Circular dichroism in high-order harmonic generation from chiral molecules

In this study, circularly polarized high-order harmonic generation (CP-HHG) from a chiral molecule, limonene, by a CP counter-rotating two-color laser field was found to possess circular dichroism. A high-order harmonic spectrum from a limonene enantiomer depends on the combination of the chirality of the enantiomer and the rotation direction of the superimposed two-color laser field in comparison with that of an achiral atom, helium. From the R enantiomer, the harmonic orders with clockwise polarization were generated more efficiently than those with counterclockwise polarization and vice versa. CP-HHG can be a sensitive probe of the chirality of biomolecules on the femtosecond and attosecond timescales.