Refractive index sensing utilizing parallel tapered nano-slotted photonic crystal nano-beam cavities

We demonstrate refractive index sensing using parallel tapered nano-slotted photonic-crystal nano-beam cavities with three-dimensional (3D) finite-difference time-domain (3D-FDTD) simulation. The electric field of the cavity mode is strongly concentrated in the slot region leading to a large light-matter overlap, which is expected to add a significant contribution to sensitivity, and thus we present high refractive-index sensitivity of more than 600 nm/refractive index units. Additionally, the quality (Q)-factor in the proposed design is theoretically investigated, and through tapering the diameter of the pores outside the Bragg mirrors in nano-beam cavities and the width of the adjacent nano-slots, an optimal Q-factor of 11770 is obtained. A high figure of merit (FOM = 4637) of the designed model has been obtained. We anticipate that this geometry is potentially an ideal platform for refractive-index based bio-sensing. (C) 2014 Optical Society of America