Plasmon enhanced photoelectron spectroscopy and the generation of isolated attosecond XUV pulses for use with condensed matter targets
- Author(s): Nagel, Phillip Michael
- Advisor(s): Leone, Stephen R
- et al.
Surface plasmon resonances (SPRs), collective oscillations of quasi-free electrons in metals, can produce strong electric field enhancements at the surface of nanoparticles. These oscillations typically occur at optical frequencies (thus having a period on the order of one to a few femtoseconds) and only remain coherent for a few to tens of femtoseconds. Because of their increasing importance in various applications, it is important to understand SPRs at a fundamental level. The ultrafast nature of the processes involved with SPRs make time-resolved spectroscopy an important tool for probing their dynamics.
Recently developed light sources capable of producing isolated attosecond (10^-18 s) pulses of light can provide snapshots of electron dynamics on a sub-femtosecond timescale. Fewer than a dozen laboratories in the world currently have the ability to produce such light pulses. In this dissertation I discuss the development and construction of an experimental apparatus capable of producing and utilizing isolated attosecond pulses to study condensed matter, including surface plasmon dynamics. The ultimate goal of the experiments presented here is to laser-excite plasmonic resonances in metallic nanostructures and to detect the field enhancement at the surface of the nanostructures by measuring photoelectron spectra.
In the first experiment presented, electron photoemission from lithographically prepared gold nanopillars using nominally few-cycle, 800 nm laser pulses is described. Electron kinetic energies are observed that are higher by up to tens of eV compared to photoemission from a flat gold surface at the same laser intensities. A classical electron acceleration model consisting of multiphoton ionization followed by field acceleration qualitatively reproduces the electron kinetic energy data and suggests average enhanced electric fields due to the nanopillars that are between 25 and 39 times greater than the experimentally used laser fields.
In the second experiment presented, attosecond streaking from a W(110) single crystal and from an amorphous Cr thin film is demonstrated. In addition, a novel concept for SPR enhanced attosecond streaking is proposed and evaluated with the aid of a numerical model.