Patent ID: 6872479

Claim:
A coated optical material suitable for use as an optical path material in lasers operating below 250 nm comprising: a shaped optical monocrystal having an entry face and an exit face for laser radiation entering and exiting said crystal, and a coating on at least the exit face of said monocrystal, said coating selected from the group consisting of MgF 2 doped fused silica and fluorine doped fused silica; wherein when the coating is MgF 2 doped fused silica and the MgF 2 content of said MgF 2 doped fused silica is in the range of 0.2% to 4% by weight; and wherein when the coating is fluorine doped fused silica and the fluorine content of said fluorine doped fused silica is in the range of 0.2 to 4% by weight.