Reversible photoinduced change of refractive index in ion-conducting chalcohalide glass

When irradiated by the focused Ar+ ion laser of below band-gap photon energy (2.41 and 2.54eV), a large increase of refractive index (e.g., Δn=6% at 1550nm) was observed in 60GeS2–20Ga2S3–20AgI bulk glass (with bandgap of 2.71eV). We found it surprisingly that such a large Δn quickly smeared out after the illumination even at room temperature, i.e., the refractive index will return to almost initial value within only 2h. It is fairly rare among chalcogenides ever reported. The plausible correlation between the photorefraction effect and the ion-conducting property of glasses was also suggested.