Efficient Ultraviolet Nanosources Based on Third‐Harmonic Generation in Dielectric–Metal Composite Nanodisks

Dielectric materials with high indices have recently attracted much attention in the community of nanophotonics. Severe optical losses in visible–ultraviolet (UV) region, however, limit their applications. This article proposes dielectric–metal nanocomposites as alternative high‐index materials for Mie‐resonance‐based applications. Such composite materials have high indices in the range of wavelength longer than plasmon resonance of inclusion metal nanoparticles, while they have much lower losses in the range from blue‐violet down to near‐UV compared with commonly used high‐index materials such as silicon, enabling near‐UV generation with high efficiency based on third‐harmonic generation (THG). The numerical results show that ZnO nanodisk containing silver nanoparticles can generate near‐UV radiation at 351.3 nm via THG with an efficiency about 20 times higher compared with silicon nanodisk under same pumping condition. Significantly high THG efficiency of 0.015% has been predicted with such a composite nanodisk supported by aluminum substrate under pumping with a peak intensity of 20 GW cm−2, a spot size of 0.8 μm, a duration of 50 fs at 1054 nm, respectively. Dielectric‐metal nanocomposites are proposed as alternative high‐index materials for dielectric nanophotonics. They have much lower losses in the range from blue to near ultraviolet (UV) compared with commonly used high‐index dielectrics, enabling highly efficient UV generation. ZnO nanodisk containing silver nanoparticles generates third‐harmonic radiation at 351.3 nm with an efficiency about 20 times higher than the case of silicon nanodisk.