Investigation of spectroscopic properties and energy transfer between Ce and Dy in (Lu0.2Gd0.8−x−yCexDyy)2SiO5 single crystals

Abstract

In this paper we present results of spectroscopic investigations of single crystals with general formula (Lu0.2Gd0.8−x−y)2SiO5 codoped with x% of Ce3+ and y% of Dy3+ ions. Investigated materials exhibit strong optical anisotropy what can be easily observed in polarized absorption and emission spectra. Based on room temperature polarized absorption spectra calculations in framework of phenomenological Judd–Ofelt model was carried out. Intensity parameters Ωt were evaluated to be Ω2=7.08 (±0.39), Ω4=2.76 (±0.44), and Ω6=3.36 (±0.21) [10−20cm2] for sample doped with 1% of cerium and Ω2=10.72 (±0.33), Ω4=1.98 (±0.37), and Ω6=2.11 (±0.18) [10−20cm2] for sample doped with 3% of cerium. Influence of cerium admixture on Judd Ofelt intensity parameters is discussed. Value of experimental lifetime of 4F9/2 multiplet of Dy3+ ion in sample doped with 1at% Ce is 0.5ms (τrad=0.45ms), while for sample doped with 3at% of Ce, experimental lifetime is 0.45ms (τrad=0.43ms). Absorption bands located between 440 and 460nm, can be utilized for optical pumping of material by GaN laser diodes. Intense and broad emission bands at 465–495 and 560–590nm, with experimental branching ratio strongly depending on polarization, give high chance for obtaining white luminophore, due to appropiate mixing of blue and yellow luminescence. By means of a pump and probe experiment optical amplification was demonstrated in the codoped sample with 1at% of Ce and 1at% Dy at 575nm corresponding to the emission of Dy3+ with a high net gain coefficient of 34cm−1. Such high amplification was obtained under 359nm excitation (at the maximum of intense absorption band of Ce3+ ions).