Abstract
An ultrafast laser delivering 10.4 kW average output power based on a coherent combination of 12 step-index fiber amplifiers is presented. The system emits close-to-transform-limited 254 fs pulses at an 80 MHz repetition rate, and has a high beam quality (M2≤1.2) and a low relative intensity noise of 0.56% in the frequency range of 1 Hz to 1 MHz. Automated spatiotemporal alignment allows for hands-off operation.
Highlights
Coherent beam combination (CBC, [6]) of several amplifiers in an interferometric setup allows to surpass these limits
N amplifiers are seeded by a common source and their output beams are made to interfere constructively, resulting ideally in a single output beam with up to N-times the brightness of a single amplifier channel
Deviations in the spatial and temporal output characteristics of the amplifiers will result in a loss [7], which is quantified by the combining efficiency, defined as the ratio of combined power to the sum of all individual amplifier output powers
Summary
Coherent beam combination (CBC, [6]) of several amplifiers in an interferometric setup allows to surpass these limits. The state of the art are ytterbium-doped thin-disk [1], slab [2] and fiber [3] chirped-pulse amplifiers delivering 1 kW-level average power in fundamental mode operation. CBC allows for power scaling by orders of magnitude compared to a single amplifier, as the passive combination elements support higher peak and average power than the laser-active media.
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