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We fabricated a GaInNAs semiconductor optical amplifier (SOA) by applying a facet coating to a buried-ridge-stripe GaInNAs laser. Due to a low reflectivity (<0.1%) and a wide bandwidth (70 nm) coating, Fabry–Perot (FP) modes of the GaInNAs laser were suppressed sufficiently, and thus a 1.3 µm traveling-wave GaInNAs SOA was realized for the first time. Peak chip gains of more than 9.6 dB and a 3-dB-gain bandwidth above 49 nm (9 THz) were obtained simultaneously with a cavity length between 600 µm and 900 µm. In addition, on/off ratios between 20 and 30 dB were obtained by switching the current on and off, which seems sufficient for the SOA to work as a switching device. With the temperature characteristics, we found that the ASE intensity and the gain coefficient of the GaInNAs SOA were much less dependent on temperature than those of conventional InP-based SOAs. These results demonstrate the superior temperature characteristics of the GaInNAs SOA compared with conventional InP-based SOAs.

The effects of growth temperature and V/III flux ratio on the GaAsSb crystalline quality were studied. Phase separation was suppressed within a narrow window of growth temperature. 1-μm-thick GaAsSb layers which exhibited single peaks in X-ray diffraction (XRD) measurement were successfully obtained grown at the optimum temperature. XRD and photoluminescence (PL) measurements revealed that V/III flux ratio also has an optimum value. It was found that the type-II InGaAs/GaAsSb superlattice with GaAsSb grown at the optimized growth condition seems to have an excellent optical property, because the PL peak energy exhibited peculiar dependence on temperature suggesting transition between the conduction band of InGaAs and the valance band of GaAsSb.