Volume 14 Issue 6, June 2020

Asymmetric forward and backward transmission through photonic structures can be achieved via optical nonlinearities, but existing systems have typically used slow thermo-optic effects. A new resonator design has now enabled low-loss, non-reciprocal pulse routing based on the Kerr nonlinearity in integrated silicon waveguides.

Advanced computational imaging techniques have the potential to extract neural activity patterns from scattered data without reconstructing images.

A monolithic chip-scale ring laser gyroscope based on both Brillouin and Sagnac effects provides a sensitivity sufficient to measure sinusoidal rotations with an amplitude as small as 5 degrees per hour, thus enabling the first on-chip Earth rotation measurement.

A Sagnac gyroscope based on Brillouin ring lasers on a silicon chip is presented. The stability and sensitivity of this on-chip planar gyroscope allow measurement of the Earth’s rotation, with an amplitude sensitivity as small as 5 deg h⁻¹ for a sinusoidal rotation, an angle random walk of 0.068 deg h^−1/2 and bias instability of 3.6 deg h⁻¹.

By applying a spiral phase in a pulse shaper, a three-dimensional wave packet, which is a spatiotemporal optical vortex with a controllable purely transverse orbital angular momentum, is demonstrated.

Using a femtosecond mode-locked laser and a frequency-locked electric signal, a displacement measurement method that offers a >MHz measurement speed, sub-nanometre precision and a measurement range of more than several millimetres is achieved, facilitating the study of broadband, transient and nonlinear mechanical dynamics in real time.

By exploiting low-contrast fluctuating speckle patterns from extended fluorescence sources using an advanced signal-processing algorithm, functional signals through highly scattering tissues can be extracted.

Optically induced magnetization is experimentally demonstrated using gold nanoparticles. The inverse-Faraday-effect-enabled magnetization may lead to new types of compact optical isolator.

Optical nonlinearity is exploited for non-reciprocal transmission and integrated frequency comb-based optical ranging.

Continuous-wave lasing in strained GeSn alloys is reported at temperatures of up to 100 K. The approach offers a route towards a group-IV-on-silicon laser.

A deep-learning-enabled metasurface cloak actively self-adapts to take into account changing microwave illumination and varying physical surroundings.

The first operation of the European X-ray free-electron laser facility accelerator based on superconducting technology is reported. The maximum electron energy is 17.5 GeV. A laser average power of 6 W is achieved at a photon energy of 9.3 keV.