Fig. 4
From: Graphene saturable absorbers applications in fiber lasers
Mechanical properties of grapheme. a Scanning electron microscopy (SEM) image of a graphene flake spanning an array of circular holes (scale bar, 3 μm) and b Schematic illustration of nanoindentation on membranes; c and d show graphene oxide paper and its cross-section in SEM. Reproduced with permission from (a and b) and (c and d). Copyright: 2008 American Association for the Advancement of Science (a and b) and 2007 Nature Publishing Group (c and d). Taken from [58]