Search

Seven scientists share their views on some of the latest developments in attosecond science and X-ray free electron lasers (XFELs) and highlight exciting new directions.

Ultrashort laser pulses strongly drive electrons in glass and manipulate its optical properties on the attosecond timescale. A new spectroscopic study reveals the full interaction dynamics, with promising ramifications for future lightwave-driven petahertz electronics.

Short X-ray pulses from free-electron lasers enable coherent diffractive imaging of noncrystalline objects such as single molecules. Here, the authors reconstructing full image information from a single-shot diffraction pattern by using two sufficiently separated objects to act as references for each other.

2D Raman spectroscopy, based on fifth-order optical nonlinearity, is performed with a single beam of shaped fs optical pulses. The scheme inherently eliminates the cascade signal, making the vibrational coupling information easy to extract.

The high harmonic emission that accompanies the recombination of an electron with its parent molecular ion in an intense laser field provides a snapshot of the structure and dynamics of the recombining system. Experiments on CO₂ molecules now show how to extract information from the properties of the emitted light about the underlying multi-electron dynamics with sub-Ångström spatial resolution and attosecond temporal resolution

Sub-cycle phase-resolved attosecond interferometry is developed. The obtained phase information enables us to decouple the multiple quantum paths induced in a light-driven system, isolating their coherent contribution and retrieving their temporal evolution.

The Berry phase is resolved in light-driven crystals, via attosecond interferometry, in which the electronic wavefunction accumulates a geometric phase as it interacts with the laser field, mapping its coherence into the emission of high-order harmonics.

Attosecond-gated interferometry is developed by combining sub-cycle temporal gating and extreme-ultraviolet interferometry. By measuring the electron’s relative phase and amplitude under a tunnelling barrier, the quantum nature of the electronic wavepacket is identified.

A time-domain approach that can continuously tune the polarization state of extreme-ultraviolet attosecond pulses allows the isolation and amplification of extremely weak chiral signals, extending vectorial measurements to the attosecond and nanometre scales.

High-harmonic waves are generated from a MgO crystal under experimental conditions where the simple semi-classical analysis fails. High-harmonic generation spectroscopy directly probes the strong-field attosecond dynamics over multiple bands.

A single-molecule attosecond interferometry that can retrieve the spectral phase information associated with the structure of molecular orbitals, as well as the phase accumulated by an electron as it tunnels out, is demonstrated.

The absolute phase difference of the harmonic emission of Ar, Ne and He atoms is measured by XUV interferometry with temporal resolution of 6 as. This measurement provides a direct insight into the quantum properties of the photoelectron wavefunctions.

Single photon ionization—one of the most fundamental light matter interactions—can be significantly altered in a strong-field environment. Here the authors demonstrate a self-probing spectroscopy technique, resolving the evolution of the interaction in helium atoms with attosecond precision.

Field induced tunneling is one of the fundamental processes of light-matter interaction. Here the authors reconstruct the  temporal properties of tunneling using two-color electron holography with attosecond time resolution using argon atoms.

A method of laser-induced recollision permits measurement with attosecond resolution of the times at which the electron leaves the tunnelling barrier and discriminates between the ionization times of two carbon dioxide orbitals.

Modifications of the effective band structure of MgO crystal is investigated on a timescale within one-quarter cycle of the electromagnetic-field oscillation. The high-harmonic generation spectra show a signature of laser-induced closing of the bandgap.

Yaron Silberberg of the Weizmann Institute in Israel passed away in April. Here, some of his former students and friends remind us of who Yaron was: a creative researcher and a mentor without ego with major achievements in nonlinear optics, microscopy and quantum physics.

Even for simple systems, the interpretations of new attosecond measurements are complicated and provide only a glimpse of their potential. Nonetheless, the lasting impact will be the revelation of how short-time dynamics can determine the electronic properties of more complex systems.

Double-blind holography allows reconstruction of the missing spectral phases and characterization of the unknown signals in both isolated-pulse and double-pulse scenarios, facilitating the study of complex electron dynamics via a single-shot and linear measurement.

An interferometric measurement based on high-harmonic generation now provides direct access to the electron wavefunction during field-induced tunnelling.