https://doi.org/10.1140/epjst/e2014-02244-5
Regular Article
A high efficiency label-free photonic biosensor based on vertically stacked ring resonators
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
a e-mail: vittorio.passaro@poliba.it
Received: 22 April 2014
Revised: 4 August 2014
Published online: 6 October 2014
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.
© EDP Sciences, Springer-Verlag, 2014
