Down-conversion from blue to near infrared in Tm³⁺-Yb ³⁺ codoped Y₂O₃ transparent ceramics

Down-conversion from blue to near infrared (NIR) has been demonstrated in Tm³⁺-Yb³⁺ codoped Y₂O₃ transparent ceramics. Upon the 464-nm excitation, the energy transfer (ET) mechanisms consisted of the Tm³⁺ : ¹G₄→ 2Yb ³⁺ : ²F_5/2 cooperative down-conversion and the phonon assisted Tm³⁺ : ¹G₄+Yb³⁺ : ²F_7/2 → Tm³⁺ : ³H₅ + Yb³⁺ : ²F_5/2 cross relaxation. The low quantum yield of the latter process, together with the low absorption cross section of Tm³⁺ at 464 nm and the low quenching concentration of Yb³⁺ in the Y₂O₃ host, made the Yb³⁺ 1030-nm NIR emission too weak for practical application.