An antenna is a device used to propagate, receive and / or transmit electromagnetic waves that may have information embedded within them. Most people think of radio waves when they think of antennas. Radio waves are just one type of electromagnetic wave. For example, a sound wave can be translated into an electronic signal that is sent to a transmitter (antenna). The antenna creates an electromagnetic wave that carries the original buried sound information through the atmosphere / space around it. An antenna at a different location receives the electromagnetic wave, sending it to the circuitry (its radio), which then translates it to an electronic signal and then back to a sound wave.
The term nantenna (nano-antenna) is sometimes used to refer to an optical rectin, or an optical antenna by itself. At present, Idaho National Laboratories has designed an optical antenna to absorb wavelengths in the range of 3-15 μm. These wavelengths correspond to photon energies of 0.4 eV to 0.08 eV. Based on antenna theory, an optical antenna can efficiently absorb any wavelength of light as long as the antenna size is optimized for that specific wavelength. Ideally, antennas would be used to absorb light at wavelengths between 0.4 and 1.6 μm because these wavelengths have higher energy than far infrared (longer wavelengths) and represent about 85% of the spectrum of solar radiation.