Attosecond Pulse-Tailoring with a Two-Color Field and the Time-Resolved Quantum-Path Interference Measurement of Cu(111)

Abstract

This work investigates high harmonics generated by electron dynamics in a strong, slowly varying electric field. Attosecond light sources based on high-harmonic generation have enabled probing dynamics in matter on the natural timescale of electron motion. Typically, attosecond measurements involve generating an electron wavepacket by absorbing the attosecond pulse, with dynamics being deduced from the wave packet’s attributes and known spectral components of the pulse. Theoretical models of previous experimental work on attosecond pulse trains show that the intensity ratio and phase shift are key control mechanisms. Spectral phases computed using Strong-Field Approximation (SFA) theory qualitatively match the spectral characteristics of high harmonic radiation in single- and multi-color fields. Calculations for a fundamental intensity of 200 TW/cm² and various intensity ratios and phases between 400 nm and 800 nm components of the driving field demonstrate precise periodicity control of the attosecond pulse and a novel method to experimentally retrieve temporal properties of the electron's ejection. Additionally, technical developments of an end-station for solid-state materials are presented, with initial measurements of time-resolved quantum-path interference on the Γ𝑀̅ symmetry axis in Cu(111) compared with a similar measurement in argon.