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.
The review article summarizes the research on low-dimensional materials-based field-effect transistors, which will help in device downscaling.
On-chip plasmon-induced transparency (PIT) possessing the unique properties of controlling light propagation states is a promising way to on-chip ultrafast optical connection networks as well as integrated optical processing chips. On-chip PIT has attracted enormous research interests, the latest developments of which have also yield progress in nanophotonics, material science, nonlinear optics, and so on. This review summarizes the realization methods, novel configurations, diversiform materials, and the improved performance indexes. Finally, a brief outlook on the remaining challenges and possible development direction in the pursuit of the application of a practical on-chip photonic processor based on PIT is also afforded.
Ultracompact chip-integrated all-optical halfand full-adders are realized based on signal-light induced plasmonic-nanocavity-modes shift in a planar plasmonic microstructure covered with a nonlinear nanocomposite layer, which can be directly integrated into plasmonic circuits. Tremendous nonlinear enhancement is obtained for the nanocomposite cover layer, attributed to resonant excitation, slow light effect, as well as field enhancement effect provided by the plasmonic nanocavity. The feature size of the device is <15 μm, which is reduced by three orders of magnitude compared with previous reports. The operating threshold power is determined to be 300 μW (corresponding to a threshold intensity of 7.8 MW/cm 2 ), which is reduced by two orders of magnitude compared with previous reports. The intensity contrast ratio between two output logic states, "1" and "0," is larger than 27 dB, which is among the highest values reported to date. Our work is the first to experimentally realize on-chip halfand full-adders based on nonlinear plasmonic nanocavities having an ultrasmall feature size, ultralow threshold power, and high intensity contrast ratio simultaneously.This work not only provides a platform for the study of nonlinear optics, but also paves a way to realize ultrahighspeed signal computing chips.
Nonlinear optical materials are cornerstones of modern optics including ultrafast lasers, optical computing, and harmonic generation. The nonlinear coefficients of optical materials suffer from limitations in strength and bandwidth. Also, the nonlinear performance is typically monotonous without polarization selectivity, and to date, no natural material has been found to possess nonlinear coefficients with positive or negative signs simultaneously at a specific wavelength, all of which impede practical applications in the specific scenario. Here, we realize broadband large optical nonlinearity accompanied with ultrafast dynamics in a coupled system composed of gold dolmens and an epsilon-near-zero material for dual orthogonal polarizations simultaneously. The system also shows the polarization-selected nonlinearity transition properties, where the sign of the optical nonlinear refractive indexes can be converted via polarization switching. This guarantees active transitions from self-focusing to self-defocusing by polarization rotation without tuning wavelength in practical utilizations. The measured nonlinear refractive index and susceptibility demonstrate more than three orders of magnitude enhancement over a 400-nm-bandwidth compared with the constituents, while maintaining the sub-1 ps time response. The realized enhanced, ultrafast response, and the polarization tunability ensure the designed system a promising platform for the development of integrated ultrafast laser sources, all-optical circuits and quantum chips.
Active control of light polarization is necessary for the development of laser physics, optical communications, and also the molecular dynamics. Conventional polarization control methods suffer from low speed, and the existing all‐optical switching based on nonlinear materials solely has a lot of conducting restrictions, impeding its practical utilizations. Herein, an all‐optical polarization switching in the near‐IR range, composed of the plasmonic gratings deposited on an indium tin oxide (ITO) film with epsilon‐near‐zero response, is realized. A sub‐1 ps response speed and the 19° rotation of the polarization ellipse are determined with the excitation power of 1.37 GW cm−2. The device is demonstrated to output the varied signal with tuning the incident polarization and intensity in a spectral range from 1200 to 1500 nm. The ultrafast processing speed, broadband, and diverse tunability ensure the designed device a promising and necessary element for practically integrating into the next‐generation signal‐processing systems with high performance and large capacity.
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