Loss reduction of GeO2-doped silica waveguide with high refractive index difference by high-temperature annealing

The effect of a GeO2-doped core on high-temperature annealing has been inve stigated to reduce the propagation loss of a waveguide device with high ref ractive index difference (a). A SiO2-GeO2 waveguide con was prepared on a f used silica substrate by rf magnetron sputtering and reactive ion etching. With increasing the annealing temperature, the roughness of the core side-w all gradually disappears and the rectangular core gradually becomes rounded . The effect of smoothing and rounding the cores was a significant reductio n of the scattering loss, and moreover, it enabled the complete embedding o f narrow gaps between cores in cladding glass using conventional plasma che mical vapor deposition. The propagation loss of the waveguide with a Delta of 1.5% was 0.07 dB/cm at 1.55 mu m wavelength, the effect of which was dem onstrated in the fabrication of an arrayed-waveguide grating demultiplexer.