Spectroscopic properties of Er3+ doped bismuth leadtelluroborate glasses for 1.53 μm optical amplifiers

Abstract

A new series of Er3+ doped bismuth leadtelluroborate glasses with the composition 25TeO2+10H3BO3+30PbO+(25−x)Bi2O3+10CdO+xEr2O3 were prepared by varying the Er3+ ion content following melt quenching technique and their spectroscopic behaviours were studied through XRD, SEM, EDS, FTIR, Raman, absorption, luminescence and decay measurements. The local structure around the Er3+ ions were investigated using phonon side band (PSB) spectra and their phonon modes are correlated with the FTIR and Raman spectral measurements. The Judd–Ofelt (JO) theory has been applied to interpret the local environment of the Er3+ ion site and covalency of the Er–O bond. The various lasing parameters such as stimulated emission cross-section (σpE), experimental and calculated branching ratios (βR) and radiative lifetime (τcal) have been calculated for the 4S3/2→4I15/2 and 4I13/2→4I15/2 emission transitions. The luminescence intensity decreases with the increase in Er3+ ion concentration beyond 0.5wt% and the same was discussed through various energy transfer mechanism take place between Er3+ ions. The absorption and emission cross-section for the 4I13/2→4I15/2 transition (1.532μm) were calculated using McCumbar theory and compared with the reported Er3+ doped glasses. Further, the results obtained from the McCumbar theory also found to be in good agreement with the results obtained from JO theory. The gain coefficient (G) of the 1.532μm emission band also calculated using absorption and emission cross-sections to explore the suitability of the prepared glasses for broad band amplification. The decay curves of the 4I13/2 level have been measured and the fall in lifetime value with the increase in Er3+ ion content can be attributed to the cross-relaxation between Er3+ ions to the free OH− radical and non-radiative rate through the OH content and the same has been discussed and compared with the reported Er3+ doped glasses. The decay curves have been analysed through Inokuti–Hirayama model to identify the nature of the energy transfer among the Er3+ ions and the electrostatic dipole–dipole interactions are responsible for the dominant energy transfer takes place between Er3+–Er3+ ions.