Loss in heterostructure waveguide bends formed on a patterned substrate

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An experimental comparison is made of the loss of Al/sub x/Ga/sub 1-x/As heterostructure waveguide routing geometries at approximately 860 nm that were 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 as described by T. Shiina et al. (Opt. Lett., vol.11, p.736-8, 1986). The measured transition distance for 3-dB loss was approximately 300 mu m for 100- mu m offset guides in the s-bend geometry for the patterned substrate samples using wet and dry etching methods. For the so-called Shiina bend, the measured angle corresponding to the 3-dB loss was about 13 degrees for both etching methods.>