Improvement of Laser Damage Resistance of Fused Silica Using Oxygen-Aided Reactive Ion Etching

Reactive ion etching (RIE) with fluorocarbon plasma is a facile method to tracelessly remove the subsurface damage layer of fused silica but has the drawback of unsatisfactory improvement in laser damage resistance due to the induction of secondary defects. This work proposes to incorporate O2 into the CHF3/Ar feedstock of RIE to suppress the formation of secondary defects during the etching process. Experimental results confirm that both the chemical structural defects, such as oxygen-deficient center (ODC) and non-bridging oxygen hole center (NBOHC) defects, and the impurity element defects, such as fluorine, are significantly reduced with this method. Laser-induced damage resistance is consequently greatly improved, with the 0% probability damage threshold increasing by 121% compared to the originally polished sample and by 41% compared to the sample treated with conventional RIE.