Volume 16 Issue 7, July 2022

The ability to create complex three-dimensional structures of light has reached new heights with the experimental observation of two distinct kinds of toroidal pulses, the optical analogue of smoke rings.

Ferroelectric domain switching controlled by electrical pulses provides a controllable means to tune the refractive index of BaTiO₃ thin films. Now, a device based on this material is presented that is capable of implementing low-power, high-speed and CMOS-compatible programmable phase shifters in silicon photonic chips.

Coherent multi-octave mid-infrared waveforms are created and manipulated by cascaded intrapulse difference-frequency generation, demonstrating absolute phase control, and adding to the growing arsenal of techniques for arbitrary light-wave control.

One hundred years ago, in 1922, Léon Brillouin discovered the scattering of light by sound waves. Within an optical fibre, Brillouin scattering may be used to create narrow-linewidth filters and spectrometers. A twisted optical fibre is now used to reduce these linewidths by over an order of magnitude, down to the sub-MHz level.

Researchers demonstrate low-threshold multiple exciton generation and photocurrent quantum efficiency exceeding 100% from high-energy photons in perovskite nanocrystals.

Researchers demonstrate a multilevel non-volatile phase shifter memory that is based on the monolithic integration of BaTiO₃ thin films and silicon waveguides. By manipulating ferroelectric domains in BaTiO₃ with electrical control signals, they achieve analogue and non-volatile optical phase tuning.

Tunable sub-megahertz spectral features are demonstrated without resonators. The approach, which exploits gain-enhanced polarization pulling in a twisted birefringent medium, may be useful in applications such as microwave photonic filters, slow and fast light, and optical sensing.

A new strategy to reduce charge leakage in quantum-dot light-emitting diodes enables high external quantum efficiencies of 28.7% and 21.9% and excellent T₉₅ lifetimes of 580,000 h and 4,400 h for green and blue devices, respectively.

Continuously adjustable single-cycle waveform spanning from 0.9 to 12.0 μm is obtained by cascaded intrapulse difference-frequency generation in a ZnGeP₂ crystal. The cascade-associated phase response—distinct for different spectral bands—provides a new tuning parameter for waveform adjustment.

A new solution to Maxwell’s equations, photonic toroidal vortex, is experimentally realized.

Pulses of light with a toroidal structure are experimentally realized in the terahertz and optical regions.

Researchers demonstrate a persistent spin helix in an organic–inorganic hybrid ferroelectric halide perovskite whose layered nature makes it intrinsically like a quantum well. They demonstrate a switchable spin-polarized band structure via an intrinsic ferroelectric field.

Structured light is shown to be robust against unitary perturbations.