L.H. Brixner

Fabrication and characterization of optical waveguides in KTiOPO4

Planar and channel optical waveguides have been fabricated in KTiOPO4 (KTP) using ion exchange processes. The exchange kinetics are diffusion limited and depend strongly on composition and surface orientation. Increases in surface refractive index of up to 0.23 and waveguide thicknesses of up to 15 μm have been observed. A simple waveguide modulator has been fabricated which shows electro‐optic r coefficients in the waveguide region to be similar to bulk KTP.

Fluorescence lifetime and quantum efficiency for 5d → 4f transitions in Eu2+ doped chloride and fluoride crystals☆

Abstract An investigation of the relevant parameters for broadly tunable lasers utilizing the efficient, broad-band 5d → 4f emission in a number of Eu2+ doped metal fluorides, chlorides, and fluoro-chlorides has been performed. Results of measurements of absorption and emission spectra, quantum efficiencies, and fluorescence lifetimes in MF2 and MCl2 (M = Ca, Ba, Sr) and MFCl (M = Ba, Sr) are presented. A calculation of the pump energy threshold for laser action in CaF2 : Eu2+ based on our spectroscopic data is made. Although the estimation indicated that laser threshold in CaF2 : Eu can be easily achieved, strong excited-state absorption in this system was found to prohibit laser oscillation.

PHOTOSTIMULABLE PHOSPHORS FOR X-RAY IMAGING : APPLICATIONS AND MECHANISM

Abstract X-ray imaging via photostimulated luminescence (PSL) in barium fluorohalides is becoming important for various applications, in particular medical imaging. We describe the requirements for a PSL phosphor and then review the current understanding of the mechanism underlying the high PSL efficiency of BaFCl:Eu 2+ and BaFBr:Eu 2+ . In particular, recent results indicate the important role played by H - ions in these materials, and suggest that they are an integral part of the photostimulated luminescence complex.

Luminescence of materials based on LuTaO4

Abstract The photoluminescence and X-ray luminescence of samples of LuTaO4-A (A=Ti, Pr, Sm, Eu, Gd, Tb, Dy, Tm) are reported. The results can be interpreted using simple models. Many samples show pronounced thermoluminescence after X-ray irradiation at room temperature. Several of the materials possess great potential as X-ray phosphors.

The intensity of vibronic transitions in the emission spectrum of the trivalent gadolinium ion

Abstract The intensity of the vibronic transitions in the emission spectrum of the Gd3+ ion is discussed using new data as well as data from the literature. As model compounds the following compositions are used: (i) the ordered perovskites Ba2LnTaO6:Gd (Ln = La, Y, Lu) where Gd3+ occupies a site with octahedral symmetry; (ii) the hydroxide Y(OH)3:Gd where purely cooperative vibronic transitions occur. The vibronic intensities vary by an order of magnitude over the series of compositions under discussion. The relevant theories are summarised. It is shown that they are able to account qualitatively for all trends and phenomena observed.

Rare earth fluorescence in some LnOCl type hosts

Abstract LaOCl, LuOCl and ScOCl represent three different structures with the Ln ion coordination changing from 9 to 7 and 6. The rare earth ions Sm +3 , Eu +3 , Tb +3 , Dy +3 and Tm +3 can be introduced into all three of these hosts and the luminescence is discussed as a function of the local crystal symmetry.

X-ray excited luminescence of oxides doped with D10 ions

Abstract The X-ray excited luminescence of CaO-Ga(III), CaO-In(III) and InBO 3 is reported. The metal ions with d 10 configuration are responsible for the luminescence, but the nature of the optical transitions remains unclear.

Structure and Luminescence of the La1 − x Gd x F 3 System

The trifluorides of La and Gd crystallize in different structures: LaF{sub 3} is of the hexagonal tysonite (P{bar 3}1c) type, while GdF{sub 3} crystallizes in orthorhombic (Pnma) symmetry. Solid solutions of the type La{sub 1 {minus}x}Gd{sub x}F{sub 3} exist in the hexagonal structure to x = 0.5 and convert to the orthorhombic phase at x = 0.75. In this paper, lattice parameters are reported and the x-ray excited luminescence of Gd{sup 3+} in these compounds is discussed with particular emphasis on the Gd{sup 3+} site symmetry difference C{sub 2} in LaF{sub 3} and C{sub s} in GdF{sub 3}.

High-resolution x-ray-excited Gd3+ emission in the C-type Y2O3 structure

Abstract Y2O3, Lu2O3, and Sc2O3 are isomorphous, crystallizing in the cubic space group Ia3, and Gd3+ can readily be incorporated into each of these three compounds. The rare earths occupy two different sites with symmetry C2 and S6. As a consequence, the Gd 3+ 6 P 7 2 → 8 S transition is split into eight crystalfield lines. Other electronic transitions as well as vibronic side bands are also observed and the differences between the spectra of the three compounds are discussed.

The Gd3+ luminescence in lanthanide hydroxycarbonate (LnOHCO3) and hydrated carbonate (Ln2(CO3)3·6H2O)

The X-ray excited emission of Gd3+ in YOHCO3: Gd and Gd2(CO3)3·6H2O is reported. The vibronic lines due to coupling with the carbonate, the hydroxyl and the water vibrations are discussed.