The optical constants <i>n</i> and <i>k</i> of evaporated platinum films on glass substrates have been measured in the spectral region 4500Å–7500 Å. The reflectance <i>R<sub>m</sub></i> of gold and platinum films on a potassium tantalate (KTaO<sub>3</sub>) substrate has been measured from the substrate side and found to be somewhat lower than the calculated values. This discrepancy may be explained by relatively small alternations in <i>n</i> and/or <i>k</i> of the metal film or by scatter at the KTaO<sub>3</sub>—metal interface.
V. L. RIDEOUT and S. H. WEMPLE, "Optical Constants of Evaporated Gold and Platinum Films on Potassium Tantalate," J. Opt. Soc. Am. 56, 749-750 (1966)