Effect of Nd2O3 Concentration on Crystallization Mechanism and Third-Order Optical Nonlinearity of Lanthanide-Titanium-Tellurite Glass and Glass-Ceramics

Rare-earth (RE)-doped transparent tellurite glass-ceramics (GCs) embedded with "anti-glass" crystallites not only exhibit superior emission properties but can also be a potential medium for nonlinear optical (NLO) applications. Both of these properties depend on their transparency. Keeping this in view, we aimed to elucidate the effect of Nd3+ ion concentration (0.5–2 mol %) on the crystallization mechanism of lanthanum-gadolinium-titanium-tellurite (LGTT) glass in retaining the transparency and NLO properties. XRD reveals the precipitation of (La/Nd)2T6O15 and Gd2Te6O15 "anti-glass" crystallites upon ceramization of these glasses. Particle-size-dependent DSC confirms competition between the growth of these two crystalline phases at higher Nd3+ concentration that aids in controlling crystal growth. The FE-SEM microstructures demonstrate a change in morphology of the crystallites from rectangular (1.5 μm) to spherical (120 nm) with increasing Nd2O3 concentration from 0.5 to 2 mol % and thereby retaining optical transparency (12% → 55%) in GCs. Photoluminescence spectra reveal a maximum emission intensity for 1 mol % of Nd2O3-doped glass; however, the lifetime is maximum (156 μs) for 0.5% Nd2O3 doping. This study also discloses an enhancement of third-order NLO properties as a function of Nd2O3 concentration in LGTT glasses under femtosecond laser excitation at 800–1200 nm due to resonant nonlinearity. Emission intensity and NLO responses are increased in the GCs compared to their parent glasses. A maximum nonlinear absorption coefficient (α2) of 4.986 × 10–10 m/W and nonlinear refractive index (n2) of 3.115× 10–17 m2/W has been obtained from LGTT-Nd2(GC-36h) GCs at 800 nm. GCs exhibits an optical limiting threshold of 4.14 mJ/cm2, suggesting its great potential for intense radiation shielding.