(The) InGaAs/InGaAsP multi-quantum well twin-guide laser diode with grooved corner reflector

Abstract

We have fabricated and investigated the characteristics of the InGaAs/InGaAsP multi-qunatum well ITG-LD with grooved corner reflector. The improvement in reflectivity from the etched corner reflector is offset by their tendency to favor odd-order transverse modes. The threshold current density rapidly increases due to the large diffraction at the corner reflector, as the cavity width of the ITG-LD with corner reflector decreases. Therefore, by introducing the groove at the center of active cavity, we can reduce optical loss otherwise occurred at the corners, and simultaneously enhance the traveling wave characteristic such as mode purity. Especially, Grooved corner reflector will be good candidate for low threshold operating device with good mode purity in the case of small width of cavity. Normal mode analysis was utilized for the simulation of ITG-LD with grooved corner reflector. For smooth and almost vertical dry-etched facet, we set up the InP/InGaAsP RIBE etching conditions using $Ar/Cl_2/H_2$. The RMS roughness of dry etching surface is about 290Å, which remains within the requirement for acceptable losses from the etched facet. For low threshold operation, we set up LP-MOCVD growth conditions for multi quantum well structure based on the InGaAs/InGaAsP material system. In the case of the ITG-LD with grooved corner reflector, the threshold current is measured to be 33mA. The emission peak wavelength is about 1.62㎛. The fabricated device showed single mode operation, which was maintained at current levels more than 1.7 times of the threshold current. Their spectrum characteristics and near fields are compared with those of the ITG-LD without the groove.