The optimum facet reflectivities for high-power and highly reliable operation of 980-nm InGaAs/AlGaAs FP laser diodes

980-nm InGaAs/AlGaAs Fabry-Perot ridge waveguide laser diodes were fabricated for pumping Er-doped fiber amplifiers (EDFAs). The dependence of the output power on the facet coatings was investigated theoretically and experimentally. The expected output power was not achieved by decreasing the reflectivity at the front facet. It was found that a large mirror loss yields an increase in internal loss due to longitudinal and lateral spatial hole-burnings, which significantly affect the differential quantum efficiency of the devices. Taking the hole burning effects into account, the front facet reflectivity was optimized so that the operating current was minimum for a given output power.