We investigated infrared luminescent phenomena in bismuth lanthanum borate glasses. In bismuth lanthanum borate glasses, the absorption peak was observed at 460 nm. The absorption peak was observed only when the glass was melted in Al2O3 crucible, whereas no peak was seen in the case of Pt crucible and the case of Al2O3 doped sample melted in Pt crucible. The infrared emission peak was observed at 1300 nm excited at 800nm. Life time at 1300 nm was 56.7 μs. We suggested that the absorption and infrared emission have been associated with pentavalent Bi ions in the glasses. It was estimated by La 3d XPS spectra and ESR spectra. INTRODUCTION Broad infrared luminescent materials can be used as a broadband amplifier and a high-power tunable laser, and hence the exploration of novel glass systems exhibiting a broad bismuth luminescence is extensively continued. Fujimoto and Nakatsuka found an infrared luminescence of bismuth in 0.3Bi2O3-2.2Al2O3-97.5SiO2 glass, where the luminescence was observed at 1300 nm and the full width at half maximum (FWHM) was over 200 nm. They suggested that the infrared emission was associated with pentavalent Bi ions in the glass. Peng and Qiu also reported the infrared luminescence in 1Bi2O3-3Al2O3-96GeO2 glass, and they concluded that the infrared emission was associated with monovalent Bi ions in the glass. Thus, the infrared luminescence was assigned to the different valence states of Bi ions. In this study, the valence and electronic states of Bi ions in Bi2O3-La2O3-Al2O3-B2O3 glasses were investigated, from which the origin of the broad infrared luminescence was clarified. EXPERIMENTAL The compositions of glasses prepared in this study and melting temperatures are shown in Table 1. Reagent grade powders of La2O3, B2O3, Bi2O3, and Al2O3 were weighed, and the 10 g batches were melted in Pt or Al2O3 crucibles for 40 minutes. The melts were poured onto a brass plate and quickly pressed by a stainless steel plate. The glasses were polished before optical measurements. As described below, infrared luminescence was observed only in the glasses melted in Al2O3 crucible. Then, in order to examine the influence of Al2O3, 6mol% Al2O3 doped glasses were also prepared by using a Pt crucible, where Al2O3 content was determined from energy dispersive X-ray (EDX) analyses. Optical absorption spectra (190 ~ 2500 nm) were measured on a spectrophotometer Page 1 of 7