Sensitivity analysis of 1D and 2D photonic crystals sensors based on change of thickness and refractive index in material

Abstract

A detail study was done on the sensitivities of 1-D photonic crystal (PC) and 2-D PC coupled cavity sensors with changing sensing layer parameters of thickness and refractive index (RI). Though both refractive index and thickness are interrelated they have significant individual affects on device response. In 1-D PC shifts in normal transmission peak due to surface change in thickness and RI and in 2-D PC coupled cavity shifts in transmission dip due to surface changes are observed. Here sensitivity analysis in change in thickness and RI on these devices was done for four cases; case 1: change in thickness from 2nm-10nm on PC sensors, case 2: change in thickness from 75nm-175nm on PC sensors, case 3: change in RI in thin film (6nm) on surface and case 4: change in RI in thick film (100nm) on sensors surface. Sensitivities due to change in thickness (S_t) of 1-D PC and 2-D PC coupled cavity were calculated from the slope of the sensitivity curves and found to be (for RI of 1.4) 1.423nm/nm and 2.285nm/nm for case 1 and 0.455nm/nm and 0.801nm/nm for case 2. Sensitivities due to change in RI (S_r) of 1-D PC and 2-D PC coupled cavity were obtained from the transmission peak and dip shifts due to change in RI from 1(air) to 2. Sr for 1-D PC and 2-D PC coupled cavity were found to be 70nm/RIU and 103nm/RIU for case 3 and 143nm/RIU and 213nm/RIU for case 4. The results are based on FDTD simulations.