Terahertz radiation has become an important diagnostic tool in the development of new technologies. However, the diffraction limit prevents terahertz radiation (λ ≈ 0.01–3 mm) from being focused to the nanometre length scale of modern devices. In response to this challenge, terahertz scanning probe microscopy techniques based on coupling terahertz radiation to subwavelength probes such as sharp tips

The 2014 Nobel laureate, Isamu Akasaki, sadly passed away in April at the age of 92. He was highly regarded for his work on the invention of efficient blue light-emitting diodes and research into new semiconductor materials.

Recent years have witnessed a much broader use of Brillouin inelastic light-scattering spectroscopy for the investigation of phonons and magnons in novel materials, nanostructures and devices. Driven by the developments in instrumentation and the strong need for accurate knowledge on the energies of elemental excitations, Brillouin–Mandelstam spectroscopy is rapidly becoming an essential technique

Fractals are fascinating, not only for their aesthetic appeal but also for allowing the investigation of physical properties in non-integer dimensions. In these unconventional systems, many intrinsic features might come into play, including the fractal dimension and the fractal geometry. Despite abundant theoretical studies, experiments in fractal networks remain elusive. Here we experimentally investigate

The adiabatic encirclement of exceptional points in non-Hermitian systems is known to produce surprising non-adiabatic effects. A new study finds a cheat code to exactly emulate this behaviour without ever having to produce an exceptional point.

Reducing the footprint of optical spectrometers is a critical requirement for many in-field applications. Now, a single black phosphorus photodetector with a wavelength-scale size enables mid-infrared computational spectrometry.

A ‘twin-field’ repeater-less protocol has enabled an experimental demonstration of secure quantum key distribution over a 511-km long-haul optical fibre link.

Laser-induced electron tunnelling—which triggers a broad range of ultrafast phenomena such as the generation of attosecond light pulses, photoelectron diffraction and holography—has laid the foundation for strong-field physics and attosecond science. Using the attoclock constructed by single-colour elliptically polarized laser fields, previous experiments have measured the tunnelling rates, exit positions

Metal halide perovskite solar cells have demonstrated a high power conversion efficiency (PCE), and further enhancement of the PCE requires a reduction of the bandgap-voltage offset (WOC) and the non-radiative recombination photovoltage loss (ΔVOC,nr). Here, we report an effective approach for reducing the photovoltage loss through the simultaneous passivation of internal bulk defects and dimensionally

Light with spatiotemporal orbital angular momentum (ST-OAM) is a recently discovered type of structured and localized electromagnetic field. This field carries characteristic space–time spiral phase structure and transverse intrinsic OAM. Here, we present the generation and characterization of the second harmonic of ST-OAM pulses. We uncover the conservation of transverse OAM in a second-harmonic generation

A chip-based optical frequency comb has enabled the realization of a 300 GHz signal with record low phase noise. The development could yield ultra-compact, ultra-low-noise sources for millimetre-wave applications in telecommunications, remote sensing and precision spectroscopy.

Dynamic control over the conduction band electrons of a semiconductor is a central technological pursuit. Beyond electronic circuitry, flexible control over the spatial and temporal character of semiconductor currents enables precise spatiotemporal structuring of magnetic fields. Despite their importance in science and technology, the control of magnetic fields at the micrometre spatial scale and femtosecond

The basic principle of quantum mechanics1 guarantees the unconditional security of quantum key distribution (QKD)2,3,4,5,6 at the cost of forbidding the amplification of a quantum state. As a result, and despite remarkable progress in worldwide metropolitan QKD networks7,8 over the past decades, a long-haul fibre QKD network without a trusted relay has not yet been achieved. Here, through the sending-or-not-sending

Light–matter interactions can create and manipulate collective many-body phases in solids1,2,3, which are promising for the realization of emerging quantum applications. However, in most cases, these collective quantum states are fragile, with a short decoherence and dephasing time, limiting their existence to precision tailored structures under delicate conditions such as cryogenic temperatures and/or

Precision optical-frequency and phase synchronization over fibre is critical for a variety of applications, from timekeeping to quantum optics. Such applications utilize ultra-coherent sources based on stabilized table-top laser systems. Chip-scale versions of these systems may dramatically broaden the application landscape by reducing the cost, size and power of such exquisite sources. Links based

Anderson’s groundbreaking discovery that the presence of stochastic imperfections in a crystal may result in a sudden breakdown of conductivity1 revolutionized our understanding of disordered media. After stimulating decades of studies2, Anderson localization has found applications in various areas of physics3,4,5,6,7,8,9,10,11,12. A fundamental assumption in Anderson’s treatment is that no energy

The unique optical properties of graphene were combined with lithium-ion battery technology to produce multispectral optical devices, with colour-changing capabilities.

Parity–time reversal symmetry (PT symmetry) in non-Hermitian systems realizes spontaneous symmetry breaking, thereby leading to counterintuitive phenomena. A coupled system with antisymmetric gain/loss profiles is required to introduce PT symmetry into photonics. As photons are intrinsically non-interactive, selection of two-photonic components is inevitable to mediate indirect coupling via near-fields

Short period, femtosecond transient gratings in a sample can now be produced by X-rays. The approach promises to reveal the excitation behaviour of complex materials with high temporal and spatial resolution.

Webb’s work helped fundamentally reshape basic research and advanced manufacturing in the generation and application of photonics across disciplines, from fundamental and applied physics to the biosciences.

Twin-field (TF) quantum key distribution (QKD) fundamentally alters the rate-distance relationship of QKD, offering the scaling of a single-node quantum repeater. Although recent experiments have demonstrated the new opportunities for secure long-distance communications allowed by TF-QKD, formidable challenges remain to unlock its true potential. Previous demonstrations have required intense stabilization

Quantum theory stipulates that if two particles are identical in all physical aspects, the allowed states describing the system are either symmetric or antisymmetric with respect to permutations of single-particle states1,2,3,4,5. Experimentally, the symmetry of the states can be inferred indirectly from the fact that neglecting the correct exchange symmetry in the theoretical analysis leads to dramatic

On-chip polarization-sensitive photodetectors offer unique opportunities for next-generation ultra-compact polarimeters. So far, mainstream approaches have relied on the anisotropic absorption of natural materials or artificial structures. However, such a model is inherently restricted by correlation between the polarization ratio (PR) and diattenuation, leading to small PR values (1 < PR < 10). Here

Over the past decade, metal halide perovskite photovoltaics have been a major focus of research, with single-junction perovskite solar cells evolving from an initial power conversion efficiency of 3.8% to reach 25.5%. The broad bandgap tunability of perovskites makes them versatile candidates as the subcell in a tandem photovoltaics architecture. Stacking photovoltaic absorbers with cascaded bandgaps

In 1982, Capasso and co-workers proposed the solid-state analogue of the photomultiplier tube, termed the staircase avalanche photodiode. Through a combination of compositional grading and small applied bias, the conduction band profile is arranged into a series of steps that function similar to the dynodes of a photomultiplier tube, with twofold gain arising at each step via impact ionization. A single-step

Free-electron lasers producing ultrashort pulses with high peak power promise to extend ultrafast non-linear spectroscopic techniques into the extreme-ultraviolet–X-ray regime. Key aspects are the synchronization between pump and probe, and the control of the pulse properties (duration, intensity and coherence). Externally seeded free-electron lasers produce coherent pulses that can be synchronized

Tunnelling currents inside plasmonic nanostructures are fast enough to gain direct access to the oscillating electric field of near-infrared and visible light, opening up exciting routes towards attosecond metrology of light–matter interaction and unique approaches to spectroscopy.

The successful demonstration of two-stage acceleration driven by terahertz pulses bodes well for the future development of compact, efficient particle accelerators.

Tunnelling is one of the most fundamental manifestations of quantum mechanics. The recent advent of lightwave-driven scanning tunnelling microscopy has revolutionized ultrafast nanoscience by directly resolving electron tunnelling in electrically conducting samples on the relevant ultrashort length- and timescales. Here, we introduce a complementary approach based on terahertz near-field microscopy

A new way to define the shape of tiny light-emitting semiconductor pixels provides a means to fabricate arrays of InGaN blue micro-LEDs with a resolution as high as 8,500 pixels per inch.

Optical frequency combs are lightwaves composed of a large number of equidistant spectral lines. They are important for metrology, spectroscopy, communications and fundamental science. Frequency combs are most often generated by exciting dissipative solitons in lasers or in passive resonators, both of which suffer from important limitations. Here we show that the advantages of each platform can be

Sources of quantum light, in particular correlated photon pairs that are indistinguishable for all degrees of freedom, are the fundamental resource for photonic quantum computation and simulation. Although such sources have been recently realized using integrated photonics, they offer limited ability to tune the spectral and temporal correlations between generated photons because they rely on a single

One of the most fascinating aspects of quantum networks is their capability to distribute entanglement as a nonlocal communication resource1. In a first step, this requires network-ready devices that can generate and store entangled states2. Another crucial step, however, is to develop measurement techniques that allow for entanglement detection. Demonstrations for different platforms3,4,5,6,7,8,9

Photonics offers high hopes for next-generation neural network processors. Now it has been shown that even entirely using off-the-shelf photonics allows surpassing speed and energy efficiency of cutting-edge GPUs.

Colloidal quantum dots are promising photoactive materials that enable plentiful photonic and optoelectronic applications ranging from lasers, displays and photodetectors to solar cells1,2,3,4,5,6,7,8,9. However, these applications mainly utilize the linear optical properties of quantum dots, and their great potential in the broad nonlinear optical regime is still waiting for full exploration10,11

Nonlinearity in complex systems leads to pattern formation through fundamental interactions between components. With integrated photonics, precision control of nonlinearity explores novel patterns and propels applications. In particular, Kerr-nonlinear resonators support stationary states—including Turing patterns—composed of a few interfering waves, and localized solitons composed of waves across

On-chip spectrometers with compact footprints are being extensively investigated owing to their promising future in critical applications such as sensing, surveillance and spectral imaging. Most existing miniaturized spectrometers use large arrays of photodetection elements to capture different spectral components of incident light, from which its spectrum is reconstructed. Here, we demonstrate a mid-infrared

A Correction to this paper has been published: https://doi.org/10.1038/s41566-021-00817-8

Rapid progress in the development of metamaterials and metaphotonics allowed bulky optical assemblies to be replaced with thin nanostructured films, often called metasurfaces, opening a broad range of novel and superior applications of flat optics to the generation, manipulation and detection of classical light. Recently, these developments started making headway in quantum photonics, where novel opportunities

Optical-domain transient grating (TG) spectroscopy is a versatile background-free four-wave-mixing technique that is used to probe vibrational, magnetic and electronic degrees of freedom in the time domain1. The newly developed coherent X-ray free-electron laser sources allow its extension to the X-ray regime. X-rays offer multiple advantages for TG: their large penetration depth allows probing the

Optical frequency division via optical frequency combs has enabled a leap in microwave metrology, leading to noise performance never explored before. Extending this method to the millimetre-wave and terahertz-wave domains is of great interest. Dissipative Kerr solitons in integrated photonic chips offer the unique feature of delivering optical frequency combs with ultrahigh repetition rates from 10 GHz

Viscosity is an important property of out-of-equilibrium systems such as active biological materials and driven non-Newtonian fluids, and for fields ranging from biomaterials to geology, energy technologies and medicine. Non-invasive viscosity measurements typically require integration times of seconds. Here, we demonstrate measurement speeds reaching 20 μs, with uncertainty dominated by thermal molecular

The Indian scientist and passionate entrepreneur responsible for pioneering work on optical fibres and biomedical optics has passed away aged 94.

A Correction to this paper has been published: https://doi.org/10.1038/s41566-021-00816-9.

Optical acoustic sensors have gained interest for use in photoacoustic imaging systems, but can they dethrone conventional piezoelectric sensors altogether?

We demonstrate an on-chip, optoelectronic device capable of sampling arbitrary, low-energy, near-infrared waveforms under ambient conditions with sub-optical-cycle resolution. Our detector uses field-driven photoemission from resonant nanoantennas to create attosecond electron bursts that probe the electric field of weak optical waveforms. Using these devices, we sampled the electric fields of ~5 fJ

There is an ever-growing demand for artificial intelligence. Optical processors, which compute with photons instead of electrons, can fundamentally accelerate the development of artificial intelligence by offering substantially improved computing performance. There has been long-term interest in optically constructing the most widely used artificial-intelligence architecture, that is, artificial neural

Random scattering of light in disordered media is an intriguing phenomenon of fundamental relevance to various applications1. Although techniques such as wavefront shaping and transmission matrix measurements2,3 have enabled remarkable progress in advanced imaging concepts4,5,6,7,8,9,10,11, the most successful strategy to obtain clear images through a disordered medium remains the filtering of ballistic

An exclusive advantage of semiconductor spintronics is its potential for opto-spintronics, which will allow integration of spin-based information processing/storage with photon-based information transfer/communications. Unfortunately, progress has so far been severely hampered by the failure to generate nearly fully spin-polarized charge carriers in semiconductors at room temperature. Here we demonstrate

When the nanophotonics research community finally gets back to in-person conferences, the rooms will have empty chairs on the first row. The chairs will be reserved for Professor Mark I. Stockman.

A Correction to this paper has been published: https://doi.org/10.1038/s41566-021-00805-y.

Optical materials with colour changing abilities have been explored for use in display devices1, smart windows2,3 or in the modulation of visual appearance4,5,6. The efficiency of these materials, however, has strong wavelength dependence, which limits their functionality to a specific spectral range. Here, we report graphene-based electro-optical devices with unprecedented optical tunability covering

Imaging evanescent waves is of crucial importance for sub-wavelength-scale investigation of various phenomena. However, frequently used techniques for near-field imaging require either a strong perturbation of the field, long acquisition times or complex electron-based tools. Here, we introduce nonlinear near-field optical microscopy (NNOM), which is capable of real-time evanescent wave imaging by

Four-wave mixing near atomic resonances offers new opportunities for spectral control of extreme ultraviolet pulses.

All light has structure, but only recently has it been possible to control it in all its degrees of freedom and dimensions, fuelling fundamental advances and applications alike. Here we review the recent advances in ‘pushing the limits’ with structured light, from traditional two-dimensional transverse fields towards four-dimensional spatiotemporal structured light and multidimensional quantum states

InGaN-based blue light-emitting diodes (LEDs), with their high efficiency and brightness, are entering the display industry. However, a significant gap remains between the expectation of highly efficient light sources and their experimental realization into tiny pixels for ultrahigh-density displays for augmented reality. Herein, we report using tailored ion implantation (TIIP) to fabricate highly

A Correction to this paper has been published: https://doi.org/10.1038/s41566-021-00795-x.

Laser-like radiation with a very large spectral coverage is obtained with a comb-like spectrum by concatenating nonlinear processes. Such a light source is extremely useful for detecting molecular trace gases.

We introduce MINSTED, a fluorophore localization and super-resolution microscopy concept based on stimulated emission depletion (STED) that provides spatial precision and resolution down to the molecular scale. In MINSTED, the intensity minimum of the STED doughnut, and hence the point of minimal STED, serves as a movable reference coordinate for fluorophore localization. As the STED rate, the background

A self-seeded X-ray free-electron laser (XFEL) is a promising approach to realize bright, fully coherent free-electron laser (FEL) sources in the hard X-ray domain that have been a long-standing issue with longitudinal coherence remaining challenging. At the Pohang Accelerator Laboratory XFEL, we have demonstrated a hard X-ray self-seeded XFEL with a peak brightness of 3.2 × 1035 photons s–1 mm–2 mrad–2