Optical constants of fused silica and sapphire from 0.3 to 25 microm.
We have measured the optical constants of fused silica and sapphire in regions where they are transparent and where they are opaque—from 0.3 to 50 μm. The technique we used was the Kramers-Kronig method whereby the complex re­ flectivity (reflectance) was measured at normal incidence over the entire spectrum. Three different instruments were used: a Perkin-Elmer model 450 spectrometer from 0.3 to 3 μm; a Perkin-Elmer model 137 from 2 to 15 μm; a Beckman model IR 12 from 15 to 40 μm; and a Beckman IR 11 from 40 to 50 μm. Freshly evaporated aluminum was used as a reference Fig. 1. Optical constants of fused silica. The ordinate represents either n or k.