A high efficiency label-free photonic biosensor based on vertically stacked ring resonators |
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Authors: | C E Campanella C M Campanella F De Leonardis V M N Passaro |
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Institution: | 1. Photonics Research Group, Politecnico di Bari, via Orabona 4, 70125, Bari, Italy 2. Integrated Photonics Laboratory, Boston University, 8 Saint Mary’s St., Boston, MA, 02215, USA
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Abstract: | In this paper we propose an optical biosensor based on two vertically stacked Silicon on Insulator (SOI) micro-ring resonators interacting with a microfluidic ring channel. This device behaves as a resonant optical coupler and it is very sensitive to the variation of the coupling coefficient between the two vertically stacked ring resonators. A ring microfluidic channel is proposed in the coupling region between the two vertically stacked ring resonators. The inner walls of the channel are funzionalized in order to the trap a specific biological species. Assuming a biotin-streptavidin system, the straptividin trapping gives rise to a change of the biological thickness of about 3 nm. This thickness increase of the deposited layer leads to a consequent change in the coupling strength between the two rings. These theoretical predictions have been validated by using both 3D Finite-Difference Time-Domain (FDTD) and 3D full-vectorial Finite Element Method (FEM) approaches. Moreover, by appropriately choosing the design parameters of the micro-resonant structure, we evaluate a sensitivity of the spectral response to the streptavidin adlayer variation of about 20% nm?1 for TE polarization and 34% nm?1 for TM polarization, which represents an important achievement to obtain selective SOI bio-sensors with ultra-high resolution. |
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