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New applications of ultrafast laser systems require parameters, which are out of reach for classical single amplifier channels. Coherent pulse combining can help to circumvent the limitations, which state-of-the-art laser systems are facing. For that purpose, passive optical resonators, so-called enhancement cavities, can be used to stack laser pulses, thus, drastically increasing their pulse energy. Extracting such an enhanced pulse from the cavity, could lead to a set of laser parameters, not accessible to other amplifier technologies. Enhancement cavities running at 80 MHz or above have been used as pulse stacking devices before, employing acousto-optic-modulators (AOM) as switches to extract the stacked energy. However, the nonlinear phases, as introduced by self-phase-modulation in the AOM, commonly limit the achievable intra-cavity energy of a so-called stack-and-dump cavity. By lengthen such cavities to 10 MHz, the extractable energies from such a device were improved by three orders of magnitude from 200 nJ to 160 J compared to former experiments. While longer cavities could allow for even higher energies, they are difficult to set-up and are often limited by their complexity and stability related issues. This is why, novel switches would have to be introduced, if the potential of stack-and-dump cavities is to be exhausted. A rotating element in the cavity is identified as one possible solution. It circumvents acceleration-related limitations and could allow for fast extraction of the enhanced pulse without disturbing the enhancement process. Possible switches based on rotation include a chopper wheel with mirror-segments attached to its side-facet and a rotating-cavity-caustic. Both have been investigated and identified to be viable solutions. |
