Synopsis: Nanowire Lasing Explained

A careful reassessment of zinc oxide nanolasers finds that the electrons and holes in the material are not bound together as others have suggested.
Synopsis figure
Courtesy M. Versteegh, Utrecht University

A nanoscale wire of zinc oxide can perform as a tiny ultraviolet laser at room temperature, but despite a decade of research, physicists have yet to reach consensus over what exactly produces this lasing. Now, new experiments and theoretical calculations reported in Physical Review Letters make the case that a traditional lasing mechanism is at the heart of zinc oxide nanolasers.

Zinc oxide is a semiconductor with a large band gap that makes it interesting for many electronic and optical applications. It has unusually stable excitons, which are hydrogenlike bound states between electrons and holes. Scattering by these excitons could be responsible for the room-temperature lasing observed in zinc oxide nanowires. However, some scientists instead contend that the electrons and holes in zinc oxide are in a free, “plasma” state. And therefore, like most semiconductor lasers, light is produced when the electrons and holes combine.

To sort out these two possibilities, Marijn Versteegh and colleagues from the Utrecht University in the Netherlands performed a series of experiments in which they varied the external laser pulse used to excite zinc oxide nanowires of various sizes. The measured electron-hole densities at the lasing threshold were too high for excitons to be present. Instead, the densities—as well as the laser emission spectra—were consistent with an electron-hole plasma. The team verified this with calculations based on a quantum many-body theory that they had recently developed to describe the optical properties of zinc oxide. – Michael Schirber


More Announcements »

Subject Areas

Semiconductor PhysicsNanophysics

Previous Synopsis

Particles and Fields

W Marks the Spot

Read More »

Next Synopsis

Related Articles

Viewpoint: Sharing Quantum States
Condensed Matter Physics

Viewpoint: Sharing Quantum States

A quantum dot can form a mesoscopic quantum state together with the electrons of a cavity in which the dot is embedded. Read More »

Viewpoint: Where the Weyl Things Are

Viewpoint: Where the Weyl Things Are

Analogs to massless fermions predicted by particle physicists 80 years ago have been found in a crystalline metal and in a photonic crystal. Read More »

Focus: Shaking Cleans Nanoscale Surface

Focus: Shaking Cleans Nanoscale Surface

An oscillatory motion dramatically reduces the number of contaminant molecules at the interface between two surfaces. Read More »

More Articles