Enhancing weak optical signals using a plasmonic Yagi-Uda nanoantenna array

Nanoantennas have been used in a wide range of applications in sensing, spectroscopy, and imaging-in general, the antennas can enhance physical phenomena such as the local electric field or concentrate light in a certain direction. We have fabricated an array of 80 plasmonic Yagi-Uda nanoantennas on the cladding of an optical fiber and, by doing this, we show that the signal reaching the fast detector can be increased by a factor of 5 dB. The experiment demonstrates that plasmonic directive nanoantennas can indeed collect and concentrate electromagnetic radiation along a certain direction and eventually could be used to enhance weak signals.