Artistic view of the temporal compression of optical data packets (from green to purple) by a nonlinear focusing mirror effect created by a counter-propagating readout pulse (light blue) in an optical fibre. Compression factors up to 13,000 can be achieved by exploiting such four-wave mixing interactions and the method could find applications where ultrafast optical data or waveforms are required.

See Berti et al.

Artistic impression of how ultrasound-generated bubbles inside biological tissue can reduce optical scatter, allowing higher-quality laser microscopy at greater depths.

See Kim et al. and Beard and Dholakia

Artistic impression of the dipole–dipole interactions between two closely spaced, optically trapped Rydberg atoms that have been excited by a laser pulse. As such interactions are ultrafast and coherent they are promising for realizing a quantum gate.

See Chew et al. and Xu and Zhan

Artistic impression of a rare-earth-doped upconversion nanoparticle of NaGdF4:Yb3+/Er3+ located in a plasmonic nanocavity formed by a silver nanocube and a silver microsheet. The cavity shortens the luminescence decay time from ~50 μs to sub-50 ns. The result is an enhanced, ultrafast upconversion emission, that is highly directional with applications in nanolasers and quantum optics.

See Chen et al.

Artistic image of a self-calibrating programmable photonic chip featuring a reference waveguide (green) and a signal processing core (denoted by the blue waveguides). The Kramers–Kronig relationship is used to recover the chip's phase response and accurately tune on-chip heaters (denoted as red/white rectangular structures) using machine learning algorithms.

See Xu et al.

Artistic image of a vortex-ring light pulse. In such pulses, the field lines follow the shape of a torus (a donut shape), and they can be considered as an optical analogue of a smoke ring or bubble ring — common structures found in fluid dynamics.

See Wan et al., Zdagkas et al. and Cardano and Marrucci

Artistic image of a high-efficiency, single-pass terahertz free-electron laser (THz FEL). Bunches of electrons (small pink spheres) are accelerated inside a tapered helical magnetic undulator (coloured periodic structure) and an inner waveguide with a circular cross-section guides the emitted terahertz radiation. The result is a compact THz FEL with a 10% efficiency of operation at 160 GHz using a 1-m-long undulator.

See Fisher et al. and Yan and Liu

Artistic image of crystals that feature chiral phonons that can be probed by terahertz chiral spectroscopy. The approach brings new opportunities for the analysis and identification of important, medically relevant substances such as amino acids, peptides and amyloid nanofibrils.

See Choi et al. and Kim and Tsurusk

Artistic impression of a network of optically interconnected quantum memristors, which in the future could be the basis for a quantum neural network. Each quantum memristor, comprised of tunable integrated Mach–Zehnder interferometers operating on single photons, is able to encode and transmit quantum information while retaining a memory of the previously processed quantum states.

See Spagnolo et al. and Lamata

Artistic impression of a topologically protected quantum entanglement emitter on a silicon-photonics chip. Entangled states, which are immune to some defects and imperfections, are generated along the boundary of the chip, which emulates an anomalous Floquet topological insulator.

See Dai et al.

The news that third-harmonic Mie scattering from nanoscale helices of cadmium telluride is strongly influenced by the chirality of the scatterers opens new opportunities for high-throughput analysis of chiral compounds using very small sample volumes.

See Ohnoutek et al. and Kivshar

Artistic image of an electrically tunable nonlinear metasurface that combines a plasmonic nanocavity and a quantum-engineered semiconductor heterostructure. The magnitude and phase of local nonlinear responses of the metasurface are controlled by bias voltage through the quantum-confined Stark effect, enabling dynamic intensity modulation and beam steering.

See Yu et al.