“…Implementation of the chemical etch and deposited oxide, coupled with large areas of high quality LPE grown AlGaAs [1], has already allowed us to reduce a to values which consistently lay between 0.5 and 2 cm"" for single rib guides and directional coupler pairs at both 0.87 and 1.06pm wavelength. This low a includes a dominant contribution by free carrier absorption, calculated to be about 0.3 cm for our undoped layers.…”