deposition and in-situ reduction of graphene oxide in glass microcapillaries and application to photonics

Films of graphene oxide (GO) were produced on the inner walls of glass microcapillaries via insertion of a GO water suspension followed by quick drying with a hot finger (no previous surface functionalization required). Individual capillaries from an array could also be selectively GO coated. Raman hyperspectral images revealed the films to be continuous along tens of centimeters. Furthermore, the films could be thermally reduced through an annealing process, which also decreased the concentration of defects. As a proof of principle application, the microcapillaries of photonic crystal fibers were covered with a GO film, leading to the demonstration of fiber polarizers and mode lockers for pulsed fiber lasers. A comparison between GOand reduced GO-coated fibers revealed that shorter pulses are obtained with the latter.