“…These limitations are avoided, in theory, by controlling all three stress components. Stress generation processes capable of independently controlling three stress components include patterned thin films [18][19][20], ion implantation [21], excimer laser writing [22], patterned viscoelastic films [23], magnetostrictive films [24], and ultrafast laser writing [25][26][27][28]. So far, stress figuring has not been widely applied for creating freeform optics because no method has yet been shown to be accurate, stable, and scalable to high throughput or large optics.…”