ER-DOPED GLASS RIDGE-WAVE-GUIDE AMPLIFIERS FABRICATED WITH A COLLIMATED SPUTTER-DEPOSITION TECHNIQUE

We report a new fabrication process for Er-doped glass ridge waveguide s. The process does not require etching of an Er-doped film in definin g the lateral dimension of a waveguide, but involves a liftoff process using polyimide as a sacrificial layer. An Er-doped soda-lime silicat e glass film (1.5-mu m thick) was deposited at 350 degrees C using a c ollimated sputtering technique. Conventional sputtering techniques hav e been known to be incompatible with a liftoff process. The collimated sputtering, however, allowed us easy liftoff of Er-doped films, and p roduced well-defined ridges with smooth surface profiles. A 1.7-cm-lon g waveguide thus fabricated shows a 1.55-mu m signal enhancement of 15 .4 dB with a 980-nm pump power of 40 mW. This enhancement fully compen sates for both Er absorption and waveguide losses, and results in a ga in of 7.2 dB.