Plasma instability and amplification of electromagnetic waves in low-dimensional electron systems

TL;DR

This paper develops a quantum-mechanical electrodynamic theory for 2D electron systems with gratings, revealing how drift-induced plasma instabilities can amplify infrared radiation, especially with quantum wire gratings that lower the threshold velocity.

Contribution

It introduces a comprehensive theory combining quantum 2DES and classical electrodynamics to analyze plasma instabilities and wave amplification in structured electron systems.

Findings

Threshold drift velocity for plasma instability can be reduced with quantum wire gratings.

Resonant interaction enhances grating coupling efficiency.

Potential for creating tunable infrared emitters and amplifiers.

Abstract

A general electrodynamic theory of a grating coupled two dimensional electron system (2DES) is developed. The 2DES is treated quantum mechanically, the grating is considered as a periodic system of thin metal strips or as an array of quantum wires, and the interaction of collective (plasma) excitations in the system with electromagnetic field is treated within the classical electrodynamics. It is assumed that a dc current flows in the 2DES. We consider a propagation of an electromagnetic wave through the structure, and obtain analytic dependencies of the transmission, reflection, absorption and emission coefficients on the frequency of light, drift velocity of 2D electrons, and other physical and geometrical parameters of the system. If the drift velocity of 2D electrons exceeds a threshold value, a current-driven plasma instability is developed in the system, and an incident far infrared radiation is amplified. We show that in the structure with a quantum wire grating the threshold velocity of the amplification can be essentially reduced, as compared to the commonly employed metal grating, down to experimentally achievable values. Physically this is due to a considerable enhancement of the grating coupler efficiency because of the resonant interaction of plasma modes in the 2DES and in the grating. We show that tunable far infrared emitters, amplifiers and generators can thus be created at realistic parameters of modern semiconductor heterostructures.