Ultrafast optical rotation in chiral molecules with ultrashort and tightly focused beams

Abstract

Sculpting the subcycle temporal structure of optical waveforms allows one to image and even control the electronic clouds of atoms, molecules, and solids. Here, we show how the transverse spin component arising upon spatial confinement of such optical waveforms enables extremely efficient chiral recognition and control of ultrafast chiral dynamics. When an intense and ultrashort linearly polarized laser pulse is tightly focused into a medium of randomly oriented chiral molecules, the medium generates light that is elliptically polarized, with opposite helicities and opposite rotations of the polarization ellipse in media of opposite handedness. In contrast to conventional optical activity of chiral media, this new nonlinear optical activity is driven by purely electric–dipole interactions. It leads to giant enantio-sensitivity in the near VIS–UV domain, where optical instrumentation is readily available, already in optically thin media. Adding a polarizer turns the rotation of the polarization ellipse into a highly enantio-sensitive intensity of nonlinear optical response. We also show that subcycle optical control of the incident light wave enables full control over the enantio-sensitive response. The proposed all-optical method not only enables chiral discrimination with extreme enantio-efficiency, but also ultrafast imaging and control of chiral dynamics using commercially available optical technology.