arXiv subjects

D. Hoff

Publications and source records attributed to D. Hoff.

5 recordsLinked to original sources

arXiv2026

Parity-mixing interference in laser-assisted photoionization

Photoionization of atoms by high-order harmonics in the presence of a laser may lead to quantum interference from which information about the photoionization dynamics or the light fields can be extracted. Traditionally, this interference arises from two-photon transitions involving the absorption of consecutive harmonics combined with the absorption and stimulated emission of a laser photon. In this process, parity is conserved. Here, we investigate interference between one- and two-photon transitions in helium using high-order harmonics generated by a few-cycle laser and three-dimensional electron detection. In this case, parity is not conserved. We identify four parity-mixing interference pathways, involving two different harmonic fields or a single harmonic, together with absorption or emission of a probe photon.

physics.atom-ph↗

arXiv2025

Subcycle phase matching effects in short attosecond pulse trains

Attosecond pulses produced by High-order Harmonic Generation (HHG) in gases driven by intense laser fields have become a cornerstone technique for probing ultrafast electronic motion in matter. These applications require a good knowledge of the temporal and spectral properties of the emitted radiation. In this work, we generate a train of two to three attosecond pulses that we characterize using two-color laser-assisted photoionization. \textcolor{black}{An unexpected spectral behavior, with more pulses at high energies than at low energies, is observed when the carrier-to-envelope phase of the laser field is changed by 90$^\circ$.} HHG simulations indicate that the time-dependent phase matching of the harmonics contributes in a non-trivial way to the structure of the pulse train. Two-color laser-assisted photoionization enables us to unravel the dynamical influence of subcycle phase matching on the spectral properties of the attosecond pulse train, going beyond the predictions of the response of a single atom to a strong laser field.

physics.atom-ph↗

arXiv2021

High-order phase-dependent asymmetry in the above-threshold ionization plateau

Above-threshold ionization spectra from cesium are measured as a function of the carrier-envelope phase (CEP) using laser pulses centered at 3.1 $\mu$m wavelength. The directional asymmetry in the energy spectra of backscattered electrons oscillates three times, rather than once, as the CEP is changed from $0$ to $2\pi$. Using the improved strong-field approximation, we show that the unusual behavior arises from the interference of few quantum orbits. We discuss the conditions for observing the high-order CEP dependence, and draw an analogy with time-domain holography with electron wave packets.

physics.atom-ph↗

arXiv2019

Vectorial optical field reconstruction by attosecond spectral interferometry

An electrical pulse E(t) is completely defined by its time-dependent amplitude and polarisation direction. For optical pulses the manipulation and characterisation of the light polarisation state is fundamental due to its relevance in several scientific and technological fields. In this work we demonstrate the complete temporal reconstruction of the electric field of few-cycle pulses with a complex time-dependent polarisation. Our experimental approach is based on extreme ultraviolet interferometry with isolated attosecond pulses and on the demonstration that the motion of an attosecond electron wave packet is sensitive to perturbing fields only along the direction of its motion. By exploiting the sensitivity of interferometric techniques and by controlling the emission and acceleration direction of the wave packet, pulses with energies as low as few hundreds of nanojoules can be reconstructed. Our approach opens the possibility to completely characterise the electric field of the pulses typically used in visible pump-probe spectroscopy.

physics.optics↗

arXiv2018

Attosecond electronic recollision as field detector

We demonstrate the complete reconstruction of the electric field of visible-infrared pulses with energy as low as a few tens of nanojoules. The technique allows for the reconstruction of the instantaneous electric field vector direction and magnitude, thus giving access to the characterisation of pulses with an arbitrary time-dependent polarisation state. The technique combines extreme ultraviolet interferometry with the generation of isolated attosecond pulses.

physics.optics↗