Atmospheric pressure plasma jet machining technology provides a flexible and efficient way to fabricate precise freeform optics. Due to the pure chemical material removal mechanism based on a dry etching process using fluorine containing gas, the choice of materials that can be treated is limited. Fused silica, Si, SiC or ULE? are easy to machine since the etching products formed are solely volatile. Recently, plasma jet machining has been also adopted to treat optical glasses like N-BK7? which contain amongst others alkali metals that form a solid residual layer during etching. In the paper a new approach to apply deterministic plasma jet etching on optical glass coping with complex etch characteristics caused by the residual layer is introduced.
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