Refractive index less than two: photonic nanojets yesterday, today and tomorrow [Invited]

TLDR

Materials with refractive indices below two, such as glass, quartz, polymers, and ceramics, form the core of most optical components and their behavior is largely governed by Mie theory for spherical particles. This review surveys phenomena and potential applications resulting from light interacting with sub‑two‑index particles. The authors examine various particle shapes—spheroidal, cubic, etc.—and configurations, mapping how these geometries influence field enhancement and super‑resolution nanoscopy applications. The review outlines how sub‑two‑index particles can generate photonic nanojets that enhance fields and enable super‑resolution nanoscopy.

Abstract

Materials with relatively small refractive indices (n<2), such as glass, quartz, polymers, some ceramics, etc., are the basic materials in most optical components (lenses, optical fibres, etc.). In this review, we present some of the phenomena and possible applications arising from the interaction of light with particles with a refractive index less than 2. The vast majority of the physics involved can be described with the help of the exact, analytical solution of Maxwell’s equations for spherical particles (so called Mie theory). We also discuss some other particle geometries (spheroidal, cubic, etc.) and different particle configurations (isolated or interacting) and draw an overview of the possible applications of such materials, in connection with field enhancement and super resolution nanoscopy.