Atomically thin semiconductors like tungsten disulfide (WS2) are emerging as key materials for next-generation photonic technologies. Even though they are only a single layer of atoms, they can host tightly bound excitons, which are electron and 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 properties, they are promising for applications in quantum optics, sensing, and compact on-chip light sources. However, their extreme thinness also creates a challenge. With so little material available, light has limited interaction, which often results in weak emission and inefficient frequency conversion unless the surrounding photonic environment is carefully designed.
A study published in Advanced Photonics presents a new strategy to overcome this limitation by modifying not the material itself, but the space beneath it. In this approach, a single layer of WS2 is placed on nanoscale air cavities, called Mie voids, which are carved into a high-index crystal of bismuth telluride (Bi2Te3). These tiny voids significantly boost light emission and nonlinear optical signals. They also make it possible to directly observe localized optical modes, offering new insight into how light behaves at very small scales.
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