No abstract

No abstract

The small signal gain of Er 3ϩ -doped P 2 O 5 -SiO 2 planar waveguides is described with a homogeneous upconversion model. The homogeneous upconversion process accurately describes the absorption saturation at a wavelength of 0.98 m. Interpretation of the absorption saturation provides homogeneous upconversion coefficients of 4ϫ10 Ϫ15 cm 3 s Ϫ1 for a 0.54 wt % Er 3ϩ -doped 14.6 wt % P 2 O 5 codoped silica waveguide and 6ϫ10 Ϫ18 cm 3 s Ϫ1 for a 0.46 wt % Er 3ϩ -doped 21.6 wt % P 2 O 5 codoped silica waveguide. The upconversion process occurs in the Er 3ϩ ion rich phase in the P 2 O 5 -SiO 2 core glass. A calculation that includes the homogeneous upconversion process proves that the gain can be enhanced by codoping the planar waveguide with P 2 O 5 . A gain of 20 dB is calculated with an Er 3ϩ ion concentration of 0.4-0.7 wt % and a waveguide length of 40 cm when the pump power is 100 mW and 20 wt % P 2 O 5 codoped Er 3ϩ -doped silica-based planar waveguides are used.

The superconducting oxide Y-Ba-Cu-O has successfully been fabricated by the sol-gel method using Y, Ba, and Cu alkoxides as starting materials. Powders with specific surface area of 15 m2/g are prepared by this method. An X-ray diffraction pattern attributed to a 1-2-3 structure appears at 750°C and a bulk sample with Tc of 90 K is made by 900°C sintering in an oxygen atmosphere. A film of Tc=80 K with c-axis orientation is also fabricated using the sol-gel paste on an yttrium-stabilized ZrO2 substrate.

No abstract