Using nanometer-scale components, Georgia Tech researchers have demonstrated the first optical rectenna, a device that combines the functions of antennas and a rectifier diode to convert light directly into DC current. Optical rectennas could provide new technology for photodetectors, energy harvesters that convert waste heat to electricity – and ultimately more efficient solar energy capture. In the new devices, the carbon nanotubes act as antennas to capture light from the sun or other sources. As the waves of light hit the nanotube antennas, they create an oscillating charge that moves through rectifier devices attached to them. The rectifiers switch on and off at record high petahertz speeds, creating a small direct current.