High-sensitivity optical rotation detection of low-activity chiral compounds using a common-path weak-measurement system

Chiral detection plays a critical role in food safety, pharmaceutical quality control, and biochemical analysis. However, conventional polarimetric methods often struggle to detect compounds with low specific optical rotation due to their limited sensitivity and resolution. Here, we report an alignment-tolerant, common-path weak-measurement sensor that amplifies minute polarization rotations via dual-peak spectral centroid analysis. The system combines a superluminescent diode source, Z-cut quartz phase tuning, and near-orthogonal polarization pre-/post-selection to achieve 183.08 nm/° sensitivity and 7.65×10 −5 ° resolution at 100 ms/point. The common-path architecture inherently suppresses alignment drift, while selectivity tests with sodium chloride confirm robustness against non-chiral interference. Validation in clarified apple juice demonstrates linearity (R 2 =0.9997) despite turbid matrices, highlighting its capability to operate in optically complex media. This work establishes a high-sensitivity, alignment-resistant platform for label-free chiral sensing, with potential applications in biochemical monitoring, environmental sensing, and optical diagnostics of low-activity compounds.