Circularly Polarized High Harmonic Generation For Probing Molecular Chirality

Chirality of molecules play an important role in biological activity. Chiral molecules are not superimposable on their own mirror images, called enantiomers, and do not have a symmetry plane nor a center of inversion symmetry. The chemical reactivity of the enantiomers sometimes depends on the chirality. Hence the distinguishing the enantiomers is important and circularly polarized light has been used to discern the enantiomers for a long time. The development of ultrashort pulse technology enables us to investigate nonlinear interactions of chiral molecules with an intense light field. Among various nonlinear optical interactions, we focus on high harmonic generation as the probe into molecular chirality. Here, we describe two our recent results: one is circularly polarized high harmonic generation (CP-HHG) from a chiral molecule, limonene, driven by a CP counter-rotating two-color laser field. The other is the development of elliptically polarized single-order high harmonic light source for the application to photoelectron spectroscopy of chiral molecules.