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arXiv · 2504.19465

Ultra High-Q tunable microring resonators enabled by slow light

Priyash Barya·Ashwith Prabhu·Laura Heller·Edmond Chow·Elizabeth A. Goldschmidt
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Abstract

High-Q nanophotonic resonators are crucial for many applications in classical and quantum optical processing, communication, sensing, and more. We achieve ultra-high quality factors by preparing a highly transparent and strongly dispersive medium within a resonator, causing a reduction in the group velocity that leads to a nearly three order of magnitude increase in the quality factor. We implement this via spectral hole burning in erbium-doped thin-film lithium niobate microring resonators, and show Q-factors exceeding $10^8$. Additionally, we show that the interplay between the spectrally narrowed resonance and the broader bare resonance produces a Fano lineshape, which we dynamically control via electro-optic tuning. Finally, we present a theoretical model for our experimentally observed resonator linewidths, which are not well-described by the standard Bloch equations. Our results show a dramatic reduction in the erbium dephasing rate under a strong optical drive, leading to much narrower linewidths than would otherwise be expected given the large circulating intensity in the resonator.

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Priyash Barya, Ashwith Prabhu, Laura Heller, Edmond Chow, Elizabeth A. Goldschmidt. 2025-04-28. Ultra High-Q tunable microring resonators enabled by slow light. https://arxiv.org/abs/2504.19465

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