Kenzo Awazu

Oxygen penetration into CaF2:Sm2+ crystals

Abstract The diffusion of O −− ions into CaF 2 :Sm 2+ crystals has been directly observed by means of the decoloration of the crystals. In the presence of water vapor the O −− ions penetrate easily into the crystals, but in an O 2 atmosphere penetration is quite limited. The penetration is isotropic, and the activation energy for diffusion is estimated to be 45±4 Kcal/mole. The dependence of the Sm 3+ fluorescence on the penetration process has also been investigated. The emission spectrum of Sm 3+ ions in the transparent zone shows the presence of both Type I ( C 3 ) and Type II ( C 4 ) centers. It was found that Sm 3+ ions are charge compensated not only by O −− ions but also by interstitial − ions, in spite of thermal treatment in an H 2 O atmosphere. The emission spectrum in the opaque zone shows only Type I centers.

Electrooptic Light Beam Deflection with Sr0.75Ba0.25Nb2O6 Prism

An experimental investigation was performed on the electrooptic light beam deflection with a Sr0.75Ba0.25Nb2O6 isosceles prism at 6328 A. Although measured deflection angle was large (e.g. 3m rad. for an electric field of 6 kV/cm), deflection characteristic was considerably nonlinear and what is called butterfly hysteresis loop was observed in the ferroelectric phase. Sign and magnitude of the polarization were easily changeable and the coercive field was found to be as low as 1.3 kV/cm at 33°C. The electrooptic effect is dominated by a quadratic term with respect to the polarization. The unclamped value of the quadratic electrooptic g-coefficient g33 was determined to be 0.14 m4/C2. An electrically-induced spot distortion was observed, which was most remarkable at the polarization reversal.

Nonresonant Energy Transfer from Er3+ to Yb3+ in LaF3

Energy transfer in LaF3; Er, Yb is studied by observing the lifetimes of Er3+ in excited states and the excitation spectra both at room temperature and at 77 °K. It is found that the energy transfer from Er3+ (4S3/2→4I13/2) to Yb3+ (2F7/2→2F5/2) is associated with the emission of three phonons of about 350 cm−1, and that the energy transfer from Er3+ (2H9/2→4F9/2) to Yb3+ accompanied by the absorption of phonons takes place.

Development of Fluorescent Lamp with a Colour Rendering Index Ra=99

Fluorescent lamps were studied to improve colour rendering properties without the use of filters to absorb blue light.The general colour rendering index Ra could be improved effectively, when both blue-violet mercury lines and continious radiations from phosphors are controled.A new Sr-borophosphate phosphor, with a chemical formula of [2 (Sr, Eu) O·0.84 P2O5·0.16 B2O3] was discovered and its applicability in fluorescent lamp of accurate colour rendition was examined.This phosphor absobs not only UV radiations but also the visible blue radiation and emits bluegreen light, hauing lower radiant power blue-violet spectral region than the usual antimony activated Ca-halophospate phosphor.The use of this phosplor is very effective to contol the radiant powes in blue-violot spectral region, and makes it possible to produce fluorescent lamps having Ra value of as high as 99 and luminous efficacy 60 lm, /W, increased about 20%, without the use of filters.