Abstract:This study proposes a hybrid structure consisting of a double-layer dislocated metal grating and an inclined dielectric grating to address the issues of low fluorescence intensity and omnidirectional divergence in fluorescence detection. Using the finite-difference time-domain method, we investigated the effects of polarization state and position, quantum dot positioning, and metal grating period on enhancing directed fluorescence emission. Additionally, we analyzed the enhancement effect during fluorescence excitation. By embedding the up-conversion quantum dots as fluorescent materials within the polymethyl methacrylate layer, the proposed structure achieved significant fluorescence far-field directional enhancement. The results demonstrated that, compared to free space, when quantum dots were placed in dislocated metal gratings, fluorescence excitation was enhanced by 40-fold, directional fluorescence emission was increased by 26-fold, and the far-field radiation angle was reduced, thereby improving the sensitivity of fluorescence-based biological detection.
