Abstract

The high-speed and ultra-long distance optical communication system can be obtained using 1.5-1.6µm wavelength region [1] if the light source with narrow dynamic spectral width is developed [2]. The lasers with periodic structure, for example DBR-ITG lasers can be operated in single longitudinal mode even under high-speed modulation condition [3]. In order to obtain high-quality DBR laser, it is important to realize highly efficient coupling between active region and DBR region which forms in a low-loss external waveguide. Various types of integrated lasers, namely, lasers with integrated external waveguide, have been studied thus far [4]. Direct-coupling integrated lasers reported in GaAs/AlGaAs system [5][7] have the advantage that the pure un-doped external waveguide can be obtained without disturbing the injection properties of the based wafer. In GaAs direct-coupling integrated lasers, coupling efficiencies were relatively low because the external waveguide structure was not optimized. However if the external waveguide is formed uniformly even at the joint with active layer, coupling efficiency of more than 90% is theoretically possible by the optimized external waveguide structure with relaxed fabrication-tolerance. It is, therefore, interesting to develop this type of GaInAsP/InP integrated laser.

© 1982 Optical Society of America