Fabrication and Optical Measurements of Germanium-Doped Silica Ridge Waveguides Using a Novel Colloidal Suspension Approach

Prototypes of germanium doped silica ridge waveguides for planar lightwave circuits (PLCs) were fabricated using novel colloidal suspensions and optically characterized. Compared to conventional deposition techniques for PLCs, the colloidal sol-gel route has advantages such as high deposition rate, low cost, doping flexibility and patterning versatility. 

Fully dense, micron scale, spin coated thick films were obtained after a consolidation process at 1300 °C on silicon substrates. The refractive index of silica-germania films increased linearly with germanium concentration in the range of 0 to 11.1 mol %. The propagation loss of a 3.1 mol % germanium doped silica ridge waveguides without an overcladding layer was 3.3 ± 0.5 dB/cm.