Generation of few-cycle and attosecond pulses and their use in probing ultrafast dynamics in gases and surfaces

• Main Author: Arrell, Christopher
• Other Authors: Marangos, Jonathan ; Tisch, John
• Published: Imperial College London 2010
• Subjects: 535
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.530265

A laser-based system to allow the temporal evolution of plasmonic fields on surfaces with attosecond resolution is presented. Sub 7fs carrier envelope phase stabilised infra-red (IR) pulses with 450μJ have been generated using a hollow fiber compression system utilising self phase modulation to produce a 400nm FWHM bandwidth centred at 790nm and subsequent compression with chirped mirrors. The isolated attosecond pulse was produced using spectra selection of a continuum of extreme ultraviolet (XUV) photons generated from a single half cycle emission from the IR driving field. The isolated XUV was characterised using the atomic streak camera technique and a pulse duration of 270as was retrieved using a frequency resolved optical gating algorithm. An ultra high vacuum (10⁻¹⁰mbar) surface science system for attosecond pump-probe studies of surfaces was designed and built, connecting directly to the attosecond beamline. A sample manipulator was developed to precisely position surface samples in the IR and XUV foci. Novel vibrational decoupling mechanisms were developed, achieving only 10nm of motion measured of the sample head. An electron spectrometer with a resolution of 0.05eV for 30eV was used to measure localised nanoplasmonic intensity enhancement of 10³ from a rough silver surface (4mm RMS roughness) by collecting 35eV photoelectrons emitted by a few-cycle IR field with an intensity of ~10¹⁰W/cm². A 2-photon photoemission XUV-IR cross correlation measurement probing hot electron dynamics in a gold surface is reported, revealing femtosecond dynamics of electron thermalisation.