High-order harmonic spectroscopy of polycrystalline graphene

Abstract

Present mass production of large-area single-layer graphene relies fundamentally on chemical vapor deposition methods. The generation of grain boundaries, which divides the sample into a set of crystalline domains, is inherent to these fabrication methods. Recent studies have demonstrated a strong anisotropy in the ultrafast non-linear response of single-layer graphene when subjected to non-perturbative, intense laser fields below the damage threshold. We propose to exploit this anisotropy to characterize the size distribution of graphene domains in polycrystals via high-order harmonic polarimetry. Our simulation results demonstrate the sensitivity of the harmonic polarization state to details of the polycrystal grain distribution. In particular, we show that the rotation in the polarization tilt of the highest-order harmonics holds information about the grain distribution in the polycrystal. As a proof-of-concept, we propose a method to determine the standard deviation of the grain size distribution from the values of the most frequent grain size and the standard deviation of the harmonic tilt rotation from a set of hypothetical measurements on different polycrystal realizations. Our work reveals the capability of high-order harmonic polarimetry to characterize polycrystalline two-dimensional materials.