Laboratory studies of alkali metal filter deposition, ultraviolet transmission, and visible blocking.
Far-ultraviolet alkali metal or Wood's filters have been produced and tested supporting the production of a flight filter for the Wide Field Planetary Camera 2 on the Hubble Space Telescope. Sodium layers 0.5-1-microm thick transmit up to 40% in the ultraviolet while efficiently blocking visible wavelengths. The prevention of visible pinholes is assisted by a clean, sleek-free surface and a cooled substrate during deposition. The coatings are stabilized efficiently by a bismuth overcoating whose transmission spectrum is presented. We also report for the first time, to our knowledge, the first demonstrated long-wavelength cutoff from a lithium filter, with a shorter cutoff wavelength than sodium and potentially higher stability for astronomical imaging.
Clarke
J T
JT
Space Physics Research Laboratory, University of Michigan, 2455 Hayward, Ann Arbor, Michigan 48109-2143, USA. clarke@umich.edu
Skinner
W R
WR
Vincent
M B
MB
Irgang
T
T
Suratkal
V
V
Grassl
H
H
Trauger
J T
JT