Hamed Merdji and Marta Fajardo recognised for their research collaboration

Hamed Merdji and Marta Fajardo met at Ecole Polytechnique at the Laboratoire pour l'Utilisation des Lasers Intenses (Intense Lasers Laboratory LULI*) where they both did their PhD. They then became researchers in the field of photonics, Hamed Merdji at CEA and Marta Fajardo at Instituto Superior Técnico de Lisboa, and their work on light brought them together in 2005, with the aim of carrying out X-ray imaging at the nanometric scale. This long-term collaboration has now been rewarded by the Mariano Gago International Prize of the Academy of Sciences, which recognises the work carried out by pairs of French and Portuguese researchers.

X-rays are electromagnetic waves, like visible light. But there are few or no optical elements that can deflect these rays and be used in an imaging system. This is why, for example, medical X-rays simply involve illuminating a part of the body and measuring its transparency or opacity with a detector. "To go further and observe objects at the nanometre scale, we can use a coherent source of X-rays, in which all the photons are in phase, as if they were 'dancing' together," explains Hamed Merdji. The object to be imaged disturbs this dance and this perturbation can be detected. The challenge is to create a coherent X-ray source using lasers, which is more compact than the current sources that require large particle accelerators. Observing viruses or the surface of materials are among the potential applications.

In this context, the team was recently awarded the NanoXCAN project of excellence by the European Innovation Council in May 2022. This project is based in particular on the structuring of light from the XCAN laser developed at the Ecole Polytechnique by Jean-Christophe Chanteloup and Gérard Mourou, who won the Nobel Prize in Physics in 2018. Hamed Merdji has just joined the Laboratoire d'optique appliquée (Applied Optics Laboratory LOA*) at Ecole Polytechnique and part of the research with Marta Fajardo will take place in the same experiment room that they used during their thesis. A kind of homecoming, in a way.

*LULI: a joint research unit CNRS, École Polytechnique - Institut Polytechnique de Paris, CEA, Sorbonne Université

*LOA: a joint research unit CNRS, École Polytechnique - Institut Polytechnique de Paris, ENSTA Paris - Institut Polytechnique de Paris