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

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) [10−20 cm2] for sample doped with 1% of cerium and Ω2=10.72 (±0.33), Ω4=1.98 (±0.37), and Ω6=2.11 (±0.18) [10−20 cm2] 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 1 at% Ce is 0.5 ms (τrad=0.45 ms), while for sample doped with 3 at% of Ce, experimental lifetime is 0.45 ms (τrad=0.43 ms). Absorption bands located between 440 and 460 nm, can be utilized for optical pumping of material by GaN laser diodes. Intense and broad emission bands at 465-495 and 560-590 nm, 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 1 at% of Ce and 1 at% Dy at 575 nm corresponding to the emission of Dy3+ with a high net gain coefficient of 34 cm−1. Such high amplification was obtained under 359 nm excitation (at the maximum of intense absorption band of Ce3+ ions).