Scanning planar Yagi-Uda antenna for fluorescence detection

An effective approach to improve the detection efficiency of nanoscale light sources relies on a planar antenna configuration, which beams emitted into narrow cone. Planar antennas operate like optical Yagi-Uda antennas, where reflector and director elements are made metal films. Here we introduce investigate, both theoretically experimentally, scanning implementation antenna. Using small ensemble molecules contained in fluorescent nanobeads placed antenna, independently address intensity, radiation pattern decay rate as function distance between flat-tip gold wire (reflector) thin film coated glass coverslip (director). The changes single bead it cone down angles 45{\deg} (full width at half maximum). Moreover, collected signal compared case is larger than factor 3, mainly due excitation enhancement. These results offer better understanding modification light-matter interaction by they hold promise for applications, such sensing, imaging diagnostics.