These structures could generate the most intense nanolaser beams

Jun 27, 2012 14:37 GMT  ·  By
Electron micrograph showing arrays of indefinite optical cavities made of silver/germanium multilayers
   Electron micrograph showing arrays of indefinite optical cavities made of silver/germanium multilayers

A team of experts at the US Department of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) constructed the world's smallest 3D optical cavities from metamaterials. They say that these structures have the potential to produce the most intense nanolaser beams possible today.

It's very important to note here that optical cavities are a critical component of all lasers. Within them, light is made to bounce back and forth, before being allowed to exit as the tightly focused, amplified photon beam that we normally call a laser.

Working together with colleagues at the University of California in Berkeley (UCB), the team was able to produce very small cavities inside metamaterials, which exhibit extraordinary electromagnetic properties. Metamaterials are completely artificial materials, which are constructed in the lab.

In addition to applications in the field of laser research, the structures could also be used to improve existing technologies and fields of research, from LED, optical sensing and nonlinear optics to quantum optics and photonics integrated circuits.

The 3D nanoscale cavities have been constructed by alternating extremely thin layers of silver and germanium. Once the process is complete, researchers get a so-called indefinite metamaterial, which they then carve in order to obtain the structures they want.

“Our work opens up a new approach for designing a truly nano-scale optical cavity. By using metamaterials, we show intriguing cavity physics that counters conventional wisdom,” says Xiang Zhang, the principal investigator on the new research.

“For example, the quality factor of our optical mode rapidly increases with the decrease of cavity size. The results of this study provide us with a tremendous opportunity to develop high performance photonic devices for communications,” he goes on to say.

Zhang is based at the Berkeley Lab Materials Sciences Division (MSD) and he is the director of the Nano-scale Science and Engineering Center (SINAM) at UCB. He was also the corresponding author of a new paper detailing the research.

The work, entitled “Experimental realization of three-dimensional indefinite cavities at the nanoscale with an anomalous scaling law,” appears in the latest issue of the esteemed journal Nature Photonics.

“Due to the unnaturally high refractive index supported in the metamaterials, our 3D cavities can be smaller than one tenth of the optical wavelength,” adds lead paper author, Xiaodong Yang.

“At these nanoscale dimensions, optical cavities compress the optical mode into a tiny space, increasing the photon density of states and thereby enhancing the interactions between light and matter,” concludes the expert, who is now based at the Missouri University of Science and Technology.