Efficient upconversion luminescence in Er3+/Yb3+ co-doped cubic NaYF4 single crystals by vertical Bridgman method with KF flux

摘要

Er3+/Yb3+ co-doped alpha-NaYF4 single crystals with various Yb3+ concentrations and -0.50 mol Er3+ were grown by Bridgman method using Potassium fluoride as flux. The up-conversion (UC) luminescence and its pump power dependence on UC emission of the crystals under excitation of 980 nm laser diode were investigated. The UC emissions at green similar to 522 nm,-541 nm and red-668 nm, which are attributed to H-2(11/2) --> I-4(15/2), S-4(3/2) --> I-4(15/2) and F-4(9/2) --> I-4(15/2), respectively, were obtained in Er3+/Yb3+ doped alpha-NaYF4 single crystals. The quadratic dependence of pump power on the UC emission suggests that a two-photon process is responsible for the transition from the excited Yb3+ to the lower state of Er3+ ions in alpha-NaYF4 single crystals. A favorable performance of yellowish green light can be achieved with certain Yb3+ concentrations and 0.52 mol Er3+ co-doped samples that makes further research valuable in developing UC displays for electro-optical devices. (C) 2016 The Physical Society of the Republic of China (Taiwan). Published by Elsevier B.V. All rights reserved.