Optical phase transition of Ge2Sb2Se4Te1 thin film using low absorption wavelength in the 1550 nm window

Abstract

This paper aims to study the amorphous-to-crystalline phase transition characteristics of novel optical phase change material: Ge2Sb2Se4Te1 using excitation wavelength situated in the low absorption window of the phase change material. The GSST thin film is 300 nm thick and is coated on a glass substrate. The excitation wavelength used is situated in the 1550 nm window with absorption coefficient that is 4 orders of magnitude lower compared to the visible wavelengths typically used. Finite Element Method (FEM) is carried out to simulate the spatial distribution and temporal evolution of temperature within the GSST thin film during the laser irradiation process. Experimental verification of the simulation data is then carried out. Laser intensity between 0.45 and 0.9 GW/cm2 with pulse duration in the range of 70–190 ns, respectively, are required to induce crystallization of the GSST thin film using this excitation wavelength. This work provides useful information on implementing GSST as a functional material in current telecommunication network which uses the 1550 nm wavelength band as signal carrier.