Volume 13 Issue 3, March 2019

Propagating on fibre links between multiple nodes of a network, light gets trapped by multi-path interference and forms complex states that are very sensitive to external perturbations. Now, a network of subwavelength, doped polymer fibres has been shown to operate as a network laser.

Orbital angular momentum is a property of light that has many emerging applications, but has been poorly appreciated until recently. The wavelength frontier of orbital angular momentum sources is extending beyond the ultraviolet thanks to research in fields ranging from nanostructures to free-electron lasers.

Low-cost spectroscopy, mobile phone-based imaging and laser-processed paper sensors are all examples of how photonics could help tackle India’s healthcare and environmental monitoring challenges.

Frequency comb spectroscopy is a recent field of research that has blossomed in the past five years. This Review discusses developments in the emerging and rapidly advancing field of atomic and molecular broadband spectroscopy with frequency combs.

This Review discusses the developments and applications of on-chip optical frequency comb generation based on two concepts—supercontinuum generation in photonic-chip waveguides and Kerr-comb generation in microresonators.

This Review describes quantum frequency combs that operate via photon entanglement, beginning with mode-locked quantum frequency combs followed by energy–time entanglement methods. The use of photonic integration and fibre-optic telecommunications components in enabling the quantum state control are also discussed.

Helicity of photons is exploited for preferential emission direction and sorting of valley-polarized excitons is achieved at room temperature.

Cyclometalated gold(iii) complexes are shown to offer tunable emission colours spanning from sky-blue to red and enable the fabrication of phosphorescent organic light-emitting devices with high external quantum efficiency and long lifetimes.

Red, green and blue CdSe/ZnSe quantum dot light-emitting diodes combine efficient operation with high brightness.

A time-domain approach that can continuously tune the polarization state of extreme-ultraviolet attosecond pulses allows the isolation and amplification of extremely weak chiral signals, extending vectorial measurements to the attosecond and nanometre scales.

Robust methods for creating and analysing soft X-ray modes, with as much as 30ħ angular momentum per photon, are demonstrated.

The entanglement of three remote quantum memories based on ⁸⁷Rb atoms is created via three-photon interference by enhancing the memory–photon entanglement in ring cavities, demonstrating a genuine quantum network involving more than two quantum nodes.

Temporal dissipative soliton formation in a free-space femtosecond enhancement cavity with a thin Kerr medium is reported. Locking a 350-fs, 1,035-nm pulse train with a repetition rate of 100 MHz to this cavity-soliton state generates a 37-fs sech²-shaped pulse with a peak-power enhancement of 3,200.