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arXiv · 1903.07241

Experimental Characterization of Ultrafast, Tunable and Broadband Optical Kerr Nonlinearity in Graphene

Siddharatha Thakur·Behrooz Semnani·Safieddin Safavi-Naeini·Amir Hamed Majedi
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Abstract

In this study we systematically measure the near-infrared spectral dependence, the sub-picosecond temporal evolution and pulse-width dependence of the effective Kerr coefficient ($n_{2,eff}$) of graphene in hundreds of femtosecond regime. The spectral dependence measured using the Z-scan technique is corroborated by quantum theory to extract a $n_{2,eff} \propto \lambda^2$ dependence. The temporal evolution extracted using the time-resolved Z-scan measurement shows the nonlinear response peaking at zero delay time and relaxing on a time scale of carrier relaxation. Since the Kerr-type response originated from the optically induced carrier population difference, the time-scale of the evolution of the nonlinear response is apt. The $n_{2,eff}$ shows a dependence on the pulse-width attributed to the relative heating and cooling times of the carriers. This dependence is strong when the pulse-duration is on the same time-scale as the decay constant. Throughout our study the $n_{2,eff}$ remains positive.

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Siddharatha Thakur, Behrooz Semnani, Safieddin Safavi-Naeini, Amir Hamed Majedi. 2019-03-18. Experimental Characterization of Ultrafast, Tunable and Broadband Optical Kerr Nonlinearity in Graphene. https://doi.org/10.1038/s41598-019-46710-x

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