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The lateral coupling of waveguiding structures in both and directions is studied using embedded selective area epitaxy by chemical beam epitaxy. All growth steps are carried out under the same growth conditions on InP substrates misoriented by towards . Both planar and selectively grown material exhibits bright luminescence and narrow PL linewidths (8 meV FWHM at 4 K), up to the lateral junction. Moreover, no degradation of the original material properties is observed after regrowth. SEM images show very flat layers and excellent lateral coupling for all four types of junctions. After reactive ion etching of waveguide ridges, the optical coupling losses have been determined using a Fabry-Pérot setup at 1530 nm (TE polarization). Values of 0.1 dB/interface with excellent uniformity are presented. From our results we conclude that, by optimization of the sample preparation prior to regrowth, values of 0.1 dB/interface can be obtained reproducibly for both perpendicular coupling directions.
Messerli et al. (Fri,) studied this question.