Loss in Heterostructure Waveguide Bends Formed on a Patterned Substrate

An experimental comparison is made of the loss of Al- rGa1-rAs heterostructure waveguide routing geometries at ≈860 nm patterned by two methods: Zn impurity induced layer disordering and native growth on a patterned substrate. Two multimode geometries were investigated: a raised cosine s-bend and a modified abrupt bend due to Shiina et al. [8, p. 736]. The measured transition distance for 3 dB loss was approximately 300 μm for 100 μm offset guides in the s-bend geometry for the patterned substrate samples using wet and dry etching methods. For the Shiina bend, the measured angle corresponding to the 3 dB loss was ≈13° also for both etching methods. These results represent significant improvements over the equivalent structures fabricated by impurity induced layer disordering primarily because of reduced free-carrier loss.