Paula J Holmes

US Patent:

20030217688, Nov 27, 2003

Filed:

Jun 3, 2003

Appl. No.:

10/454387

Inventors:

Michele Meyer-Fredholm - Hericy, FR
Paula Holmes - Sturbridge MA, US
Qiao Li - Westborough MA, US

International Classification:

C30B015/00
C30B021/06
C30B027/02
C30B028/10
C30B030/04

US Classification:

117/013000

Abstract:

The present invention is directed to a process or method for preparing a metal fluoride pre-melt material of a quality suitable for the preparation and growth of metal fluoride optical monocrystals. The pre-melt material of the invention is prepared using permeable graphite crucibles having a permeability (porosity) greater than 4 cm/s. Exemplary monocrystals prepared from pre-melts of the invention exhibited improved transmissivity and laser durability relative to monocrystals prepared from convention pre-melt materials. Impurities in the pre-melt arising from the use of scavenger/fluorinating agent in the pre-melt have been shown to be generally less than 10 ppb and be less than 1 ppb.