Abstract
Gas-filled multipass cells are an appealing alternative to capillaries to implement nonlinear temporal compression of high energy femtosecond lasers. Here, we provide an analytic expression for stationary beam coupling to multipass cells that takes into account nonlinear propagation. This allows a constant beam size on the mirrors and at the cell waist, thereby making the optical design more accurate, for example to avoid optical damage or significant ionization. The analysis is validated using spatio-temporal numerical simulations of the propagation in a near-concentric configuration. This is particularly important for multipass cells that are operated in a highly nonlinear regime, which is the current trend since it allows a lower number of roundtrips, relaxing the constraint on mirror coatings performance.
Highlights
Nonlinear temporal compression [1] is an important technique that allows a lot of flexibility in ultrafast laser design
We believe that improved understanding and description of the spatial aspects of nonlinear propagation in these multipass cell (MPC) will allow the expansion of their use, in particular for high energy ultrafast laser systems
We derive the stationary condition for a symmetric MPC in the nonlinear aberrationless Gaussian beam approximation
Summary
Nonlinear temporal compression [1] is an important technique that allows a lot of flexibility in ultrafast laser design. Input beam coupling in gas-filled MPCs is typically matched to the stationary Gaussian beam [13], to ensure a constant beam size evolution from one roundtrip to the next. Input beam coupling in gas-filled MPCs is typically matched to the stationary Gaussian beam [13], to ensure a constant beam size evolution from one roundtrip to the This is important to avoid damage on the mirrors or excess ionization at the MPC waist. We believe that improved understanding and description of the spatial aspects of nonlinear propagation in these MPCs will allow the expansion of their use, in particular for high energy ultrafast laser systems
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