All-Optical Control of Light in Micro- and Nanophotonics

The pursuit of high-speed and chip-scale signal processing has promoted extensive exploration of all-optical control of light in micro- and nanophotonic platforms. All-optical switching and modulation are essential operations for optical communication systems and data networks and have been implemented by exploiting varieties of linear and nonlinear optical processes. In this regard, the optical control of materials' refractive index is the primary technique, which facilitates the modulation of light attributes in a fast and reversible manner. A sustainable progress in the field of all-optical control primarily requires a deep understanding of optical phenomena that govern the manipulation of the refractive index. However, since most of such optical processes are intrinsically weak, utilizing resonating photonic structures of various kinds is often necessary to pave the way for the practical implementation of all-optical modulators for real-world applications. In this Perspective, we first present a concise description of key light-induced transient phenomena in dielectrics, metals, and epsilon-near-zero materials and then discuss the incorporation of these effects in resonant cavities to facilitate the all-optical control of light attributes in micro- and nanoscale devices. By exploring state-of-the-art material and device platforms, we elaborate existing challenges, possible solutions, and future directions for ultrafast all-optical modulation.