Multiparameter-detecting biosensors based on the surface and waveguide modes of the two-dimensional photonic crystal slab

Abstract

The refractive index sensing characteristics of the two-dimensional photonic crystal (PhC) slab are studied. The proposed symmetric and asymmetric PhC structures are composed of finite-height silicon rods sandwiched by two glass substrates immersed in the liquid environment, so it is suitable to the real-time and dynamic detection of protein's concentration. For the symmetric PhC structure, owing to the interaction of surface and waveguide modes, the resonant wavelengths and the corresponding light transmittances can be influenced by the slight thickness alteration at specific locations within a finite-size photonic crystal slab, while the localized modes work more independently for the other structure. A value of the resonant mode's quality factor more than 1000 is achieved and a slight alteration of the protein's thickness less than 20 nm can be distinguished.