Enhanced Plasmonic Trapping and Fluorescent Emission of Nitrogen-Vacancy Nanodiamonds Using a High-Efficiency Nanofocusing Device.

Fluorescent nanodiamonds (FNDs) with nitrogen-vacancy centers are pivotal for advancing quantum photonics and imaging through deterministic quantum state manipulation. However, deterministic integration of quantum emitters into photonic devices remains a challenge due to the need for high coupling efficiency and Purcell enhancement. We report a deterministic FND-integrated nanofocusing device achieved by assembling FNDs at a plasmonic waveguide tip through plasmonic-enhanced optical trapping. This technique not only increases the emission rate by 58.6 times compared to isolated FNDs but also preferentially directs radiation into the waveguide at a rate 5.3 times higher than that into free space, achieving an exceptional figure-of-merit of ∼3000 for efficient energy transfer. Our findings represent a significant step toward deterministic integration in quantum imaging and communication, opening new avenues for quantum technology advancements.