Measurement of the arrival times of annihilation photons in a detector with greater precision is opening the way to new direct forms of tomographic positron emission imaging that do not require back-projection-based reconstruction techniques.

For 20 years, nanoscale 3D printing has been based on two-photon absorption, requiring expensive pulsed lasers. Now, via a two-step absorption process, such printing has been demonstrated using a low-cost, low-power continuous-wave laser diode, showing the potential for dramatic cost reductions in 3D nanoprinting.

The National Ignition Facility at Lawrence Livermore National Laboratory reported over 1.3 MJ output, representing 70% of both input laser energy and official ‘fusion ignition’. Operations manager, Bruno Van Wonterghem, delves into the optics and what to expect next.

The quadratic optical nonlinearity arising from two-photon absorption provides the crucial spatial concentration of optical excitation in three-dimensional (3D) laser nanoprinting, with widespread applications in technical and life sciences. Femtosecond lasers allow for obtaining efficient two-photon absorption but are accompanied by a number of issues, including higher-order processes, cost, reliability

Tunable lasers in the terahertz frequency range are of great demand for many spectroscopic applications. The first continuously tunable p-Ge Landau level terahertz laser had the drawback of pulsed operation at very low temperatures. There have been promising developments of Landau level lasers based on graphene in combination with other two-dimensional materials. Extended theoretical work has resulted

The three-dimensional images generated by digital holography are usually limited to a single color. A new technique exploiting frequency combs generates holograms with hundreds of colors at once.

The direct generation of femtosecond pulses from an 8-μm quantum cascade laser could prove transformative for sensing and spectroscopy.

The quantum cascade laser has evolved to be a compact, powerful source of coherent mid-infrared light; however, its fast gain dynamics strongly restricts the formation of ultrashort pulses. As such, the shortest pulses reported so far were limited to a few picoseconds with some hundreds of milliwatts of peak power, strongly narrowing their applicability for time-resolved and nonlinear experiments.

Holography1 has always held special appeal as it is able to record and display spatial information in three dimensions2,3,4,5,6,7,8,9,10. Here we show how to augment the capabilities of digital holography11,12 by using a large number of narrow laser lines at precisely defined optical frequencies simultaneously. Using an interferometer based on two frequency combs13,14,15 of slightly different repetition

Optical phase modulators are essential to large-scale integrated photonic systems at visible wavelengths and are promising for many emerging applications. However, current technologies require large device footprints and either high power consumption or high drive voltages, limiting the number of active elements in a visible-spectrum integrated photonic circuit. Here, we demonstrate visible-spectrum

The demonstration of a germanium-based photodiode with a 3 dB bandwidth of 265 GHz and compatibility with silicon photonics and CMOS fabrication offers a cost-effective route to faster channel data rates for optical communications.

The energy of photons, that is, the wavelength of light, can be upgraded through interactions with materials in a process called photon upconversion1. Although upconversion in organic solids is important for various applications, such as photovoltaics and bioimaging, conventional upconversion systems, based on intersystem crossing (ISC), suffer from low efficiency2,3,4,5,6. Here we report a novel upconversion

On a scalable silicon technology platform, we demonstrate photodetectors matching or even surpassing state-of-the-art III–V devices. As key components in high-speed optoelectronics, photodetectors with bandwidths greater than 100 GHz have been a topic of intense research for several decades. Solely InP-based detectors could satisfy the highest performance specifications. Devices based on other materials

Extremely short, high-energy pulses are essential in modern ultrafast science. In a seminal paper in 19961, Nisoli and co-workers demonstrated the first intense pulse compression employing a gas-filled hollow-core fibre. Despite the huge body of scientific work on this technology stemming from ultrafast and attosecond research, here we identify an unexplored few-cycle visible-light generation mechanism

A special perovskite material design is demonstrated to operate as a wideband, achromatic quarter-wave plate.

The stabilization of perovskite nanocrystals (PeNCs) by a surrounding metal–organic framework (MOF) results in a simple yet effective way to make extraordinarily bright PeNC-based LEDs, with stable continuous operation of up to tens of hours.

As they race towards commercialization, perovskite solar cells are receiving critical acclaim with numerous awards.

Quantum teleportation is demonstrated between light and the vibrations of a nanomechanical resonator, realizing a key capability for quantum computing.

After over 30 years of advances, multiphoton microscopy (MPM) is now instrumental in a wide range of in vivo biological imaging applications. However, it has, until recently, remained not achievable or affordable to meet the unmet need for fast monitoring of biological dynamics and large-scale examination of biological heterogeneity. Only within the past few years have new strategies emerged to empower

Practical on-chip optical isolators providing non-reciprocal propagation are still a challenge. Now, two independent groups show that a phonon-mediated break of the chiral symmetry in waveguide resonators may offer a solution.

Optical isolators today are exclusively built on magneto-optic principles but are not readily implemented within photonic integrated circuits. So far, no magnetless alternative1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22 has managed to simultaneously combine linearity (that is, no frequency shift), linear response (that is, input–output scaling), ultralow insertion loss and large directional

Integrated photonics enables signal synthesis, modulation and conversion using photonic integrated circuits (PICs). Many materials have been developed, among which silicon nitride (Si3N4) has emerged as a leading platform particularly for nonlinear photonics. Low-loss Si3N4 PICs have been widely used for frequency comb generation, narrow-linewidth lasers, microwave photonics and photonic computing

Photonic integrated circuits hold great promise in enabling the practical wide-scale deployment of quantum communications; however, despite impressive experiments of component functionality, a fully operational quantum communication system using photonic chips is yet to be demonstrated. Here we demonstrate an entirely standalone secure communication system based on photonic integrated circuits—assembled

Optical multiplexing1,2,3,4,5,6,7,8,9,10,11 by creating orthogonal data channels has offered an unparalleled approach for information encoding with substantially improved density and security. Despite the fact that the orbital angular momentum (OAM) of light involves physical orthogonal division, the lack of explicit OAM sensitivity at the nanoscale prevents this feature from realizing nanophotonic

X-ray and gamma-ray photons are widely used for imaging but require a mathematical reconstruction step, known as tomography, to produce cross-sectional images from the measured data. Theoretically, the back-to-back annihilation photons produced by positron–electron annihilation can be directly localized in three-dimensional space using time-of-flight information without tomographic reconstruction;

Quantum teleportation, the faithful transfer of an unknown input state onto a remote quantum system1, is a key component in long-distance quantum communication protocols2 and distributed quantum computing3,4. At the same time, high-frequency nano-optomechanical systems5 hold great promise as nodes in a future quantum network6, operating on-chip at low-loss optical telecom wavelengths with long mechanical

Waveplates are widely used in photonics to control the polarization of light1,2. Often, they are fabricated from birefringent crystals that have different refractive indices along and normal to the crystal axis. Similar optical components are found in the natural world, including the eyes of mantis shrimp3,4 and the iridescence of giant clams5, fish6 and plants7. Optical retardation in biology relies

The phase of terahertz waves can now be precisely modulated electronically using a chip-based digitally coded phase shifter. The achievement is a step towards chip-scale integrated terahertz technology.

News of a 1.3-MJ-output-energy experiment at the National Ignition Facility in the United States in August has raised hopes that laser-based fusion is back on track.

Time-varying metamaterials bring in an extra degree of freedom, enabling applications unachievable by normal metamaterials and opening up new opportunities.

Solution-processed semiconductor lasers have achieved much success across the nanomaterial research community, including in relation to organic semiconductors1,2, perovskites3,4 and colloidal semiconductor nanocrystals5,6. The ease of integration with other photonic components and the potential for upscaling using emerging large-area fabrication technologies (such as roll-to-roll7) make these lasers

Research into organic light emitters employing multiple resonance-induced thermally activated delayed fluorescence (MR-TADF) materials is presently attracting a great deal of attention due to the potential for efficient deep-blue emission. However, the origins and mechanisms of successful TADF are unclear, as many MR-TADF materials do not show TADF behaviour in solution, but only as particular pure

In free-space optical communications that use both amplitude and phase data modulation (for example, in quadrature amplitude modulation (QAM)), the data are typically recovered by mixing a Gaussian local oscillator with a received Gaussian data beam. However, atmospheric turbulence can induce power coupling from the transmitted Gaussian mode to higher-order modes, resulting in a significantly degraded

Cavity solitons are optical pulses that propagate indefinitely in nonlinear resonators. They are attracting attention, both for their many potential applications and their connection to other fields of science. Cavity solitons differ from laser dissipative solitons in that they are coherently driven. So far the focus has been on driving Kerr solitons externally, at their carrier frequency, in which

Upconversion nanocrystals have been extensively investigated for optical imaging and biomedical applications1,2. However, their photoluminescence is strongly attenuated by surface quenching as the nanocrystal size diminishes3. Despite considerable efforts4,5, the quenching mechanism remains poorly understood. Here we report that surface coordination of bidentate picolinic acid molecules to NaGdF4:Yb/Tm

Second-harmonic generation is of paramount importance in several fields of science and technology, including frequency conversion, self-referencing of frequency combs, nonlinear spectroscopy and pulse characterization. Advanced functionalities are enabled by modulation of the harmonic generation efficiency, which can be achieved with electrical or all-optical triggers. Electrical control of the harmonic

Perovskite nanocrystals are exceptional candidates for light-emitting diodes (LEDs). However, they are unstable in the solid film and tend to degrade back to the bulk phase, which undermines their potential for LEDs. Here we demonstrate that perovskite nanocrystals stabilized in metal–organic framework (MOF) thin films make bright and stable LEDs. The perovskite nanocrystals in MOF thin films can maintain

Photon propagation through an array of coupled waveguides arranged in various fractal patterns serves as a useful ‘optical simulator’ for revealing insights into quantum transport in complex scenarios.

Nature Photonics spoke to Chihaya Adachi from the Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, about the potential merits of, and hurdles facing, the development of organic semiconductor lasers.

Franky So, from North Carolina State University, explains some hard truths for solution-processed emitters, but also that, fundamentally, there is no reason why OLEDS can’t ‘make it’.

A simple yet effective optical set-up, employing two controllable, indistinguishable photons, is proven to allow a direct measurement of the exchange phase due to the bosonic particle statistics.

Solution-processing of light-emitting devices is attracting much attention due to low manufacturing costs and access to new materials. In this month’s Focus issue we highlight some of the advances and challenges in the field.

Low stability of perovskite light-emitting diodes (PeLEDs) is the biggest obstacle to the commercialization of PeLED displays. Here, we cover the current status and challenges in analysing and improving the stability of PeLEDs and suggest some advice that will benefit the community to boost the operational lifetime of PeLEDs.

Near-infrared light-emitting diodes based on solution-processed semiconductors, such as organics, halide perovskites and colloidal quantum dots, have emerged as a viable technological platform for biomedical applications, night vision, surveillance and optical communications. The recently gained increased understanding of the relationship between materials structure and photophysical properties has

Colloidal quantum dots (QDs) combine the superior light-emission characteristics of quantum-confined semiconductors with the chemical flexibility of molecular systems. These properties could, in principle, enable solution-processable laser diodes with an ultrawide range of accessible colours. However, the realization of such devices has been hampered by fast optical gain decay due to non-radiative

Electromagnetic confinement in optical resonators of diminishing dimensions has enabled unprecedented light–matter interaction strengths. This miniaturization trend has a nonlocal limit, which, surprisingly, originates from the matter excitations rather than the light.

Direct phase modulation is one of the most urgent and difficult issues in the terahertz research area. Here, we propose a new method employing a two-dimensional electron gas (2DEG) perturbation microstructure unit coupled to a transmission line to realize high-precision digital terahertz phase manipulation. We induce local perturbation resonances to manipulate the phase of guided terahertz waves. By

Subwavelength electromagnetic field localization has been central to photonic research in the last decade, allowing us to enhance sensing capabilities as well as increase the coupling between photons and material excitations. The strong and ultrastrong light–matter coupling regime in the terahertz range using split-ring resonators coupled to magnetoplasmons has been widely investigated, achieving successive

The conversion efficiency of solar energy in semiconductors is fundamentally limited by ultrafast hot-carrier relaxation processes, and slowing down these processes is critical for improved energy harvesting. Here we report formamidinium tin iodide (FASnI3) nanocrystals where quantum confinement effects yield an evolution from a continuous band structure to separate energy states with decreasing nanocrystal

There has recently been growing interest in integrating and miniaturizing vapour cells to reduce cost, size and power consumption. Hereby we provide a new paradigm in chip-scale-integrated vapour cells by experimentally demonstrating the nanoatomic suspended waveguide, which introduces a nanoscale silicon nitride waveguide suspended in rubidium vapour. By doing so, the properties of the optical modes

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