Optical rotation measurement with a polarization-modified double-slit

Abstract

Measuring enantiomeric purity is an indispensable step in pharmaceutical research due to the stereoselectivity and potential toxicity of chiral drugs. While conventional methods are accurate, they are often resource-inefficient. In contrast, polarimetry is simple and inexpensive, but suffers from low sensitivity due to its reliance on intensity data. To address this, we propose a novel, highly sensitive method for measuring optical rotation using an orthogonally polarized double-slit. By adding orthogonal polarization, the double-slit produces interference fringes whose contrast varies predictably with optical rotation. We successfully established the theoretical equation and experimentally determined the relation between fringe contrast and optical rotation. The experimental results demonstrated high correlation with the theoretical curve. Ultimately, this study demonstrates that polarimetry with orthogonally polarized double-slit has the potential to measure small optical rotations from chiral drugs with high accuracy.