“A straight nanoscale antenna will mainly respond to the electric field of
light. This means that the effects of the
magnetic field of light, which holds half of the energy of light, are disregarded. For a long time this was not considered as an issue that could be solved, because most of the metals used to fabricate antennas do not respond to the magnetic field of light anyway.
“This changed recently, due to the rapid developments in metamaterial research. What seemed to be impossible in the past – making antennas that respond strongly to the magnetic field of light—can now be done by structuring metals on the nanoscale.
“With these ideas in mind, the AMOLF and Philips researchers built the pyramid shaped antenna. By carefully designing the height and inclination of the antenna’s side walls, the researchers found that the response to the magnetic field of light is almost as strong as the response to the electric field of light.
“After witnessing the described effects in individual nanoscale antennas, the researchers took it one step further and placed multiple pyramid-shaped antennas in an array. The effect that the antennas have on each other turns out to be quite striking. At certain wavelengths (colours) of light, the antennas can couple to each other via the light that is scattered on the surface of the array. This makes the group of antennas more effective in beaming light than the sum of the individual antennas. In addition, the
antenna array may operate collectively at one wavelength, while at the same time the antennas operate individually at a different wavelength. Thus, the same array of pyramid-shaped antennas may beam light of a certain colour upward, and of a different colour downward.”
Connect With Us