Silicon coupled-resonator optical-waveguide-based biosensors using light-scattering pattern recognition with pixelized mode-field-intensity distributions.
Silicon coupled-resonator optical-waveguide-based biosensors using light-scattering pattern recognition with pixelized mode-field-intensity distributions.
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DOI：
10.1038/srep07528
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发表时间：
2014-12-18
影响因子：
4.6
通讯作者：
Poon AW
中科院分区：
文献类型：
--
作者：
Wang J;Yao Z;Lei T;Poon AW
芯片级光学微腔生物传感器通常采用超高质量的微腔，需要精确的波长可调激光器来激发腔共振。然而，对于点护理应用，这种基于频谱域测量的系统容易产生设备噪声并且不便携。需要一种替代的基于微腔的生物传感器，它能够在设备中具有高灵敏度、耐噪声和潜在的便携式系统。在这里，我们展示了这种生物传感器的概念验证，使用耦合谐振光波导（CROW）在绝缘体上的硅芯片上。该传感方案基于空间域的测量，只需要在固定波长下激励CROW，并对CROW的面外弹性光散射强度模式进行成像。基于将探测波长的光散射强度模式与CROW本征态的光散射强度模式相关联，我们设计了一种模式识别算法，该算法能够从校准的相关系数集中提取应用于CROW上包层的折射率变化Δn。我们用不同浓度NaCl溶液覆盖的8微环CROW进行了实验，结果表明Δn的折射率单位（RIU）为~1.5 × 10−4，灵敏度为~752 RIU−1，噪声等效检测限为~6 × 10−6 RIU。
Chip-scale, optical microcavity-based biosensors typically employ an ultra-high-quality microcavity and require a precision wavelength-tunable laser for exciting the cavity resonance. For point-of-care applications, however, such a system based on measurements in the spectral domain is prone to equipment noise and not portable. An alternative microcavity-based biosensor that enables a high sensitivity in an equipment-noise-tolerant and potentially portable system is desirable. Here, we demonstrate the proof-of-concept of such a biosensor using a coupled-resonator optical-waveguide (CROW) on a silicon-on-insulator chip. The sensing scheme is based on measurements in the spatial domain, and only requires exciting the CROW at a fixed wavelength and imaging the out-of-plane elastic light-scattering intensity patterns of the CROW. Based on correlating the light-scattering intensity pattern at a probe wavelength with the light-scattering intensity patterns at the CROW eigenstates, we devise a pattern-recognition algorithm that enables the extraction of a refractive index change, Δn, applied upon the CROW upper-cladding from a calibrated set of correlation coefficients. Our experiments using an 8-microring CROW covered by NaCl solutions of different concentrations reveal a Δn of ~1.5 × 10−4 refractive index unit (RIU) and a sensitivity of ~752 RIU−1, with a noise-equivalent detection limit of ~6 × 10−6 RIU.
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