Discriminatory optical force for chiral molecules

By R. Cameron, Stephen M. Barnett, A. Yao. 2014

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We suggest that the force F exerted upon a chiral molecule by light assumes the form F=a∇w+b∇h?> under appropriate circumstances, where a and b pertain to the molecule whilst w and h are the local densities of electric energy and helicity in the optical field; the gradients ∇?> of these quantities thus governing the molecule's centre-of-mass motion. Whereas a is identical for the mirror-image forms or enantiomers of the molecule, b has opposite signs; the associated contribution to F therefore pointing in opposite directions. A simple optical field is presented for which ∇w?> vanishes but ∇h?> does not, so that F is absolutely discriminatory. We then present two potential applications: a Stern–Gerlach-type deflector capable of spatially separating the enantiomers of a chiral molecule and a diffraction grating to which chiral molecules alone are sensitive; the resulting diffraction patterns thus encoding information about their chiral geometry.

Subfields: Atomic and Molecular Physics, and Optics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/e541ddde614fc43678bc2814e2cda7f397f683ff