title: Laboratory studies of alkali metal filter deposition, ultraviolet transmission, and visible blocking.
abstract: 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.
authors.affiliation: Space Physics Research Laboratory, University of Michigan, 2455 Hayward, Ann Arbor, Michigan 48109-2143, USA. clarke@umich.edu
authors.forename: J T
authors.initials: JT
authors.lastname: Clarke
authors.forename: W R
authors.initials: WR
authors.lastname: Skinner
authors.forename: M B
authors.initials: MB
authors.lastname: Vincent
authors.forename: T
authors.initials: T
authors.lastname: Irgang
authors.forename: V
authors.initials: V
authors.lastname: Suratkal
authors.forename: H
authors.initials: H
authors.lastname: Grassl
authors.forename: J T
authors.initials: JT
authors.lastname: Trauger