In recent years

there has been a renaissance in the study of rare earth(RE) doped materials for applying in areas such as optical data storage

lasers

sensors and optical displays.Er

3+

can originate the red and green upconversion emission under 975 nm excitation.The glass hosts with low phonon energy can reduce the nonradiative loss due to the multiphonon relaxation(MPR)

therefore the choice of host material is quite important in the development of more efficient upconversion lasers.The intensity of red and green upconversion emission attribute to the absorption of Er

3+

4

I

15/2

→

4

I

11/2

(at around 980 nm)

which present weak ground state absorption.The sensitization of Er

3+

doped materials with Yb

3+

ions is a well-known method for increasing the optical pumping efficiency.However

there has been a backward energy transfer when Yb

3+

is more than certain concentration.So it is necessary to find the optimal doping concentration of Yb

3+

.The novel Er

3+

/Yb

3+

-codoped 45Bi

2

O

3

-45GeO

2

-10PbO glasses were prepared by the technique of high temperature melting in an electronic furnace.The absorption spectra and fluorescence spectra of Er

3+

/Yb

3+

-codoped 45Bi

2

O

3

-45GeO

2

-10PbO glasses were measured and investigated.The absorption near 980 nm becomes stronger with the increasing of Yb

3+

concentration.The intense green(532 and 545 nm) and red(673 nm) emissions are observed at room temperature.The red(673 nm) emission is weaker than green(545 nm) emission while Yb

3+

concentration is low

however it becomes much stronger when the Yb

3+

concentration is high.The upconversion process involving the sequential two-photon absorption for the green and red emissions is analyzed. It is found that the optimal Yb

3+

doping content is 2.5% when the Er

3+

doping content is fixed at 0.5% according to the results of ET efficiency and upconversion fluorescence.The results suggest that this kind of glasses may be a suitable material for practical upconversion fiber optical devices.