Recently

Yb

3+

doped solid-state materials are attractively used as gain media of high efficiency

high power laser with the development of InGaAs laser diode. Yb

3+

doped laser glass enable diode pumping without temperature stabilization because it has larger inhomogeneous width of the absorption lines. Due to broad emission lines around 1.02μm

Yb

3+

doped glass also is a good candidate as a pump source for Pr 3+ doped laser fiber

which has potential application as amplifiers in the 1.3μm communication window. Determination of energy levels and other spectroscopic parameters of interest for Yb

3+

laser action in glass is difficult because the inhomogeneous broadening of optical spectra is comparable to the Starke splitting

and hence masked the structure. However

a study of the energetic parameters of lasers and amplifiers require knowledge of the ratio between the homogeneous and inhomogeneous width of transitions. In this paper the absorption spectra of Yb

3+

doped phosphate glass were measured at different temperatures and the blue-shift of the absorption peaks was discovered. There was abnormal absorption line in absorption spectra at low temperatures

which arised possible from another group of sites occupied by small partial Yb

3+

ions. Due to the addition of B

2

O

3

Al

2

O

3

and Nb

2

O

3

[BO

4

]

[BO

3

]

[AlO

4

]and [NbO

6

]partially take the place of PO

4

tetrahedral as network formers. The [PO

4

]-Yb

[AlO

4

]-Yb

[BO

3

]-Yb and [NbO

6

]-Yb bond distances must be different and cause the great break of the symmetry of the coordination sphere of oxygens around Yb

3+

ions. When a coordination sphere is surrounded by such network formers which possess different cationic field strengths

polarizabilities and coordination numbers of oxygen

the characteristic of Yb-O bond are varied and the local structures in the vicinity of the emitting ions may be distorted strongly

which result that a small portion of ytterbium ions reside in another type sites different from those occupied by the ytterbium ions which give rise to the principal spectra. The energy levels of Yb

3+

ion in phosphate glass were obtained according to the absorption and emission spectra at low temperature. The sites selective fluorescence spectra had been investigated at low temperature

too.