  We explore broadband, wide-angle mid-infrared rectification based on
nanopatterned hyperbolic metamaterials (HMM), composed of two dissimilar metals
separated by a sub-nanometer tunnel barrier. The exotic slow-light modes
supported by such periodically trenched HMMs efficiently trap incident
radiation in massively parallel metal-insulator-metal tunnel junctions
supporting ultrafast optical rectification induced by photon-assisted
tunneling. This leads to highly efficient photon-to-electron conversion, orders
of magnitude larger than conventional rectennas. Our results promise an impact
on infrared energy harvesters and plasmonic photodetectors.
