Laser induced tunable Ge2Sb2Te5 phase-change gratings

Periodic photonic nano- and microstructures are routinely used for light manipulation at the nanoscale. However, their fabrication process is demanding in terms of time, cost and facilities. Here we demonstrate a rapid laser-assisted method for fabrication of gratings in Ge2Sb2Te5 (GST) thin films, based on the formation of laser induced periodic surface structures (LIPSS). LIPSS formation mechanisms dependent on the wavelength of the operating laser, lead to high flexibility of the process, producing gratings with tunable period and orientation with respect to the initial laser polarization. The phase-change properties of GST, on the other hand, allows to fabricate phase gratings with strong modulation of refractive index, which are rewritable in nature.