Wavefront Shaping for Optimal Extinction of Focused Light by Individual Nanoscatterers

Achieving complete optical extinction by small structures is key for applications such as photodetection and light harvesting, and constitutes a promising solution to the problem of efficient in‐and‐out coupling of light in nanophotonic devices. In this paper, we provide an innovative solution to this challenge by experimentally demonstrating optimal extinction by individual and arrayed scatterers separated from a planar reflecting surface, by shaping the wavefront of the input light. We fabricate and characterize planar particle arrays of sizes ranging from extended lattices to individual nanoparticles, separated from a planar, partially absorbing surface by a controlled distance. By optimizing the incident wavefront of a tightly focused light beam and the particle–surface separation, we achieve optimal coupling to a single nanoparticle‐on‐mirror structure. Comparison with theory shows that the optimum incident wavefronts correspond to the time‐reversed emission profiles from the nanoscatterer in the presence of the planar reflector. Using these optimal illumination conditions, we demonstrate 70% extinction of a tightly focused beam by a single plasmonic nanoparticle, and up to 90% extinction in sub‐wavelength 2 2 clusters of nanoparticles on a reflector. These results constitute a solid step toward a practical solution to the in‐and‐out light coupling problem in nanophotonics.