Spectroscopy and diode-pumped laser operation of transparent Tm:Lu3Al5O12 ceramics produced by solid-state sintering

Abstract

A transparent Tm:Lu3Al5O12 ceramic is fabricated by solid-state reactive sintering at 1830 degrees C for 30 h using commercial alpha-Al2O3 and Lu2O3/Tm2O3 powders and sintering aids - MgO and TEOS. The ceramic belongs to the cubic system and exhibits a close-packed structure (mean grain size: 21 mu m). The in-line transmission at similar to 1 mu m is 82.6%, close to the theoretical limit. The spectroscopic properties of the ceramic are studied in detail. The maximum stimulated-emission cross-section is 2.37x10(-21) cm(2) at 1749nm and the radiative lifetime of the F-3(4) state is about 10 ms. The modified Judd-Ofelt theory accounting for configuration interaction is applied to determine the transition probabilities of Tm3+, yielding the intensity parameters Omega(2) =2.507, Omega(4) = 1.236, Omega(6) = 1.340 [10(-20) cm(2)] and alpha = 0.196x10(-4) cm. The effect of excited configurations on lower-lying interconnected states with the same J quantum number is discussed. First laser operation is achieved under diode-pumping at 792 nm. A 4 at.% Tm:Lu3Al5O12 ceramic laser generated 3.12 W at 2022-2035nm with a slope efficiency of 60.2%. The ceramic is promising for multi-watt lasers at >2 mu m.