Fyzikální ústav Akademie věd ČR

We have experimentally demonstrated the evidence of structural surface modifications of polymethyl- methacrylate (PMMA) caused by simultaneous action of extreme ultraviolet (XUV) (similar to 21 nm) and visible-near infrared (visible-NIR) (820/410 nm) ultrashort pulses. Although the fluence of each individual beam was far below the surface modification threshold, very efficient and specific material expansion was observed after irradiation of PMMA by more than similar to 20 shots of mixed XUV/visible-NIR radiation. As the XUV photons generate free charge carriers, absorption of the optical radiation dramatically increases, which heats up the material and further enhances the XUV induced damage to the polymer chain.