IR/UV polished CaF2 positive/negative lenses

Calcium fluoride lenses have a low refractive index, high laser damage threshold, and low coaxial and radial stress birefringence, making them suitable for excimer lasers or for integration into infrared systems. Plus, calcium fluoride is low in solubility and can withstand harsh environments. Polished calcium fluoride surfaces can last for years, it’s twice as hard as barium fluoride, and it has better resistance to thermal shock.