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Description
Laser light can be tailored in a broad variety of ways. From standard temporal and spectral shaping, which led to the generation of ultrashort laser pulses, to harnessing light’s polarization or creating beams with properties associated to their spatial structure. Interestingly, the capability of shaping light’s symmetries and structure can be used to investigate matter’s symmetries and structure. Chirality, a universal property of objects that are not superimposable to their mirror image, is specially relevant in this context. Tailored fields allow us to probe chiral matter and ultrafast chiral dynamics in unprecendent ways. The merging of these two ingredients, tailored light and chirality, has led to new methods for studying chiral molecules [1].
On the one hand, microscopic tailoring includes shaping the electric field’s polarization by mixing frequencies, which results in a collection of Lissajous curves. A relevant polarization shaping in the context of chiral discrimination is locally chiral light, which presents a 3-dimensional polarization at each point of space [2]. On the other hand, macroscopic tailoring includes topological light, such as vortex beams, which carry orbital angular momentum associated to its azimuthally varying phase, and which have already proven to be a valuable tool for obtaining enantio-sensitity observables [3]. Another noteworthy type of topological light are vector beams, which possess a Poincaré index associated to its azimuthally-rotating polarization, being the most typical type of a vector beam radially polarized [4] (Fig. 1A). Vector beams have demonstrated to enhance super-resolution imaging and nonlinear interactions due to their improved focusing capabilities, and they offer promising applications in optical trapping, communications or laser manufacturing [5].
We propose a robust, ultrafast and highly efficient setup for distinguishing molecular enantiomers by combining ultrafast techniques with vector beams. Here, an infrared, elliptically polarized and tightly focused vector beam generates high-order harmonics in a sample of randomly oriented chiral molecules. High-order harmonic generation (HHG) results from the highly nonlinear interaction of the intense driving laser field with the target [6]. In our work, HHG leads to the emission of an ultraviolet vector beam whose intensity profile carries information about the handedness of the chiral molecules [7] (Fig. 1B-C). In particular, the handedness of the chiral molecules is imprinted in the divergence of the emitted light, leading to topological chiral rings. Our approach allows for spatial discrimination of molecular enantiomers, opening a new route for studying chirality in ultrafast time scales.
Figure 1. (A) Intensity and polarization of a radially polarized vector beam, which carries a topological charge linked to its spatial structure. (B,C) Total intensity profile of harmonic 6th after propagating to the far-field plane, emitted from the L-handed enantiomer (B) and R-handed enantiomer (C).
Notes and References
1. Habibović, D., Hamilton, K.R., Neufeld, O. and Rego, L. Nat. Rev. Phys. Emerging tailored light sources for studying chirality and symmetry. 2024, 6, 663–675.
2. Ayuso, D., Neufeld, O., Ordonez, A.F. et al. Nat. Photonics. Synthetic chiral light for efficient control of chiral light–matter interaction. 2019, 13, 866–871.
3. Mayer, N., Ayuso, D., Decleva, P. et al. Nat. Photonics. Chiral topological light for detection of robust enantiosensitive observables. 2024 18, 1155–1160.
4. Zhan, Q. Adv. Opt. Photonics. Cylindrical vector beams: from mathematical concepts to applications. 2009, 1, 1, 1-57.
5. Rosales-Guzmán, C., Ndagano, B., and Forbes, A. J. Opt. A review of complex vector light fields and their applications. 2018, 20, 123001.
6. Ferray, M., L’Huillier, A., Li, X. F., et al., J. Phys. B: At. Mol. Opt. Phys. Multiple-harmonic conversion of 1064 nm radiation in rare gases. 1988, 21, L31.
7. Rodriguez, A. and Rego, L. Ultrafast chiral sensing with an ultraviolet vector beam. 2026, arXiv:2606.13402.