Low-loss GaAs/AlGaAs optical waveguides on InP substrates

1990 
It is shown that the waveguide losses in lattice-mismatched GaAs-on-InP structures can be significantly reduced using an appropriate buffer layer. An AlGaAs buffer layer sequence was used for this purpose. A thin (400 nm) layer of Al/sub 0.7/Ga/sub 0.3/As, with an index below that of InP, was placed adjacent to the GaAs guiding layer both to maximize optical confinement in the guide and to increase the allowable guide dimensions for a single planar waveguide mode. Additional separation between guide and mismatched interface was achieved by inserting an Al/sub 0.5/Ga/sub 0.5/As layer with an index nearly equal to that of InP between the low-index buffer and InP. The final waveguide structure also included a thin ( >
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