Water window imaging opportunity

August 21, 2014
Water window imaging opportunity

Ever heard of the water window? It consists of radiations in the 3.3 to 4.4 nanometre range, which are not absorbed by the water in biological tissues. New theoretical findings show that it is possible to develop coherent radiations within the water window. These could be the basis of an optimal technique to obtain a high-contrast image of the biological samples or to be used in high-precision spectroscopy.

Now, a new theoretical study identifies the physical mechanism needed to efficiently generate the harmonic radiations—which are multiples of an incoming 's frequency—at high laser intensities that occur beyond the saturation threshold of atoms and molecules. These findings, aimed at improving conventional methods of coherent radiation production to reach the water window, were recently published in the EPJ D by José Pérez-Hernández from the Centre for Pulsated Laser, CLPU, in Salamanca, Spain, and colleagues.

When an intense and short laser pulse interacts with an atom or molecule, one of the resultant physical processes is the High-order Harmonic Generation (HHG) process, which is capable of changing the driving laser pulse into new harmonic frequencies. HHG also provides a direct way to synthesise atto-second pulses (10-18s range) and produce coherent radiation in the extreme UV range, dubbed XUV and EUV.

In previous similar work, studies focused on hydrogen as the atomic target. In the present work, the authors extend the study to argon atoms—a gas typically providing a high enough frequency conversion efficiency to detect the HHG. The authors use the same formalism as in hydrogen studies, consisting in mathematical equations combined with a quantum mechanical approach using numerical computation and providing a quantitative description of the HHG spectrum. The experimental confirmation of the reported prediction, however, still remains a challenge.

Explore further: Visible lasers offer exquisite control of x-ray light in a tabletop apparatus

More information: Pérez-Hernández, J. A. et al. (2014). High order harmonic generation at high laser intensities beyond the tunnel regime. European Physical Journal D. DOI: 10.1140/epjd/e2014-50086-6

Related Stories

Breakthrough in sFLASH seeding experiment

June 3, 2015

A team of researchers from DESY, the University of Hamburg and the Technical University of Dortmund has managed to demonstrate seeding by a procedure known as HGHG at the sFLASH test facility in April. "Seeding" is supposed ...

Attosecond science opens new avenues in femtochemistry

August 17, 2016

Attosecond Science is a new exciting frontier in contemporary physics, aimed at time-resolving the motion of electrons in atoms, molecules and solids on their natural timescale. Electronic dynamics derives from the creation ...

Recommended for you

Researchers discover new rules for quasicrystals

October 25, 2016

Crystals are defined by their repeating, symmetrical patterns and long-range order. Unlike amorphous materials, in which atoms are randomly packed together, the atoms in a crystal are arranged in a predictable way. Quasicrystals ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.