Solvent induced enhancement of nonlinear optical response of graphdiyne

Flat and crystalline materials with exceptional nonlinear optical (NLO) properties are highly desirable for their potential applications in integrated NLO photonic devices. Graphdiyne (GD), a new two-dimensional (2D) carbon allotrope, has recently evoked burgeoning research attention by virtue of its tunable bandgap along with a high carrier mobility and extended π-conjugation compared with most conventional optical materials. Here, we experimentally probe the third-order nonlinear optical response of GD dispersed in several common solvents (alcohols) using a femtosecond Z-scan technique. The measured nonlinear optical refractive index is in the order of ~10^-8 cm²/W, which is approximately one order of magnitude higher than that of most 2D materials. In particular, we find that different NLO responses can be observed from GD when dispersed in different solvents, with the strongest NLO response when dispersed in 1-propanol. It is proposed that some intrinsic properties of the solvents, such as the polarity and viscosity, could influence the NLO response of GD materials. Our experimental results confirm the assumptions on the NLO behavior in GD and demonstrate its great potential for future generations of Kerr-effect-based NLO materials and devices.