(INVITED) Impurities in large scale produced Nd-doped phosphate laser glasses. I. Cu ions

Abstract

Impurity ions such as transition metals and rare earth metals in Nd-doped phosphate laser glasses will degrade Nd-laser performance, among which Cu is the most harmful. Divalent Cu2+ not only results in an optical loss at Nd-laser wavelength, but also reduces the energy storage for laser amplification. A large-scale production of Nd-doped phosphate laser glasses is required to meet quality demand and to realize economy of scale. To balance between the controlled impurity level in the glasses and the cost of raw materials for thousands of slabs of meter-scale Nd-doped phosphate laser glasses, it is important to determine an upper limit for Nd-laser degradation due to divalent Cu2+ ions. The absorption edge of Cu singly-doped phosphate glass prepared in an oxidizing atmosphere shows the evidence of monovalent Cu+. X-ray photoelectron spectroscopy is utilized to further verify the existence of monovalent Cu+ ions in Cu, Nd codoped phosphate glass. The results show that both Cu+ and Cu2+ ions most probably coexist in Nd-doped phosphate laser glasses produced in the oxidizing atmosphere to eliminate Pt inclusions in the glasses. Accordingly, this paper discusses the extinction coefficient and the fluorescence quench factor caused by divalent Cu2+ ions, as well as their influence. Keywords: Nd-doped phosphate laser glass, Cu+, Cu2+, XPS, Optical loss, Fluorescence quench factor