Articles in 2018

Reflected light is often unwanted, causing interference, and reducing transmitted power. Controlling the non-local response of a material can lead to anti-reflection coatings with impressive properties.

Nicolaas Bloembergen made rich contributions to nuclear magnetic resonance, masers and lasers, nonlinear optics and ultrafast laser–matter interactions. The Nobel laureate sadly passed away on 5 September 2017. Here are my memories of my Harvard mentor, a remarkable person and a wonderful scientist.

With the availability of high-intensity terahertz free-electron lasers, surprisingly large multiphoton absorptions in a phosphorus atom doped in a silicon crystal have been obtained, providing the possibility of a hydrogen-like system in silicon photonics and quantum information devices.

Phosphors often suffer luminescence quenching at elevated temperatures. Now, thermal quenching can be combated with surface phonon-assisted energy transfer, enabling the luminescence of ultrasmall upconversion nanophosphors to be dramatically enhanced.

By using a terahertz free-electron laser, multiphoton transitions between impurity states in p-doped Si are investigated. The two- and three-photon integrated absorption cross-sections are found to be the highest ever reported for a discrete oscillator system.

By combining the sensitivity and high temporal resolution of phase imaging with the specificity and high spatial resolution of fluorescence microscopy, a 4D microscope is demonstrated that visualizes in three dimensions the fast cellular processes in living cells at up to 200 Hz.

This Review describes how non-fullerene electron acceptor materials are bringing improvements in the power conversion efficiency and stability of organic solar cells.

Femtosecond X-ray Fourier holography imaging with record-high lateral resolution below 20 nm is demonstrated. Phase information is encoded into the interference of the diffraction patterns of a reference particle with a measurement sample.

Green light-emitting diodes with a brightness of 460,000 cd m^–2 and a low turn-on voltage of 2.5 V are enabled by the use of a chlorination treatment to provide conductive passivation of the devices.

An experimental protocol to discern true multi-particle interference is demonstrated in a boson sampling device without dynamic reconfiguration. Statistical features of three-photon interference were evaluated in a seven-mode integrated interferometer.

Phonons on the surface of lanthanide-doped upconversion materials are used to combat thermal quenching, enabling ~2,000-fold emission enhancement.

Irradiating arrays of metal nanowires with intense femtosecond laser pulses produces high-brightness picosecond X-ray pulses. By specifically tailoring the plasma properties, up to 20% conversion efficiency of optical light into X-rays can be achieved.

Implementing non-reciprocal elements with a bandwidth comparable to optical frequencies is a challenge in integrated photonics. Now, a phonon pump has been used to achieve optical non-reciprocity over a large bandwidth.