Upconversion luminescence of Er3+ in Cd X 2 system glasses ( X =Cl, Br, I)

Near-infrared to visible upconversion characteristics of Er3+ in CdX2-based halide glasses (X=Cl, Br, or I) has been investigated. When 4I9/2 state is pumped by 800 nm radiation from an AlGaAs laser diode, the upconverted green emissions (520–560 nm) of 2H11/2+4S3/2→I15/2 transition are clearly observed in all the glasses. The linewidth of green emission in these glasses becomes narrow in the order of chloride, bromide, and iodide. The CdCl2 and CdBr2 system glasses give blue upconversion luminescence (around 410 nm) due to the 2H9/2→I15/2 transition, but this emission is not observed in the CdI2 system glass because of the absorption edge at around 450 nm. The fluorescence spectra of CdX2 system glasses suggest that the multiphonon relaxation rate depends on choice of the X species.