Abstract

Since the discovery that Al overcoated with MgF₂ or LiF produces high reflectances to wavelengths as short as 1150 Å and 1000 Å, respectively, these coatings have been used extensively in vacuum ultraviolet instruments in the wavelength region where their reflectance is high. If the instrument is intended to cover wavelengths shorter than the two given above, usually either Pt or Ir is used, with a loss of speed at the longer wavelengths. This paper presents reflectance data showing that fluoride-overcoated Al can be useful to wavelengths as short as 500 Å. Measurements were made from 1600 Å to about 300 Å at normal, 35°, and 85° angles of incidence, angles used in normal, Seya, and grazing incidence spectrometers, respectively. These measurements show that from the boundary of the high reflectance region to 500 Å, the reflectance at normal and 35° depends on the thickness of the fluoride coating and can be as high as 24% at 800 Å for a MgF₂ thickness of 150 Å. For shorter wavelengths, the reflectance shows a decreasing thickness dependence and at 304 Å is very low—about 1%. At grazing incidence, the reflectance shows some thickness dependence from 1500 Å to about 1000 Å, but toward shorter wavelengths the dependence disappears and the reflectance increases slowly to about 80% at 500 Å. In addition to the reflectance measurements, polarization effects are discussed.

© 1971 Optical Society of America

Effect of Deposition Rate and Substrate Temperature on the Vacuum Ultraviolet Reflectance of MgF₂- and LiF-Overcoated Aluminum Mirrors

E. T. Hutcheson, G. Hass, and J. T. Cox
Appl. Opt. 11(10) 2245-2248 (1972)

Monitoring the Thickness of Thin MgF₂ and LiF Films on Al by Reflectance Measurements Using the 1216-Å Line of Hydrogen

E. T. Hutcheson, J. T. Cox, G. Hass, and W. R. Hunter
Appl. Opt. 11(7) 1590-1593 (1972)

Preparation of Mirror Coatings for the Vacuum Ultraviolet in a 2-m Evaporator

A. P. Bradford, G. Hass, J. F. Osantowski, and A. R. Toft
Appl. Opt. 8(6) 1183-1189 (1969)

Further Studies on LiF-Overcoated Aluminum Mirrors with Highest Reflectance in the Vacuum Ultraviolet

J. T. Cox, G. Hass, and J. E. Waylonis
Appl. Opt. 7(8) 1535-1540 (1968)

Calculated Reflectance of Aluminum-Overcoated Iridium in the Vacuum Ultraviolet from 500 Å to 2000 Å

G. Hass and W. R. Hunter
Appl. Opt. 6(12) 2097-2100 (1967)