Metamaterial Optical Cavities (image) DOE/Lawrence Berkeley National Laboratory Caption This schematic shows (a) an indefinite metamaterial structure with alternating silver and germanium multilayers; and (b) its iso-frequency contour of light wave vectors with negative refractions along the x- and y-directions, and positive along the z-direction. Credit Courtesy of Xiang Zhang group Usage Restrictions courtesy of Xiang Zhang, et. al Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.