Opt Lett. 2023 Jul 1;48(13):3511-3514. doi: 10.1364/OL.492067.
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.
热氧化硅是全硅光子电路中常用的介电材料。此外，由于热氧化过程的湿性质，结合的羟基离子（Si-OH）会在这种材料中造成相当大的光损耗分量。一种方便的方法是通过在 1380nm 处的 OH 吸收来相对其他机制定量这种损耗。在这里，使用超高品质因数（Q 因数）的热氧化硅楔形微谐振器，在 680nm 到 1550nm 的波长范围内测量并区分了 OH 吸收损耗峰和散射损耗基线。在近可见和可见波长范围内观察到了创纪录的片上谐振器 Q 因数，在电信波段的吸收极限 Q 因数高达 80 亿。通过 Q 测量和二次离子质谱（SIMS）深度剖析推断出羟基离子含量约为 2.4ppm（重量）。
