Fig. 1. (Color online) Microwave-dressed photonic module. (a) The photonic molecule is realized by a pair of identical coupled optical microring resonators (resonant frequency ω₁  = ω₂). The system has two distinct energy levels—a symmetric and an antisymmetric optical mode. (b, c) When the applied microwave frequency is tuned to match the mode separation, dissipative coupling leads the two photonic levels to split into four levels. This effect is analogous to Autler–Townes splitting. (d) False-coloured scanning electron microscope image of the coupled microring resonators. (e) On-demand storage and retrieval of light using a photonic dark mode. Figure adapted from Ref. [10].