“…On the other hand, a waveguide array or a waveguide lattice can also be viewed 27 as fully analogous to a periodic chain of atoms, which lends itself to a broad spectrum of fascinating scientific possibilities ranging from Anderson localization of light 28,29 to parity-time symmetric effects 30 . Thus far, in most studies, the pitch associated with such relatively simple waveguide arrays/lattices has been typically large, ranging from a few micrometres to tens of micrometres (or a multiple of wavelengths) 18,19,21,31,32 . As such, the inter-coupling between waveguides can be generally weak, which helps to reduce crosstalk.…”