Survey for rare earth doped chalcogenide glasses with high intensity of luminescence.

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Chalcogenide glasses have useful properties such as low phonon energies, high refractive index, and high transmittance in the infrared. Erbium (Er^<3+>) doped chalcogenide glasses are important candidates for active optical wave guide applications at around 1550nm. We investigated Er^<3+> doped chalcogenide glasses. Bulk samples were prepared using Ge (5N), Se (5N), Ga (5N), and Er_2S_3 (3N) by melt quenching technique by quenching from 1000 ℃ to water. We evaluated the solubility of Er according to optical transmission at 1450nm and efficiency of absorption for Er^<3+>. The glasses allowed to solute 1at.% of Er over the all glass forming region except for low (<3at.%) Ga concentration. On the tie-line of stoichiometry between GeSe_2 and Ga_2Se_3 the solubility of Er is best as about 4 at.% of Er. The photoluminescence (PL) was excited from a laser operating at a wavelength of 980 nm. The maximum intensity of PL was observed on the tie-line at 10-14at.% of Ga. We found that PL intensity increased proportionally with Er^<3+> concentration up to 2 at.% and than it is constant or decreases above this concentration. Consequently Er^<3+> ions seem to be well dispersed and optically active up to Er concentration of about 2 at.% in these glass matrices. The glass matrix of Er^<3+> doped glasses becomes inhomogeneous above 18.at.% of Ga content. As this behaviour was observed only for Er-doped glasses, the presence of Er^<3+> ions seem to aid glass matrix destabilization (phase separation, or crystallization). The effect of thermal annealing and substitution of Se to Te were observed. The PL intensity increased to 50%-100% without the change of PL spectra. Er^<3+> ions would stay near the covalent bond of -Se^<-δ>-Ga^<+δ>- because the difference in the electronegativity of both atoms caused the ionic bonding between Se and Ga. Then Er^<3+> ion attracted to some number of Se atoms.