# Atomically thin semiconductors as nonlinear mirrors

## TL;DR

This paper demonstrates that monolayer transition metal dichalcogenides can act as perfect nonlinear mirrors, with reflection enhanced by exciton interactions, enabling potential applications in quantum optics.

## Contribution

It reveals that monolayer TMDs can serve as nonlinear mirrors with power-dependent reflection due to exciton interactions, a novel insight for 2D material optics.

## Key findings

- Perfect extinction of transmitted light at any incidence angle.
- Reflection enhancement with increasing power for blue-detuned light.
- Limitation of maximum reflection due to exciton interactions.

## Abstract

We show that a transition metal dichalcogenide monolayer with a radiatively broadened exciton resonance would exhibit perfect extinction of a transmitted field. This result holds for s- or p-polarized weak resonant light fields at any incidence angle, due to the conservation of in-plane momentum of excitons and photons in a flat defect-free two dimensional crystal. In contrast to extinction experiments with single quantum emitters, exciton-exciton interactions lead to an enhancement of reflection with increasing power for incident fields that are blue detuned with respect to the exciton resonance. We show that the interactions limit the maximum reflection that can be achieved by depleting the incoming coherent state into an outgoing two-mode squeezed state.