Selecting rotational two-level coherence in polar molecules by double terahertz pulses

Abstract

We demonstrate experimentally a method for controlling two-level coherence in jet-cooled rotating polar molecules by using a pair of intense terahertz pulses. The broad spectra of the terahertz pulses can induce resonant population transfer between four rotational states $J=0,1,2,3$ to establish two-level coherence. This coherence is controlled by the delay between the two terahertz pulses, resulting in selection of a single two-level coherence. This scheme can be extended to select a specific two-level coherence in a thermally distributed molecular ensemble by applying a train of terahertz pulses.