Intense visible and near infrared upconversion in M2O2S: Er (M=Y, Gd, La) phosphor under 1550nm excitation

The 1550 nm excited upconversion spectral studies of Yb 3 + and Er 3 + co doped M 2 O 2 S (M = La, Gd, Y) phosphors were reported for the first time. Studies show that all the compositions are stronger in red emission with the highest intensity in Gd 2 O 2 S and lowest in Y 2 O 2 S.The red to green emission intensity ratios are 2.7, 3.6 and 3 in Gd 2 O 2 S, La 2 O 2 S and Y 2 O 2 S respectively. Mechanisms of up conversion by multiphoton absorption and energy transfer processes are interpreted and explained.