The fluorescence properties of Cr

4+

doped inorganic glasses are of current interest

besides its potential use as a lumophore in tunable near-infrared media

Cr

4+

is also useful as a spectroscopic probe to infer information about the local environment in amorphous solids. In glass hosts

Cr

4+

ions are very likely surrounded by an oxygen tetrahedren. The Cr

4+

emission is determined by the strength of the crystal field

for low crystal field

3

T

2

is the lowest excited state

the emission is a broadband

while for high crystal field

1

E is the lowest excited state

the emission is a sharp line. Cr

4+

ions in MgCaBa-aluminate glass were found to be the case of intermediate crystal field

where the state mixing approach should be applied to analyze the emission lineshape. The room temperature fluorescence spectrum includes a sharp line at 1.18μm and a broadband in the region 1.1～1.4μm

which assigned to

1

E→

3

A

2

and

3

T

2

→

3

A

2

transition respectively. In this paper

the ASE(Amplified Spontaneous Emission) method is presented to study the optical gain

this technique could be described as below:A cylindrical lens is used to focuses laser to an equally line

then make the beam get through a length adjustable slit

detected the fluorescence from the vertical side of the sample

the emission intensity for varied excited length is:

I

(

l

)=

I

s

A/g[exp (

gl

)-1] Where

I

s

is the spontaneous emission rate per unit volume

A

is the cross sectional area of the excited volume

g

is the optical gain coefficient.Fitting the experiment result to the above equation

the optical gain coefficient of Cr

4+

:MgCaBa aluminate glass are

B

E

=(0.7±0.04)mm

-1

and

B

T

=(0.05±0.005)mm

-1

at 1.18μm and 1.24μm respectively.