Simultaneous excitation and directional emission enhancements of upconversion fluorescence enabled by optical Tamm plasmon in hybrid structure with metal-photonic crystal and grating

Metal-dielectric hybrid structures have become ideal platforms for enhancing fluorescence emission due to their ability to support strong resonances. This study presents a dual-resonance Tamm plasmon (TP) configuration integrating a one-dimensional photonic crystal (1DPC) with precisely optimized metallic gratings. By utilizing the synergistic COBYLA (Constrained Optimization BY Linear Approximations) algorithm, this design achieves comprehensive far-field enhancement of upconversion nanoparticles (UCNPs) fluorescence through synergistic excitation and emission manipulation. By exciting the optical Tamm mode within the structure, the hybrid structure successfully forms a strong localized electromagnetic field, benefiting excited-state absorption (ESA) with angle-insensitive excitation enhancement for both TE and TM polarizations. The far-field fluorescence emission enhancement was achieved for two different orientations of UCNPs. Notably, the maximum overall far-field enhancement factor reaches 1.04× 10⁵-folds for x-orientation UCNPs, taking into account the effects of relaxation during the excitation process. Additionally, the results indicate that introducing the grating into the TP structure leads to an angular FWHM of 18.7°, which plays a crucial role in confining far-field radiation and enhancing fluorescence collection efficiency, thereby promoting highly directional emission. This TP-based platform demonstrates exceptional stability and multi-modal enhancement capability, holding substantial promise for advanced photonic applications including single-molecule biosensing, upconversion lighting, and other photon-based technologies that require high stability and substantial enhancement.