1.3 MU-M TO VISIBLE UP-CONVERSION IN DY3+-CODOPED AND ER3+-CODOPED BACL2 PHOSPHOR

1.3 mum to visible upconversion is observed in a BaCl2:Dy,Er phosphor system. Yellow fluorescence is visible under 1.3 mum laser diode (5 mW) irradiation. Radiative transitions from the S-4(3/2) and F-4(9/2) levels to the ground level I-4(15/2) of the Er3+ ions cause fluorescence lines at 550 and 670 nm, respectively. This indicates that Dy3+ ions act as absorption centers at 1.3 mum (H-6(15/2)-H-6(9/2) transition) and also as energy donors to the Er3+ ions. We conclude that the suppression of multiphonon relaxation from the H-6(9/2) excited level to the lower levels of Dy3+ resulting from the low phonon energy chloride matrix, plays an important role in the upconversion process.