Investigation of Laser Damage Thresholds of an Output Coupler for TEA CO₂ Laser

Output couplers for TEA CO₂ lasers were made from Ge substrate coated with dielectric layers of ZnS, Ge and Y₂O₃ using physical evaporation technique (PVD). The laser-induced damage thresholds (LIDTs) of manufactured mirrors have been investigated using an experimental setup, based on TEA CO₂ laser. The effect of preparation conditions, such as grinding, polishing and cleaning, is shown. The maximum value of LIDT about 8 J/cm² was achieved using a fine grinding with loose abrasive grade 3 µm, then polishing with alumina powder grade 0.3 µm and finally hot cleaning with ultrasonic waves.

Keywords:
Laser-induced damage thresholds; optical materials; coupler mirrors; CO₂ laser