Oren Pedatzur

Two-Dimensional Frequency Resolved Optomolecular Gating of High-Order Harmonic Generation.

Probing electronic wave functions of polyatomic molecules is one of the major challenges in high-harmonic spectroscopy. The extremely nonlinear nature of the laser-molecule interaction couples the multiple degrees of freedom of the probed system. We combine two-dimensional control of the electron trajectories and vibrational control of the molecules to disentangle the two main steps in high-harmonic generation-ionization and recombination. We introduce a new measurement scheme, frequency-resolved optomolecular gating, which resolves the temporal amplitude and phase of the harmonic emission from excited molecules. Focusing on the study of vibrational motion in N_{2}O_{4}, we show that such advanced schemes provide a unique insight into the structural and dynamical properties of the underlying mechanism.

Robust enhancement of high harmonic generation via attosecond control of ionization

Advancements in high harmonic generation (HHG) have led to the development of table-top XUV and soft X-ray light sources for attosecond science [1]. However, the very low conversion efficiency of HHG, particularly for longer wavelength driving laser fields [2], poses a significant practical limitation for the use of these sources in many experimental applications. We show that a two colour driving field produces a considerable enhancement of the ionization rate compared to a single colour field, leading to huge increases in the HHG efficiency. We use a tunable mid-IR (1300–1600 nm) source as a driving field and a weaker 800 nm beam as an assisting field. By systematically varying the field parameters we observe increases in HHG efficiency of over two orders of magnitude. The enhancement is achieved via subcycle control of the tunnel ionization dynamics in the bichromatic driving field.