New system for nanoscale light control

The technique could open the possibility for targeted design of antenna based applications such as highly sensitive biosensors and extremely fast photodetectors which could play an important role in future diagnostic and information processing. The European / US researchers studied a special type of infrared antennas, featuring a very narrow gap at the centre. These 'gap antennas' generate an intense hot spot inside the gap allowing for highly efficient nano focusing of light. Small metal bridges were then fabricated inside the gap to examine how the presence of matter inside the gap affects the antenna behaviour. The near field oscillations of the different antennas were mapped with a modified version of a scattering type near field microscope. This was done with dielectric tips and operated in transmission mode, allowing for imaging local antenna fields in details as small as 50nm without disturbing the antenna. By monitoring the near field oscillations of the different antennas with the unique microscope, it was possible to directly visualise how matter inside the gap affects the antenna response. The effect could find interesting applications for tuning of optical antennas. With this work, the research provides the first experimental evidence that local antenna fields can be controlled by gap loading. This opens the door for designing near field patterns in the nanoscale by load manipulation, without the need to change antenna length, which could be highly valuable for the development of compact and integrated nanophotonic devices. The research was undertaken by CIC nanoGUNE, Donostia International Physics Centre DIPC, Centro de Física de Materiales of CSIC/UPV-EHU in San Sebastian, Harvard University, USA and the Max Planck Institute of Biochemistry in Munich.