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Structural properties of Tm 3+ doped AsS -Ga glasses were investigated using Raman spectroscopy and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy at As Kedge, Ga K-edge and Tm L 3-edge. The Raman spectra are interpreted on the basis of comparison with the well-known Raman spectra of As 2 S 3 glasses the structure of which mainly consists of pyramidal [AsS 3/2 ] units interconnected by S-S chains. Incorporation of Ga 2 S 3 in As 2 S 3 glass matrix induced the dissociation of S-S chains in behalf of the formation of tetrahedra [GaS 4 ]. Moreover, introduction of Tm into AsS -Ga glasses forms Tm-S bonds through the further dissociation of [AsS 3/2 ] pyramidal units. The deficiency of S in the glasses is compensated with the formation of As 4 S 4 structural units. The EXAFS results indicate that GaS bond distance in the tetrahedra [GaS 4 ] decreases from 2.29Å to 2.26Å with the increase of Tm concentration in the glass. Meanwhile, Tm-S bond distance increases from 2.66Å to 2.71Å approaching to that of crystalline Tm 2 S 3 and simultaneously, the coordination number of Tm gradually decreases from 7 to 4.

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