Spectroscopy and efficient laser operation around 2.8 μm of Er:(Lu,Sc)2O3 sesquioxide cera

Abstract

A transparent “mixed” 7 at.% Er:(Lu,Sc)2O3 sesquioxide ceramic was fabricated by hot isostatic pressing of commercial sesquioxide powders at 1750°C/200 MPa in argon atmosphere. It exhibited a cubic bixbyite-type structure (a = 10.198 Å), a mean grain size of 5.7 μm and high low-signal transmission of 79.1% in the near-IR. The spectroscopic properties of Er3+ ions were studied. For the 4I11/2 → 4I13/2 transition, the stimulated-emission cross-section σSE is 1.30 × 10−20 cm2 at 2719 nm, the corresponding luminescence branching ratio B(JJ’) is 19.9% and the radiative lifetime of the 4I11/2 state is 4.80 ms, as determined using a Judd-Ofelt theory accounting for intermediate configuration interaction. The crystal-field splitting of Er3+ multiplets was studied at 12K. The ceramic exhibits a significant inhomogeneous broadening of spectral bands. An Er:(Lu,Sc)2O3 ceramic laser generated 342 mW at 2.71 and 2.85 μm with a high slope efficiency of 41.7% (exceeding the Stokes limit) and a laser threshold of 125 mW.