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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

The luminescence parameters of Yb3+:Er3+-doped LiLa(WO4)(2) single crystal grown in the form of fiber for up-conversion green emission

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Author(s):
Gomes, Laercio ; Denaldi, Rafael Lima ; de Moraes, Jair Ricardo ; Baldochi, Sonia Licia
Total Authors: 4
Document type: Journal article
Source: Journal of Luminescence; v. 187, p. 479-485, JUL 2017.
Web of Science Citations: 2
Abstract

This report details the first study of the luminescence properties of a single crystal grown in the form of fiber for prospective application as the gain medium for fiber laser emission at 552 nm. The excited state decay processes related with the S-4(3/2)-> I-4(15/2) transition in double Yb3+:Er3+-doped LiLa(WO4)(2) crystal have been investigated using time-resolved fluorescence spectroscopy with a Er3+ concentration of 0.5 mol% and Yb3+ with 2, 5, 7, 10 and 15 mol%. Selective laser excitation of the F-2(5/2) energy level of Yb3+(972 nm) and selective laser excitations of the I-4(11/2) and I-4(13/2) energy levels of Er3+( 972 and 1550 nm), respectively has established that in a similar way to other optical materials, a strong energy-transfer up-conversion by way of a dipole-dipole interactions between an Yb3+ excited and Er3+ ions, the F-4(5/2) level (Yb3+) populates the S-4(3/2) upper laser level of the 550 nm transition. The S-4(3/2) energy level emits luminescence with peaks having the wavelength center at 550 nm with luminescence efficiency increasing from 7% for Er3+ singly doped to 36% for Yb3+(15 mol%) co-doped crystals. The S-4(3/2) lifetime of Er3+ is observed to increase due to the saturation of the multiphonon relaxation rate at high excited-state density of Yb3+ ions. At high excited-state density, Yb3+ ions saturates the accepting modes inside of a critical volume of R-C=39.4 angstrom centered at an excited Er3+(S-4(3/2)) ion, by the high-energy phonons generated from emission sideband of Yb3+ ions in Yb(x%): Er(0.5%) crystals. It is established that the green (552 nm) up-conversion luminescence of Er3+ is optimized using an Yb3+ concentration of 11.5 mol% for Er(0.5%): LiLa (WO4)(2) crystal. (AU)