Resonant Multipolar Metasurfaces for Controlled Quantum Emission

Metasurfaces composed of subwavelength dielectric or hybrid nanostructures provide an exceptional platform for controlling optical waves through engineered resonances and multipolar interactions. Our work explores resonant metasurfaces that leverage high-index dielectric nanoantennas and van der Waals materials to achieve strong field localization, tunable spectral responses and bound states in the continuum (BIC). This approach leads to design strategies for realizing compact, high-efficiency metasurfaces suitable for multifunctional photonic platforms, frequency conversion, and emission control. We demonstrate how the controlled excitation and coupling of electric and magnetic multipoles govern scattering directionality and enable high-Q quasi-BIC modes with extreme near-field enhancement. These effects are further employed to enhance nonlinear optical processes, including second-harmonic generation, by engineering overlapping resonances at fundamental and harmonic frequencies. Through numerical modeling and field analysis, we correlate the spatial field profiles with multipolar decomposition, establishing a direct link between the underlying physics and macroscopic optical response. These results demonstrate the fundamental mechanisms governing resonant light–matter interactions in nanostructured materials and their potential for next-generation nonlinear and quantum nanophotonics.