Molecularization of meta-atoms for electromagnetically induced transparency resonance and quality-factor switching

Abstract

Electromagnetically induced transparency (EIT) analogs in terahertz regimes have been actively tuned by hybridizing semiconductors into metasurfaces for effective terahertz manipulation. Although several multiple means have been adopted to modulate EIT, the active control of the EIT quality factor is less reported. Multifunctional EIT modulation should also be considered. In this study, we fabricated a terahertz metadevice by embedding Si bridges into a metasurface with optically controllable molecularization of terahertz meta-atoms and experimentally demonstrated dual-functional terahertz EIT modulation, including resonance amplitude modulation and quality-factor modulation. For a low-power pumping of 16 mW, ultrafast EIT resonance amplitude modulation can be achieved with a low-level molecularization, with a normalized amplitude modulation of up to 85%. Then, with a high-power pumping of 360 mW, we performed ultrafast EIT quality-factor switching, where the high Si-bridge conductivity altered the spatial interconnected structure and exhibited high-level molecularization. Both functions have a nanosecond-scale modulation speed. In addition, we numerically and theoretically explained the terahertz modulation and molecularization behaviors, which was consistent with the experimental results. Our proposed all-optical active terahertz metadevice with controllable molecularization provides a novel solution for multifunctional and ultrafast switchable terahertz modulators.