Frequency locking in lasing ZnO nanowire pairs

TL;DR

This paper demonstrates optical frequency locking in ZnO nanowire lasers at the nanoscale, showing controlled multi-mode and single-mode lasing through near-field coupling, advancing nanoscale light source stability.

Contribution

It is the first to experimentally show frequency locking in coupled nanowire lasers at the nanoscale, enabling tunable and stable nanophotonic light sources.

Findings

Observed full and partial frequency locking in nanowire pairs.

Achieved single-mode lasing by suppressing multi-mode modes.

Established dynamic coupling as a mechanism for spectral control.

Abstract

Frequency locking between coupled laser systems provides a powerful mechanism for stabilizing and controlling coherent emission, yet its implementation and applicability down to the nanoscale remains unknown and unexplored. Here, we demonstrate optical coupling and frequency locking in closely spaced ZnO nanowire lasers operating in the extreme near field (gap < 10 nm). We observe both full and partial frequency locking, manifested as the alignment of all or a subset of the lasing modes, by spatially controlling the optical excitation. We also observe single-mode lasing in a coupled nanowire pair where the multi-mode lasing of individual nanowires is suppressed. In contrast to previously reported coupled-cavity nanowire lasers, where spectral control arises from static filtering mechanisms such as the Vernier effect, our results indicate a dynamically established relationship between actively lasing nanowires. These findings establish frequency locking as a robust and tunable mechanism in nanowire lasers, opening new routes toward stabilized and controllable nanoscale light sources for integrated nanophotonic systems.