An ultraslow optical centrifuge with arbitrarily low rotational acceleration

We outline the design and characterization of a laser pulse shaper, which creates an "ultraslow optical centrifuge" (usCFG) - a linearly polarized field whose polarization vector rotates with arbitrarily low angular acceleration. We experimentally demonstrate that the angular acceleration of the constructed centrifuge is three orders of magnitude lower than had been attained with previous designs, which should expand its utility to molecules with significantly greater moments of inertia than have been previously studied. Our usCFG is especially well-suited to study superfluidity on the atomic scale, by rotating molecules in helium nanodroplets, where their moments of inertia are effectively increased due to interactions with helium. To test the functionality of our usCFG, we produce a direct time-frequency map of accelerated molecular rotation by measuring the alignment of gas-phase carbon disulphide molecules as they rotate within the centrifuge.