We built a new design theory for high efficiency Fabry-Perot lasers with asymmetric mirror facets considering spatial hole burning effect. Optimized laser devices exhibit a high efficiency of 50 %. Highly efficient lasing operation is one of key issues for reliable pumping sources of fiber amplifiers. To increase the efficiency, the asymmetric mirror facet structure having an AR coated front facet and a HR coated rear facet has been widely used. In this work, we investigated theoretically and experimentally asymmetric mirror facets structure for high efficiency lasers.