Two-dimensional materials and the coherent control of nonlinear optical interactions

TL;DR

This paper demonstrates that two-dimensional materials like graphene exhibit phase-controllable nonlinear optical effects, enabling coherent control of nonlinear interactions such as diffraction, phase conjugation, and negative reflection, which are distinct from bulk nonlinearities.

Contribution

It reveals the phase dependence of nonlinear optical responses in 2D materials and experimentally demonstrates coherent control phenomena in graphene.

Findings

Phase-controllable nonlinear polarization in 2D materials

Coherent control of nonlinear diffraction and phase conjugation

Observation of nonlinear mirror with negative reflection

Abstract

Deeply sub-wavelength two-dimensional films may exhibit extraordinarily strong nonlinear effects. Here we show that 2D films exhibit the remarkable property of a phase-controllable nonlinearity, i.e., the amplitude of the nonlinear polarisation wave in the medium can be controlled via the pump beam phase and determines whether a probe beam will "feel" or not the nonlinearity. This is in stark contrast to bulk nonlinearites where propagation in the medium averages out any such phase dependence. We perform a series of experiments in graphene that highlight some of the consequences of the optical nonlinearity phase-dependence, {such as} the coherent control of nonlinearly diffracted beams, single-pump-beam {induced} phase-conjugation and the demonstration of a nonlinear mirror characterised by negative reflection. The observed phase sensitivity is not specific to graphene but rather is solely a result of the dimensionality and is therefore expected in all 2D materials.