Enhanced infrared to visible upconversion emission in Er3+ doped phosphate glass: role of silver nanoparticles

Abstract

Phosphate glasses containing fixed concentration of rare-earth with and without metallic nanoparticles (NPs) having compositions (59.5-x) P2O5-MgO-xAgCl-0.5Er2O3, where 0 = x = 1.5 mol% was prepared using melt-quenching technique. Spectral characterizations were made using UV-VIS-IR spectroscopy and photoluminescence spectroscopy. Addition of silver NPs enhanced the corresponding absorption and was optimum at 1.5 mol% AgCl. Infrared to visible frequency upconversion (UC) emission were observed in the glass on pumping with 797 nm radiation. Furthermore, it was found that the emission at 540 nm, due to Er3+transition (4S3/2-4I15/2) was much more influenced by the silver NPs in comparison to the emission at 632 nm (4F9/2 - 4I15/2). These enhancements were attributed to the local fields present in the vicinity of silver NPs. Moreover, the rapid increase in the intensity of the green band as compared to the red band was due to the charge cloud effect of the plasmon band. Since green band lie more close to the plasmon frequency band of Ag and hence showed rapid increase compared to the far lying red bands. Our findings may contribute towards the development of solid state laser and sensors