Green up-conversion Luminescence in Nd^3＋-Ho^3＋ Co-loped Oxyfluorotellurite Glasses

Blue, green and red up-conversion luminescence at around 490, 545 and 650 nm, which result from the Ho^3＋5F3→5I8, （5F4,5S2）→3. 5I8 and 5F5→ 5I8 transitions, respectively, were observed in Nd3＋-Ho3. co-doped oxyfiuorotellurite glasses under 800 nm excitation. Among these up-conversion luminescence, the green emission was extremely strong and the blue and red emission intensities were very weak. Selectively strong green up-conversion luminescence of these glasses indicate a high possibility for realizing a green upconversion laser. Up-conversion processes for the blue, green and red emissions are two-photon processes assisted by Nd3^＋→Ho^3＋ energy transfer. It is proposed that the up-conversion mechanism for the blue and green emissions is different from that for the red emission. The respective mechanisms are discussed.