Enhanced optical sensor for waterborne bacteria-based photonic crystal using graded thickness index

We explore one-dimensional photonic crystal structure with defect layer to be used as optical sensor to detect waterborne bacteria in pure water. The transmission spectra of the proposed structure are computed using the well-known transfer matrix approach. The proposed optical sensor application is being studied using quarter-wave structure and to select an appropriate thickness for further research, the thickness of the defect layer is taken as an integer multiple of the unit cell. To improve the sensitivity of the prosed sensor, the graded thickness index of alternative layers is investigated. We extend our investigation to obtain optimum values for the number of unit cells and angle of incidence. For the proposed optical sensor, the sensitivity, FWHM and quality factor are achieved as 2801.515 nm/RIU, 0.063922 nm and 29554.04, respectively, for optimum parameters of the structure. © 2023, King Abdulaziz City for Science and Technology.