Observation of Bloch Flatbands and Localized States in Moiré Bilayer Grating

Le résumé fourni par la source

Here, we explore the formation of Bloch flatbands in photonic moiré bilayer grating. The stacking-induced interlayer coupling contrast serves as a crucial condition for flatband formation. The number of Bloch flatbands is related to the number of antinodes present within one unitcell of monolayer grating. By applying the band-unfolding approach to moiré supercell states, we identify that the associated localized states in moiré bilayer grating arise from the "beating" mode between Bloch standing-waves associated with two similar periods. Experimentally, we established a resonance-enhanced photon scattering setup to directly measure Bloch flatbands and observe the corresponding localized states in the moiré photonic system. Furthermore, we present the experimental demonstration of third-harmonic generation enhancement facilitated by moiré-induced flatbands. Our work provides insights into moiré-induced modulation of photonic band structures, opening up possibilities for novel optical phenomena and device applications in photonic crystals.

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