Melt-Quenched Pure and Neodymium-Doped AlCOB Glasses: A Study of Optical and Structural Properties

Abstract

Pure AlCOB and Nd:AlCOB glasses with compositions xNd 2 O 3 -(1-x)Al 2 O 3 -8CaO-3B 2 O 3 (x = 0 and 0.05) were prepared by the melt-quenching method and characterized by XRD, EDAX, FTIR, DTA, UV–Vis–NIR spectroscopy, photoluminescence and Z-scan measurements. XRD confirmed the amorphous nature of both glasses, while FTIR identified BO 3 - and BO 4 -based structural units. The optical cut-off shifted from 326 to 374 nm after Nd 2 O 3 addition, and the effective directallowed Tauc gap decreased from 3.72 ± 0.03 to 3.11 ± 0.03 eV. The reduction is associated with Nd-induced short-range network distortion, non-bridging oxygen formation, localized states and increased polarizability. Nd:AlCOB showed T_g at 421 °C and crystallization events near 512 and 582 °C. Under 582 nm excitation, emission bands occurred at 985/997, 1060 and 1330 nm, corresponding to transitions from the 4 F 3/2 level. The intense 1.06 μm emission and measurable third-order optical nonlinearity indicate the potential of Nd:AlCOB as a near-infrared laser-active and nonlinear optical glass.