Nonlinear Plasmonics

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ABSTRACT:Efficient optical frequency conversion in nonlinear crystals is made possible by phase matching - the coherent addition of the nonlinear response upon propagation through the crystal. Today, optical frequency conversion is exploited in many areas, ranging from laser fusion to laser pointers. However, in order for phase matching to occur a crystal needs to be many wavelengths in size, which is not compatible with nanoscale architectures. A strong local nonlinear response therefore relies on intrinsic material nonlinearities. This research program investigates the high optical nonlinearities of plasmonic nanostructures made of noble metals such as gold and silver. These structures make it possible to generate light locally at shifted frequencies and to exploit multispectral interactions in nanoscale devices, without the need of phase matching.This research program investigates the nonlinear response of discrete and well-defined metal nanostructures, such as nanoparticles, nanorods and particle hybrids (dimers, trimers). These structures function as optical antennas - they localize and enhance the incident fields and they facilitate the release of the nonlinear response. The goal is to identify, understand and exploit configurations that yield high nonlinear efficiencies. Many nonlinear interactions, such as harmonic frequency generation or nonlinear four-wave mixing, are coherent processes and hence the phase-sensitive interplay of local fields is important for a strong response. The investigators study the interaction of frequency-converted fields with single quantum emitters, such as quantum dots, molecules, or ions. The ability to generate light locally through nonlinear processes provides new opportunities for nanophotonics and active plasmonics.