ORIGIN OF THE INFRARED ABSORPTION IN LaMgAl₁₁O₁₉ : Ti³⁺ A POTENTIAL LASER MATERIAL

Abstract
The LaMgAl₁₁O₁₉ matrix (magnetoplumbite structure) activated with Ti₃₊ could present broadly tunable laser action between 650 and 1000 nm. The optical absorption measurements show, in addition to the ²T₂²E transition of Ti³⁺, two unexpected infrared bands. The first one, peaking at 730 nm, is attributed to an intervalence charge transfer transition of Ti³⁺ - Ti⁴⁺ pairs located in (4f) sites. The second one, at 960 nm, is attributed to a Ti²⁺ - Ti³⁺ charge transfer transition. These bands which occur in the range of the Ti³⁺ fluorescence wavelengths have to be suppressed for the lasing application of this material.