Stimulated emission-based optical sorting of fluorescent nanodiamonds

Fluorescent nanodiamonds (F-NDs) are promising materials for quantum applications, but their practical use is limited by difficulties in separating them from non-fluorescent nanodiamonds. We focus on optical manipulation as a sorting method for F-NDs and demonstrate a selection utilizing stimulated recoil force (SRF). SRF is a recoil force arising from stimulated emission that pulls particles in the direction opposite to light propagation. Compared to conventional resonant absorption force (RAF) that pushes particles in the light propagation direction, SRF enables more efficient separation by avoiding absorption saturation effects and generating larger optical forces. Using silicon-vacancy-containing NDs as a model system, we report that SRF-based sorting achieves significantly higher efficiency than RAF-based methods.