Spatially resolved plasmon coupling

Nanotechnology plays an increasing role in our daily life, ranging from cosmetic products, food, textiles, medicine to electronic devices. The development of the latter follows the need of getting smaller and faster at reduced costs. In this context miniaturized light plays an important role, which is smaller than conventional light (that cannot be smaller than its wavelength), and faster than conventional electronics. With that, fast switches in integrated circuits, novel light sources or highly sensitive biosensors for medical and chemical applications can be achieved. However, to create such miniaturized light, specific transmitters are required, that transform conventional light into its small counterpart and vice versa. In this project we study the interplay between incoming light, a transmitter and metallic structures as small as a millionth of a meter that creates miniaturized light. To do so, a dedicated measurement technique is used, that images the very small particles involved in this process and, at the same time, quantifies how efficiently the incoming light is transformed into its miniaturized form via the transmitter. Various transmitters are investigated using two different mechanisms that group this work in two parts. In the first part, so-called quantum dots and dye molecules are used, which transmit light in the visible range, while in the second part, internal vibrations of the substrate are explored that transfer light in the infrared region. It is the combination of sample fabrication and measurement technique, which makes the approach within this proposal unique and opens new possibilities. While the ultrasmall metallic structures are fabricated using a polymer mask onto which the metal is evaporated, the transmitter itself is positioned close to the metallic structure, to effectively couple light in and out of the metallic structure. The advantages of this fabrication technique are, that the size, shape and position of the metallic particle can be precisely designed to optimize the interplay with the transmitter, and the possibility to change the transmitter position relative to the metallic structure to improve its performance. To measure the transmitter process a world-wide unique instrument is used. It is based on an electron microscope to image and monitor the sample with a resolution approximately 2000 times better than conventional optical microscopes. At the same time, this instrument, called CHROMATEM, can measure how strongly the transmitter interacts with the metallic particle, in both regions, the infrared and the visible range. With this combination of sample fabrication and measurement technique, the transfer mechanism from conventional to miniaturized light via a dedicated transmitter can be explored at unprecedented high resolution.