Atomically thin semiconductors such as tungsten disulfide (WS₂) are emerging as key materials for next-generation photonic technologies. Although they consist of just a single layer of atoms, they support tightly bound excitons, which are electron-hole pairs that interact strongly with light. These materials can also produce new colors of light through nonlinear optical effects such as second-harmonic generation. Because of these capabilities, they are considered promising for quantum optics, sensing, and compact on-chip light sources.
However, their atomic-scale thickness also presents a fundamental challenge. With so little material present, light has limited opportunity to interact with it. As a result, light emission and frequency conversion processes are typically weak unless the surrounding optical environment is carefully designed to boost these interactions.
A study published in Advanced Photonics presents a new solution that focuses not on altering the two-dimensional material itself, but on reshaping the structure beneath it. In this work, researchers created a hybrid system in which a monolayer of WS₂ rests on nanoscale air cavities known as Mie voids. These voids are etched into a high-index crystal of bismuth telluride (Bi₂Te₃). The team demonstrated that this configuration significantly strengthens both light emission and nonlinear optical signals, while also making it possible to directly observe localized optical modes.
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