“Ultra-High-Q tunable microring resonators by slow light”
Abstract: We demonstrate a nearly three-order-of-magnitude enhancement in the quality factor of Er-doped lithium niobate (LN) micro ring resonators, achieving Q-factors exceeding 108 through spectral hole burning. This enhancement arises from the slow-light effect, which reduces loss rates and significantly extends photon lifetime in the resonator. Additionally, the interaction between the spectrally narrowed resonance and the cavity’s broader continuum produces a Fano lineshape, which we dynamically control via electro-optic (EO) tuning enabling an on-chip, MHz-level, electrically tunable optical filtering. Using a theoretical model based on modified Bloch equations, we also reveal an intensity-dependent dephasing rate that approaches the radiative limit (T2→ 2T1), driven by a high intracavity Rabi frequency that decouples Er ions from the spin bath. Finally, I propose the potential of this platform for quantum delay lines, atomic frequency comb memory, and the realization of a polaritonic molecule.
Bio: Priyash Barya is a 5th year Electrical and Computer Engineering graduate student working with Professor Elizabeth Goldschmidt researching on nanophotonic quantum memory platforms.