Two-Dimensional Spectral Interferometry using the Carrier-Envelope Phase

TL;DR

This paper introduces a novel two-dimensional spectroscopy method using carrier-envelope phase control, enabling the measurement of ultrafast temporal events and separating quantum pathways in attosecond pulse generation.

Contribution

The work presents a new spectroscopy technique combining spectral interferometry with CEP control to resolve ultrafast dynamics on an attosecond scale.

Findings

Separated contributions of three electron quantum paths in attosecond pulses.

Measured CEP-dependent temporal separation of attosecond pulses (~54 as).

Enhanced understanding of the transition between cutoff and plateau harmonics.

Abstract

Two- and multi-dimensional spectroscopy is used in physics and chemistry to obtain structural and dynamical information that would otherwise be invisible by the projection into a one-dimensional data set such as a single emission or absorption spectrum. Here, we introduce a qualitatively new two-dimensional spectroscopy method by employing the carrier-envelope phase (CEP). Instead of measuring spectral vs. spectral information, the combined application of spectral interferometry and CEP control allows the measurement of otherwise inseparable temporal events on an attosecond time scale. As a specific example, we apply this general method to the case of attosecond pulse train generation, where it allows to separate contributions of three different sub-cycle electron quantum paths within one and the same laser pulse, resulting in a better physical understanding and quantification of the transition region between cutoff and plateau harmonics. The CEP-dependent separation in time between two full-cycle spaced attosecond pulses was determined to modulate by (54 +/- 16) attoseconds.