Femtosecond transient absorption spectroscopy of laser-ablated graphite and reduced graphene oxide for optical switching behavior

Carbon based materials are considered as a rewarding contestant for optical devices due to its novel properties. In this study, graphite is laser-ablated and different analytical methods such as XRD and Raman spectroscopy are used to evaluate the crystalline nature. In XRD, it indicates the decreased intensity after laser ablation but no change in peak positions resulted as graphite is very strong and hard material. Scanning electron microscopy (SEM) used to evaluate structural characteristics shows the overlapping layered structure after ablation. Reduced graphene oxide (rGO) is prepared by using modified Hummers' method and reduced it by thermal reduction method. UV–Vis spectra confirmed the peaks of graphite and rGO at 274 nm and 267 nm, respectively. To study the carrier relaxation dynamics of graphite and rGO, ultrafast Visible-pump/NIR-probe femtosecond transient absorption spectroscopy was used. Carrier relaxation occurred between 260 and 309 fs even after laser ablation damage, which is useful for future application of optical switching under high laser repetition.

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