Efficient high-power diffraction-limited fiber laser with a record low quantum defect of 1.7

In this work, we demonstrate an approach to potentially lower the quantum defect to ∼1% without significant compromise of efficiency. In a first demonstration, a diffraction-limited ∼154 W laser emitting at ∼993 nm with negligible amplified spontaneous emission, pumped at ∼976 nm, was achieved with a slope efficiency of ∼75% vs the launched pump power. The laser quantum defect is a record low of 1.7% for high-power (>100 W) solid-state lasers to the best of our knowledge. The output is only limited by the available pump power.