Spectroscopic investigations of Sm3+-doped lead alumino-borate glasses containing zinc, lithium and barium oxides

Sm3+ doped lead alumino-borate glasses containing ZnO, Li2O and BaO were synthesized and characterized for their structural and spectroscopic properties using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), optical absorption and luminescence measurements. The FTIR spectra, optical band gap and the values of density indicate formation of more BO4 units and a compact structure for the glass containing ZnO. Using optical absorption spectra, three phenomenological Judd-Ofelt parameters Ωλ (λ = 2, 4, 6) have been evaluated to determine the local structure and bonding in the vicinity of Sm3+ ions; the parameters are found to follow the trend Ω4> Ω6> Ω2. The parameter Ω2, which indicates the covalency of SmO bond is found to be maximum for the glass containing zinc oxide followed by glasses with barium oxide and lithium oxide, in the decreasing order. . This result points towards a higher asymmetry and a less centro-symmetric coordination environment around the Sm3+ ions site for glass containing ZnO. The positive values of bonding parameter δ indicate a covalent nature of the SmO bond for the glasses under study. The photoluminescence spectra recorded under an excitation of 402 nm exhibited four emission bands centered at about 562 nm, 597 nm, 642 nm and 706 nm corresponding to the transitions 4G5/2 → 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively. The intensity of potential emission bands and radiative parameters such as branching ratio (βR) and stimulated emission cross-section (σ) are found to be higher for the glass containing zinc oxide. However, all other prepared glasses are also found to be efficient lasing materials showing suitability for the development of photonic materials emitting radiations in the reddish-orange range. The values of Figure of Merit (FOM) point towards a possible use of the prepared glasses as optical amplifier devices.