Sensitive label-free biosensing using critical modes in aperiodic photonic structures

In this paper, we introduce a novel approach for optical sensing based on the excitation of critically localized modes in two-dimensional deterministic aperiodic structures generated by a Rudin-Shapiro (RS) sequence. Based on a rigorous computational analysis, we demonstrate that RS photonic structures provide a large number of resonant modes better suited for sensing applications compared to traditional band-edge and defect-localized modes in periodic photonic structures. Finally, we show that enhanced sensitivity to refractive index variations as low Delta n=0.002 in RS structures results from the extended nature of critical modes and can enable the fabrication of novel label-free optical biosensors. (c) 2008 Optical Society of America.