Nanoscale Mirrorless Superradiant Lasing

TL;DR

This paper predicts a novel form of mirrorless superradiant lasing in dense nanoscopic emitter arrays, demonstrating collective emission, directional radiation, and spectral narrowing without an optical cavity, with potential applications as a frequency reference.

Contribution

It introduces the concept of free-space, mirrorless superradiant lasing in dense atomic chains, highlighting the effects of pumping fraction and atomic arrangement on lasing behavior.

Findings

Transition from subradiant to superradiant emission with increased pumping

Directional emission confined to a narrow spatial angle

Spectral lines merge into a single narrow line at high pump power

Abstract

We predict collective 'free-space' lasing in a dense nanoscopic emitter arrangement where dipole-dipole coupled atomic emitters synchronize their emission and exhibit lasing behavior without the need for an optical resonator. At the example of a subwavelength-spaced linear emitter chain with varying fractions of pumped and unpumped emitters, we present a comprehensive study of this mirrorless lasing phenomenon. The total radiated power transitions from subradiant suppression under weak pumping to superradiant enhancement at stronger pumping, while exhibiting directional emission confined to a narrow spatial angle. At the same time multiple independent spectral emission lines below the lasing threshold merge towards a single narrow spectral line at high pump power. The most substantial enhancement and line narrowing occur when a fraction of unpumped atoms is present. We show that this leads to superradiant lasing near the bare atomic frequency, making the system a promising candidate for a minimalist active optical frequency reference.