[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Airy Plasmon Pulses Investigated by Multiphoton Photoemission Electron Microscopy (PEEM)

摘要： Airy wave packets are a special class of non-diffractive solutions to the wave equation which accelerate along a bend trajectory. Their self-healing property makes them particularly interesting for integrated nanophotonic applications. Surface plasmon polaritons (SPPs), in contrast, have the beneficial property to be bound to the two-dimensional surface of a noble metal and enable sub-wavelength confinement. In two dimensions, Airy wave packets are the only non-diffracting solution of the wave equation. The high intrinsic bandwidth of a plasmonic excitation makes it ideal for ultrafast photonics. Photoemission Electron Microscopy (PEEM) represents an ideal tool to deliver images of these processes. The method has been successfully applied by us in the past to investigate the transient behavior of an optical nanoantenna emitting Hankel plasmon pulses. We have used PEEM in combination with a variable wavelength excitation from an optical parametric chirped pulse amplifier system (OPCPA) to experimentally investigate Airy plasmon pulses emitted by an excitation grating. The OPCPA system allows us to experimentally investigate the performance of the excitation in the wavelength range between 670 and 840 nm, where a 3-photon-process is necessary to emit an electron. In this way, we can sample the spectral response which is necessary to determine the ultrafast characteristics of the Airy plasmon pulse. We find that the excitation of stationary Airy plasmons is possible over a large bandwidth. However, the creation of an ultrafast hotspot requires also a matching of the spectral phase which is hard to fulfill in strong dispersing systems. We therefore accompany our measurements with rigorous finite-difference time domain simulations, a suitable nonlinear electron yield model, and analytic calculations to determine the modal purity of the Airy plasmon excitation based on reciprocity. Results support our experimental data and suggest that further improvements of the excitation scheme are necessary to obtain spatio-temporal hotspots.