# Amplification of surface plasmons in graphene-black phosphorus injection laser heterostructures

## TL;DR

This paper proposes a heterostructure combining graphene and black phosphorus to enable efficient surface plasmon amplification and potential terahertz lasing, offering a new approach for THz source development.

## Contribution

It introduces a novel graphene-black phosphorus heterostructure that facilitates surface plasmon amplification and terahertz lasing through effective electron-hole plasma cooling.

## Key findings

- Effective cooling of electron-hole plasma in graphene via hole injection from black phosphorus.
- Achievement of negative dynamic conductivity enabling surface plasmon amplification.
- Potential for new terahertz sources based on plasmon lasing.

## Abstract

We propose and evaluate the heterostructure based on the graphene-layer (GL) with the lateral electron injection from the side contacts and the hole vertical injection via the black phosphorus layer (PL) (p$^+$PL-PL-GL heterostructure). Due to a relatively small energy of the holes injected from the PL into the GL (about 100 meV, smaller than the energy of optical phonons in the GL which is about 200 meV), the hole injection can effectively cool down the two-dimensional electron-hole plasma in the GL. This simplifies the realization of the interband population inversion and the achievement of the negative dynamic conductivity in the terahertz (THz) frequency range enabling the amplification of the surface plasmon modes. The later can lead to the plasmon lasing. The conversion of the plasmons into the output radiation can be used for a new types of the THz sources.