Demonstrations of upconversion pumped by solid state lasers have enhanced the interest in excitation mechanisms that result in emission with wavelengths shorter thanthat of the pump light. Efficient upconversion is possible in rare earth-doped materials with metastable

intermediate levels that can act as a storage reservoir for the pump energy. Subsequent emission from higher lying state

can be induced by excited stateabsorption of pump photons

or by energy transfer processes. The aim of this work isgive a method for study on the optical gain of upconversion luminescence. We have astudy for optical gain of upconversion of Tm

3+

in MFT glass under 650nm excitation

and in our experimental conditions the gain coefficient of the blue upconversion luminescence of Tm

3+

were obtained by ASE techniques.In this paper

the preparation of new glass material MFT (components with 50TeO

2

-19.7PbF

2

-10AIF

3

-10BaF

3

-10BaF

2

-0.3Tm

2

O

3

) has been reported. Two blue upconversion luminescence from

1

D

2

→

3

H

4

(453nm) and

1

G

4

→

3

H

6

(476nm) transitions of Tm

3+

-doped in MFT glass under 650nm excitation has been observed. The relationshipbetween upconversion luminescence intensity and the intensity of excitation light hasbeen discussed. The optical gains of blue upconversion of Tm

3+

in MFT were measuredusing ASE technique for the first time. The values of optical gain coefficient is B

D

=1.79±0.16mm

-1

and B

G

=1.65±0.23mm

-1

for

1

D

2

→

3

H

4

and

1

G

4

→

3

H

6

emissions respectively.