Applied to ArF excimer lasers. It requires minimal reflectivity, absorption, and scattering losses, while also requiring the highest possible damage threshold.
The figure below shows a typical spectral curve, with parameters as follows:
Substrate: 7979/7980; Φ25.4 mm × 2 mm
Spectrum: Normal incidence, R < 0.1%, T > 97.5% @ 193 nm
