Enhanced and directional fluorescence emission regulated by dual resonant surface modes

Fluorescence emission regulation is of great interest for its promising applications in various fields such as microscopy, chemical analysis, encryption, and sensing. Most studies focus on the regulation of the fluorescence emission process. However, the spectral separation of excitation and emission of fluorophores requires careful design of resonances to cover both emission and excitation wavelengths, which is a better choice to enhance fluorescence intensity. In this Letter, we engineer an efficient dielectric concentric ring grating on a dielectric multilayer film with two resonate modes to enhance the excitation and emission processes. By careful design of the structure, the two resonate modes occupy similar in-plane wave vector and overlap in the fluorescence area. Experimentally, fluorescence intensity enhancement about five times and the divergence of fluorescence into free space compressed to less than 5° are achieved. Our work provides what we believe to be a new strategy for the realization of high directional on-chip light emitter at room temperature.