Ultrafast Experimental Analysis and Comparative Performance of a Graphene Saturable Mirror at 2 μm Wavelength

In this work, we conducted systematic comparisons on the nonlinear optical properties of graphene and that of commercial semiconductor saturable absorber mirror (SESAM) at 2 μm wavelength. Our results showed that graphene has significant advantages over the commercial SESAM, exhibiting ~28% less absorptive cross-section ratio of excited-state to ground-state and ~50 times faster relaxation time. This implies that graphene can be exploited as a better mode-locker than the current commercial SESAM for high power, high repetition rate and ultrafast mid-infrared laser sources.