Photonic crystal-based optical sensor for two-phase liquid compounds

Abstract

In this paper, an ultra-compact sensor based on a one-dimensional (1D) photonic crystal (PC) structure with alternative layers of TiO2 and MgF2 consisting a defect layer in the middle is investigated. Two-phase liquid compounds including heavy oil with various contents of water, ethanol with different contents of water, and sea water with different contents of salt are infiltrated into the defect layer and the reflection spectra are simulated. Simulation results based on the transfer matrix method (TMM) show that the defect mode appearing in the photonic band gap (PBG) of the PC shifts to longer wavelengths by increasing the refractive index of the defect layer. Using the Lichtennecher method, the best average sensitivities of S=0.0188 nm-1, S=0.2911 nm-1, and S=0.0426 nm-1 are obtained respectively for the heavy oil, ethanol, and seawater through which the sample content in each compound can be calculated.