Enhancing Enantioselective Absorption Using Dielectric Nanospheres

Separation of enantiomers is crucial to the pharmaceutical and chemical industries, but prevailing chemical methods are economically costly and time-consuming. Illumination with circularly polarized light (CPL) provides a potentially cost-effective and versatile alternative but can achieve only 2% enantiomeric excesses with substantial yield. Here, we theoretically show that high-index dielectric nanoparticles can increase enantiomeric excesses 7 times beyond CPL in free space. Mie theory and a local optimization algorithm indicate that magnetic multipolar Mie resonances supported by submicrometer silicon spheres increase Kuhn's dissymmetry factor 7-fold, compared to CPL in free space. Further, the circular dichroism signal can be enhanced 170-fold. Importantly, these local enhancements maintain the total molecular absorption rate, enabling efficient selective photoexcitation. Even greater enhancements in Kuhn's dissymmetry factor can be achieved with lower loss and higher refractive index nanoparticles. Our results provide a path toward more efficient all-optical chiral resolution techniques.