Designing a Transition Photonic Band with a Moir? Synthetic Sphere

In recent years, twisted bilayer graphene has become a hot topic and inspired the upsurge of research on the photonic moire lattice. Here, we design a photonic moire superlattice with two synthetic twist angles and construct a synthetic moire sphere based on these two angles. Thus, we have more degrees of freedom to design the band structure flexibly. A type of transition photonic band (TPB) is obtained in such a moire superlattice. We investigate the influence of two twist angles on TPBs and find a series of magic angle pairs with optimal band compression of the TPB. Interesting optical properties of TPBs are experimentally demonstrated, including pulse delay, nonlinear optical enhancement, and pulse-width compression. Our work introduces an alternative path to explore multitwist-angle moire superlattices and reveals that the designed photonic moire superlattice based on moire spheres has broad application prospects, including optical signal processing, nonlinear optic processes, and other light-matter interactions.