High intracavity power thin-disk lasers for continuous-wave strong alignment of molecules

Many experiments aiming at recording the “molecular movie”, i.e., the imaging of the structural dynamics of chemical processes, rely on molecules fixed-in-space. One of the most promising approaches to capture such processes is time-resolved x-ray-diffractive imaging. Modern x-ray light sources, such as the upcoming free-electron lasers with very large photon fluxes such as the European XFEL, LCLS II, or synchrotrons, operate at high repetition rates with ten-thousands to millions of pulses per second, sometimes in burst modes. To allow for efficient measurements, the aligned molecules should be available for all of these pulses. However, the necessary electric field strengths for strong adiabatic alignment of gas-phase ensembles of molecules exceeds 10¹⁰ W/cm² and this field strength must be applied over durations comparable to the rotation periods of the molecules of hundreds of picoseconds to even nanoseconds. So far, these intensities are only available from pulsed amplifier systems with repetition rates in the few-Hz to low-kHz range, which does not allow for providing aligned molecules for all pulses of the x-ray probe sources. Thus, it prohibits efficient use of these sources.