An integrated numerical approach for microdamage detection using nanophotonic sensors

Abstract

Photonic bandgap materials (PBM) are synthetic materials that artificially manufactured at the nano-scale to control light propagation. These crystals have the ability to control light propagation in three dimensions by opening a frequency gap in which light is forbidden to propagate. When light is reflected by a nano photonic (NP) crystal a spectral signature that is directly related to its crystalline structure periodicity can be observed. It is suggested here that microscale damage in a substrate attached to the NP sensor might result in a significant change in the spectral signature of the NP sensor, hence allowing for micro-scale damage detection and quantification. To demonstrate the use of sensors for microdamage detection in structural materials an integrated numerical modelling approach was used. The approach augments two numerical methods to simulate the effect of microdamage in the material substrate on the spectrum signature of NPC sensors. First, the finite element method (FEM) was used to simulate structural response of the NP sensor under strain induced in the substrate with and without substrate damage. Second, the results of the finite element analysis were used as inputs to simulate the optical response of the NP sensors using the finite difference time domain method (FDTD). The integrated numerical approach was applied to a wood pile NP sensor attached to a silicon substrate. The numerical analysis showed promising results. Changes in the NP spectral signatures due microdamage in the silicon substrate were successfully identified.