Large nonlinear Kerr effect in graphene

TL;DR

This paper demonstrates that graphene exhibits a giant nonlinear refractive index, significantly larger than traditional materials, with potential applications in nonlinear photonics, by distinguishing and measuring its complex nonlinear optical effects.

Contribution

The study unambiguously separates saturable absorption and nonlinear phase shift in graphene and quantifies its complex nonlinear refractive index, revealing its exceptional nonlinear properties.

Findings

Graphene's nonlinear refractive index n2=10^-7 cm^2/W

Nonlinear index decreases with excitation flux, but more slowly than absorption

Graphene's nonlinear properties are promising for photonics applications

Abstract

Under strong laser illumination, few-layer graphene exhibits both a transmittance increase due to saturable absorption and a nonlinear phase shift. Here, we unambiguously distinguish these two nonlinear optical effects and identify both real and imaginary parts of the complex nonlinear refractive index of graphene. We show that graphene possesses a giant nonlinear refractive index n2=10-7cm2W-1, almost nine orders of magnitude larger than bulk dielectrics. We find that the nonlinear refractive index decreases with increasing excitation flux but slower than the absorption. This suggests that graphene may be a very promising nonlinear medium, paving the way for graphene-based nonlinear photonics.