Low-loss plasmonics based on alkali metals: from fundamentals to applications: tutorial

Plasmonics offers a groundbreaking avenue for manipulating light beyond the diffraction limit, finding utility in diverse applications ranging from optical cloaking and chemical sensing to super-resolution imaging. Despite these promising applications, plasmonic devices are always born with significant energy dissipation, posing substantial challenges to their efficiency and practical implementation. In the realm of plasmonics, researchers in the field of plasmonics have spent decades exploring alternatives to noble metals. Recently, alkali metals have garnered revived attention as promising candidates due to their exceptional light-manipulation capabilities and low losses. We elucidate the fundamental physical mechanisms behind the optical low-loss nature in alkali metals, alongside methodologies for characterizing alkali metal losses. To discern the suitable applications for alkali metal materials, we compare their advantages and disadvantages with those of other plasmonic materials. Furthermore, we introduce experimental techniques for measuring plasmonic losses and fabrication techniques and highlight potential applications of low-loss alkali metals.