Optical Absorption and NIR Photoluminescence of Nd 3+ -Activated Strontium Phosphate Glasses

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https://doi.org/10.1007/s11664-020-08383-5  2020 The Minerals, Metals & Materials Society

Optical Absorption and NIR Photoluminescence of Nd3+-Activated Strontium Phosphate Glasses R.N.A. PRASAD,1 N. VIJAYA,2 P. BABU,3 N. KRISHNA MOHAN,1 and R. PRAVEENA 4,5 1.—Department of Physics, Akkineni Nageswara Rao College, Gudivada 521 301, India. 2.—Department of Physics, Sri Venkateswara University, Tirupati 517 502, India. 3.—Department of Physics, Government Degree College, Palamaner 517 408, India. 4.—Department of Physics, Gayatri Vidya Parishad College of Engineering (A), Visakhapatnam 530 048, India. 5.—e-mail: [email protected]

Strontium phosphate glasses with various concentrations of Nd2O3 have been prepared by melt quenching method. Absorption and photoluminescence spectra and lifetime measurements have been carried out to obtain the optical properties of these glasses. From the absorption spectrum, intensity and radiative parameters have been evaluated using Judd–Ofelt analysis. Nearinfrared photoluminescence spectra consist of three bands centered at 875 nm, 1056 nm and 1327 nm, among which the highest intensity has been noticed for the band at 1056 nm that corresponds to the 4F3/2 fi 4F11/2 transition of Nd3+ ion. Laser parameters such as branching ratio, band width, stimulated emission cross section and gain bandwidth for the 4F3/2 fi 4F11/2 transition are found to be 0.52, 28 nm, 2.31 9 1020 cm2 and 6.5 9 1026 cm3, respectively. Decay curves of the 4F3/2 level of Nd3+ ions exhibit a single exponential nature at lower concentrations, while they become non-exponential at higher concentrations (‡ 0.1 mol.%) due to non-radiative energy transfer processes. This feature is also associated with shortening of lifetime from 307 ls to 82 ls when the Nd3+ ion concentration increases from 0.1 mol.% to 4.0 mol.%. The results have been compared with those of barium and magnesium phosphate glasses and commercial glasses. The results suggest that these glasses have potential applications as infrared laser materials at 1.05 lm. Key words: Nd3+ ion, strontium phosphate glasses, JO parameters, NIR luminescence, laser applications

INTRODUCTION Trivalent lanthanide (Ln3+) ion-doped glasses have attracted much attention as they have potential applications in the fields of plasma display panels, photovoltaics, antibacterial activity, optical detectors, fiber grating, drug carriers, photocatalysis, lasers, fiber amplifiers, waveguides and telecommunications.1–3 Owing to the optical properties of the Ln3+-doped glasses and with the prompt evolution of the diode-pumped solid-state lasers,

(Received February 21, 2020; accepted July 31, 2020)

investigation on newly developed laser glasses has gained more attention.4,5 Among the various Ln3+ ions, Nd3+ ion is one of the important and most extensively studied ions for near-infrared (NIR) lasers as it emits very useful wavelengths at 880 nm, 1050 nm, 1350 nm and 1800 nm corresponding to 4F3/2 fi 4IJ/2 (J = 9, 11, 13 and 15) transitions, respectively. Out of these four transitions