Injection Locking of a Semiconductor Double Quantum Dot Micromaser

TL;DR

This paper demonstrates linewidth narrowing of a semiconductor double quantum dot micromaser through injection locking, aligning experimental results with standard laser models despite charge noise challenges.

Contribution

It shows for the first time that injection locking can significantly reduce linewidth in a DQD micromaser affected by charge noise.

Findings

Linewidth reduced by over a factor of 10 via injection locking.

Injection locking range matches predictions from the Adler equation.

Distortion sidebands are quantitatively characterized.

Abstract

Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models.