Controlled Optical Contrast Caused by Reversible Laser-Induced Phase Transitions in GeTe and Ge2Sb2Te5 Thin Films in the Spectral Range from 500 to 20,000 nm

In this paper, we present the results of an experimental study of the controlled contrast of optical properties of Germanium Telluride (GeTe) and Germanium Antimony Telluride (Ge₂Sb₂Te₅ or GST) 100 nm thin films, caused by laser-initiated reversible phase transitions from the amorphous-tocrystalline state, and vice versa. We demonstrate a high contrast in the transmissivity and reflectivity spectra in the wide wavelength range from 500 to 20,000 nm. We show that such a contrast of optical properties can be controlled in the set–reset mode, when samples of thin films are exposed to a nanosecond laser pulse at a wavelength of 532 nm, with a spatial distribution close to “top hat.” We confirm the laser-initiated changes in the thin film structures by X-ray diffraction analysis methods.