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 A broadband, sub-wavelength time-domain microscope is described, enabling the observation that terahertz light trapped within a cavity can mediate attractive interactions in a tunable van der Waals material.

Strain in Si nanostructures is used to achieve higher carrier mobility, making these devices candidates for the next generation of transistors. Minamisawaet al. fabricate silicon nanowires subject to elastic tensile strain up to 4.5%, exceeding the limit achievable with the use of SiGe virtual substrates.

Highly strained germanium on silicon samples with up to 3.1% uniaxial strain are fabricated and then investigated by Raman spectroscopy. During optical pumping, changes in both the emission wavelength and output power are observed, indicating that bandgap modification and optical gain are occurring.

The atom-like electronic structure of semiconductor quantum dots makes them ideal for storing well-defined numbers of electrons. This in turn can be used in the development of standards for current, to independently define the ampere.

The seeding of native species is critical to the success of dryland restoration efforts. Here the authors evaluate success of seeding establishment at 174 sites on six continents, finding that some sites had nearly 100% of species successfully recruit, while 17% of sites had zero seedling success.

Researchers have constructed a terahertz quantum cascade laser using quasi-periodic distributed feedback gratings based on the Fibonacci sequence. Features that go beyond traditional distributed feedback lasers are demonstrated, such as directional output independent of the emission frequency and multicolour operation.

Realizing tunable metamaterials across a broad spectral range is of great interest. Here, Liu et al. introduce hybrid structures comprising graphene plasmonic resonators strongly coupled to conventional split-ring resonators and reach 60% transmission modulation with an operating speed above 40 MHz.

Lasing is experimentally demonstrated in a direct bandgap GeSn alloy, grown directly onto Si(001). The authors observe a clear lasing threshold as well as linewidth narrowing at low temperatures.

Germanium (based) lasers are a promising route towards a fully CMOS-compatible light source, key to the further development of silicon photonics. Here, the authors realize lasing from strained germanium microbridges up to 100 K, finding a quantum efficiency close to 100%.

A terahertz quantum cascade laser that uses a grating etched into a double-metal waveguide to greatly improve the laser's performance is reported. The grating enhances the laser's optical power extraction and provides control over its emission wavelength and beam quality, yielding a single-mode beam that has a divergence of less than 10 degrees in both axes and a power of up to 15 mW.

Entangled photons are efficiently generated from highly symmetric, site-controlled InGaAs/GaAs quantum dots grown in inverted pyramids. Fine-structure splitting of the intermediate exciton level is suppressed without the application of electric, magnetic or strain fields. Polarization entanglement is demonstrated by measurements of the two-photon density matrix and the confirmation of several entanglement criteria.

Applications of microdisk lasers are intrinsically limited by their planar and isotropic emission. Now, by implementing appropriate diffraction gratings along the disk circumference, scientists present a vertically emitting terahertz quantum-cascade microdisk laser, shedding light on the fabrication of arrays of single-mode, highly collimated and powerful terahertz sources.

Traditionally, thermodynamics deals with the study of macroscopic systems comprised of a large number of particles. Skrzypczyk et al. present a framework—including a thermal bath and work-storage device—to extract the optimal amount of work from individual quantum systems.

The design flexibility of quantum cascade lasers has enabled their expansion into mid-infrared wavelengths of 3–25 μm. This Review focuses on the two major areas of recent improvement: power and power efficiency, and spectral performance.

Field emitter arrays are key components for X-ray sources, microwave generators, RF communication and advanced light sources. Tsujinoet al., report double-gate field emitter arrays with competitive beam qualities to the state of the art UV photoexcited cathodes.