Augustin-Jean Fresnel predicted in 1822 that a light beam would split into two beams as it enters a chiral liquid—that is, one containing molecules that lack mirror symmetry. The splitting in a chiral liquid occurs because right-handed circularly polarized light and left-handed circularly polarized light travel at different speeds and hence see different indexes of refraction. Fresnel proposed an experiment to measure the angular splitting in a chiral solution, but the angle of splitting, on the order of microradians, is too small for Fresnel to have detected it. He did, however, observe the double image produced by light that had traversed a quartz crystal, which is birefringent because of its anisotropy. He used the effect to prove the existence of circularly polarized light.
Recently, Ambarish Ghosh and Peer Fischer of the Rowland Institute at Harvard University used a scheme similar to Fresnel’s to measure the tiny angle of splitting between...
