Patent ID: 7670685

Claim:
A composite consisting essentially of a magnesium aluminate spinel and a non-electrically conducting germanate glass bonded together having transmission in the mid-infrared wavelength region, wherein said composite has transmission in excess of 50% in the 0.4-5 μm wavelength region, wherein the coefficient of thermal expansion of said spinel and said glass are within 1×10 −6 /K; and wherein said glass is a BGG glass that contains one selected from the group consisting of Al 2 O 3 , La 2 O 3 , ZnO, CaO, ZrO 2 , In 2 O 3 , Y 2 O 3 , Gd 2 O 3 , Na 2 O, K 2 O, Cs 2 O, Rb 2 O, SrO and mixtures thereof in the amount up to 10%.