Porous photonic crystal structure for sensing applications

A multilayer photonic band gap structure is proposed for sensing applications in visible wavelength range. The structure is designed by introducing alternate layers of dielectric material on a glass substrate. To ease the analyte infiltration and to improve the sensitivity, porosity is introduced deliberately within each layer. Extensive analysis is carried out to optimize the number of dielectric layers, their thickness, and percentage of porosity. The transmission/reflection spectral characteristic and sensitivity of the proposed structure are analyzed by a three-dimensional finite difference time domain method. The porosity value and structural parameters are optimized to obtain highest possible sensitivity. The proposed structure exhibits a 0.05-nm shift in reflection/transmission wavelength with corresponding refractive index change of ^{10 - 3}. Analyte can also be distinguished by seeing the sample color change with naked eyes. Thus, multiparametric characterization of the proposed structure demonstrates its potential for sensing applications.