Slowing Light Down to Supercharge Optical Chips

High-quality nanophotonic resonators are the unsung heroes of modern optical technology, essential for tasks ranging from quantum processing to precision sensing. A research team has now unlocked a method to dramatically boost the performance of these devices by manipulating the speed of light itself.

The scientists achieved ‘ultra-high quality factors’—a metric describing how efficiently a resonator stores energy—by creating a specific environment that slows down the group velocity of light. This technique involves preparing a highly transparent but strongly dispersive medium inside the resonator. While previously limited to bulky systems, the team successfully implemented this in a compact erbium-doped thin-film lithium niobate microring resonator.

Using a process known as spectral hole burning, the researchers enhanced the quality factors (Q-factors) by nearly three orders of magnitude, exceeding 100 million (10⁸). Furthermore, they demonstrated the ability to dynamically control these resonances through electro-optic tuning. Theoretical modelling suggests the observed linewidths are much narrower than standard equations predict, indicating a dramatic reduction in the erbium dephasing rate under strong optical drive. This breakthrough offers a robust new platform for high-performance classical and quantum optical applications.