Improved sensitivity of the photonic crystal slab biosensors by using elliptical air holes

We investigate the dependence of sensitivity and quality factor of the resonant mode in photonic crystal H1 cavity on the slab thickness. Three-dimensional finite difference time domain calculations is performed to study the dependence of quality factor and sensitivity on shape and size of the nearest neighbor holes of the cavity to obtain the optimum structures. For the slab thickness of 0.7a, the sensitivity can achieve 322 nm/RIU (refractive index unit) while the quality factor keeps a relatively high value of 5291 when the refractive index is 1.54.