Multiband plasmon-induced transparency based on silver nanorods and nanodisk hybrid model

<sec>In this paper, the dual-band and four-band plamon-induced transparency(PIT) hybrid model based on silver nanorod and silver nanodisk hybrid model are proposed. The electromagnetic characteristics of the two PIT hybrid models are also estimated respectively. The results show that in the double-band PIT model, the silver nanodisk (bright mode) and the silver nanorod (dark mode) can form the bright-dark-dark mode coupling. Because of the destructive interference produced by nanodisk and nanorod and the emergence of new SPs resonance modes between nanorod and nanorod, the double-band PIT model can produce two transparent windows. When the length of the nanorods and the distance between the nanorods and nanodisk are changed, the resonant frequencies and transmission amplitudes of two transparent windows will be changed accordingly. </sec><sec>In the four-band PIT model, the silver nanodisk and the silver nanorods will form the dark-dark-bright-dark-dark mode coupling. The resonant peaks of four transparent windows almost coincide with those of the two asymmetric double-band PIT models. Therefore, the four-band PIT model can be regarded as the superposition of two asymmetric double-band PIT models. The resonant frequencies and transmission amplitudes of four transparent windows also vary with the the length of nanorods and the distance between nanorods and nanodisk.</sec><sec>Finally, the sensing performance of the four-band PIT model is investigated. It is found that the model can produce four transparent windows from beginning to end when the refractive index of the background material is changed. As the refractive index is changed from 1.0 to 1.4, the resonant frequencies in four transparent windows are approximately linearly related to the refractive index. At the same time, the maximum sensitivity of the four transparent windows can reach 326.2625 (THz/RIU) and the maximum figure of merit can arrive at 26.4 (1/RIU), which is higher than those of similar similar sensors in other literatures. This work provides the theoretical support for these models’ potential applications in many areas such as optical storage, absorption, filtering and the design of sensors in infrared band.</sec>