Rapid thermal annealing of chalcogenide thin films for mid-infrared sensing and nonlinear photonics

Abstract

The influence of rapid thermal annealing (RTA) onto chalcogenide Ge-Sb-Se thin films is reported, focusing on changes in optical properties. These materials possess broad mid-infrared transparency covering the most critical absorption bands for (bio)chemical sensing and high third-order optical nonlinearities for potential applications in nonlinear photonics. The parameters of the RTA process within this study include the annealing temperature, heating rate, and the two sample processing methods – one by placing the sample inside the graphite susceptor and the other by simply laying the sample onto the silicon wafer. Selenide thin films were found to undergo a shift of the absorption edge upon the RTA, resulting in an optical bandgap energy increase (bleaching effect) and a notable refractive index decrease. As a result of structural relaxation, such changes show a great potential of RTA in fine-tuning of optical performance of chalcogenide thin films and planar chalcogenide waveguides. The authors acknowledge the IBAIA (101092723) Horizon Europe project, the ANR AQUAE (ANR-21-CE04-0011-04) project of the French National Research Agency (ANR), and project No. 22-05179S of the Czech Science Foundation (GAČR) for financial support.