Chiral interactions are prevalent in nature, driving a variety of bio-chemical processes. Discerning the two non-superimposable mirror images of a chiral molecule, known as enantiomers, requires interaction with a chiral reagent with known handedness. Circularly polarized light beams are often used as a chiral reagent. Here, we demonstrate efficient chiral sensitivity with linearly polarized helical light beams carrying an orbital angular momentum of ±lh, in which the handedness is defined by the twisted wavefront structure tracing a left-or right-handed corkscrew pattern as it propagates in space. By probing nonlinear optical response, we show that helicity dependent nonlinear absorption occurs even in achiral molecules and can be precisely controlled. We model this effect by considering induced multipole moments in light-matter interactions. Design and control of light-matter interactions with helical light opens new opportunities in chiroptical spectroscopy, light-driven molecular machines, optical switching, and in-situ ultrafast probing of chiral systems and magnetic materials.

chiral molecules and their interactions are critical in a variety of chemical and biological processes. circular dichroism (cD) is the most widely used optical technique to study chirality, often performed in a solution phase. However, CD has low-efficiency on the order of 0.01-1%. therefore, there is a growing need to develop high-efficiency chiroptical techniques, especially in gas-phase, to gain background-free in-depth insight into chiral interactions. By using mass spectrometry and strongfield ionization of limonene with elliptically polarized light, we demonstrate an efficient chiral discrimination method that produces a chiral signal of one to two orders of magnitude higher than the conventional cD. the chiral response exhibits a strong dependence on wavelength in the range of 1,300-2,400 nm, where the relative abundance of the ion yields alternates between the two enantiomers. The origin of enhanced enantio-sensitivity in intense laser fields is attributed to two mechanisms that rely on the recollision dynamics in a chiral system: (1) the excited ionic state dynamics mediated either by the laser field or by the recollision process, and (2) non-dipole effects that alter the electron's trajectories. our results can serve as a benchmark for testing and developing theoretical tools involving non-dipole effects in strong-field ionization of molecules. Chiral molecules lack S n symmetry (improper rotation axis) due to the presence of a chiral center in which an atom is connected to four different groups of atoms 1. Consequently, there is a handedness to the molecule. The left-and right-handed molecules are non-superimposable mirror images of each other, called enantiomers. They have identical physical and chemical properties making it difficult to differentiate them. Chiral discrimination requires an interaction between two chiral systems-a chiral reagent with known handedness that can induce enantio-selectivity in the second chiral system. In nature, bio-molecules such as amino acids that make up life on earth are homochiral, where one enantiomer exists predominantly over the other due to asymmetric interactions 2. Homochirality plays a pivotal role in our daily life by serving as a chiral reagent for enantio-selectivity. For example, olfactory receptors in our nose, responsible for the sense of smell, interact differently with the two enantiomers of a chiral system. For instance, the right-handed enantiomer of limonene has an orange odour while the left-handed enantiomer has a lemon odour 3. In practice, enantio-selectivity can be achieved using circularly polarized light (CPL) as a chiral reagent. CD is one of the most widely used chiroptical techniques. It arises due to the coupling of the electric and magnetic dipole transitions, thereby resulting in a differential absorption of left-and right-circularly polarized light 1,4-8. CD has low-efficiency on the order of 0.01-1% because magnetic dipole transitions are involved 9-12. Moreover, CD measurements are mostly conducted in solution phase, making it diffi...

Chiral interactions are prevalent in nature, driving a variety of bio-chemical processes. Discerning the two non-superimposable mirror images of a chiral molecule, known as enantiomers, requires interaction with a chiral reagent with known handedness. Circularly polarized light beams are often used as a chiral reagent. Here, we demonstrate efficient chiral sensitivity with linearly polarized helical light beams carrying an orbital angular momentum of $\pm\it{l\hbar}$, in which the handedness is defined by the twisted wavefront structure tracing a left- or right-handed corkscrew pattern as it propagates in space. By probing nonlinear optical response, we show that helicity dependent nonlinear absorption occurs even in achiral molecules and can be precisely controlled. We model this effect by considering induced multipole moments in light-matter interactions. Design and control of light-matter interactions with helical light opens new opportunities in chiroptical spectroscopy, light-driven molecular machines, optical switching, and in-situ ultrafast probing of chiral systems and magnetic materials.

A novel chiroptical sensing technique was recently introduced that utilized the helical phase of the structured light as a chiral reagent instead of polarization of light to differentiate enantiopure chiral liquids. The unique advantage of this non-resonant, nonlinear technique is that the chiral signal can be scaled and tuned. In this paper, we extend this technique to enantiopure powders of alanine and camphor by dissolving them in solvents of varying concentrations. We show the differential absorbance of helical light to be an order of magnitude higher relative to conventional resonant linear techniques and is comparable to nonlinear techniques that use circularly polarized light. The origin of helicity dependent absorption is discussed in terms of induced multipole moments in nonlinear light–matter interaction. These results opens up new opportunities in using helical light as a primary chiral reagent in nonlinear spectroscopic techniques.