Yasutake Ohishi

Optical properties of transparent Li2O–Ga2O3–SiO2 glass-ceramics embedding Ni-doped nanocrystals

Transparent Li2O–Ga2O3–SiO2 (LGS) glass-ceramics embedding Ni:LiGa5O8 nanocrystals were fabricated. An intense emission centered around 1300nm with the width of more than 300nm was observed by 976nm photoexcitation of the glass-ceramics. The lifetime was more than 900μs at 5K and 500μs at 300K. The emission could be attributed to the T2g3(F3)→A2g3(F3) transition of Ni2+ in distorted octahedral sites in LiGa5O8. The product of stimulated emission cross section and lifetime for the emission was about 3.7×10−24cm2s and was a sufficiently practical value.

Tellurite glasses for ultrabroadband fiber Raman amplifiers

Tellurite glasses optimized for higher Raman gain and broad bandwidth have been realized. These glasses were found to have improved thermal stabilities, which make them suitable for fiber devices applications. While maintaining the Raman gains at higher values, the Raman bandwidths could be broadened by proper addition of alkaline earth oxides and heavy metal oxides in to the tellurite glasses. The relative Raman gain and Raman cross sections of the present glasses are better than the tellurite-based glasses reported earlier. Thus, higher Raman gain and much broader Raman amplifications could be possible by using this tellurite glass system as a gain medium compared with the conventional tellurite-based fiber Raman amplifiers.

Optical properties of Er3+ and Tm3+ ions in a tellurite glass

Optical spectroscopic properties of Er3+ and Tm3+ ions in a tellurite glass, TeO2-BaO-SrO-Nb2O5 (TBSN), were investigated for C- and S-band optical amplifications. On the basis of consideration for cross relaxation among Tm3+ ions and multiphonon relaxation, it was shown that the presence of Nb2O5, which was a source of the highest energy phonon, contributed to the relaxation processes in TBSN glasses.

Phospho-tellurite glasses containing heavy metal oxides for ultrabroad band fiber Raman amplifiers

Multicomponent phospho-tellurite glasses containing heavy metal oxides and alkaline earth oxides have been fabricated. These glasses have thermal stabilities as high as 224 °C, which make them suitable for various fiber devices applications. The Raman intensities and cross sections of these glasses are compared relative to silica. These glasses show superior relative Raman cross sections than silica and conventional tellurite glasses. The presence of heavy metal oxides and alkaline earth oxides makes the Raman bands due to TeO2 and P2O5 continuous and one such glass has continuous Raman bandwidths exceeding 700cm−1. Thus, these glasses could be potential candidates for ultrawide band fiber Raman amplifiers.

Optical properties of erbium and thulium co-doped in tellurite glasses for the S+C band optical amplification

Optical spectroscopic properties of Er3+ and Tm3+ ions in new niobium tellurite glasses, Te02-Ba0-Sr0-Nb205 (TBSN), were investigated for (S+C)-band optical amplifications. On the basis of consideration for cross-relaxation among Tm3+ions and multi-phonon relaxation, it was shown that the presence of Nb205, which was source of the highest energy phonon, contributed to relaxation processes in TBSN glasses. The C-band amplification transition for Er3+ and the S-band amplification transition for Tm3+ are both sufficiently efficient in TBSN glasses and the Er3+-Tm3+ co-doped TBSN fibers could be efficient seamless (S+C)-band amplification media by selecting the concentrations of Er3+ and Tm3+

Ultra-broad band phospho-tellurite glasses containing heavy metal oxides for fiber Raman amplifiers

Phospho-tellurite glasses containing heavy metal oxides and alkaline-earth oxides have been fabricated. Presence of these oxides makes the Raman bands due to TeO<inf>2</inf>and P<inf>2</inf>O<inf>5</inf>continuous and suitable for ultra-broad band fiber Raman amplifiers.

New tellurite glasses for ultra-broadband fiber Raman amplifiers

In this paper, we report performance of the newly researched phosphor-tellurite glass which has broadest Raman gain to the best of our knowledge, than the conventional tellurite glass to realize highly efficient ultra-broadband fiber Raman amplifiers.