BUTT-COUPLING LOSS OF 0.1 DB INTERFACE IN INP/INGAAS MQW WAVE-GUIDE-WAVE-GUIDE STRUCTURES GROWN BY SELECTIVE-AREA CHEMICAL BEAM EPITAXY/

The lateral coupling of waveguiding structures in both [0 1 1] and [0 (1) over bar 1] directions is studied using embedded selective area ep itaxy by chemical beam epitaxy. All growth steps are carried out under the same growth conditions on (1 0 0) InP substrates misoriented by 0 .5 degrees towards (1 1 1)B. Both planar and selectively grown materia l exhibits bright luminescence and narrow PL line widths (8 meV FWHM a t 4 K), up to the lateral junction, Moreover, no degradation of the or iginal 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 optica l coupling losses have been determined using a Fabry-Perot setup at 15 30 nm (TE polarization). Values of 0,1 to 0.2 dB/interface with excell ent uniformity are presented for both perpendicular coupling direction s. From our results we conclude that by optimization of the sample pre paration prior to regrowth, values of 0.1 dB/interface can be obtained reproducibly. (C) 1998 Elsevier Science B.V. All rights reserved.