Silicon-based optofluidic devices are very attractive for applications in biophotonics and chemical sensing. Understanding and controlling the properties of their dielectric waveguides is critical for the performance of these chips. We report that thermal annealing of PECVD-grown silicon dioxide (SiO2) ridge waveguides results in considerable improvements to optical transmission and particle detection. There are two fundamental changes that yield higher optical transmission: 1) propagation loss in solid-core waveguides is reduced by over 70%, and 2) coupling efficiencies between solid- and liquid-core waveguides are optimized. The combined effects result in improved optical chip transmission by a factor of 100-1000 times. These improvements are shown to arise from the elimination of a high-index layer at the surface of the SiO2 caused by water absorption into the porous oxide. The effects of this layer on optical transmission and mode confinement are shown to be reversible by alternating subjection of waveguides to water and subsequent low temperature annealing. Finally, we show that annealing improves the detection of fluorescent analytes in optofluidic chips with a signal-to-noise ratio improvement of 166x and a particle detection efficiency improvement of 94%.

中文翻译：

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通过基于 PECVD 的 SiO2 波导的热退火增强 ARROW 光子器件性能

硅基光流控器件对于生物光子学和化学传感领域的应用非常有吸引力。了解和控制其介电波导的特性对于这些芯片的性能至关重要。我们报告说，PECVD 生长的二氧化硅 (SiO2) 脊形波导的热退火可显着改善光学传输和粒子检测。有两个根本性的变化可以产生更高的光传输：1) 实芯波导中的传播损耗降低了 70% 以上，2) 实芯和液芯波导之间的耦合效率得到了优化。综合效果使光学芯片的传输率提高了 100-1000 倍。这些改进被证明是由于多孔氧化物吸收水分而消除了 SiO2 表面的高折射率层。通过将波导交替置于水和随后的低温退火中，该层对光传输和模式限制的影响是可逆的。最后，我们表明，退火改善了光流控芯片中荧光分析物的检测，信噪比提高了 166 倍，颗粒检测效率提高了 94%。