The fundamentals of harnessing the magneto-optics of quantum wires for designing optical amplifiers: Formalism

TL;DR

This paper develops an analytical framework for quantum wires' magnetoplasmon excitations, revealing negative group velocity phenomena that could enable nanoscale optical amplifiers and lasers.

Contribution

It provides exact analytical solutions for magnetoplasmon eigenstates in quantum wires with a harmonic potential under magnetic and electric fields, highlighting the potential for novel optical device design.

Findings

Identification of magnetoroton excitations with negative group velocity

Analytical expressions for eigenfunctions and eigenenergies of quantum wires

Proposal of magnetoroton features for nanoscale optical amplifiers

Abstract

Quantum wires occupy a unique status among the semiconducting nanostructures with reduced dimensionality -- no other system seems to have engaged researchers with as many appealing features to pursue. This paper aims at a core issue related with the magnetoplasmon excitations in the quantum wires characterized by the confining harmonic potential and subjected to a longitudinal electric field and a perpendicular magnetic field in the symmetric gauge. Despite the substantive complexity, we obtain the exact analytical expressions for the eigenfunction and eigenenergy, using the scheme of ladder operators, which fundamentally characterize the quantal system. Crucial to this inquiry is an intersubband collective excitation that evolves into a magnetoroton -- above a threshold value of magnetic field -- which observes a negative group velocity between the maxon and the roton. The evidence of negative group velocity implies anomalous dispersion in a gain medium with the population inversion that forms the basis for the lasing action of lasers. Thus, the technological pathway that unfolds is the route to devices exploiting the magnetoroton features for designing the novel optical amplifiers at nanoscale and hence paving the way to a new generation of lasers.