Reviews & Analysis

Carefully designed nanophotonic silicon waveguides, when pumped at long wavelengths to avoid inherent losses, are opening the door to useful nonlinear processes in the mid-infrared.

Entangled photons are a key ingredient in optical quantum technologies, but researchers have so far been unable to produce a single pair of entangled photons. Now, two groups from China and Austria independently report just that, with a technique that avoids the need to infer entanglement from detection signatures.

Common sense suggests that complex phenomena such as Bose–Einstein condensation require complicated experimental set-ups to be observed. But when it comes to the field of photonics, the simplest system may sometimes reveal the most unexpected surprises.

The demonstration of an integrated terahertz transceiver featuring a quantum cascade laser and a Schottky diode mixer promises new applications for compact and convenient terahertz photonic instrumentation.

The generation of entangled photon pairs is usually a complex process involving optically driven schemes and nonlinear optics. The recent demonstration of an electrically powered light-emitting diode that is capable of this task looks set to greatly simplify experiments in the field of quantum information processing.

Owing to their excellent optoelectronic properties, Ge-on-Si photodetector can be monolithically integrated with silicon-based read-out circuits for applications such as high-performance photonic data links and low-cost infrared imaging at low power consumption. This Review covers the major developments in Ge-on-Si photodetectors, including epitaxial growth and strain engineering, free-space and waveguide-integrated devices, as well as recent progress in Ge-on-Si avalanche photodetectors.

Silicon lasers have long been a goal for semiconductor scientists. This Progress Article reviews the most recent developments in this field, including silicon Raman lasers, the first germanium-on-silicon lasers operating at room temperature, and hybrid silicon microring and microdisk lasers. Challenges and opportunities for the present approaches are also discussed.

CMOS-compatible silicon optical modulators with high modulation speeds, large bandwidths, small footprints, low losses and ultralow power consumption are needed for current optical communications systems relying on highly integrated on-chip optical circuits. This Review summarizes the techniques used to implement silicon optical modulators, gives an outlook for these devices, and discusses the candidate solutions of the future.

The increasing capability for manufacturing a wide variety of optoelectronic devices from polymer and polymer–silicon hybrids, including transmission fibre, modulators, detectors and light sources, suggests that organic photonics has a promising future in communications and other applications.

The increasing capability for manufacturing a wide variety of optoelectronic devices from polymer and polymer–silicon hybrids, including transmission fibre, modulators, detectors and light sources, suggests that organic photonics has a promising future in communications and other applications.

Frequency combs are created by stabilizing the evolution of the carrier–envelope phase of a mode-locked laser. Researchers have now demonstrated a simplified method of creating frequency combs that enables trains of identical pulses to be easily produced.

High-performance, ultracompact lenses are needed in the quest to miniaturize optical systems. It now seems that carefully engineered subwavelength gratings can function as almost perfect mirrors with custom-designed focusing properties.

Europe has always been a hub of innovation for photonics, and this year's Photonics Europe conference has shown that young inventors are still coming up with great ideas for commercialization.

Packets of light persisting in a continuously driven nonlinear resonator in the time domain offer new possibilities not only for applications in all-optical storage, pulse reshaping and wavelength conversion, but also for fundamental experiments in nonlinear science.

A composite photonic crystal that allows on-chip control over the emission direction of a semiconductor laser diode looks set to benefit mobile projection displays, lasers printers and chip-to-chip optical communication.

A new gating scheme based on polarization control and second-harmonic generation is greatly simplifying the production of isolated attosecond pulses.