Dm2700 microscope

Confocal images were recorded using an inVia™ confocal Raman microscope spectrometer (Renishaw plc, Gloucestershire, UK) equipped with a 633 nm excitation laser line and a Leica DM2700 microscope with 5×, 20×, 50× and 100× objectives and a Deep Depletion Renishaw CCD Centrus array detector (Renishaw plc, Gloucestershire, UK).

Pr ${}^{3+}$ /Yb ${}^{3+}$ codoped lead-bismuth-borate glasses were prepared by melt-quenching method. The glasses have molar composition of $(59.5-x)B_2{O}_3+25B{i}_2{O}_3+15PbO+0.5P{r}_6{O}_{11}+xY{b}_2{O}_3$ (x = 0, 0.1, 0.5, 1.0, 2.0 and 3.0). Analytical grade reagents of $H_{3}B{O}_3$ , $B{i}_2{O}_3$ , PbO, $P{r}_6{O}_{11}$ and $Y{b}_2{O}_3$ were used as raw materials, from which nominal batches of 10 g were prepared and mixed in an agate mortar. Then, the mixture was melted in porcelain crucible at 1050 ${}^{\circ }$ C in air for 1 h 30 min and melt was poured into stainless steel moulds. The obtained glass samples were cut and polished for optical characterization.
Differential Scanning Calorimetry was performed with NETZSCH DSC 404F3 with heating rate of 10 ${}^{\circ }$ C/min in order to determine the glass transition $(T_g)$ and crystallization temperature $(T_x)$ of the glass samples. Raman spectra were recorded with a Renishaw inVia spectrometer coupled with a Leica DM2700 microscope with 633 nm laser excitation. Optical absorption spectra of the glass were recorded on UV-2500 (SHIMADZU) and NIR (BRUKER MPA—Multi Purpose Analyzer) spectrophotometers. Luminescence measurements were performed on Florolog3-iHR HORIBA fluorescence spectrometer upon 443 nm excitation. Density of the glass samples were estimated with distilled water as immersion liquid by Archimedes’ method. All the measurements were conducted at room temperature.