Investigation of Ge based chalcogenide glasses doped with Er, Pr and Ho

Bulk chalcogenide glasses, Ge based sulphides Ge25Ga10S65 and (GeS2)80(Ga2S3)20, and tellurides Ge20Se80 − xTex, x ∈ < 0,15>, and those doped with Er, Pr and Ho ions have been prepared by direct synthesis and investigated by optical transmission and low temperature photoluminescence spectroscopy. It has been demonstrated by using (GeS2)80(Ga2S3)20 glasses and by monitoring the intensity decrease of the broad band host glass luminescence that increasing Er doping leads to the partial removal of native defects generated by network disorder. Luminescence properties of Ge25Ga10S65:(Er, Pr, Ho) systems have further been studied by varying the excitation wavelengths. The base glass luminescence band has been found shifted from 1200 to 1050 nm when excitation wavelength is decreased from 632.8 to, or below 500 nm. The decreased excitation wavelength enables electron transfer over the band gap in Ge–Ga–S system and into higher metastable states of RE3+ ions. This is manifested by the shift of the base glass luminescence band to higher energy and by observation of new radiative 4f–4f transitions. The efficiency of 4f–4f transitions in Ge–Se–Te:RE glasses is steadily decreasing with increasing Te content. A pronounced re-absorption of the host glass luminescence is observed in telluride glasses doped with Pr and Er.