Laser interaction with solids is routinely used for functionalizing materials' surfaces. In most cases, the generation of patterns/structures is the key feature to endow materials with specific properties like hardening, superhydrophobicity, plasmonic color‐enhancement, or dedicated functions like anti‐counterfeiting tags. A way to generate random patterns, by means of generation of wrinkles on surfaces resulting from laser melting of amorphous Ge‐based chalcogenide thin films, is presented. These patterns, similar to fingerprints, are modulations of the surface height by a few tens of nanometers with a sub‐micrometer periodicity. It is shown that the patterns' spatial frequency depends on the melted layer thickness, which can be tuned by varying the impinging laser fluence. The randomness of these patterns makes them an excellent candidate for the generation of physical unclonable function tags (PUF‐tags) for anti‐counterfeiting applications. Two specific ways are tested to identify the obtained PUF‐tag: cross‐correlation procedure or using a neural network. In both cases, it is demonstrated that the PUF‐tag can be compared to a reference image (PUF‐key) and identified with a high recognition ratio on most real application conditions. This paves the way to straightforward non‐deterministic PUF‐tag generation dedicated to small sensitive parts such as, for example, electronic devices/components, jewelry, or watchmak.

The ultrafast electron energy transport is investigated in laser-heated warm dense copper in a high flux regime (2.5 AE 0.7 × 10 13 W=cm 2 absorbed). The dynamics of the electron temperature is retrieved from femtosecond time-resolved x-ray absorption near-edge spectroscopy near the Cu L3 edge. A characteristic time of ∼1 ps is observed for the increase in the average temperature in a 100 nm thick sample. Data are well reproduced by two-temperature hydrodynamic simulations, which support energy transport dominated by thermal conduction rather than ballistic electrons.

We present the Aurore platform for ultrafast sciences. This platform is based on a unique 20 W, 1 kHz, 26 fs Ti:Sapphire laser system designed for reliable operation and high intensity temporal contrast. The specific design ensures a high stability in terms of pulse duration, energy and beam pointing necessary for extended experimental campaigns. The laser supplies 5 different beamlines, all dedicated to a specific field: attosecond science (Aurore 1), ultrafast phase transitions in solids (Aurore 2 and 3), ultrafast luminescence in solids (Aurore 4), femtochemistry (Aurore 5). The technical specifications of these five beamlines are described in details and examples of recent results are given.