Dielectric Environment Manipulation toward Versatile Light Scattering of High Refractive Index Nanoparticles

Optical scattering process is of fundamental importance for manipulating light–matter interaction at the subwavelength scale. Dielectric nanoparticles with high refractive index have been a long-proven candidate for supporting optical Mie resonances and are recently regaining considerable attention thanks to a combination of their low-loss property as well as the compatibility with modern micro-/nanoprocessing technologies. Changing the surrounding environment of nanoparticles can exert great influence on the scattering behaviors, especially in the case of plasmonic particles, whose ability to sensitively detect index change has been well implemented in the field of optical sensing. However, few reports can be found scrutinizing the detailed mechanism concerning dielectric nanoparticles, and the systematic research on how surrounding environment can shape their scattering behaviors remains largely uncharted waters. Therefore, it is necessary to elucidate to what extent can surrounding environment affect the optical responses of high refractive index nanoparticles. In this paper, we theoretically and numerically investigate three representative geometries, namely individual nanosphere, individual nanodisk, and two-dimensional nanodisk array (metasurfaces). For the individual nanosphere, we examine the influence of the surrounding medium by applying well-established analytical solutions. For the individual nanodisk, multipole expansion is utilized for unveiling the mode evolutions of the decomposed modes upon altering the surrounding environment. For metasurfaces, we demonstrate mode overlap and split phenomena through dynamically tuning the refractive index of the embedded medium. This work may find applications in sensing and optical switching devices composed of high refractive index dielectric nanoparticles.