Independent manipulation of dual high-Q modes for multifunctionalities

Subwavelength light trapping in periodic structures with high quality (Q) factors is discovered to hold strong light-matter interactions for a variety of applications. Although dual-band or even multiple-band high-Q resonances are applicable to extend the operation range of a nanophotonic device, manipulating the high-Q modes individually is a necessity to implement plural intriguing applications in one system as well as optimize the capabilities across each spectrum. In this work, a novel approach is presented to independently control dual high-Q modes with distinct origins in an all-dielectric metasurface system. The structure consists of hollow nanorod dimers and is found to support a symmetry-protected bound state in the continuum and a guided mode resonance induced by Brillouin-zone-folding effect. Independent and deliberate Q-factor control of these two high-Q optical resonances can be achieved by breaking the disparate mode symmetries. The two modes are found to have distinct polarization properties and Q-factor features across the momentum space. With rich tunable structural parameters, it is possible to develop a multifunctional device meeting specific requirements at each band. This work provides a new method for operating band broadening, performance optimization, and functionality enrichment for nanophotonic devices.