Quite recently, the first observations of strong-field phenomena in the interaction of ultrashort laser pulses with metallic and dielectric solid state nanostructures have been reported. These studies open up new routes for studying electron dynamics on short timescales, XUV sources, plasmonics as well as particle acceleration. They address fundamental questions on strong field behavior and allow new and unprecedented control of matter wave manipulation on timescales intrinsic to electrons in matter. The work combines light-field driven electron control, called strong-field or attosecond physics, and plasmonics, namely the research field comprising collective electron phenomena in metals.
The field of plasmonics is well-established, with most successful research results that are nowadays already so much advanced and well controlled that real-world applications start to become important. For example, nano-plasmonic particles are currently investigated as a means to locally heat up cancerous tissue and thus to destroy a tumor with local heat treatment. For this to work, the plasmonics community has developed intricate and most advanced material science recipes to produce the required nanostructures with the proper optical response. Vice versa, the understanding of plasmonic materials as a means to generate nano-localized optical fields is tremendous, resulting in nano-plasmonics imaging tools such as scanning near-field optical microscopes (SNOMs). More recently the field of plasmonics has moved to the investigation of single plasmonic nanostructures. By carefully optimizing size and shape, it is possible to engineer the interaction of light with the metallic structures themselves, but also with matter positioned in their near-field. This led to the spaser and to the observation of effects so far only known from the realm of cavity-quantum electrodynamics. Broadband nano antenna structures are nowadays used to study incoherent and coherent interactions of light and quantum matter.
The field of strong-field and attosecond physics is slightly younger than plasmonics but is also well-established. The vast majority of work in these domains was focused on gas phase experiments in the last two decades. Atoms, molecules and clusters in the gas phase allow most easily reaching into the desired field strength range, and the observed phenomena can be understood in terms of relatively simple and insightful atomic physics based pictures. With the invention of the femtosecond frequency comb and carrier-envelope phase control it is now possible to generate isolated attosecond long fully coherent XUV light pulses, which has opened many new fields of research, from inner-shell spectroscopy to time-resolved atomic transition recording.
While both research fields, plasmonics and strong-field physics, hinge on controlling optical fields, there is even a deeper connection that was only demonstrated in the last five years: The strong-field physics picture that is underlying attosecond physics has to be invoked to understand phenomena at metal nanostructures. For example, electron re-scattering, the pivotal effect in attosecond pulse generation describing a photo-emitted electron to return to its parent matter, has also been clearly identified to show up at sharp metal tips. So the underlying physics of strong-field effects has been observed in plasmonically enhanced fields at a metal structure – in the solid-state phase. Other examples of how the fields of plasmonics and attosecond physics touch each other comprise electron acceleration in enhanced fields, the observation of metallization of a dielectric in strong-fields, and reaching the regime of a non-linear index of refraction.
The scope of this workshop encompasses all the topics discussed in the preceeding paragraphs, with the aim to deepen the understanding of this exciting and emerging new field of physics at the boundary of plasmonics and strong-field and attosecond physics.