High sensitivity and high <i>Q</i>-factor nanoslotted parallel quadrabeam photonic crystal cavity for real-time and label-free sensing

Abstract

We experimentally demonstrate a label-free sensor based on nanoslotted parallel quadrabeam photonic crystal cavity (NPQC). The NPQC possesses both high sensitivity and high Q-factor. We achieved sensitivity (S) of 451 nm/refractive index unit and Q-factor &amp;gt;7000 in water at telecom wavelength range, featuring a sensor figure of merit &amp;gt;2000, an order of magnitude improvement over the previous photonic crystal sensors. In addition, we measured the streptavidin-biotin binding affinity and detected 10 ag/mL concentrated streptavidin in the phosphate buffered saline solution.