VIS-IR transmitting BGG glass and glass-ceramics

BaO-Ga2O3-GeO2(BGG) glasses have the desired properties for window applications in the 0.5-5micrometers wavelength region. These glasses are low cost alternatives to the currently used window materials and are being scaled- up to large sizes for various Department of Defense (DoD) applications. Fabrication of a high optical quality 6.5' x 8.5' x 0.5' rectangular BGG glass window has already been demonstrated. A transmitted wave front error of about (lambda) /15 at 632nm has been achieved in polished BGG glasses. Recently a 20' round glass window blank has been cast. Although the mechanical properties of BGG glass are acceptable for various window applications, it is demonstrated here that they can be further improved significantly either by the glass-ceramization process or by forming a composite. Neither process adds any significant cost to the final window material. The glass composite transmits in the 0.5-5micrometers region while the crystallite size in the glass-ceramic currently limits its transmission to the 2-5micrometers region.