Pedestal subwavelength grating metamaterial waveguide ring resonator for ultra-sensitive label-free biosensing
Pedestal subwavelength grating metamaterial waveguide ring resonator for ultra-sensitive label-free biosensing
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DOI：
10.1016/j.bios.2019.111396
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发表时间：
2019-09-15
影响因子：
12.6
通讯作者：
Chen, Ray T.
中科院分区：
文献类型：
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作者：
Chang, Ching-Wen;Xu, Xiaochuan;Chen, Ray T.
模态体积重叠因子是决定传感器灵敏度的参数之一。在过去的几十年中，已经提出了许多方法来增加模式体积重叠。由于增加的模体积重叠因子导致减小的模限制，因此最大值最终由感测装置的折射率分布的微结构和纳米结构确定。由于绝缘体上硅平台上沿垂直方向的折射率分布沿着不对称，进一步提高基于亚波长光栅超材料（SGM）波导的传感器的灵敏度是具有挑战性的。在本文中，我们提出并证明了嵌入式SGM，它减少了不对称性，从而允许进一步增加光场和分析物之间的相互作用。基座结构可以通过受控的底切蚀刻容易地形成。理论分析和实验验证表明，该方法灵敏度有了显著提高.体灵敏度和表面灵敏度分别提高了28.8%和1000倍。还通过共振位移的真实的-时间监测证明了在0.1 ng/mL（类似于1.67 pM）的低浓度下的链霉亲和素的检测。基于来自双位点结合模型拟合的链霉亲和素检测结果的实时测量，预期使用0.01nm分辨率光谱分析仪的链霉亲和素检测限类似于400 fM。
Mode volume overlap factor is one of the parameters determining the sensitivity of a sensor. In past decades, many approaches have been proposed to increase the mode volume overlap. As the increased mode volume overlap factor results in reduced mode confinement, the maximum value is ultimately determined by the microand nano-structure of the refractive index distribution of the sensing devices. Due to the asymmetric index profile along the vertical direction on silicon-on-insulator platform, further increasing the sensitivity of subwavelength grating metamaterial (SGM) waveguide based sensors is challenging. In this paper, we propose and demonstrate pedestaled SGM which reduces the asymmetricity and thus allows further increasing the interaction between optical field and analytes. The pedestal structure can be readily formed by a controlled undercut etching. Both theoretical analysis and experimental demonstration show a significant improvement of sensitivity. The bulk sensitivity and surface sensitivity are improved by 28.8% and 1000 times, respectively. The detection of streptavidin at a low concentration of 0.1 ng/mL (similar to 1.67 pM) is also demonstrated through real- time monitoring of the resonance shift. A similar to 400 fM streptavidin limit of detection is expected with a 0.01nm resolution spectrum analyzer based on the real-time measurement of streptavidin detection results from two-site binding model fitting.