Volume 15 Issue 7, July 2021

A chip-based optical frequency comb has enabled the realization of a 300 GHz signal with record low phase noise. The development could yield ultra-compact, ultra-low-noise sources for millimetre-wave applications in telecommunications, remote sensing and precision spectroscopy.

The unique optical properties of graphene were combined with lithium-ion battery technology to produce multispectral optical devices, with colour-changing capabilities.

Short period, femtosecond transient gratings in a sample can now be produced by X-rays. The approach promises to reveal the excitation behaviour of complex materials with high temporal and spatial resolution.

By converting Li-ion battery into an optical device using graphene electrodes, an electrochemical optical device which enables colour changing ability over the entire wavelength range from visible to microwave is demonstrated.

A four-wave mixing technique is developed in the hard X-ray range. A diamond phase grating in an X-ray beam path creates a periodic excitation pattern on a sample via the Talbot effect. The response of the periodic excitation is probed by an optical pulse.

A nondestructive and complete Bell-state measurement is demonstrated between two 60-m-distant atomic qubits in different optical cavities. The main building block is a photon-atom gate, which is executed upon reflection of the photon from the cavity.

A simple coating of a sub-200-nm-thick quantum dot film on two-dimensional materials can drastically enhance their nonlinear optical responses through nonlinear-excitation resonance energy transfer by a high-efficiency remote dipole–dipole coupling.

A 300 GHz signal is generated by the combination of a low-noise stimulated Brillouin scattering process, dissipative Kerr soliton comb and optical-to-electrical conversion. A phase noise of −100 dBc Hz⁻¹ is achieved at a Fourier frequency of 10 kHz.

By amplifying a soliton in a multistage cascade, few-femtosecond extreme-ultraviolet free-electron laser pulses are achieved.

Twin-field quantum key distribution over 600 km is demonstrated. The key ingredient for success is the dual-band phase stabilization that dramatically reduce the phase fluctuations on optical fibre by more than four orders of magnitude.

By adding a carefully designed amplification section in a passive resonator, but pumping it below the lasing threshold, ultra-stable high-power cavity solitons can be formed, effectively removing the important barrier of having to work in low-loss environments.

Indistinguishable photon pairs are generated via four-wave mixing in a two-dimensional array of ring resonators that exhibit topological edge states. They show tunable spectral−temporal correlations and robustness against fabrication disorders.