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Updated: Jun 13, 2026

Microwave Photonics Systems Based on Whispering-gallery-mode Resonators
Published on: August 5, 2013
Q Factors Exceeding 104 in Wavelength-to-Subwavelength-Scale Free-Space Resonators with Dual Asymmetry Control
Darrell E Omo-Lamai1, Varun Dolia1, Yanyu Xiong1
1Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States.
Abstract:
Free-space-addressable optical resonators with high quality factors (Q) and wavelength-to-subwavelength mode volumes (Vm) enhance light-matter interactions in sensing, nonlinear optics, and quantum photonics. However, experimental Q factors in this mode volume regime remain limited to ∼103 because existing asymmetry-driven designs couple geometric and optical perturbation components, constraining access to high-Q regimes. Here, we show that independently tuning these two asymmetry axes unlocks a biaxial radiative landscape with iso-Q contours connecting geometrically and optically distinct perturbations of equivalent Q. We demonstrate this framework in very-large-scale-integrated Si nanoantenna pixel (VINPix) resonators with 35-150 nm out-of-plane perturbations of amorphous Si, SiNx, and SiO2. Experimentally, we achieve Q up to 76 000 at Vm of ∼1.7 λ03neff-3 across arrays of >80 resonators in water. Computationally, slotted VINPix resonators reach Q of >106 at Vm of ∼0.2 λ03neff-3. This biaxial framework establishes a generalizable design strategy for ultrahigh-Q free-space nanophotonic resonators.
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