Tunable terahertz emission from difference-frequency in biased superlattices

TL;DR

This paper demonstrates that biased superlattices can produce tunable terahertz radiation through difference-frequency generation, with high susceptibility and efficient continuous wave operation.

Contribution

It introduces a method to achieve in-situ tunable terahertz emission in superlattices by exploiting doubly resonant conditions and excitonic effects.

Findings

Susceptibility can reach $10^{-5}$ m/V due to excitonic enhancement.

Tunable emission range spans several terahertz.

Continuous wave operation with 1% quantum efficiency is feasible.

Abstract

The terahertz emission from difference-frequency in biased superlattices is calculated with the excitonic effect included. Owing to the doubly resonant condition and the excitonic enhancement, the typical susceptibility can be as large as $10^{-5}$ m/V. The doubly resonant condition can always be realized by adjusting the bias voltage and the laser frequencies, thus the in-situ tunable emission is efficient in a range of several terahertz. Continuous wave operation with 1% quantum efficiency and $\mu$W output power is feasible as the signal absorption in undoped superlattices is negligible.