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Recent demonstrations of modulators, polarization rotators and isolators have indicated the potential of graphene for photonic applications. The present study investigates the fundamental limits and near-optimal design of graphene modulators and non-reciprocal devices.

Optical frequency combs are vital tools for precision measurements, and extending them further into the mid-infrared 'molecular fingerprint' range will open new avenues for spectroscopy. Using crystalline microresonators, Wang et al. demonstrate Kerr combs at 2.5 μm as a promising route into the mid-infrared.

Spin-based electronics offers significantly improved efficiency, but a major challenge is the electric manipulation of spin. Here, Powalla et al find a large gate induced spinpolarization in graphene/WTe2 heterostructures, illustrating the potential of such heterostructures for spintronics.

Finding ways to accumulate electronic spins of a given polarization in a given location is important to the development of spintronics. Endres et al.demonstrate a device that uses light to drive the accumulation of spin using a similar principle that a solar cell uses to drive the accumulation of charge.

Researchers have demonstrated spontaneous soliton formation in an edgeless photonic crystal resonator.

Time-resolved measurements show that current-induced magnetization switching in ferrimagnetic devices is faster and more energy-efficient than in ferromagnet devices.

New fully integrated semiconductor laser architectures are shown to be able to generate bright and background-free picosecond solitons at GHz repetition rates in the mid-infrared range.

Energy deposition inside silicon with ultrashort laser pulses is intrinsically restricted. Here, authors demonstrate that this filamentation-driven ceiling is universal in semiconductors. Extreme nonlinearities are quantified to predict and optimize involume laser-semiconductor interaction.

Femtosecond laser pulses allow for extremely fast switching of magnetization in ferromagnetic films, but all examples so far contained gadolinium. Here the authors demonstrate room temperature all-optical toggle switching in a ferrimagnetic manganese-based half-metal without gadolinium.

A non-destructive scanning method harnesses nonlinear micro-ring resonators as on-chip optical power discriminators to directly measure loss and gain of components in photonic integrated circuits with sub-0.1 dB precision.

Magneto-ionics are a promising approach for controlling magnetism via electric fields, but most studies have been limited to thin films, rather than the nanostructures that would form the basis of a magneto-ionic memory unit. Here, Spasojevic et al demonstrate magneto-ionic control over transitions among paramagnetic, single domain, and vortex states in an array of nanodots.

Spin currents can be generated by passing electric currents through ferromagnets, but the process is too slow for ultrafast spintronics. Here, the authors show an approach for laser-driven thermal spin generation that has the potential to attain much higher speeds.

Chip-based frequency combs promise many applications, but full integration requires the electrical pump source and the microresonator to be on the same chip. Here, the authors show such integration of a microcomb with < 100 GHz mode spacing without additional filtering cavities or on-chip heaters.

Strong stimulated Brillouin scattering is incorporated in a standard silicon nitride platform via a tellurium oxide layer. The authors demonstrate applications including a silicon-nitride-based Brillouin amplifier (net optical gain, 5 dB), a compact intermodal stimulated Brillouin laser capable of high-purity radio-frequency signal generation (intrinsic linewidth, 7 Hz) and a widely tunable microwave photonic notch filter (ultranarrow linewidth, 2.2 MHz).

Hybridized modes are realized through strong tripartite coupling between a three-dimensional microwave cavity, a granular-aluminium superconducting thin-film microwave resonator circuit and an antiferromagnetic crystal, with implications for sensing and for frequency conversion between the microwave and terahertz regimes.

Topological phases are challenging to identify in systems with general, strong nonlinearities. Here, the authors establish the analytic methodology that defines the topological invariant of nonlinear normal modes. Strongly nonlinear topological boundary modes are guaranteed by the nontrivial topological index.

At the ultrafast timescale the propagation of light pulses through a dielectric material is not only determined by the envelope, but also by nonlinear interactions that evolve within one optical cycle. Here, the authors demonstrate a method to determine the subcycle-resolved delay to a probe pulse in ultrafast, high-field pump–probe experiments.

Researcher demonstrate the line-by-line pulse shaping of frequency combs generated in silicon nitride ring resonators, and observe two distinct paths to comb formation that exhibit strikingly different time domain behaviours.

By exploiting an optical thermodynamic framework, researchers demonstrate universal routing of light. Specifically, light launched into any input port of a nonlinear array is universally channelled into a tightly localized ground state. The principles of optical thermodynamics demonstrated may enable new optical functionalities.

Boosting conversion efficiency, coherence and spectral bandwidth of optical signals generated in integrated photonic devices is an important current challenge. Here, the authors present their observations of two-colour dissipative solitons, breathers and frequency combs resulting from second-harmonic generation in lithium-niobate ring microresonators.

Symmetry breaking is often assumed to coincide with underlying exceptional points. The authors show that certain Jacobian-derived subsets instead occur as precursors, highlighting the need to identify the correct exceptional points when predicting specific symmetry-breaking transitions.

Kagome materials, such as CsV3Sb5, a rich array of correlated phase, including a time-reversal symmetry breaking phase, which could possibly be the result of loop currents. Attempts to verify this with magneto-optical measurements have yielded mixed results. Here, Farhang et al show that the magneto-optical signals are due to specular optical rotation. ‘

The intrinsic Kerr nonlinearity in ring resonators is exploited to demonstrate passive isolation of a continuous-wave laser. Up to 35-dB isolation with 5-dB insertion loss was achieved on-chip.

Superluminescent diodes, that provide a broadband spectrum are typically used in spectral domain coherence tomography. Here, the authors use chipscale silicon nitride resonators to generate soliton microcombs with a lower noise flor that could substitute the diode sources.

Photonic crystal microresonators permit precise control of nonlinear optical processes. By suppressing specific parasitic processes, they enable the efficient and robust generation of single-mode squeezed vacuum states of light.

Homochirality, a key feature of life, has unknown origins. Magnetic mineral surfaces can act as chiral agents, but are only weakly magnetized by nature. Here, the authors report the uniform magnetization of magnetite by an RNA precursor that spreads across the surface like an avalanche.

High kinetic inductance materials are widely used in superconducting circuits, yet their loss mechanisms are not fully understood. Here the authors study quantum circuits incorporating nanowires made of quasi-2D disordered superconductor WSi and identify localized quasiparticles as the dominant source of loss.

While the spin generation in topological insulators is well studied, little is known about the interaction of the spins with external stimuli. Here, Seifert et al. observe a helical, bias-dependent photoconductance at the lateral edges of topological Bi₂Te₂Se platelets for perpendicular incidence of light, distinct to common longitudinal photoconductance phenomena.

Free-running stable optical dissipative solitons, called Nozaki–Bekki solitons, are created in a ring semiconductor laser; their spontaneous formation with tuning of laser bias eliminates the need for an external optical pump.

The propagation of high-intensity light beams through transparent media can lead to unusual non-linear effects. Here Panagiotopoulos et al.show that a high-intensity ring-Airy beam transforms into a robust non-linear light bullet.

Isotopic labeling of organic compounds is crucial for advancements in life sciences and is extensively utilized in drug discovery. Here, the authors report the development of an in situ prepared catalyst for hydrogen isotope exchange reactions with deuterium or tritium gas as the isotope source to selectively label peptides in aqueous solutions.

The use of electric fields to control the magnetization of ferromagnetic materials could enable more efficient electronics. Lei et al.show that by applying lateral strain to a magnetostrictive nanowire with a piezoelectric, voltage-controlled gating of magnetic domain wall motion in the wire can be achieved.

Despite remarkable optical properties in lead halide perovskites, spin control in these materials is largely unexplored. Herein Belykh et al. study the coherent spin dynamics of electrons and holes in cesium lead bromide perovskites, and evidence interaction of electron and lattice nuclear spins.

Using time-stretch dispersive Fourier transform, scientists directly observe the spectro-temporal dynamics of the mode-locking transition on a single-shot basis over long record lengths of ∼900,000 consecutive pulses.

Despite larger nonlinear coefficients, waveguide losses have prevented using semiconductors instead of dielectric materials for on-chip frequency-comb sources. By significantly reducing waveguide loss, ultra-low-threshold Kerr comb generation is demonstrated in a high-Q AlGaAs-on-insulator microresonator system.

It is now shown that femtosecond optical excitation can be used as a tool to investigate the spin-polarization properties of half-metals, and provide a clear distinction between those and metals. Such knowledge is of fundamental importance for the use of these materials in spintronics applications.

Whispering-gallery mode microresonators are powerful sensing tools, but spectrum acquisition has taken milliseconds or longer. Here, Rosenblum et al.introduce cavity ring-up spectroscopy, in which sharply rising detuned probe pulses capture spectra of microresonators on nanosecond timescales.

The integration of 2D materials on photonic devices provides advanced functionalities in sensing applications. The authors demonstrate a graphene functionalized microcomb sensor by exploiting spectrally trapped Stokes solitons. They obtain both multispecies gas identification and individual molecule sensitivity.

This Review summarizes the use of topological modes to enable compact laser architectures, alongside emerging research directions involving non-Hermitian band topology, non-linear gain dynamics and quasiperiodic ordering.

Signatures of magnetism control by the flow of angular momentum are observed in Pt/Al/Fe/GaAs(001) multilayers by the application of an in-plane charge current in Pt.

In a ferromagnetic layer, an electric current parallel to the magnetization generates opposite spin–orbit torques on the two surfaces of the magnetic film, which is attributed to the generation of spin currents with a spin polarization transverse to the magnetization within the ferromagnet.

The Landé factors govern all the spin-related basic phenomena and are the key parameters which guide spintronics applications. Here, Kirstein et al. demonstrate a universal dependence of the Landé factors on the bandgap energy of several perovskite materials.

Temporal dissipative solitons are observed in a nonlinear, high-finesse, optical microresonator driven by a continuous-wave laser. This approach enables ultrashort pulses to be generated in spectral regimes lacking broadband laser gain media and saturable absorbers, making it potentially useful for applications in broadband spectroscopy, telecommunications, astronomy and low-phase-noise microwave generation.

Optical switching of ferromagnets has attracted interest for use in ultrafast spintronics but the physical origin of the effect remains unclear. Here the authors determine the contributions of two proposed mechanisms, the inverse Faraday effect and optical spin-transfer torque.

This work reports optical studies of circular and linear dichroism to image, respectively, chiral and nematic spin ordering in the layered triangular-lattice antiferromagnet Co1/3TaS2. Phases with co-existing chirality and nematicity are revealed.