15min:

LYKOURGOS BOUGAS, G. E. KATSOPRINAKIS, T. P. RAKITZIS, Department of Physics, University of Crete, and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas 71110 Heraklion-Crete, Greece.

We demonstrate the absolute measurement of optical rotation using a four-mirror cavity-ring-down polarimetric setup. A four-mirror bow-tie cavity allows counter-propagating laser beams, for which symmetry is broken with a longitudinal magnetic field acting upon an intracavity magneto-optic window (producing a Faraday rotation _F). A chiral sample is introduced in one arm of the cavity, producing a chiral rotation __C. The different symmetry of the two rotations produces a total rotation of ( _F + __C) for one laser beam, and ( _F + __C) for the counter-propagating beam. These rotations produce a polarization beating in the cavity ring-down, of frequency __CW and __CCW for the clockwise and counter-clockwise beams, respectively. Analysis of the difference ( __CW- __CCW) yields the chiral rotation angle \pm __C, where the sign of the angle is determined by the sign of the applied magnetic field. Therefore, subtracting the signals using +\vecB and Ð\vecB yields 2 __C, allowing the absolute determination of __C, without needing to remove the sample [1]. We demonstrate these absolute optical rotation measurements for chiral gases ( -pinene) and chiral liquids.
This work is a proof-of-principle demonstration of the experimental setup proposed for the measurement of parity non-conserving optical rotation in atomic systems [1].

\beginitemize em[1] L. Bougas, G. E. Katsoprinakis, W. von Klitzing, J. Sapirstein, and T. P. Rakitzis, Phys. Rev. Lett 108, 210801 (2012). \enditemize