Excitation of Er3+ emission by host glass absorption in sputtered films of Er-doped Ge10As40Se25S25 glass

Photoluminescence and photoluminescence excitation (PLE) spectroscopy have been carried out on the similar to 1550 nm I-4(13/2) --> I-4(15/2) Er3+ emission from thin films of Er-doped A(s4)0Ge(10)Se(25)S(25) glass deposited on silicon substrates by radio frequency sputtering. The PLE spectroscopy shows that the Er3+ emission is excited in the 1-mu m-thick film by the Urbach absorption edge of the host glass rather than direct absorption by the Er3+ intra-4f shell transitions. This enables the use of a broad range of pump wavelengths and novel pumping geometries. Comparison of the PLE spectra of the Er emission obtained before and after a rapid thermal anneal (RTA) clearly manifests a blue shift in the band gap induced by the RTA process. These results reveal that the broad band Er PLE mechanism discovered recently in Er-doped bulk chalcogenide glasses and attributed to host glass Urbach edge optical absorption and energy transfer mediated by native defects also occurs in sputtered films of Er-doped chalcogenide glass. (C) 1998 American Institute of Physics. [S0003-6951(98)03948-5].