Near-infrared to visible up-conversion emissions of Er3+ doped Al2O3 powders derived from the sol-gel method

Abstract

The Er 3+ doped Al 2 O 3 powders were prepared by the sol-gel method using the aluminium isopropoxide [Al(OC 3 H 7 ) 3 ]-derived Al 2 O 3 sols with addition of the erbium nitrate [Er(NO3 ) 3 . 5H 2 O]. The different phase structure, including three crystalline types of (Al,Er) 2 O 3 phases, γ, θ, α, and two Er-Al-O phases, ErAlO 3 and Al 10 Er 6 O 24 , was obtained with the 1 mol% Er 3+ doped Al 2 O 3 powders at the different sintering temperatures of 600-1200℃. The green and red up-conversion emissions centered at about 523, 545 and 660 nm, corresponding respectively to the 2 H 11/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ , were detected by a 978 nm semiconductor laser diodes excitation. The phase structure and OH content had evident influence on the up-conversion emissions intensity. The maximum intensities of both the green and red emissions were obtained respectively for the Er 3+ doped Al 2 O 3 powders sintered at 1200 ℃, which was composed mainly of α-(Al,Er) 2 O 3 , less of ErAlO 3 and Al 10 Er 6 O 24 phases, and with the least OH content. The two-photon absorption up-conversion process was involved in the green and red up-conversion emissions of the Er 3+ doped Al 2 O 3 powders. Er 3+ doping, up-conversion, Al 2 O 3 , excited state absorption, cross-relaxationRecently, rare-earth ion Er 3+ doped materials play an important role due to their potential application in optical communication [1,2] . The infrared sources can achieve a high efficiency with the advances in both solid-state laser and semiconductor laser diodes (LD). As a result, up-conversion emission, where the absorption of two or more lower energy photons is followed by the emission of a higher energy photon, has received significant attention. Due to the availability of low-cost near-infrared LD, conversion of infrared radiation to visible fluorescence generates much of the current interests in upconversion emission. In the near-infrared spectral region, Er 3+ has a favorable energy level structure with 4 I 15/2 → 4 I 11/2 transition which can be easily excited by using a 978 nm semiconductor LD as the excitation source. Now, there are also considerable increasing interests to the characteristics of up-conversion emission of the Er 3+ doped materials for their potential applications in the fields of color display, optical data storage, biomedical diagnostics and temperature sensors [3][4][5][6] . Developing the Er 3+ doped optical devices, the influence factors of matrix being doped must be preferably considered, such as the dispersion of Er 3+ , luminescence efficiency, decay time, chemical durability, thermal stability, and mechanical strength. Extensive researches of the properties of the Er 3+ doped Al 2 O 3 indicated that Al 2 O 3 is more appropriate as the Er 3+ doped matrix [1,[7][8][9][10] . Though the Er 3+ doped Al 2 O 3 material has previously been prepared by many methods, and their corresponding researches concentrated on infrared emission centered at about 1.533 μm for optical amplifier have been reported...

Assignments of the Raman modes of monoclinic erbium oxide

“…As mentioned earlier, Er 3þ exhibits abundant absorption and radiation bands in the visible and IR regions. [3][4][5][18][19][20][21][22] When the excitation wavelength is near the absorption bands of Er 3þ , the excited spectrum may contain Raman vibrational signals and photoluminescent signals; thus, unambiguously identifying Raman modes is difficult. In addition, pure B-Er 2 O 3 is not available in single-crystal form; thus, its vibrational modes cannot be assigned through polarized Raman scattering spectroscopy.…”