Plasmonic generation of attosecond pulses and attosecond imaging of surface plasmons
b"Attosecond pulses are ultrashort radiation bursts produced via high\\nharmonic generation (HHG) during a highly nonlinear excitation process\\ndriven by a near infrared (NIR) laser\\npulse. Attosecond pulses can be used\\nto probe the electron dynamics in ultrafast processes via the attosecond\\nstreaking technique, with a resolution on the\\nattosecond time scale.\\nIn this thesis it is shown that both the generation of attosecond (AS) pulses\\nand the probing of ultrafast processes by means of AS pulses, can\\nbe extended to cases in which the respective driving and streaking fields are produced by \\nsurface plasmons excited on nanostructures at NIR wavelengths.\\nSurface plasmons are optical modes generated by collective oscillations of the surface\\nelectrons in resonance with an external source.\\n\\nIn the first part of this thesis, the idea of high harmonic generation (HHG) \\nin the enhanced field of a surface plasmon is analyzed in detail by means of numerical simulations. \\nA NIR pulse is coupled \\ninto a surface plasmon propagating in a hollow core tapered \\nwaveguide filled with noble gas. The plasmon field intensity \\nincreases for decreasing waveguide radius, such that at the apex\\nthe field enhancement is sufficient for producing high harmonic radiation.\\nIt is shown that with this setup it is possible to generate isolated AS pulses\\nwith outstanding spatial and temporal structure, but with an intensity of orders of magnitude smaller than in standard gas harmonic\\narrangements. \\n\\nIn the second part, an experimental technique for the imaging\\nof surface plasmonic excitations on nanostructured surfaces is proposed, \\nwhere AS pulses are used to probe the surface field by means of\\nphotoionization. The concept constitutes an\\nextension of the attosecond streak camera \\nto ``Attosecond Photoscopy'', which allows\\nspace- and time-resolved imaging of the plasmon dynamics during \\nthe excitation process. It is numerically demonstrated that the relevant parameters of the \\nplasmonic resonance buildup phase can be determined with subfemtosecond precision.\\n\\nFinally, the method used for the numerical solution of\\nthe Maxwell's equations is discussed, with \\nparticular attention to the problem of absorbing boundary conditions.\\nNew insights into the mathematical formulation of the absorbing \\nboundary conditions for Maxwell's equations are provided."