A Novel Photonic Material for Designing Arbitrarily Shaped Waveguides in Two Dimensions

We investigate numerically optical properties of novel two-dimensional photonic materials where parallel dielectric rods are randomly placed with the restriction that the distance between rods is larger than a certain value. A large complete photonic gap (PG) is found when rods have sufficient density and dielectric contrast. Our result shows that neither long-range nor short-range order is an essential prerequisite to the formation of PGs. A universal principle is proposed for designing arbitrarily shaped waveguides, where waveguides are fenced with side walls of periodic rods and surrounded by the novel photonic materials. We observe highly efficient transmission of light for various waveguides. Due to structural uniformity, the novel photonic materials are best suited for filling up the outer region of waveguides of arbitrary shape and dimension comparable with the wavelength.Comment: 4 figure

Electrical conductivity of vanadium phosphate glasses containing ZnO or GeO2

Glasses containing up to 80 mol% V2O5 were obtained when ZnO : P2O5 or GeO2 : P2O5 was 1 in the mole ratio. The temperature dependence of dc conductivity, σ, was exponential with σ = σ0/Texp (-W/k Τ), σ and W of glasses containing the same amount of V2O5 were affected slightly by the kind of the additive oxides ZnO or GeO2, when V2O5 ⪆ 50 mol%. In this region, σ0 varied slightly with the change of V2O5 content, and the hopping conduction was adiabatic. When V2O5 ⪅ 50 mol%, adiabatic approximation could not be valid for the hopping conduction. σ0 and the transition probability decreased remarkably with decreasing V2O5 content, σ and W of the glasses containing the same amount of V2O5 depended on the kind of the additive oxides. The relationship between the anionic molar volume or Tg and V2O5 content indicated that the glass structure changed at V2O5 ≈ 50 mol%. The conduction mechanism was discussed in relation to the glass structure