Reviews & Analysis

This Review discusses the physics of nonreciprocal radiation and Kirchhoff’s law generalization in the context of nanophotonics-enabled nonreciprocal thermal applications.

Chiral materials and related mechanisms are reviewed, with a focus on applications for circularly polarized light-emitting diodes.

A review of NIR-II fluorescence imaging is presented, with a focus on fluorophores, probes and imaging techniques.

Advances in the understanding of optical skyrmions, within a unified topological framework, are reviewed. The field structure of such optical quasiparticles, and their topological characteristics, may be useful for fields ranging from imaging to quantum technologies.

The progress made in developing light-emitting technologies that are wearable, attachable or implantable is reviewed and potential applications and challenges are discussed.

This Review covers a comparison between various label-free biomedical imaging techniques, their advantages over label-based methods and relevant applications.

Optical analogues of electronic memristors are desirable for applications including photonic artificial intelligence and computing platforms. Here, recent progress on integrated optical memristors is reviewed.

Robotic and other devices often demand ever more compact and sophisticated sensors. This Review assesses the opportunities for metasurfaces to provide optical functionality solutions for such applications.

Nonlocal effects—in which the optical response of a system at a given spatial point depends on the field in the surrounding space—are reviewed in the context of metasurfaces and flat optics. Nonlocal flat optics may be useful for controlling light in ultra-thin platforms.

Recent advances in optical metalenses are reviewed with a focus on their unique features and applications in the space of optical metasystems.

Recent developments in reconfigurable metasurfaces are reviewed with a focus on case studies that are promising for commercialization and associated challenges.

Progress in generating and harnessing high harmonics in solid-state media is reviewed.

Recent progress of table-top isolated attosecond light sources is reviewed with a focus on the related technologies for high-average-flux and high-peak-intensity attosecond bursts of light. An outlook on its applications is also provided.

This Review details the fundamental photonics and thermodynamics concepts that underlie the processes of radiative cooling, and discusses a few emerging directions associated with radiative cooling research.

An examination of the strategies for generating optical frequency combs using integrated photonics.

X-ray detectors based on solution-processed metal halide perovskites are reviewed. Promising materials, fabrication techniques and device architectures are discussed, as is the potential for medical imaging applications.

Progress on Landau level lasers—based on external magnetic field splitting of electronic states—is reviewed, with particular attention paid to the potential for tunable terahertz lasers.

This Review summarizes the latest state-of-the-art technologies for high-speed multiphoton (fluorescence) microscopy, especially at kilohertz 2D frame rate, and 3D video rate or beyond—a speed regime that was generally inconceivable until very recently, as well as the prospects and challenges of these emerging technologies.

A summary of recent advances in the near-infrared light-emitting diodes that are fabricated by solution-processed means, with coverage of devices based on organic semiconductors, halide perovskites and colloidal quantum dots.

Colloidal quantum dots may offer solution-processable lasers, with a wide range of colours available. Technical hurdles and progress towards realization of useful quantum dot laser diodes is reviewed.