A novel optical biosensor using a one-dimensional photonic crystal structure in a total-internal-reflection geometry (PCTIR) is presented and investigated for label-free biosensing applications. This simple configuration forms a micro Fabry- Perot resonator in the top layer which provides a narrow optical resonance to enable label-free, highly sensitive measurements for the presence of analytes on the sensing surface or the refractive index change of the surrounding medium in the enhanced evanescent field; and at the same time it employs an open sensing surface for real-time biomolecular binding detection. The high sensitivity of the sensor was experimentally demonstrated by bulk solvent refractive index changes, ultrathin molecular films adsorbed on the sensing surface, and real-time analytes binding, measuring both the spectral shift of the photonic crystal resonance and the change of the intensity ratio in a differential reflectance measurement. Detection limits of 7×10^-8 RIU for bulk solvent refractive index, 6×10^-5 nm for molecular layer thickness and 24 fg/mm² for mass density were obtained, which represent a significant improvement relative to state-ofthe- art surface-plasmon-resonance (SPR)-based systems. The PC-TIR sensor is thus seen to be a promising technology platform for high sensitivity and accurate biomolecular detection.

Date Published: 16 February 2009
PDF: 12 pages
Proc. SPIE 7188, Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications VI, 71880B (16 February 2009); doi: 10.1117/12.808369

Published in SPIE Proceedings Vol. 7188:
Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications VI
Alexander N. Cartwright; Dan V. Nicolau, Editor(s)