Hydroxyl ion absorption in on-chip high-Q resonators

Thermal silica is a common dielectric used in all-silicon photonic circuits. Additionally, 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 t...

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Bibliographic Details
Published in:Optics letters 2023-07, Vol.48 (13), p.3511-3514
Main Authors: Wu, Lue, Gao, Maodong, Liu, Jin-Yu, Chen, Hao-Jing, Colburn, Kellan, Blauvelt, Henry A, Vahala, Kerry J
Format: Article
Language:English
Subjects:
Absorption
Depth profiling
Hydroxyl ions
Oxidation
Photons
Q factors
Resonators
Secondary ion mass spectroscopy
Silicon
Silicon Dioxide
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Summary:Thermal silica is a common dielectric used in all-silicon photonic circuits. Additionally, 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-quality factor (Q-factor) thermal-silica wedge microresonators, the OH absorption loss peak is measured and distinguished from the scattering loss baseline 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. Hydroxyl ion content level around 2.4 ppm (weight) is inferred from both Q measurements and by secondary ion mass spectroscopy (SIMS) depth profiling.
ISSN:0146-9592
1539-4794
DOI:10.1364/OL.492067