Patent ID: 6855203
Filing Date: 2005-02-15
Classification: C30B

Abstract:
1. A process of making a 157 nm transmitting barium fluoride optical crystal comprising: providing at least one barium fluoride crystal graphite crucible, said at least one barium fluoride crystal crucible comprised of a permeable graphite having a permeability greater than 4 cm providing a barium fluoride crystal feedstock having an oxygen contamination level no greater than 150 ppm by weight, loading said barium fluoride crystal feedstock having an oxygen contamination level no greater than 150 ppm by weight into said at least one barium fluoride crystal crucible with a graphite permeability greater than 4 cm melting said loaded barium fluoride crystal feedstock in said at least one barium fluoride crystal crucible with a graphite permeability greater than 4 cm inside said at least one barium fluoride crystal crucible with a graphite permeability greater than 4 cm and removing said grown barium fluoride crystal from said barium fluoride crystal crucible with a graphite permeability greater than 4 cm 2 /s to provide a high 157 nm transmitting barium fluoride crystal with a 157 nm internal transmission greater than 99%/cm.