Controlling lasing around Exceptional Points in Coupled Nanolasers

TL;DR

This paper investigates the behavior of coupled nanolasers above threshold, exploring mode evolution around exceptional points, and demonstrates control over lasing properties for potential on-chip optical applications.

Contribution

It introduces a method to study coupled nanolasers significantly above threshold and maps mode evolution around exceptional points, revealing new spectral control mechanisms.

Findings

Lasing gaps due to reversed pump dependence observed.

Mode evolution mapped around exceptional points.

Coupling enables control of lasing threshold and wavelength.

Abstract

Coupled nanolasers are of growing interest for on-chip optical computation and data transmission, which requires an understanding of how lasers interact to form complex systems. The non-Hermitian interaction between two coupled resonators, when excited selectively, can lead to parity-time symmetry, the formation of exceptional points, and subsequently spectral control and increased sensitivity. These investigations have been limited to pump energies close to the lasing threshold, and large or narrow-line lasers. Here, by programmable optical excitation we study two coupled nanolasers significantly above threshold, where mode instability plays an important role. We map the mode evolution around two exceptional points, and observe lasing gaps due to reversed pump dependence which compare well with nonlinear theory. Finally, the coupling can be exploited to control the lasing threshold and wavelength, and for frequency switching around the lasing gap. Controlled and integrated nanolasers constitutes a promising platform for future highly sensitive and programmable on-chip laser sources.