Optical characterization of a-As2S3 thin films prepared by magnetron sputtering

Abstract

It is well known that thermally evaporated a -As 2 S 3 thin films are prone to oxidation when exposed to ambient environment. These As 2 O 3 crystals can have a devastating effect on propagating light by introducing a major source of scattering loss in submicron optically integrated circuits. Magnetron sputtering a -As 2 S 3 not only produces films that have optical properties closer to their equilibrium state like their bulk glass counter parts, the as-deposited films also show no detectable signs of As 2 O 3 crystals in them when they are exposed to the ambient environment. These attributes are unique to a magnetron sputtered a -As 2 S 3 film and are probably caused by the “photoannealing” effect from the visible light emitted by the argon plasma during the sputtering process. The optical properties of a magnetron sputtered a -As 2 S 3 film and its propagation loss on a Ti diffused LiNbO 3 waveguide are reported here. The thin film results agree closely with published data on As 2 S 3 bulk glass, and the optical properties of the as-deposited film are found to be closer to its bulk glass values than films made by thermal evaporation and pulsed laser deposition. The TM propagation loss at λ = 1.5 μ m of the as-deposited a -As 2 S 3 waveguide on Ti : LiNbO 3 was 0.20 ± 0.05 dB / cm .