Numerical Modeling of Abnormal Blocking Effect for the Design of Novel Optical Sensor Element Constructed by Periodic Grating Strips Over Si/SiO2 Wire Waveguide

In this paper the numerical modeling of periodic structures for implementation of a novel type of photonic sensors by using the 3D finite difference time domain (FDTD) method is presented. The sensing is based on the optical phenomena occurring in the segmented grating which is placed on the thin silica buffer over the silicon wire waveguide in the silicon-on-insulator (SOI) structure. This design provides the effective resonance interaction of the guided wave with the virtual leaky wave supported by the segmented grating evanescently coupled with the silicon wire. The dropping wavelength of this interaction is strongly dependent on the grating environment and it provides a strong refractometricsensitivity (S-n > 420 nm RIU-1) and surface sensitivity S-h > 0.17, evaluated in the case of water. The modeling proves that the effect of abnormal blocking due to virtual leaky wave could be the base for the design of optical sensors with extremely high sensitivity.