Polarization Shaping for Unidirectional Rotational Motion of Molecules

Abstract

Control of the orientation of the angular momentum of linear molecules is demonstrated by means of laser polarization shaping. For this purpose, we combine two orthogonally polarized and partially time-overlapped femtosecond laser pulses so as to produce a spinning linear polarization which in turn induces unidirectional rotation of N2 molecules. The evolution of the rotational response is probed by a third laser beam that can be either linearly or circularly polarized. The physical observable is the frequency shift imparted to the probe beam as a manifestation of the angular Doppler effect. Our experimental results are confirmed by theoretical computations, which allow one to gain a deep physical insight into the laser-molecule interaction.

Alignment enhancement of molecules embedded in helium nanodroplets by multiple laser pulses

“…[7] and the first experiments demonstrating the effect on isolated molecules, employing two alignment pulses, were reported shortly after [8,9]. Since then, many more works, theoretically as well as experimentally, have further explored the use of laser pulse sequences and shaped laser pulses to optimize and control rotations of isolated molecules, including demonstration of eight-pulse alignment [10], field-free 3D alignment [11,12], permanent planar alignment [13], and controlling the sense of molecular rotation [14][15][16][17].…”

Observation of the field-free orientation of a symmetric-top molecule by terahertz laser pulses at high temperature

“…In this setting, molecular alignment and orientation can be identified as crucial prerequisites before exploring more complex control scenarios [16,4]. The alignment process [17] is by now a well-established concept from both the experimental and theoretical points of view with recent extensions ranging from the deflection of aligned molecules [18], the introduction of planar alignment [19], the control of molecular unidirectional motion [20,21,22], the study of molecular superrotors [23,24,25] or the analysis of dissipation effects due to molecular collisions [26,27,28,29]. The description and the control of molecular orientation are not currently at the same degree of improvement, in particular from the experimental point of view.…”

Phase and polarization changes of pulsed Gaussian beams during focusing and propagation

“…Of course, the control given by this additional degree of freedom is exploited not just to provide three-dimensional experience during watching films in movie theaters, but also in the different areas of femtosecond sciences. Using pulses with more complex polarization states than linear can yield polarization-formed terahertz fields [64], or can help to reach optimal control on the irradiated molecules or other materials, which is often mentioned as a way of coherent control [65][66][67][68][69]. On a similar basis, polarization control showed to be advantageous in pump-probe measurements of two-dimensional spectroscopy techniques [70,71].…”

“…As it was detailed in the introduction, tailoring the temporal variation of the polarization state of few-cycle pulses has been introduced recently as a new way of coherent control [64][65][66][67][68][69][70][71][72]. In the experiments, these polarization-shaped pulses are also focused.…”

“…While in the majority of laser applications the polarization state is not considered -because the generated pulsed light is usually linearly polarized and can be treated theoretically as a scalar -, more and more studies are published where pulsed waves with complex polarization states are used [41,[64][65][66][67][68][69][70][71][72].…”