Volume 14 Issue 12, December 2020

Unexpected multimode solitary waves can be formed spontaneously in hollow-core fibres, hinting at a vast world of exciting nonlinear optics, with applications for generating few-cycle, ultra-intense pulses.

Beneath a forest in Villigen, Switzerland, a new compact free-electron laser facility is generating brilliant X-ray flashes.

The manipulation of the quantum properties of light involves its technically challenging strong interaction with matter. Now, an experiment shows that when light propagates through a waveguide it only takes a weakly coupled line of atoms to single out its photons, or bunch them together, unveiling and controlling its quantum nature.

Strongly correlated photon states are achieved using only weak coupling thanks to an ensemble of non-interacting waveguide-coupled atoms and collectively enhanced nonlinear interactions.

Inhomogeneity of the photogenerated carrier spacetime distribution enables transient symmetry breaking in a metasurface. As a result, broadband transient dichroism is demonstrated.

A method to control the topological properties of two-dimensional (2D) materials on few-femtosecond timescales is proposed. By controlling the sub-cycle structure of non-resonant driving fields, it may be possible to coherently write, manipulate and read selective valley excitation.

The formation of multidimensional solitary states through the nonlinear propagation of high-energy pulses in a molecular gas-filled large-core hollow-core fibre is demonstrated, offering new opportunities for studying multimodal spatiotemporal dynamics in the high-energy regime.

Enhanced second-harmonic generation is achieved through random quasi-phase-matching in three-dimensional Mie resonant disordered microspheres realized by the bottom-up assembly of barium titanate nanocrystals.

The first lasing results at SwissFEL, an X-ray free-electron laser, are presented, highlighting the facility’s unique capabilities. A general comparison to other major facilities is also provided.

Relativistic 35 MeV electron bunches with charges of 60 pC are accelerated in a terahertz-wave-driven dielectric waveguide. When the terahertz pulse energy is 0.8 μJ, an accelerating gradient of 2 MeV m⁻¹ and energy gain of 10 keV are achieved.

An ytterbium sublattice in an erbium-sensitized multilayer core–shell structure enables photon upconversion from lanthanide ions under 1,530 nm irradiation.