Reviews & Analysis

The reciprocity of light pulse propagation in a disordered photonic structure can be 'switched off' by creating a local, ultrafast nonlinearity.

Hydrogen from solar-driven water splitting has the potential to provide clean energy. Current progress towards artificial photosynthetic devices is reviewed, with particular focus on visible light active nanostructures. A vision for a future sustainable hydrogen fuel community based on artificial photosynthesis is outlined.

Using a real-time measurement technique to study the single-shot properties of modulation instability, scientists have shown that its initial stochastic nature in an optical system can lead to specific correlation properties in both the spectral and temporal domains.

Researchers in the field of metamaterials are not only making advances in existing areas of plasmon dispersion control and slow-light propagation in photonic crystals, but also tackling new topics such as quantum metamaterials.

Phase-space optics is an indispensable tool for optical imaging and sensing. New optical hardware for light-field photography and pupil engineering for imaging with extended depth of field promote the use of phase-space representations as the primary object of optical signal processing.

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.

Fibre lasers in the mid-infrared regime are useful for a diverse range of fields, including chemical and biomedical sensing, military applications and materials processing. This Review summarizes the different rare-earth cations and host materials used in mid-infrared fibre laser technology, and discusses the future applications and challenges for the field.

This Review discusses the emerging field of mid-infrared frequency comb generation, including technologies based on novel laser gain media, nonlinear frequency conversion and microresonators, as well as the applications of these combs in precision spectroscopy and direct frequency comb spectroscopy.

Exploiting the spatial shapes of 'twisted' photons makes it possible to enhance the bit rate of free-space optical communications without requiring more bandwidth.

Electronic implants have been used to restore visual function lost as a result of retinal degeneration. Combining subretinal high-pixel-density arrays with optically powered serial photovoltaic sensors may alleviate some of the difficulties associated with today's devices, which rely on implanted arrays and inductive coils.

The full quantum description of an optical detector not only reveals how it operates at the most fundamental level but also promises new opportunities in quantum information processing.

Recent research shows that quantum-mechanical tunnelling through individual semiconductor quantum dots can be promoted or inhibited using a low-intensity focused laser beam. This phenomenon may be useful for low-level light detection or quantum information applications.

Controlling the velocity of neutral particles is an experimental challenge, owing to their absence of charge. Scientists have now demonstrated a technique that can be used to accelerate neutral argon atoms by polarizing them in moving optical lattices.

Interrogation schemes based on quantum physics look set to push the data-handling capabilities of optical communication channels to new levels of performance.

Quantum plasmonics, Fano resonances, surface plasmon–polariton Airy beams and plasmon-enhanced Raman spectroscopy are some of the new aspects of plasmonics that are now being explored.

Scientists have shown that wrinkles and folds can be used to maximize the absorption of low-energy photons by efficiently redirecting them into a thin absorbing film. This inexpensive technique for structuring photonic substrates could be used to increase the efficiency of many organic photovoltaic cells.