Optical properties of 3d transition metal ion-doped aluminophosphate glasses

P₂O₅–Al₂O₃–SiO₂-GeO₂-Li₂O glasses doped with 3 d-transition metal (TM) ions from Sc to Zn were prepared by the conventional melting-quenching method. Their optical properties were investigated. The oxidation states, which were revealed from the UV–vis–NIR transmittance spectra, excitation and emission spectra of the studied glasses, are Sc(III), Ti(III), V(III), Cr(III), Mn(II), Fe(II,III), Co(II), Ni(II), Cu(I, II) and Zn(II). Scandium exhibits weak, broad emission at 321 nm in aluminophosphate glass probably ascribed to the formation of the Sc_Al center. Cr³⁺ emission at 890 nm due to the ⁴T₂(⁴F)→⁴A₂(⁴F) transition of Cr³⁺ ions at the weak crystal field octahedral sites was observed under excitation at 296, 457, 658, and 684 nm. Mn²⁺ emission at 603 nm with a distinct shoulder at ∼513 nm due to the ⁴T₁(⁴G) → ⁶A₁(⁶S) transition of Mn²⁺ ions in an octahedral coordination and tetrahedral coordination environment, respectively, were observed under excitation at 346 nm and 408 nm. Cu⁺ emission at 468 nm with excitation at around 290 nm was ascribed to transition from excited s state to ground d state (d⁹s→d¹⁰) of Cu⁺. No other 3d^N TM ions are found to give strong visible emission in aluminophosphate glass at room temperature. Temperature dependent emission spectra for V, Cr, Mn, Fe, Cu doped aluminophosphate glass with laser excitation have also been investigated.