Ultrafast, all-optical, and highly enantiosensitive imaging of molecular chirality

Just like our hands, chiral molecules exist in pairs of opposite “mirror twins” called enantiomers, which behave identically unless they interact with another chiral “object”. Distinguishing them is vital, e.g. as most biomolecules are chiral, but it can also be a challenging task.

Traditional optical methods for chiral recognition rely on the linear response of the molecules to circularly polarised light, which draws a (chiral) helix in space. However, the pitch of this helix, determined by the field’s wavelength, is orders of magnitude larger than the molecules. Consequently, the tiny molecules perceive this helix as a planar circle, hardly feeling its chirality.

In this presentation, I will show that we can overcome this fundamental limitation by encoding chirality not in space, but in time. Indeed, we can create synthetic chiral light that is locally chiral: the Lissajous figure that the tip of the electric-field vector of the laser draws in time is three-dimensional and chiral [1]. As a result, the nonlinear optical response of randomly oriented chiral molecules is enantiosensitive already within the electric-dipole approximation.

Our numerical results show that locally chiral fields can force one of the two enantiomers of a chiral molecule to emit bright light at harmonic frequencies while its mirror twin remains dark, both in the strong-field regime [1,2] and in the low-order nonlinear regime [3], reaching the ultimate efficiency limit of enantiosensitivity: 100%. This creates exciting opportunities for ultrafast and highly efficient imaging and manipulation of molecular chirality.

1. D Ayuso et al, Nature Photonics 13, 866 (2019)
2. D Ayuso et al, Nature Communications 12, 3951 (2021)
3. J Vogwell et al, Science Advances 9, eadj1429 (2023)