Thulium-doped barium tellurite glasses: structural, thermal, linear, and non-linear optical investigations

A systematic study of structural, thermal, linear, and non-linear optical properties on 60TeO 2 –20ZnO–(16 − x)BaCO 3 –4BaF 2 –xTm 2 O 3 ( x = 0.25 to 2 mol%) glasses synthesized by melt-quenching technique is reported. Thermal stability of the samples was found to be around 100 °C, while their energy bandgap values varied between 3.08 and 3.57 eV. Measured properties showed a dominant effect of thulium ions in modifying the properties of the glassy matrix. Structural studies using Raman spectroscopy showed the presence of non-bridging oxygen (NBO) dominated by the matrix effect and also aided by the rare earth dopants, while the presence of hydroxyl impurities was elucidated from infrared spectroscopy. Optical absorption spectra showed characteristic thulium bands and the increment in spectroscopic quality factor calculated from measured absorption data indicating the lasing capability of the material. Luminescence spectra yielded two strong 3 H 4 → 3 F 4 and 3 F 4 → 3 H 6 emission transitions in the infrared region around 1460 nm and 1863 nm for all the samples, intensities of which were affected by increasing rare earth concentrations. Open aperture Z-Scan measurements indicated a reverse saturable absorption behavior for all the samples owing to two-photon absorption. Formation of more NBO led to the reduction of optical limiting threshold values from 3.91 × 10 12 to 2.38 × 10 12 W/m 2 with thulium doping which indicated that this glass can be tuned to act as mid-infrared source as well as excellent optical limiter.