Direct single-pass writing of two-phase binary diffraction gratings in a Ge2Sb2Te5 thin film by femtosecond laser pulses

Abstract

The formation of alternating amorphous-crystalline structures on the surface of Ge2Sb2Te5 thin film upon the single-pass direct writing by a femtosecond laser beam was demonstrated. We obtained high quality periodic surface structures in non-ablative mode and determined the optimal laser fluence, pulse number and scanning speed for their scaling. The produced structures were stripes up to 1-mm long and consisted of up to 50 parallel amorphous-crystalline lines oriented perpendicular to the light polarization. These two-phase binary stripes had a period equal to the recording beam wavelength and exhibited diffraction grating behavior due to remarkable optical contrast. Diffraction spectra were investigated experimentally and also simulated using scalar and vector theory of diffraction.