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arXiv · 2303.17814

OH absorption in on-chip high-Q resonators

Lue Wu·Maodong Gao·Jin-Yu Liu·Hao-Jing Chen·Kellan Colburn·Henry A. Blauvelt·Kerry J. Vahala
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Abstract

Thermal silica is a common dielectric used in all silicon-photonic circuits. And bound hydroxyl ions (Si-OH) can provide a significant component of optical loss in this material on account of the wet nature of the thermal oxidation process. A convenient way to quantify this loss relative to other mechanisms is through OH-absorption at 1380 nm. Here, using ultra-high-Q thermal-silica wedge microresonators, the OH absorption loss peak is measured and distinguished from the scattering loss base line over a wavelength range from 680 nm to 1550 nm. Record-high on-chip resonator Q factors are observed for near-visible and visible wavelengths, and the absorption limited Q factor is as high as 8 billion in the telecom band. OH ion content level around 2.4 ppm (weight) is inferred from both Q measurements and by Secondary Ion Mass Spectroscopy (SIMS) depth profiling.

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Lue Wu, Maodong Gao, Jin-Yu Liu, Hao-Jing Chen, Kellan Colburn, Henry A. Blauvelt, Kerry J. Vahala. 2023-03-31. OH absorption in on-chip high-Q resonators. https://doi.org/10.1364/ol.492067

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