Nanoscale gradient index media fabrication for extreme control and tunability of optical wave propagation

Gradient Index Media have multiple applications for controlling the wave propagation and harvesting its received energy or processing its embedded data. A nanofabrication process was developed to produce a Luneburg lens on silicon, to operate in the optical regime, with feature sizes smaller than 100nm. The focused energy of the Luneburg lens is compared with lenses of non-spatially-varying index as well as a linear spatial variation, and its enhanced focusing is clearly demonstrated. In addition, a mechanism of thermal tunability of such devices is proposed and is supported by our results.