A Cu-doped/Fe-doped low expansion glass ceramic composition comprising: wherein the total amount of SiO.sub.2, Al.sub.2 O.sub.3 and P.sub.2 O.sub.5 is 80-89 wt. %, and said glass ceramic contains as a dopant 0.1-3 wt. % CuO, 0.1-1 wt. % Fe.sub.2 O.sub.3 or a combined CuO+Fe.sub.2 O.sub.3 amount of 0.1-4 wt. %. The glass ceramic composition is suitable for use as a cladding material for solid laser energy storage mediums as well as for use in beam attenuators for measuring laser energy level and beam blocks or beam dumps used for absorbing excess or unused laser energy.
The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.