Optical loss mechanism in yttria thin film waveguides

It is well known that the imperfections in thin film optical devices would cause absorption, radiation, and scattering loss of the guiding beam, and such losses are mostly unavoidable. To reduce the propagation loss, the conditions for film deposition should therefore be optimized. Yttria (Y2O3) thin film was chosen for the study. Yttria thin film waveguide was deposited on silicon and thermally oxidized silicon wafers by reactive sputtering in a rare gas–oxygen discharge. The deposition process was controlled by the substrate temperature, total gas pressure, oxygen flow rate, and rare gases (Ar, Ne). The yttria thin films were characterized for the optical losses based upon the film structures. Relationships between deposition parameters and the propagation losses were discussed.