Absorption and steady-state emission spectra of two fluorescent dyes are measured in a series of aprotic solvents with similar refractive index and different polarity. The spectra are interpreted in terms of a two-state electronic model accounting for the coupling to internal vibrations and to an effective solvation coordinate. The proposed approach naturally accounts not only for solvatochromic shifts of absorption and emission bands but also for the evolution of band shapes with solvent polarity and for the observation of nonspecular absorption and fluorescence bands. The good agreement between experimental and calculated spectra confirms the validity of a two-state picture for the low-energy spectral properties of these donor−acceptor molecules, provided that the molecular polarizability is fully accounted for. The role of conformational degrees of freedom in flexible chromophores is also addressed.

Optical quantum memories are essential elements in quantum networks for long-distance distribution of quantum entanglement. Scalable development of quantum network nodes requires on-chip qubit storage functionality with control of the readout time. We demonstrate a high-fidelity nanophotonic quantum memory based on a mesoscopic neodymium ensemble coupled to a photonic crystal cavity. The nanocavity enables >95% spin polarization for efficient initialization of the atomic frequency comb memory and time bin–selective readout through an enhanced optical Stark shift of the comb frequencies. Our solid-state memory is integrable with other chip-scale photon source and detector devices for multiplexed quantum and classical information processing at the network nodes.

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