Surface Plasmon Instability Leading to Emission of Radiation

TL;DR

This paper introduces a novel method for converting dc electric energy into terahertz radiation using hybrid 2D semiconductor structures, exploiting surface plasmon instabilities to generate coherent radiation.

Contribution

It demonstrates the control of surface plasmon instabilities in hybrid 2D structures to produce tunable terahertz emission, a new approach for energy conversion and radiation sources.

Findings

Low-frequency plasmons become unstable beyond a critical wave vector.

Instability occurs only at ultra long wavelengths for isolated pairs of 2D layers.

Frequency agility is achieved by manipulating system parameters.

Abstract

We propose a new energy conversion approach from a dc electric field to a terahertz wave based on hybrid semiconductors by combining two-dimensional (2D) crystalline layers and a thick conducting material with possible applications as a source of coherent radiation. The hybrid nano-structure may consist of a single or pair of sheets of graphene, silicene or a 2D electron gas as would occur at a semiconductor hetero-interface. When an electric current is passed through a layer, we discover that the low-frequency plasmons may become unstable beyond a critical wave vector $q_c$. However, there is no instability for a single driven layer far from the conductor and the instability of an isolated pair of 2D layers occurs only at ultra long wavelengths. To bring in frequency agility for this spontaneous radiation, we manipulate the surface-plasmon induced instability, which leads to the emission of radiation (spiler), to occur at shorter wavelengths by choosing the conductor electron density, layer separation, distances of layers from the conductor surface and the driving-current strength. Applications of terahertz radiation from spiler for chemical analysis, security scanning, medical imaging and telecommunications are expected.