# A Versatile Approach to Stabilize Whispering Gallery Microresonators Toward Reliable Photonic Labeling

## TL;DR

This paper introduces a method to stabilize optical sensors called WGM microresonators, making them more reliable for detecting tiny changes in their environment.

## Contribution

A novel stabilization protocol for WGM microresonators is introduced, addressing thermal and temporal drifts caused by solvent release.

## Key findings

- Thermal and temporal drifts in WGM microresonators are caused by residual solvent release over days.
- A simple protocol effectively locks resonances into stable modes, enabling long-term stability.
- The stabilization method enhances the reliability of WGM microresonators for sensing and tracking microscale changes.

## Abstract

Whispering gallery
mode (WGM) microresonators provide ultrasensitive
optical fingerprints that are ideal for photonic labels capable of
detecting minute variations in size and refractive index. WGM microresonators
can be obtained through convenient self-assembly protocols, for instance,
by loading polystyrene microparticles with colloidal quantum dots.
However, despite their ultrasharp spectral signatures, these resonators
exhibit significant thermal and temporal drifts that limit their applications.
We combine experiments and modeling to show that these drifts originate
from the slow, days-long release of residual solvent trapped within
the microparticles, which can be monitored via WGM spectroscopy. We
establish a simple protocol to suppress this instability, locking
the resonances into stable, sharply defined modes. This approach provides
a straightforward route for long-term stabilization of WGM microresonators,
advancing their reliable use as robust optical platforms, noninvasive
sensors, and precise self-trackers of physicochemical changes at the
microscale.