Bloch oscillations in the angular momentum of laser-kicked N142 molecules. The above figure displays the simulated population of the angular momentum levels J, as a function of the number of laser pulses. The initial rotational temperature is 298 K. The considered pulse train parameters are τ=8.36 ps (0.2% less than the revival time of 8.38 ps) and an effective interaction strength of P=5.
Simplified sketch of the experimental setup. A Ti:sapphire source generates an 800 nm pulse that enters a pump-probe setup. The pump is split into an eight pulse train using three nested interferometers. The probe pulse is converted to circularly polarized 400 nm with variable path length. The beams are focused using an off-axis parabola (depicted as a lens). Molecular alignment triggered by the strong pump train causes birefringence that alters the circular polarization of the weak probe pulse. The probe’s polarization is split and measured, yielding a time-dependent molecular alignment signal that can be time-averaged to yield population alignment. The abbreviations used are BS, beam splitter; IF, interferometer; HWP, half wave plate; L, lens; DL, automated delay line; BBO, β-BBO crystal; QWP, quarter wave plate; BPF, blue pass filter; GC, gas cell; GTP, Glan-Taylor polarizer; and PD, photodiode.
Measured and simulated time-averaged alignment signal. Compared the measured and simulated time-averaged alignment signals for periodically kicked nitrogen molecules, for different values of the kick strength P and the detuning δ. The statistical error of the experimental data is much less than the plot symbols and therefore not plotted.
This research is published in Physical Review Letters.