Research advances in polaritonics based on near-field optical imaging technique

Polaritons, as hybrid excitations of light and matter, are important for miniaturizing the integrated nano-optoelectronic devices due to their capability of manipulating nanolight. Recently, the state-of-the-art nano-imaging technique (e.g. scattering-type scanning near-field optical microscope) has visualized various types of polaritons and revealed the physical mechanism behind them. The nanometer-resolution imaging not only deepens our understanding of fundamentals of polaritons but also promotes the studies of polariton manipulation and applications. In this review paper, we systematically summarize the recent near-field study of polaritons. Rather than other previous reviews focusing on polaritons in two-dimensional materials, our review extends the polaritonic systems to multiple dimensions (3D/2D/1D), at the same time we also collect the latest progress of polaritons in anisotropic systems. Moreover, we show the recent study of polariton manipulation and their corresponding applications, e.g. sub-diffractional imaging, focusing, optical modulator, nanostructure diagnosis and molecular sensing. Our review also look forward to future opportunities of polaritonics and its nanophotonic applications.