Etching parameter optimization of photonic integrated waveguides based on chalcogenide glasses for near- and mid-infrared applications

This study presents the etching parameters optimization of GeSbSe-based chalcogenide glass (ChG) for near and mid-infrared integrated photonic applications. Single-mode Se4 (Ge19.4Sb16.7Se63.9) on Se2 (Ge28.1Sb6.3Se65.6) waveguides were designed and fabricated. The Se2 and Se4 layers were first deposited via the RF magnetron sputtering technique. The waveguide structures were then patterned using combined reactive ion -inductively coupled plasma (RIE-ICP) etching and optimized by introducing argon gas to the fluorine (CHF3)-based chemistry etching. Parametric investigation of etching conditions, particularly the Ar/(CHF3 + Ar) ratio and total gas flow rates, led to significant improvements in waveguide sidewall morphology and roughness. Consequently, propagation losses were reduced from 7.5 dB/cm to 2.6 dB/cm, at near-infrared wavelengths (lambda=1,55 mu m). In the mid-infrared region, the optimized process achieved a low propagation loss of (1.45 +/- 0.81) dB/cm at 4.11 mu m, with an average loss of approximately 4 dB/cm across the 4.1-4.55 mu m wavelength range. This marks a substantial improvement over the initial process, which exhibited an average loss of 15 dB/cm. Advanced characterization techniques, including SEM-based roughness extraction and optical scattering loss modeling, were employed to correlate surface morphology with etching parameters. The Payne-Lacey model was used to predict propagation losses, showing good agreement with experimental results. This comprehensive approach provides valuable insights into the relationship between etching conditions and waveguide performance, contributing significantly to the development of low-loss chalcogenide-based photonic devices for near- and mid-infrared applications.