Surface defect analysis on formed chalcogenide glass Ge₂₂Se₅₈As₂₀ lenses after the molding process

Chalcogenide glass (ChG) is increasingly used in infrared optical systems owing to its excellent infrared optical properties and scalable production using precision glass molding (PGM). However, surface scratches affected by the molding temperature and microdimples on the lens surface caused by gas release seriously impair the quality of the formed lens. To reduce these surface defects when molding Ge₂₂Se₅₈As₂₀ ChG, the temperature effect must be studied, and the gas generation must be minimized, while the gas escape must be maximized. In this work, we studied the effect of temperature on the surface defects. Additionally, we studied the influences of the roughness and curvature of the contact surfaces, as well as the pressing force on the formation of the microdimples. It was found that the molding temperature should be approximately 30°C higher than the softening temperature (T_s) to avoid surface scratches. The gas generation could be inhibited by increasing the pressing force and decreasing the roughness of the mold surface, and finally, increasing the curvature difference between the mold and glass preform surfaces improved the gas escape.