Development of Upconversion Material with Higher Efficiency

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Some rare earth ions such as Er^<3+>, Ho^<3+>, Tm^<3+>, Pr^<3+> and Nd^<3+> when incorporated into a suitable host lattice, can upconvert infrared light to visible one. This upconversion phenomenon receives much interest, mainly because the visible source pumped in the near infrared light is required for optical devices which are used for the infrared light detector or the short wavelength upconversion laser. The remarkable result obtained in this study is following.1. Among fluoride glasses, we found that IPBL glass in the composition of 1ErF_3-48InF_3-24PbF_2-24BaF_2-3LaF_3, phonon energy of which is only as small as 270 cm^<-1> showed the highest upconversion efficiency at this moment.2. Another important objective is to demonstrate CW lasing at room temperature. It is considered that the optical fiber is a possible candidate of CW room temperature upconversion lasing material, because of its ability of light confinement over long lengths. We have found the CW room temperature upconversion lasing. Study of upconversion lasing of Er3+-doped fiber is attractive, since the pumping wavelength employed exists at around infrared (800nm) region where the high power laser diode is available and all-solid-state green devices based on a combination with the infrared laser diode might be applied for optical data storage, undersea communications and projection televisions.3. We have found that Tm^<3+>-doped fluoride glass showed blue and ultraviolet light at room temperature when pumped with a red krypton laser of 647 nm. Subsequently, We have found that Pr^<3+>-doped fluoride fibers exhibited green, yellow and red lights when pumped with infrared light of 800nm-1000nm wavelength.