Influence of OH-group concentration on optical properties of silica glass in terahertz frequency region

We evaluated the optical properties of various types of silica glass with different OH-group concentrations by using terahertz (THz) time-domain spectroscopy. The results show that the absorption coefficient in the THz frequency region varied with the OH-group concentration and that the variation depended only on the OH-group concentration, irrespective of the glass-manufacturing process. On the other hand, the refractive index did not depend on the OH-group concentration. Thus, the THz optical properties of silica glass can be predicted based on the OH-group concentration in the glass, and vice versa.