Tellurite glass has attracted considerable attention and development effort as a host for broad EDFA and EDWA.But the phonon energy of tellurite glass is relatively low as 770 cm

-1

thus

the

4

I

11/2

→

4

I

13/2

nonradiative decay is too slow to allow pumping at 980 nm.Tungsten-tellurite glass has higher phonon energy of 930 cm

-1

which makes it possible pumping at 980 nm.The 1.5 μm emission bandwidth of Er

3+

in tungsten-tellurite glass is also broad.The spectroscopic properties of Yb

3+

/Er

3+

-codoped TeO

2

-WO

3

-ZnO (TWZ) glasses were investigated

too. The Yb

3+

/Er

3+

-codoped TWZ glasses were prepared by traditional melting-quenching method.The absorption cross-section was calculated based on measured absorption spectra at room temperature.The emission cross-section was calculated by McCumber theory.The peak values of absorption cross-section and emission cross-section at 1.5 μm are 0.78 pm

2

and 0.90 pm

2

respectively.The 1.5 μm emission spectra

upconversion emission spectra and fluorescence lifetimes of Er

3+

excited at 970 nm

were also measured.The dependence of Yb

3+

doping concentration on the 1.5 μm emission and upconversion luminescence of Er

3+

was studied.The calculated energy transfer efficiency from Yb

3+

to Er

3+

in Yb

3+

/Er

3+

-codoped TWZ glasses is about 65%.Yb

3+

-codoping can enhance the 1.5 μm emission intensity effectively.The optimum Yb

3+

doping concentration is about 7.28×10

20

ions/cm

3

which is triple of the Er

3+

doping concentration.The emission bandwidths of Er

3+

at 1.5 μm in Yb

3+

/Er

3+

-codoped TWZ glasses are broad and the obtained full width at half maximum is between 67 nm and 72 nm.Three upconversion emission bands centered at about 533

547 and 668 nm

were observed.The three emission bands originate from the radiative transitions

2

H

11/2

→

4

I

15/2

4

S

3/2

→

4

I

15/2

and

4

F

9/2

→

4

I

15/2

respectively.The green and red upconversion emission are both double-photon process.With the increasing of Yb

3+

doping concentration

the green and red upconversion emission intensity both increase.This can be ascribed to the increased energy transfer rate from Yb

3+

to Er

3+

.