“…Simultaneously, silica glass, the host material, has various advantages including transparency in the UV down to λ ∼ 200 nm, 11,12 extraordinary mechanical strength, strong chemical and radiation resistance, and compatibility with existing silica-based components. The silica network has a high phonon energy (ṽ ∼ 1100 cm 1 ); therefore, transitions among the 6 D J , 6 I J and 6 P J energy levels in Gd 3+ -doped silica tend to be dominated by non-radiative multi-phonon relaxation due to the small energy gaps. Previous studies of Gd-doped samples in film, bulk, and powder form under electron-beam, vacuum ultraviolet (VUV), and X-ray excitation [13][14][15] suggest that the emission at λ ∼ 312 nm, given by the 6 would be a promising candidate for the generation of light in the UV.…”