This issue celebrates the progress being made in the field of quantum optics by bringing together a selection of commissioned articles in the area. Topics covered include quantum communication, quantum memories, single-photon detectors and integrated optical circuitry (illustrated on the cover) for quantum information processing.

Cover design by Tom Wilson.

The eye of a particular species of mantis shrimp is well-known to have the most complex vision system in nature. A new study into the optical waveplate within its eye demonstrates an astonishing level achromaticity. Researchers hope the study will enable scientists to copy the design and thus improve the performance of man-made polarization optics.

Cover design by Roy Caldwell.

Letter by N. W. Roberts et al.

An artist's illustration of a cross-section through a spherical liquid-crystal microresonator. Made from droplets of liquid crystal housed in a sheet of transparent elastomer, such microresonators can tune their resonant wavelength over an unprecedented scale when exposed to an electric field.

Cover design by Humar et al.

Article by Humar et al.

Artist's illustration of an optical beam being scanned over a lithium niobate nonlinear crystal, resulting in the removal of unwanted impurities. The treatment process increases the crystal’s optical damage threshold and in principle may allow congruent material, which is far cheaper than specially doped alternatives, to be used in optical applications.

Cover design by Tom Heinen.

Letter by Kösters et al.

Repulsive optical forces between coupled parallel photonic waveguides have now been observed for the first time. The sign of the force can be controlled by the relative phase between the guided modes. This effect could be used in planar optical-force devices fabricated on a CMOS-compatible platform.

Cover design by Tom Wilson.

Letter by Li et al.

The advent of super-resolution imaging schemes that allow optical imaging beyond the diffraction limit of light is revolutionizing sample analysis in the biological and physical sciences. This issue features a special focus on the topic.

Cover design by Stefan Hell.

Progress article by Stefan W. Hell et al.

An image from a yellow-red display made from colloidal quantum dots - light-emitting semiconductor nanocrystals held in an organic solution. The attraction of the technology for displays is that it is bright, potentially cheap to manufacture, does not require a backlight and suits use in very thin designs that can be scaled to large sizes.

Cover design by Tom Wilson.

Article by Cho et al.

Electronic paper that offers a large contrast, strong saturated colours and a bright appearance in ambient light may soon be a realistic prospect thanks to the development of an electrofluidic display. The display reported by Jason Heikenfeld and his co-workers operates by using electromechanical forces to control the extent to which water-based inks cover the surface of miniature aluminium reflectors that serve as pixels.

Cover design by Tom Wilson.

Article by Heikenfeld et. al

In nonlinear media, internal wave mixing typically renders signal information unreadable. Now Christopher Barsi and his coworkers have shown how digital holography techniques can deconvolve the nonlinear distortions and reconstruct the image-wave anywhere along its propagation path. In the future, the technique may benefit applications such as material characterization and super-resolved microscopy.

Cover design by Michele Fiaschi.

Letter by Barsi et.al

By changing the twist angle of unit cells in a metamaterial, Harald Giessen and co-workers have shown that it is possible to independently control, and thus optimize, the electronic and magnetic coupling in the material. Their so-called 'stereometamaterials' may have applications for creating ultra-thin elements for controlling polarization or creating sophisticated sensors.

Cover design by Michele Fiaschi.

Article by Na Liu et.al

For many years, one-way valves for light, commonly known as optical isolators, based on magnetic materials and the Faraday effort have been widely used in photonics. The problem is that due to the design and materials used such devices cannot easily be miniaturized and exploited in integrated optical circuits. Now Zongfu Yu and Shanhui Fan suggest that the use of a travelling refractive-index modulation in a silicon waveguide may be an elegant answer.

Cover design by Michele Fiaschi.

Letter by Mahler Zongfu Yu and Shanhui Fan.

Although great progress has been made in THz semiconductor laser development, most designs are edge-emitting. Now, Lukas Mahler and colleagues in Italy, Switzerland and the UK, have constructed vertically emitting microdisk lasers by patterning specially shaped diffraction-gratings along the disk circumference. The team used THz quantum cascade structures and show a fifty times increase in power compared with the structures without gratings.

Cover design by Michele Fiaschi.

Letter by Mahler et al.