Multi-kW near-diffraction-limited single-frequency Nd:YAG laser

Northrop Grumman is developing a laser architecture that can scale to >100 kW with a near-term goal of a 25 kW demonstration. The near-term 25 kW design is based on two chains of four slab amplifiers that produce average power of 12.5 kW each. Adaptive optics sense the output wavefront and piston relative to a reference, then adjust the phase of the master oscillator input to each chain to keep the wavefronts of each chain uniform and in phase. To reach the goal of 12.5 kW per chain, Northrop has demonstrated power scaling of individual amplifiers by extracting 4.5 kW form a single amplifier using a multimode resonator. This is well above the minimum needed to achieve 12.5 kW from a four-amplifier chain.