We reveal experimentally waveguiding characteristics and group-velocity dispersion of line defects in photonic crystal slabs as a function of defect widths. The defects have waveguiding modes with two types of cutoff within the photonic band gap. Interference measurements show that they exhibit extraordinarily large group dispersion, and we found waveguiding modes whose traveling speed is 2 orders of magnitude slower than that in air. These characteristics can be tuned by controlling the defect width, and the results agree well with theoretical calculations, indicating that we can design light paths with made-to-order dispersion.

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Development of erbium-doped silica sensor probe for fiber-optic fluorescence thermometer Rev. Sci. Instrum. 76, 094902 (2005); 10.1063/1.2038508 Low temperature fluorescence thermometer application of long afterglow phosphorescent Sr Al 12 O 19 : Eu 2 + , Dy 3 + crystals Rev. Sci. Instrum. 76, 084901 (2005); 10.1063/1.1988147 Fiber-optic thermometer using Cr-doped YAlO 3 sensor head Rev. Sci. Instrum. 74, 3883 (2003); 10.1063/1.1589582 Fabrication of ruby sensor probe for the fiber-optic thermometer using fluorescence decay Rev. Sci. Instrum. 73, 3656 (2002);Long duration phosphorescent SrAl 2 O 4 phosphors doped with various auxiliary activators ͑Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu͒ have been evaluated for the fiber-optic thermometer application. In this thermometer, temperature was measured based on the temperature dependence of the lifetime and/or intensity of the afterglow phosphorescence which was dominated by the thermal excitation of trapped carriers. Characteristics of the long phosphorescent fiber-optic thermometer are quite different from those of the conventional thermometer using fluorescent lifetime of the phosphors. Lifetime and intensity of the afterglow phosphorescence from the long afterglow phosphorescent sensor heads show large positive temperature coefficients in the narrow temperature region around room temperature. Sensitivity and temperature range of the long phosphorescent fiber-optic thermometer depend strongly on the trap depth and the trap density of phosphors. Since the trap depth and the trap density vary with auxiliary activator elements, a variety of fiber-optic thermometers with high sensitivity in various temperature ranges will be able to be developed using Eu 2ϩ doped SrAl 2 O 4 codoped with various auxiliary activator Ln 3ϩ ions ͑LnϭY,

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