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Ho3+-doped and Ho3+/Yb3+-codoped lead bismuth gallate (PBG) oxide glasses were prepared and their spectroscopic properties were investigated. The derived Judd–Ofelt intensity parameters (Ω2=6.81×10-20 cm2, Ω4=2.31×10-20 cm2, and Ω6=0.67×10-20 cm2) indicate a higher asymmetry and stronger covalent environment for Ho3+ sites in PBG glass compared with those in tellurite, fluoride (ZBLAN), and some other lead-contained glasses. Intense frequency upconversion emissions peaking at 547, 662, and 756 nm as well as infrared emissions at 1.20 and 2.05 μm in Ho3+/Yb3+-codoped PBG glass were observed, confirming that energy transfer between Yb3+ and Ho3+ takes place, and a two-phonon-assisted energy transfer from Yb3+ to Ho3+ ions was determined by the calculation using phonon sideband theory. The 1.20 μm emission observed was primarily due to the weak multiphonon deexcitation originated from the small phonon energy of PBG glass (∼535 cm-1). A large product of emission cross-section and measured lifetime (9.93×10-25 cm2 s) was obtained for the 1.20 μm emission and the gain coefficient dependence on wavelength with population inversion rate (P) was performed. The peak emission cross-section for 2.05 μm emission was calculated to be 4.75×10-21 cm2. The relative mechanism of Ho3+-doped and Ho3+/Yb3+-codoped PBG glasses on their spectroscopic properties was also discussed. Our results suggest that Ho3+/Yb3+-doped PBG glasses are a good potential candidate for the frequency upconversion devices and infrared amplifiers/lasers. [ABSTRACT FROM AUTHOR]

10 mol % of bismuth oxide was designed to add in making novel Ho3+ doped heavy metal tellurite glasses (LKBBT) with large refractive indices and glass densities. Based on optical absorption, Judd-Ofelt parameters Ω2, Ω4, and Ω6 have been derived to be 4.373×10-20, 1.906×10-20, and 1.451×10-20 cm2, respectively, which indicate higher asymmetry and stronger covalent environment in LKBBT glasses compared with ZnF2–CdF2, oxyfluorobotate, and zirconium-barium-lanthanum-aluminum-sodium-fluoride glasses. Efficient visible upconversion emission bands peaked at 544, 657, and 753 nm in Ho3+/Yb3+ codoped LKBBT glass system have confirmed that two photons contribute to the upconversion processes under the pumping of a 974 nm diode laser. Owing to large absorption and emission cross sections, Yb3+ ion is considered to be a preferable sensitizer for catching enough pumping energy and transferring considerable energy to Ho3+ in LKBBT glasses. Low maximum phonon energy and high spontaneous transition probabilities of Ho3+ are beneficial in obtaining efficient upconversion and IR emission in the glass system. [ABSTRACT FROM AUTHOR]

Abstract: Efficient infrared emissions at 1.20μm [5I6 → 5I8 transition] and 1.38μm [(5 F4, 5 S2)→ 5I5 transition] from Ho3+-doped lithium–barium–bismuth–lead (LBBP) glass were observed. The stimulated emission cross-sections were calculated to be 0.29×10−20 and 0.25×10−20 cm2 for 1.20 and 1.38μm emissions, respectively. Judd-Ofelt characteristic parameters Ω2, Ω4 and Ω6 for Ho3+ in LBBP glass were calculated to be 6.72×10−20, 2.35×10−20 and 0.61×10−20 cm2, respectively, which indicates a strong asymmetry and a covalent environment between the Ho3+ ions and the ligands in this glass. The optical amplifications operating at these relatively unexplored wavelength regions were evaluated and discussed. [Copyright &y& Elsevier]

Abstract: Tm3+/Ho3+/Yb3+ triply doped aluminum germanate glasses exhibiting multicolor upconversion fluorescences have been fabricated and characterized. Efficient three-photon blue upconversion emission of Tm3+ and two-photon green and red upconversion fluorescences of Ho3+ have been observed. The strong red emission of Ho3+, which is more than eight times higher than that of the green emission, is desirable in achieving high color rendering index. By varying the excitation power of the 974nm wavelength laser diode, a series of white fluorescences with a large range of correlated color temperature (CCT) was obtained, and the fluorescence colors can be tuned from yellowish white to warm white, pure white, cool white, and bluish white with different CCT. The upconversion color tunability via pump power adjustment will promote the development of three-dimensional solid-state displays and upconversion illumination devices. [Copyright &y& Elsevier]

Abstract: Sm3+- and Eu3+-doped rare-earth borate glasses (Li2O–BaO–La2O3–B2O3) have been fabricated and characterized optically. The density, refractive index, optical absorption, Judd-Ofelt parameters, and spontaneous transition probabilities have been measured, calculated and analyzed. Sm3+ and Eu3+ emit intense reddish-orange and red lights under blue and UV light excitations, respectively. In Sm3+ and Eu3+ co-doped glasses, the excitation wavelength range of Eu3+ emission is broadened owing to the energy transfer from Sm3+ to Eu3+. This broadening makes the Ar+ 488nm wavelength laser a powerful excitation source for Eu3+ fluorescence. The rare-earth doped glasses with various visible emissions are useful for developing new color light sources, fluorescent display devices, UV-sensor and tunable visible lasers. [Copyright &y& Elsevier]

Abstract: Tm3+/Yb3+-doped alkali-barium-bismuth-tellurite (LKBBT) glasses have been fabricated and characterized. Density, refractive index, optical absorption, absorption and emission cross-sections of Yb3+, Judd–Ofelt parameters and spontaneous transition probabilities of Tm3+ have been measured and calculated, respectively. Intense blue three-photon upconversion fluorescence and near-infrared two-photon upconversion fluorescence were investigated under the excitation of a 980nm diode laser at room temperature. Wide infrared transmission window, high refractive index and strong blue three-photon upconversion emission of Tm3+ indicate that Tm3+/Yb3+ co-doped LKBBT glasses are promising upconversion optical and laser materials. [Copyright &y& Elsevier]

Efficient emission at 1.38 mum wavelength from holmium (Ho(3+))-doped low-phonon-energy gallate bismuth lead (GBL) oxide glasses, owing to the Ho(3+): ((5)S(2),(5)F(4))-->(5)I(5) transition, was observed, and the stimulated emission cross section was calculated to be 2.4x10(-21) cm(2). Population inversions between the ((5)S(2),(5)F(4)) and (5)I(5) levels have been achieved, and a broad gain bandwidth from 1350 to 1450 nm was obtained. The large product of emission cross section and measured lifetime also support this characteristic. The results indicate that a Ho(3+)-doped GBL glass system is a promising candidate for the development of E-band (1360-1460 nm) fiber-optic amplifiers.