Reviews & Analysis

The generation of hot electrons in plasmonic nanostructures is of scientific and technological interest, putting the community under pressure to better understand the hot-electron mechanisms and to increase the light conversion efficiency of plasmonic nanosystems for chemical reactions and photodetection.

A chip-based optical frequency comb source has now been successfully used to send 661 Tbit s^–1 over 9.6 km of multicore fibre, bringing considerable savings in the energy consumption and size of data transmission equipment.

Interferometric analysis of the weak light scattered from proteins makes it possible to determine their mass.

Efficient photon upconversion is desired for applications ranging from molecular sensing to solar-energy harvesting. Now, the population of hidden triplet state electrons, created on dye antennas and rare-earth-doped nanoparticles, has been amplified to brighten upconversion by five orders of magnitude.

The finding that the quasi-1D crystal BaTiS₃ features a large optical anisotropy and a broadband birefringence spanning the infrared is likely to reignite interest in quasi-1D optical materials.

The demonstration of broadband, electrically tunable third-order nonlinear optical responses in graphene is promising for a host of nonlinear optical applications.

The electromagnetic instability associated with a dense, ultra-relativistic electron beam propagating in a thin conductor could offer a new approach to realizing ultra-bright sources of gamma-rays.

The evolution of modulational instability sidebands in an optical fibre are shown to provide new insights into Fermi–Pasta–Ulam–Tsingou recurrences.

Exquisitely low-loss optical resonators have thus far remained discrete. Monolithic integration of waveguides with silica resonators that have Q factors >100 million charts a path toward incorporating these devices in photonic circuits.

High-order harmonics in the extreme-ultraviolet regime can be produced and a stable waveform-locked attosecond pulse can be formed when quartz is excited by a strong short-pulsed laser, providing a robust path towards attosecond photonics.

In the quest for nanoscopy with super-resolution, consensus from the imaging community is that super-resolution is not always needed and that scientists should choose an imaging technique based on their specific application.

The polarization state of isolated attosecond pulses generated by high-order harmonic generation can now be manipulated at will. The development opens the door for a multitude of ultrafast experiments to investigate chiral media.

Optical trapping of metal nanoparticles with conventional ‘tweezers’ can be challenging due to absorption and heating. Now, an opto-thermoelectric trapping approach that exploits heating has been demonstrated.

Observing ultrafast transient dynamics in optics is a challenging task. Two teams in Europe have now independently developed ‘optical oscilloscopes’ that can capture both amplitude and phase information of ultrafast optical signals. Their schemes yield new insights into the nonlinear physics that takes place inside optical fibres.