Twist-tunable moiré optical resonances

Multilayer stacks of twisted optical metasurfaces are considered as a prospective platform for chiral nanophotonic devices. Such structures are primarily used for the realization of circularly polarized light sources, artificial optical rotation, and circular dichroism. At the same time, the behavior of their hybrid photonic modes is strongly affected by the moiré pattern of superimposed periodic constituents. In this paper, we show that moiré periodicity in bilayer dielectric photonic crystal slabs (PCSs) leads to a rise of unlimitedly narrow optical resonances, which are very sensitive to the relative twist and gap width between the sublayers. We demonstrate the structure providing twist-tuning of the hybrid mode wavelength in the range of 300-600 nm with the quality factor varying from 10² up to 10⁵ correspondingly. The obtained results pave the way for the utilization of moiré-assisted effects in multilayer PCSs.