Photoinduced non-linear optics of Eu2O3 DOPED TeO2–GeO2–PbO glasses

During the coherent bicolour optical treatment of Eu2O3 doped telluride glasses at temperatures near the glassing points, an efficient second-order susceptibility equal to about 2.1 pm V−1 at fundamental wavelength 1907 nm was achieved. Bicolour optical treatment was performed by two coherent laser beams originating from 50 ps Nd-YAG laser (λ = 1.32 µm) exciting the high pressure hydrogen laser cell emitting at 1907 nm. The non-centrosymmetric grating of the medium was formed by coherent superposition of the fundamental laser at 1907 nm and the doubled frequency one at 953.5 nm. The maximal optical second harmonic generation (SHG) signal occurs for 0.5% of Eu2O3 (in wt%). It was discovered that the photoinduced SHG achieves saturation during the treatment at about 6–8 min. The ratio between the fundamental beam with power density of about 1.3 GW cm−2 and the writing beam of about 0.024 GW cm−2 corresponds to the optimal photoinduced SHG. The remaining value of the photoinduced SHG is larger for the samples with higher second-order susceptibility. It is necessary to emphasize that the efficient grating process is possible only within the narrow temperature range corresponding to the glassing phase transitions and the effect disappeared for nondoped glasses and for glasses doped with 5% of Eu2O3 (in wt%). Possible physical mechanisms of the phenomenon observed are discussed.