Nd³⁺-Doped Lead Boro Selenate Glass: A New Efficient System for Near-Infrared 1.06 μm Laser Emission

An exotic series of glasses with the composition 39PbO—(60–x)B₂O₃–xSeO₂:1.0 Nd₂O₃ (10 ≤ x ≤ 50) is prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) techniques. Results of infrared (IR), Raman, and X-ray photoelectron spectroscopy (XPS) studies reveal that the glass network comprises quarantined selenite [SeO₃]²⁻ groups (that act as modifiers) and selenate [SeO₄]²⁻ groups in addition to BO₃ and BO₄ units. With the increase in SeO₂ content, the concentration of selenite groups is found to be dominant. The optical absorption (OA) spectra exhibit several bands due to ⁴I_9/2→²P_1/2, ²G_9/2, ⁴G_9/2,7/2,5/2, ²H_11/2, and ⁴F_{9/2, 7/2,5/2,3/2} transitions. The spectra are characterized using J–O theory and J–O parameters are found to follow the order: Ω₂ > Ω₆ > Ω₄. The emission spectra recorded at λ_exc= 808 nm exhibit bands due to ⁴F_3/2 → ⁴I_9/2, ⁴I_11/2, and ⁴I_13/2 transitions. With increase in SeO₂ content, intensity of all emission bands significantly increases. The quantum efficiency evaluated from the measured and calculated lifetimes of the ⁴F_3/2 → ⁴I_11/2 transition is found to be enhanced by 20% with increase in SeO₂ from 10 to 50 mol%. The spectra are further analyzed quantitatively using kinetic rate equations of various excited levels and the reasons for enhancement of photoluminescence (PL) emission are identified and discussed.