Fabrication of ridge waveguides from sol-gel derived Nd-doped SiO 2-TiO2-Al2O3 glass films

Rare earth doped glass waveguide amplifiers are being actively researched because of their potential applications in DWDM networks. We have fabricated ridge channels from sol-gel derived Nd-doped SiO₂ -TiO₂-Al₂O₃ glass films using laser writing lithography and reactive ion etching (RIE). The SEM pictures show that the ridge is properly formed according to our design. The top surface of the ridge is smooth as a result of the Ti and Ni cap protection. However, the side-wall and the etched substrate are much rougher. We believe that the side-wall can be smoothed by re-annealing the channel and the propagation loss can be further reduced by burying the channel through depositing an upper cladding layer around the ridge