A pair of counter-propagating high-Q whispering-gallery modes (WGMs) can couple to each other and produce two new modes with a significant resonance splitting when single or multi-Rayleigh scatterers are adsorbed on the microcavity surface. In this paper, we investigate the mode-splitting-based biosensing by using a biorecognition-covered WGM microcavity because the pre-covering is essentially necessary for label-free detection of specific biological targets. It is shown that the quantitative detection, e.g., nanoparticle sizing, is strongly affected by the biorecognition, and the minimum target size suitable for detection is subjected to the surface pre-covering ratio. To eliminate this degradation induced by biorecognition, we further propose to use the total linewidth broadening of the two new modes as the detection signal, which is immune to thermal fluctuation.
Mode-splitting-based optical label-free biosensing with a biorecognition-covered microcavity
Xu Yi, Yun-Feng Xiao, Yin Feng, Dong-Ying Qiu, Jing-Yi Fan, Yan Li, Qihuang Gong; Mode-splitting-based optical label-free biosensing with a biorecognition-covered microcavity. J. Appl. Phys. 1 June 2012; 111 (11): 114702. https://doi.org/10.1063/1.4725424
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