Ultrafast all-optical switching, possessing the unique function of light controlling light, is an essential component of on-chip ultrafast optical connection networks as well as integrated logic computing chips. Ultrafast all-optical switching has attracted enormous research interests, the latest great developments of which have also yield progress in nanophotonics, integrated optics, nonlinear optics, material science, and optical communications, and so on. This review summarizes the fundamental realization principles, novel configurations, fancy materials, improved performance indexes, and ameliorated trigger method (transitioning from a traditional impractical free-spacevertical trigger to a more practical on-chip trigger) of ultrafast all-optical switching. Not only a systematic discussion of the current state-of-the art is provided, but also a brief outlook on the remaining challenges in the pursuit of the application of a practical on-chip ultrafast all-optical switching is also afforded.www.advopticalmat. de

Epsilon‐near‐zero (ENZ) photonics is the study of light–matter interactions in the presence of structures with near‐zero permittivity and has been emerging as an important field of research in recent years. The introduction of zero permittivity structures also introduces a number of unique features to traditional photonic systems, including decoupling of their spatial and temporal field variations, tunneling through arbitrary channels, constant phase transmission, strong field confinement, and ultrafast phase transitions. Along with the continued developments in the theoretical research on ENZ photonics, many novel functional photonic devices are proposed and demonstrated experimentally, thus indicating the broad prospects of ENZ photonics for fabrication of high‐performance integrated photonic chips. Zero‐epsilon materials, which represent a singular point in optical materials, are expected to lead to remarkable developments in the fields of integrated photonic devices and optical interconnections. This review summarizes the underlying principles, the related novel physical effects, the fundamental principles for realization of ENZ photonic systems, and the integrated device applications of ENZ photonics. The review concludes with a brief overview of the challenges to be confronted and the potential development directions that may be pursued to realize extensive applications of ENZ photonics in the field of integrated photonic signal processing.

Recently, organometal halide perovskite-based optoelectronics, particularly lasers, have attracted intensive attentions because of its outstanding spectral coherence, low threshold, and wideband tunability. In this work, high-quality CH NH PbBr single crystals with a unique shape of cube-corner pyramids are synthesized on mica substrates using chemical vapor deposition method. These micropyramids naturally form cube-corner cavities, which are eminent candidates for small-sized resonators and retroreflectors. The as-grown perovskites show strong emission ≈530 nm in the vertical direction at room temperature. A special Fabry-Pérot (F-P) mode is employed to interpret the light confinement in the cavity. Lasing from the perovskite pyramids is observed from 80 to 200 K, with threshold ranging from ≈92 µJ cm to 2.2 mJ cm , yielding a characteristic temperature of T = 35 K. By coating a thin layer of Ag film, the threshold is reduced from ≈92 to 26 µJ cm , which is accompanied by room temperature lasing with a threshold of ≈75 µJ cm . This work advocates the prospect of shape-engineered perovskite crystals toward developing micro-sized optoelectronic devices and potentially investigating light-matter coupling in quantum optics.