NATIVE-OXIDE-DEFINED LOW-LOSS ALGAAS-GAAS PLANAR WAVE-GUIDE BENDS

Data are presented on planar waveguide S-bends fabricated from AlxGa1- xAs-GaAs p-n quantum well heterostructure (QWH) laser material by a we t native oxidation process. The oxide's low refractive index (n approx imately 1.55) is used to define approximately 3.5-mum-wide single mode guides exhibiting low excess losses for raised-cosine S-bends with 10 0 mum offsets. The waveguide's routing properties are determined by th e lateral effective index profile which is controlled by the native ox ide thickness. Guides with two different oxidation depths are investig ated. For the deepest oxidation, excess bend losses of 3 dB are measur ed for transition distances of approximately 180 mum and less-than-or- similar-to 120 mum for transverse electric (TE) and transverse magneti c (TM) polarizations, respectively. Theoretical loss calculations for the guides show good agreement with measured data. Guides with a shall ow oxidation exhibit 3 dB transition lengths of approximately 260 mum and approximately 220 mum for the TE and TM polarizations.