Enhanced Plasmonic\nTrapping and Fluorescent Emission\nof Nitrogen-Vacancy Nanodiamonds Using a High-Efficiency Nanofocusing\nDevice

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