Mechanically Tunable Nanogap Antennas: Single-Structure Effects and Multi-Structure Applications

摘要

By mechanically changing the width of a nanometer gap between two optical antennas, the coupling condition for the antennas can be seamlessly modified. This leads to a shift in the antenna's localized surface plasmon resonance wavelength, and a modification of the intensity in the antenna hotspot, which can reach extraordinarily high values for nanometer gaps. Such systems have in recent years been realized, for example, by using flexible polymers as substrates that are mechanically stretched or bent, or by combining break junctions with plasmonic antennas. Applications can be found, amongst others, in plasmonic strain sensing via color shift sensors, or tunable surface-enhanced Raman spectroscopy platforms. In this article an overview is given over recent work on mechanically tunable gap antennas, with a specific focus on studies at the single-nanostructure level. Different techniques used for mechanical tuning, optical read-out signals that are influenced by the gap width, and potential applications of the resulting structures are presented. Plasmonic break junctions offer a new perspective that allows for added functionalities. The mechanical activation is discussed within the context of single nanoantenna gap tuning by using alternative stimuli.