Coherent combining of high brightness tapered amplifiers for efficient non-linear conversion

We report on a coherent beam combination of three high-brightness tapered amplifiers, which are seeded by a single-frequency laser at lambda = 976 nm in a simple architecture with efficiently cooled emitters. The maximal combined power of 12.9 W is achieved at a combining efficiency of > 65%, which is limited by the amplifiers' intrinsic beam quality. The coherent combination cleans up the spatial profile, as the central lobe's power content increases by up to 86%. This high-brightness infrared beam is converted into the visible by second harmonic generation. This results in a high non-linear conversion efficiency of 4.5%/W and a maximum power over 2 W at 488 nm, which is limited by thermal effects in the periodically poled lithium niobate (PPLN). (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement