CHIRAL CAVITY RING-DOWN: ABSOLUTE MEASUREMENT OF OPTICAL ROTATION IN GASES AND LIQUIDS WITH SIGNAL REVERSALS
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Date
2013
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Publisher
Ohio State University
Abstract
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 $\theta_{\rm{F}}$). A chiral sample is introduced in one arm of the cavity, producing a chiral rotation $arphi_{_{\rm{C}}}$. The different symmetry of the two rotations produces a total rotation of ($\theta_{\rm{F}} + arphi_{_{\rm{C}}}$) for one laser beam, and ($\theta_{\rm{F}} + arphi_{_{\rm{C}}}$) for the counter-propagating beam. These rotations produce a polarization beating in the cavity ring-down, of frequency $\omega_{_{\rm{CW}}}$ and $\omega_{_{\rm{CCW}}}$ for the clockwise and counter-clockwise beams, respectively. Analysis of the difference ($\omega_{_{\rm{CW}}}-\omega_{_{\rm{CCW}}}$) yields the chiral rotation angle $\pm arphi_{_{\rm{C}}}$, where the sign of the angle is determined by the sign of the applied magnetic field. Therefore, subtracting the signals using +$ec{B}$ and ?$ec{B}$ yields $2arphi_{_{\rm{C}}}$, allowing the absolute determination of $arphi_{_{\rm{C}}}$, without needing to remove the sample [1]. We demonstrate these absolute optical rotation measurements for chiral gases ($\alpha$-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]. [1] L. Bougas, G. E. Katsoprinakis, W. von Klitzing, J. Sapirstein, and T. P. Rakitzis, Phys. Rev. Lett {\bf 108}, 210801 (2012).
Description
Author Institution: Department of Physics, University of Crete, and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas 71110 Heraklion-Crete, Greece