Volume 9 Issue 5, May 2010

Charles Townes played a crucial role in the invention and realization of the first masers and lasers, for which he shared the 1964 Nobel Prize in Physics. Nature Materials speaks to him about his historic contributions.

It was the realization of semiconductor lasers that led to the commercial success of lasers. Herbert Kroemer explains to Nature Materials his contributions to the design principle of these lasers, for which he shared the 2000 Nobel Prize in Physics.

The quantum cascade laser has liberated laser properties from materials limitations, enabling light emission to be tailored over a broad spectral range. Nature Materials talks to Federico Capasso about the development of these lasers in his laboratory.

Coherent synchrotron radiation has revolutionized the study of molecules and materials. Talking to Nature Materials, Gerhard Materlik, CEO of the Diamond Light Source, discusses the many uses of synchrotron sources and free electron lasers.

Patching carbon and boron nitride nanodomains emerges as an efficient way to engineer bandgaps in graphene, opening a new avenue for optoelectronic devices.

The use of a ferroelectric tunnel junction to control the spin polarization of adjacent magnetic electrodes promises a new approach to the use of interface effects for low-power-consumption spintronic devices.

So far, flow-induced transitions and structures formed by the assembly of surfactant micelles have been reversible. Now, a microporous extensional flow process forms a permanent gel, which remains intact even after flow has stopped.

The prediction of interface structures is an uncertain and time-consuming task. A technique merging ab initio calculations with a genetic algorithm simplifies the process and provides suitable solutions of the atomic structures that would be hard to envisage a priori.

Carbon nanotubes direct chemically produced thermal waves, providing propulsion and thermopower waves that create electrical energy.

Transformation optics describes the capability to design the path of light waves almost at will through the use of metamaterials that control effective materials properties on a subwavelength scale. In this review, the physics and applications of transformation optics are discussed.

While superconductivity experts investigate the fundamental properties of iron pnictides, it is worth wondering whether the properties of these materials are good enough for applications. A strategy for growing high-quality BaFe₂As₂ thin films shows that the use of an appropriate buffer layer allows very high critical currents to be reached.

Resistive nanowire arrays are intensively pursued as easy-to-fabricate memory technology, where data can be written and read through simple voltage–current operations. However, problems encountered in achieving stable switching independent of external influences has hampered their progress. The complementary, antiserial arrangement of two memory elements is now shown to lead to the desired stability.

So far, the realization of negative-refractive-index materials has required the use of resonating metallic structures, leading to an inherently narrowband operation around those resonances. Here, negative-refractive-index materials are proposed that consist of single coaxial waveguide layers, with a negative refractive index at a broad range of visible wavelengths.

Approaches for controlling surface wettability and liquid spreading are numerous and diverse, but introducing directionality to the control of these phenomena is far from trivial. Nanostructured surfaces are now used to allow the propagation of a liquid in a single direction, while constraining it in the other three directions.

Efforts in predicting crystal structures from first principles have mainly focused on the bulk materials. A general approach based on a genetic algorithm is now proposed to simulate grain boundaries and heterophase interfaces in multicomponent systems. The efficiency of the approach is demonstrated in the case of grain boundaries in SrTiO₃.

An exothermic chemical reaction coupled with a one-dimensional conductor has been predicted to give rise to self-propagating waves with high thermal conductivity. This is now demonstrated experimentally with carbon nanotubes used as guides for the waves, which propagate with high thermal conductivity and with electric pulses of very intense power.

Despite having many similarities with graphene, single-layer boron nitride has a very large bandgap. Now, single-layer hybrids consisting of a blend of domains of boron nitride and graphene have been synthesized. By varying the percentage of boron nitride it is possible to tune the electronic properties, which is a very promising development for potential devices.

Viscoelastic gels can be made by using flow to induce structure into solutions containing surfactant micelles. However, the gels disintegrate soon after flow stoppage. By using a microfluidic-assisted laminar-flow process to generate very high extension rates, it is now shown that permanent gels can be made, creating new opportunities for applications.

Understanding the interaction of water with oxide surfaces at the molecular level could prove to be significant for controlling the catalytic activity of complex nanoparticles on insulating films. Two types of selective dissociation pathway involving electronic and vibrational excitation are now observed for a single water molecule on MgO thin films.

Despite recent advances in lithium batteries, fundamental issues of practical importance such as energy efficiency have not been adequately considered. A general model for the occurrence of inherent hysteretic behaviour in insertion storage systems containing multiple particles is now proposed.

Peptoids are synthetic polymers designed to mimic the structure and functionality of proteins. When a one-to-one blend of two oppositely charged peptoids is mixed in solution, giant, 2.7-nm-thick free-floating sheets are formed. The sheets can specifically bind a corresponding protein, and offer potential for producing functional two-dimensional nanostructures in the future.

Fifty years ago this month the first laser was demonstrated. In this focus issue we look at the history of the laser, its applications, and how to this day basic research continues to rejuvenate our understanding of the fundamental physics of the laser.