All‐Dielectric Metalens for Efficient Chiral Characterization

Efficient chiral excitation and polarization‐insensitive collection are critical to the detection of Raman optical activity, the selective excitation/addressing of specific states, and quantum information processing. Traditional chiral characterization relies on bulky and expensive components such as objectives, dichroic mirrors, and waveplates, severely limiting the miniaturization and practical application of the system. Herein, a versatile all‐dielectric metalens is reported for compact and efficient chirality characterization. In silicon (Si) nanopillars with large height, it is revealed that the phases of two closely spaced wavelengths can be controlled independently without crosstalk. With an optimized nanofabrication process, Si nanopillars with record‐breaking aspect ratio and the corresponding multifunctional metalens have been realized experimentally. The experimental efficiencies of focusing 850 nm chiral light and 780 nm unpolarized light to the same focal point are 54% and 45% respectively, far exceeding the previous multifunctional metalenses. This work paves a key step toward compact systems for quantum information processing and spin‐dependent optical detection.