54 nanotimes News in Brief

Nanolasers & Optical Sensors // First 3D Nanoscale Optical Cavities from Metamaterials © Based on Material by UC Berkeley, USA

The world’s smallest three-dimensional optical cavities with the potential to generate the world’s most intense nanolaser beams have been created by a scientific team led by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley. In addition to nanolasers, these unique optical cavities with their extraordinary electromagnetic properties should be applicable to a broad range of other technologies, including LEDs, optical sensing, nonlinear optics, quantum optics and photonic integrated circuits. By alternating super-thin multiple layers of silver and germanium, the researchers fabricated an "indefinite metamaterial" from which they created their 3D optical cavities. In natural materials, light behaves the same no matter what direction it propagates. In indefinite metamaterials, light can actually be bent backwards in some directions, a property known as negative refraction. The use of this indefinite metamaterial enabled the scaling down of the 3D optical cavities to extremely  deep subwavelength (nanometer) size, resulting in a "hyperboloid iso-frequency contour" of light wave vectors (a measure of magnitude and direction) that supported the highest optical refractive indices ever reported.

"Our work opens up a new approach for designing a truly nano-scale optical cavity," Zhang says. "By using metamaterials, we show intriguing cavity physics that counters conventional wisdom. 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."

Xiaodong Yang, Jie Yao, Junsuk Rho, Xiaobo Yin, Xiang Zhang: Experimental realization of three-dimensional indefinite cavities at the nanoscale with anomalous scaling laws, In: Nature Photonics, Vol. 6(2012), No. 7, July 2012, Pages 450-454, DO:10.1038/nphoton.2012.124:

http://dx.doi.org/10.1038/nphoton.2012.124