Quantum derivatives and high-frequency gain in semiconductor superlattices

TL;DR

This paper develops simple difference formulas to analyze small-signal absorption and gain in microwave-driven semiconductor superlattices, offering a geometric interpretation that aids in optimizing THz gain conditions.

Contribution

It introduces a new theoretical approach with simple formulas and geometric insights to connect quasistatic and dynamic regimes in ac-driven superlattices.

Findings

Derived simple difference formulas for small-signal absorption.

Provided geometric interpretation for gain optimization.

Linked quasistatic and dynamic regimes in superlattices.

Abstract

We derive simple difference formulas describing a small-signal absorption of THz field in a semiconductor superlattice driven by a microwave pump. We give a transparent geometric interpretation of these formulas that allows a search of optimum conditions for the gain employing only a simple qualitative analysis. Our theoretical approach provides a powerful tool for finding the correspondence between quasistatic and dynamic regimes in ac-driven semiconductor superlattices.