Infrared-to-Visible Conversion by Rare-Earth Ions in Crystals

Abstract

An analysis of infrared conversion to visible and ultraviolet radiation by Yb3+–Er3+, Yb3+–Ho3+, and Yb3+–Tm3+ ions in crystals is presented. The expression for the visible power output in the presence of back transfer from the active ion to the energy-transferring ion (Yb3+) is given and the relationship between the intermediate state transfer and back transfer coefficients for maximum output is found. If this relationship is satisfied the visible output in the presence of back transfer is equal to the maximum output with no back transfer. The behavior of the power output when the transfer and back transfer coefficients depart significantly from this optimum condition is examined and the parameters which govern the power output under these conditions are determined. The analysis is applied to Yb3+–Er3+, Yb3+–Ho3+, and Yb3+–Tm3+ ions in BaYF5 and BaY2F8. Measurements on the brightest composition of Yb3+–Er3+ ions in BaYF5 indicate that the advantage of a long-lived intermediate state is diminished by back transfer. A power-conversion efficiency of 0.1% has been obtained for the green emission from BaYF5:Yb3+–Er3+ when pumped by 0.93-μ radiation from a 17% efficient Si–GaAs diode. Conversion efficiencies of 0.03% are obtained for the green emission from BaY2F8:Yb3+–Ho3+ and for the blue emission at 4800 Å from BaYF5:Yb3+–Tm3+. Efficient conversion of 1.5-μ radiation to the visible by BaYF5:Er3+ is also described.

Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium

“…These materials are only available as powders, and cannot be readily grown as single crystals (in contrast to the Na2Y3F1I material). A significant number of other~hre-earth co-doped phosphors have been discussed and evaluated, including green emitters -YF3:Yb,Er [1 1,12,13,14] [13,15], and LaF3:Yb,Er [16,17], as well as fluoride glasses [18] and OXyfluoride ceramics [19]; red emitters -YOCl:Yb,Er [12,13] and BaYF5:Yb,Er [15]; and blue emitters -YF3:Yb,Tm [12,13,14,20] and BaYF5:Yb,Tm [15]. Chloride hosts have also been examined [21].…”

Preparation and characterization of stable aqueous suspensions of up-converting Er3+/Yb3+-doped LiNbO3 nanocrystals

“…In fact, this mechanism is well characterized in many materials, including LNB:Er 3+ /Yb 3+ bulk crystals [16][17][18][19][20][21]. Therefore, in the present work the fabrication of Er 3+ /Yb 3+ -doped LNB nanoparticles by milling and their subsequent optical characterization has been explored, with particular emphasis on whether the characteristic up-conversion phenomena remain unaltered by the process.…”

Temporal dynamics of IR-to-visible up-conversion in LiNbO_3:Er^3+/Yb^3+: a path to phosphors with tunable chromaticity

“…It is well known that the 980 nm pumping scheme in Er 3+ /Yb 3+ codoped materials gives rise to two intense visible emission bands in the green and red spectral ranges, associated to the 2 [15]. Figure 1 shows the upconverted emission spectra (normalized to the red emission band) measured in the Er 3+ /Yb 3+ co-doped LiNbO 3 sample, after 980 nm pumping, for two symmetric square pulses of different width (1 ms, dotted black line; 60 ms, continuous red line).…”

“…In order to further quantify the up-conversion temporal dynamics, we shall describe it by using the rate equations formalism [15,26,42] incorporating all the above mentioned processes. The temporal evolution of the population densities in the different manifolds is given by the following rate equations: …”

“…In addition, the availability of such high performance IR diode lasers for pumping rareearth doped materials has also driven renewed interest in the preparation of new materials and novel applications which include displays, lasers and amplifiers, optical temperature sensors, biological markers and multiphotonic microscopy [15][16][17][18][19][20][21][22][23]. Particularly interesting at the moment is the development of materials with multiple emissions, suitable as biological markers and the control of their chromaticity [16,18,24,25].…”