Laser-induced frequency tuning of Fourier-limited single-molecule emitters

TL;DR

This paper demonstrates laser-induced, persistent frequency tuning of single-molecule emitters at cryogenic temperatures, enabling independent resonance control for quantum photonics applications.

Contribution

It introduces a novel laser-based method to achieve stable, local frequency shifts of single molecules, facilitating their independent tuning on photonic chips.

Findings

Laser can shift molecular transition frequencies by hundreds of linewidths.

Multiple molecules can be tuned into resonance within twice their linewidth.

The method preserves the natural emission linewidth, enabling high-quality quantum emitters.

Abstract

The local interaction of charges and light in organic solids is the basis of distinct and fundamental effects. We here observe, at the single molecule scale, how a focused laser beam can locally shift by hundreds-time their natural linewidth and in a persistent way the transition frequency of organic chromophores, cooled at liquid helium temperatures in different host matrices. Supported by quantum chemistry calculations, the results are interpreted as effects of a photo-ionization cascade, leading to a stable electric field, which Stark-shifts the molecular electronic levels. The experimental method is then applied to a common challenge in quantum photonics, i.e. the independent tuning and synchronization of close-by quantum emitters, which is desirable for multi-photon experiments. Five molecules that are spatially separated by about 50 microns and originally 20 GHz apart are brought into resonance within twice their linewidth. Combining this ability with an emission linewidth that is only limited by the spontaneous decay, the system enables fabrication-free, independent tuning of multiple molecules integrated on the same photonic chip.