Dipole and quadrupole trapped modes within bi-periodic silicon particle array realizing three-channel refractive...

In this research paper, multiple trapped modes within a bi-periodic silicon particle array were studied numerically both through finite difference time domain method and finite element method. Anti-phased electric dipole, magnetic dipole, and magnetic quadrupole collective resonances in the two arrays result in three distinct trapped modes, which interact with the corresponding "bright modes" generating three sharp asymmetric Fano profiles in reflection. The lineshapes can be easily tailored by particle radius to achieve very narrow linewidth, while still remains 100% modulation depth. As a three-channel refractive sensor, the sensitivities for three working frequencies are 155 nm/RIU, 725 nm/RIU, and 190 nm/RIU.