Measuring the Nonlinear Refractive Index of Graphene using the Optical Kerr Effect Method

TL;DR

This paper measures the nonlinear refractive index of graphene at telecom wavelengths using the optical Kerr effect method with heterodyne detection, revealing a negative value that contrasts prior reports and discussing possible reasons for discrepancies.

Contribution

It introduces a novel application of the OHD-OKE technique to characterize graphene's nonlinear response and compares it with Z-scan results and literature, highlighting the negative nonlinear index.

Findings

Measured a negative nonlinear refractive index for graphene.

Discrepancies found between OHD-OKE and Z-scan measurements.

Discussed effects of doping and experimental parameters on results.

Abstract

By means of the ultrafast optical Kerr effect method coupled to optical heterodyne detection (OHD-OKE), we characterize the third order nonlinear response of graphene at telecom wavelength, and compare it to experimental values obtained by the Z-scan method on the same samples. From these measurements, we estimate a negative nonlinear refractive index for monolayer graphene, $n_2 = - 1.1\times 10^{-13} m^2/W$. This is in contradiction to previously reported values, which leads us to compare our experimental measurements obtained by the OHD-OKE and the Z-scan method with theoretical and experimental values found in the literature, and to discuss the discrepancies, taking into account parameters such as doping.