Nanofocusing performance of the crescent-shaped cylinder for various surrounding media

In this work, adjustable broadband light harvesting and field enhancement on the surface of a crescent-shaped cylinder were achieved by considering the surrounding medium in conformal transformation theory. The continuous absorption spectrum shows that the broadband effect is quite robust to the surrounding media. By considering the material properties, we provide a comprehensive discussion of how the material properties of the nanosystem affect the field enhancement and nanofocusing. Furthermore, an optical gain medium is employed to compensate for the absorption losses in the materials. A considerable field enhancement and super-nanofocusing are thus expected. The presented results provide important guidance for optimizing such a nanosystem in experimental studies.