Over 240 Resonances on a Metasurface‐Pixelated Silicon Wafer in an Octave‐Spanning Terahertz Range

Metasurfaces hold tremendous promise for various innovative sensing applications, thanks to their remarkable ability to manipulate light. A recent significant advancement in this research direction is using quasi‐BIC (bound states in the continuum) metasurfaces for mid‐infrared molecular sensing, which relies on creating a series of nearly uniformly spaced, sharp resonances on a single device. Although many studies have highlighted the potential of adopting this method in the terahertz (THz) regime, experimental demonstration is lacking. In this work, the first experimental demonstration of such frequency comb‐like, quasi‐BIC resonances on a single device is presented in the THz regime. By pixelating a 6‐inch Si wafer with 25 different metasurfaces that possess both high‐order quasi‐BIC modes and a geometric scaling, a set of 241 sharp resonances ranging from 350 to 750 GHz is produced based on numerical simulation. By using a high‐resolution vector network analyzer, 140 peaks that fall into the detection range from 500 to 750 GHz are confirmed experimentally, and their frequencies match well with the simulated results. By experimentally demonstrating frequency comb‐like, quasi‐BIC THz resonances on a single device, this work shows a new path for metasurface‐based sensing in the THz regime. By using 25 pixelated metasurfaces, quasi‐BIC resonances induced by high‐order (up to TE9) confined modes and a geometric scaling, a single 6‐inch silicon wafer produces over 240 sharp resonances in the THz regime. The resonances distribute roughly uniformly across a frequency octave until 750 GHz, at a high peak density of 0.6 GHz−1.