Nonlinear optical response of a two-dimensional atomic crystal

TL;DR

This paper extends classical boundary light wave theory to a zero-thickness two-dimensional atomic crystal, analyzing its nonlinear optical response, especially second harmonic generation, and explaining experimental observations with a simplified model.

Contribution

It introduces a theoretical framework for nonlinear optical responses of 2D atomic crystals as zero-thickness interfaces, focusing on second harmonic generation.

Findings

Generalized reflection and refraction laws for 2D crystals

Analytical explanation of harmonic generation experimental data

Simplified model captures essential physical features

Abstract

The theory of Bloembergen and Pershan for the light waves at the boundary of nonlinear media is extended to a nonlinear two-dimensional atomic crystal, i.e. a single planar atomic lattice, placed in between linear bulk media. The crystal is treated as a zero-thickness interface, a real two-dimensional system. Harmonic waves emanate from it. Generalization of the laws of reflection and refraction give the direction and the intensity of the harmonic waves. As a particular case that contains all the essential physical features, second order harmonic generation is considered. The theory, due to its simplicity that stems from the special character of a single planar atomic lattice, is able to elucidate and to explain the rich experimental details of harmonic generation from a two-dimensional atomic crystal.