Low optical loss synthetic quartz

Abstract

Transmission and calorimetric measurements show that hydrothermally prepared quartz has sufficiently low optical attenuation to make it a possible starting material for optical fiber transmission lines. Absorption losses as low as 2.2 dB/km have been observed in bulk samples at the 1.06 μm wavelength of the YA l G:Nd laser. Preliminary experiments indicate that it is possible to vitrify the material and that improvements in the starting materials and crystallization technique could be expected to further reduce the impurity content and the loss. We have found that the magnitude of the absorption at 1.06 μm is quadratically related to the concentration of OH impurity. This unusual dependence can be explained by the assumption that the 1.06 μm absorption is due principally to Fe 2+ and other divalent impurity ions whose concentration in the solid is governed by coupled substitution between Fe 2+ and 2H + impurities.