Enhancing Diamond Fluorescence via Optimized Nanorod Dimer Configurations

Light extraction from silicon (SiV) and nitrogen (NV) vacancy diamond color centers coupled to plasmonic silver and gold nanorod dimers was numerically improved. Numerical optimization of the coupled dipolar emitter—plasmonic nanorod dimer configurations was realized to attain the highest possible fluorescence enhancement by simultaneously improving the color centers excitation and emission through antenna resonances. Conditional optimization was performed by setting a criterion regarding the minimum quantum efficiency of the coupled system ( cQE ) to minimize losses. By comparing restricted symmetric and allowed asymmetric dimers, the advantages of larger degrees of freedom achievable in asymmetric configurations was proven. The highest 2.59 × 10 8 fluorescence enhancement was achieved with 46.08% cQE via NV color center coupled to an asymmetric silver dimer. This is 3.17-times larger than the 8.19 × 10 7 enhancement in corresponding symmetric silver dimer configuration, which has larger 68.52% cQE . Among coupled SiV color centers the highest 1.04 × 10 8 fluorescence enhancement was achieved via asymmetric silver dimer with 37.83% cQE . This is 1.06-times larger than the 9.83 × 10 7 enhancement in corresponding symmetric silver dimer configuration, which has larger 57.46% cQE . Among gold nanorod coupled configurations the highest fluorescence enhancement of 4.75 × 10 4 was shown for SiV color center coupled to an asymmetric dimer with 21.8% cQE . The attained enhancement is 8.48- (92.42-) times larger than the 5.6 × 10 3 (5.14 × 10 2 ) fluorescence enhancement achievable via symmetric (asymmetric) gold nanorod dimer coupled to SiV (NV) color center, which is accompanied by 16.01% (7.66%) cQE .