Mid-infrared active quasi-BIC based on the chalcogenide metasurface

Abstract

High quality factor (high-Q) resonances provide potential applications in many fields such as ultrasensitive sensors or non-linear optics. Bound states in the continuum (BIC) has infinite Q-factor and with slight perturbation in the in-plane symmetry of unit cells, the BIC could be turned to quasi-BIC (QBIC), which could be realized in real experiment and still keep a high Q-factor. Metasurface-based QBIC has been studied a lot. However, the active QBIC metasurface remains less explored and is waiting for more experimental studies. Here, a kind of Chalcogenide phase change materials, Ge2Sb2Te5 , is used to realize the active modulation of QBIC’s amplitude and resonance position in metasurface. We first numerically verifies the feasibility of QBIC mode and studies the dimension of unit cell structure’s effect on the QBIC mode and active modulation ability, based on which we make the optimization of the unit cell. Besides, we also consider polarization dependence of QBIC. In experiment, we verify the existence of QBIC and actively tuning the resonance by heating. This study explores a new way to actively control the QBIC mode and represents a major advance toward the mid-infrared QBIC research.