“Attosecond metrology of VUV high-order harmonics generated in semiconductors via laser-dressed photoionization of alkali metals” was published in Nature Commun.

In an experimental and theoretical study published in Nature Commun.,16,1428 (2025), an international team of researchers from ELI-ALPS (Szeged, Hungary), ICFO (Barcelona, Spain) Guangdong Technion-Israel Institute of Technology (Guangdong, China), Technische Universität Wien (Vienna, Austria), Université de Bordeaux–CNRS–CEA (Bordeaux, France), and the Institute of Electronic structure and Laser at Foundation for Research and Technology-Hellas (IESL-FORTH), have demonstrated a scheme capable of generating and characterizing VUV attosecond pulses generated by laser driven semiconductor crystals. The study opens new spectral windows for attosecond science, enabling studies of bound-state dynamics in natural systems, while facilitating the generation of quantum light in the visible-VUV.

https://doi.org/10.1038/s41467-025-56759-0

Vacuum-ultraviolet attosecond pulses for tracing ultrafast processes of natural systems

A team of researchers has presented a new technique in Nature Communications capable of generating and characterizing vacuum-ultraviolet attosecond (10^-18 seconds) light pulses using laser driven semiconductors. With these pulses, the study of ultrafast dynamics in natural systems in all states of matter becomes possible.

Electrons in atoms interact with each other and with other particles, changing their motion, energies, and other features at incredibly fast timescales, on the order of attoseconds (10^-18 seconds). Capturing these ultrafast changes demands ultrafast light pulses. The pulse’s duration needs to be more or less the same as the effect’s; otherwise, it would be like trying to capture a hummingbird’s wing motion with a slow, long-exposure camera.

At the end of the XIX^th century, physicists thought that only femtosecond pulses (10^-15 seconds) were technically possible. That started to change in the late 1980s, when physicists linked high harmonic generation with attoscience. High harmonic generation (HHG) is a process that up converts low-frequency photons to higher frequencies, and what these researchers showed was that, when multiple harmonics are emitted, they can combine to form an attosecond pulse of light —something that was finally realized in 2001.

Attosecond science was born by generating and then employing extreme-ultraviolet (XUV) pulses, and as a consequence the methods developed to detect and characterize them focused in this frequency range. More than 20 years later, the creation of attosecond pulses to perform attoscience tasks remains XUV centered. Despite the many advances that XUV attosecond pulses have provided, they also pose a challenge. Most atoms, when hit by such an energetic light source, loose one or more electrons and become positively charged — a process known as ionization. But many worth studying processes in nature occur with non-ionized atoms, which remain in the so-called bound states. Since XUV light does not provide access to the bound states of the natural systems, their study has remained out of reach for attoscience. To address this, a source delivering less energetic attosecond pulses (for instance, in the vacuum-ultraviolet spectral range) and new methods to measure their main features (duration, intensity, etc.) are needed.

This has now been done by an international team of from ELI-ALPS (Szeged, Hungary), ICFO (Barcelona, Spain) Guangdong Technion-Israel Institute of Technology (Guangdong, China), Technische Universität Wien (Vienna, Austria), Université de Bordeaux–CNRS–CEA (Bordeaux, France), and the Institute of Electronic structure and Laser at Foundation for Research and Technology-Hellas (IESL-FORTH). For the first time, the team has demonstrated that semiconductors illuminated by strong mid-infrared laser light emit vacuum-ultraviolet (VUV) attosecond pulses, has retrieved the pulses’ temporal shape and has measured their total duration. These unprecedented results, published in Nature Communications [1], establish the basis of a novel technique for probing the ultrafast changes that occur in most natural systems, preserving their bound state rather than inducing their ionization.

These new tools and methodology could be used for conducting studies in natural systems, investigating their ultrafast dynamics and even possibly using them to engineer novel quantum light states.

Reference:

[1] A. Nayak, D. Rajak, B. Farkas, C. Granados, P. Stammer, J. Rivera-Dean, Th. Lamprou, K. Varju, Y. Mairesse, M. F. Ciappina, M. Lewenstein and P. Tzallas, Nature Commun., 16, 1428 (2025). (https://doi.org/10.1038/s41467-025-56759-0).

Η δημοσίευση των Ioannis Katsantonis (IESL post-doctoral fellow), Anna C. Tasolamprou (IESL's faculty member), Eleftherios N. Economou (Professor Emeritus), Thomas Koschny and Maria Kafesaki (IESL's faculty member) “Ultrathin, Dynamically Controllable Circularly Polarized Emission Laser Enabled by Resonant Chiral Metasurfaces, ACS Photonics, 12, 1, 71-78 (2025), https://pubs.acs.org/doi/10.1021/acsphotonics.4c01005?articleRef=control επελέγη από τους Editors του ACS Photonics για  Cover του Volume 12, Issue 1, 15/1/2025.

From paper's abstract:

"This is a simple, low-cost, and ultracompact chiral resonant metasurface design, which, by strong local coupling to a quantum gain medium (quantum emitters), allows to implement an ultrathin metasurface laser, capable of generating tunable circularly polarized coherent lasing output. According to detailed numerical investigations, the lasing emission can be transformed from linear to circular and switch from right- to left-handed circularly polarized (CP) not only by altering the metasurface chiral response but also by changing the polarization of a linearly polarized pump wave, thus enabling dynamic lasing-polarization control."

Scientists at our institute have achieved a major advancement in gas sensing technology. By optimizing perovskite materials, they have created highly sensitive and stable ozone sensors that function effectively at room temperature. This research not only improves our ability to monitor environmental pollutants but also lays the foundation for developing advanced sensors for a variety of applications, contributing to a safer and more sustainable future.

This work is part of Dr Aikaterini Argyrou PhD Thesis, in collaboration with Mrs Rafaela Maria Giappa and Prof. Ioannis Remediakis from the University of Crete, Dr Emmanouil Gagaoudakis from IESL, and Prof. Vassilios Binas from Department of Chemistry, Aristotle University of Thessaloniki and IESL.

Corresponding authors from IESL: Drs Konstantinos Brintakis, Athanasia Kostopoulou, Emmanuel Stratakis

More details: https://doi.org/10.1002/smll.202404430

Dear friends and colleagues,
 

On behalf of IESL Scientific Council we welcome you to the 'IESL Science Days 2022' which will be held at the main amphitheater of FORTH on December 15-16, 2022. This is the second such meeting following the successful organization of the first one in 2019 aspiring to establish it as an IESL tradition.

Please find below the program of the meeting and the corresponding book of abstracts.
 

• [Science Days Program in PDF Format]
• [Science Days Book of Abstract in PDF Format]

Looking forward to seeing you all and having a fruitful event.

The Organizing Committee

Kiki Chrissopoulou and Petros Samartzis

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