Upconversion luminescence of Er3+ in chloride glasses based on ZnCl2 or CdCl2

Abstract

Upconversion luminescence of Er³⁺ in the chloride glass system has been investigated in ZnCl₂‐BaCl₂‐KCl‐ErCl₃ and CdCl₂‐BaCl₂‐KCl‐ErCl₃ glasses. Under 800 nm excitation, the glasses gave upconversion luminescence with barely detectable red (around 660 nm), very intense green (around 525–560 nm), and considerably intense blue (around 410 nm) emissions. The intensity of blue emissions was far stronger than that observed for any of other Er³⁺‐doped glass systems, revealing that Er³⁺‐doped chloride glasses can efficiently convert the infrared light into much shorter wavelengths. The green emission is attributed not only to the thermally coupled ²H_11/2 and ⁴S_3/2→⁴I_15/2 transition but also to the ²H_9/2→⁴I_13/2 transition. The blue emission is due to the ²H_9/2→⁴I_15/2 transition. The blue and green upconversion luminescence results from a two‐photon process.