Annular one-dimensional photonic crystals for salinity sensing.

The use of annular one-dimensional (1D) photonic crystals (PCs) for salinity sensing is studied in this research. Annular 1D-PCs provide small and integrated structures that facilitate the creation of portable and miniaturized sensor equipment appropriate for field use. In order to generate annular 1D-PCs, the research explores the finite element method (FEM) simulation technique utilizing the COMSOL Multiphysics approach, highlighting the significance of exact control over layer thickness and uniformity. Furthermore, we construct a 1D annular PCs structure in the form [Formula: see text], where A is silicon ([Formula: see text]) and B is silicon dioxide ([Formula: see text]) of 40 nm and 70 nm, respectively, with a number of periods equal to 9. By incorporating a central defect layer of saline water (220 nm thickness), the sensor achieves optimum performance at normal incidence with a sensitivity (S) of [Formula: see text], a quality factor (Q) of 10.22, and a figure of merit (FOM) of [Formula: see text]. The design that is suggested has several advantages over past work on planners and annular 1D-PCs, including ease of implementation, performance at normal incidence, and high sensitivity.