Crystal growth and optical properties of Cr3+, Er3+, RE3+: Gd3Ga5O12 (RE=Tm, Ho, Eu) for mid-IR laser applications

In this paper we report on the optical properties of triply Cr3+, Er3+, and RE3+ (RE=Tm, Ho, Eu) doped Gd3Ga5O12 crystals that were grown by the Czochralski method. Optical absorption, near-infrared (NIR), and mid-infrared (mid-IR) fluorescence spectra were characterized for the fabricated crystals and corresponding luminescence decay measurements under 654 nm excitation were also carried out. Based on the analysis of energy transfer process between Er and RE (RE=Tm, Ho, Eu) ions, the energy transfer efficiency (ETE) values were evaluated, correspondingly. From the spectral data of all the studied crystals, it is observed that the co-doped Cr3+ ion highly increases the absorption pump power and the three kinds of co-doped RE3+ ions depopulate the Er:4I13/2 energy level effectively. The spectral analysis shows that titled rare earth doped crystals are promising materials for ∼3.0 μm mid-IR laser applications and among them Cr,Er,Eu:GGG is relatively more suitable due to its excellent optical properties compared with others.