Tunable Plasmonic Absorber Using a Nanoslit Array Patterned on a Ge2Sb2Te5 -Inserted Fabry–Pérot Resonator

A wavelength-selective tunable plasmonic absorber is required for various applications, such as thermal imaging sensors, active biosensors, and switching devices in integrated optics. Using Ge₂Sb₂Te₅ (GST), which is a representative phase change material showing a large change in optical characteristics, we propose a tunable plasmonic absorber that consists of a metal nanoslit array patterned on a GST-inserted dielectric layer. Based on systematic optimization, the proposed structure achieved a nearly zero reflectance for both states of the inserted GST film with a very large resonance shift after the phase transition. Moreover, the resonance wavelength of the proposed absorber could be flexibly tuned within a broad near-infrared range by tuning the geometric conditions of the nanoslit array and the thicknesses of the dielectric-GST-dielectric multilayer.