Tailoring Electric and Magnetic Dipole Emission of Er ³⁺ Ions via Toroidal Dipole Resonance of Si Nanodisk Hexagonal Array

A hexagonal array of silicon (Si) nanodisks is investigated for its ability to control the 1.5‐µm emission of Er 3+ ions via toroidal dipole (TD) resonances. Numerical simulations reveal that the TD resonance forms accessible magnetic hot spots on the nanodisk surface, which enhances the magnetic dipole transitions of Er 3+ ions and directs the emission along the surface normal through the Purcell effect. This effect is experimentally investigated in a silica film containing Er 3+ ‐doped Si nanocrystals formed on a Si nanodisk hexagonal array. The photoluminescence spectra show that the magnetic dipole transition of Er 3+ ions is strongly enhanced by the TD resonance and preferentially directed in the surface‐normal direction. A maximum enhancement factor of 130 is achieved under doubly resonant conditions, where both the excitation and emission wavelengths are simultaneously matched to the corresponding resonances.