@article {34470, title = {Optical transitions and nonreciprocity in spatio-temporally periodic layers of spherical particles}, journal = {Advanced Optical Materials}, volume = {11}, year = {2023}, pages = {2202812 (9 pages)}, abstract = {An extension of the photonic layer multiple scattering methodology to dynamic spherical scatterers, which exhibit a periodic time-varying response, is presented. The applicability of the method is demonstrated on specific examples of single- and bi-layers of periodically modulated high-refractive-index spherical particles arranged on a square lattice. The results provide compelling evidence for strong and tunable inelastic scattering effects under the triple resonance condition, fulfilled for optical transitions between neighboring high-Q\ lattice modes of the appropriate symmetry, which originate from multipolar Mie resonances. A consistent interpretation of the underlying mechanisms is provided and potential applications in the design of nonreciprocal devices are\ discussed.}, author = {E. Panagiotidis and E. Almpanis and N. Papanikolaou and N. Stefanou} }