Figure 2.

Optical absorption spectra of dense silica glass doped with the copper precursor. (A) Before any reduction process; inset: zoomed scale near 800 nm. (B) After hydrogenation at 80°C without any further heat treatment (curve a) and after annealing at 100°C (curve b), 300°C (curve c), 500°C (curve d) and 700°C (curve e). Inset: a picture of the silica rod heated at 700°C.