Low-loss optical resonators fabricated in chip-scale waveguides are of great interest to a wide range of technologies –. Notably, low-loss silicon nitride ring resonators have been demonstrated to function as optical gyroscopes . Virtually all applications of optical resonators benefit from the minimization of propagation loss. Previous analyses of ultralow loss silicon nitride ring resonators have attributed a majority of propagation loss to absorption and sidewall scattering, but here we present new resonators which yield a record-low loss of 0.123 dB/m at an optical wavelength of 1563 nm, and near-infrared images of these resonators indicate that loss is heavily impacted by the presence of randomly positioned scattering elements incorporated into the structure during fabrication.
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