# Atomically thin mirrors made of monolayer semiconductors

## TL;DR

This paper demonstrates that a monolayer of MoSe2 can act as an electrically switchable mirror with high reflectance at cryogenic temperatures, enabling new opportunities in quantum optics and miniaturized optical devices.

## Contribution

It shows that monolayer MoSe2 can serve as a highly reflective, electrically tunable mirror due to excitonic coherence, with nonlinear optical properties demonstrated under various excitation conditions.

## Key findings

- Reflects up to 85% of incident light at cryogenic temperatures
- Exhibits power- and wavelength-dependent nonlinearities
- Enables exploration of quantum nonlinear optics and topological photonics

## Abstract

Transition metal dichalcogenide monolayers are promising candidates for exploring new electronic and optical phenomena and for realizing atomically thin optoelectronic devices. They host tightly bound electron-hole pairs (excitons) that can be efficiently excited by resonant light fields. Here, we demonstrate that a single monolayer of molybdenum diselenide (MoSe2) can dramatically modify light transmission near the excitonic resonance, acting as an electrically switchable mirror that reflects up to 85% of incident light at cryogenic temperatures. This high reflectance is a direct consequence of the excellent coherence properties of excitons in this atomically thin semiconductor, encapsulated by hexagonal boron nitride. Furthermore, we show that the MoSe2 monolayer exhibits power- and wavelength-dependent nonlinearities that stem from exciton-based lattice heating in the case of continuous-wave excitation and exciton-exciton interactions when fast, pulsed laser excitation is used. These observations open up new possibilities for studying quantum nonlinear optical phenomena and topological photonics, and for miniaturizing optical devices.

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Source: https://tomesphere.com/paper/1705.07245